Patent Application
20160186068
The present disclosure generally relates to processing of cellulosic biomass solids, and, more specifically, to methods and systems for processing a reaction product comprising lignin that may be obtained by a hydrothermal reaction of cellulosic biomass.
This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art.
A number of substances of commercial significance may be produced from natural sources, including biomass. Cellulosic biomass may be particularly advantageous in this regard due to the versatility of the abundant carbohydrates found therein in various forms. As used herein, the term “cellulosic biomass” refers to a living or formerly living biological material that contains cellulose. The lignocellulosic material found in the cell walls of higher plants is the world's largest source of carbohydrates. Materials commonly produced from cellulosic biomass may include, for example, paper and pulpwood via partial digestion, biofuels, including bioethanol by fermentation.
Development of fossil fuel alternatives derived from renewable resources have received recent attention. Cellulosic biomass has garnered particular attention in this regard due to its abundance and the versatility of the various constituents found therein, particularly cellulose and other carbohydrates. Despite promise and intense interest, the development and implementation of bio-based fuel technology has been slow. Existing technologies have heretofore produced fuels having a low energy density (e.g., bioethanol) and/or that are not fully compatible with existing engine designs and transportation infrastructure (e.g., methanol, biodiesel, Fischer-Tropsch diesel, hydrogen, and methane). Moreover, conventional bio-based processes have typically produced intermediates in dilute aqueous solutions (>50% water by weight) that are difficult to further process. Energy- and cost-efficient processes for processing cellulosic biomass into fuel blends having similar compositions to fossil fuels would be highly desirable to address the foregoing issues and others.
Further, in addition to the desired carbohydrates, other substances may be present within cellulosic biomass that can be especially problematic to deal with in an energy- and cost-efficient manner. For example, during cellulosic biomass processing, significant quantities of lignin present in cellulosic biomass may lead to fouling of processing equipment, potentially leading to costly system down time. The lignin can also lead to realization of a relatively low conversion of the cellulosic biomass into useable substances per unit weight of feedstock.
As evidenced by the foregoing, an efficient conversion of cellulosic biomass into fuel blends and other materials is a complex problem that presents immense engineering challenges. The present disclosure addresses these challenges and provides related advantages as well.
Recovery of various compounds from a product of reactions involving cellulosic biomass may be challenging due to the various components contained therein, including lignin. The present disclosure provides methods and systems for processing cellulosic biomass, particularly separation of a reaction product of a hydrothermal reaction containing lignin and lignin-derived products, where the reaction product is a mixture of various compounds and typically in more than one liquid phase. One phase of the reaction product is usually water. While feasible, distillation of a reaction product with multiple liquid phases that contains water into various product fractions can result in poor product separation and steam stripping, where water vapors carry heavier compounds, like phenols, into the overhead fraction. Although this may be addressed by conducting the distillation at higher pressure and temperature where multiple phases can be reduced or minimized, the higher pressure and temperature presents additional expenses including equipment costs, as well as risks to product from onset of undesired degradation reactions at higher temperatures. While the water in the reaction product can be removed through flashing prior to full distillation into product fractions, doing so can also result in steam stripping, thereby resulting in less efficient product separation in a subsequent distillation process.
The methods and systems provided in the present disclosure address the foregoing issues by providing liquid-liquid extraction (or solvent extraction) to isolate the phases so that the phases can be further processed independent of each other. As used herein, liquid-liquid extraction refers to extraction of a substance from one liquid phase (e.g., an aqueous phase) into a different liquid phase (e.g., a non-aqueous phase) based on the relative solubility of the substance in each of the phases. Accordingly, liquid-liquid extraction can provide for a certain amount of extraction of various compounds from the aqueous phase. These compounds can include certain light compounds can be further processed into a fuels product and can include those with a normal boiling point of less than about 150 degrees C., including but not limited to monohydric alcohols (e.g., mono-oxygenates), aldehydes, ketones, acids, and any combination thereof.
More than one liquid-liquid extraction step may be used to extract a major portion of desired compounds in the aqueous phase such that a flashing or distillation step of the aqueous phase to recover these compounds may be eliminated. For instance, a first liquid-liquid extraction step may use a first extraction solvent that can extract from the aqueous phase certain light compounds, as described herein including but not limited to mono-oxygenates, and certain middle-boiling compounds, as described herein including but not limited to certain phenols and alcoholic compounds (e.g., tetrahydrofurfuryl alcohol (THFA) and hexanol). The extraction provides non-aqueous phase(s) containing extracted light and middle-boiling compounds and an aqueous phase containing residual desirable compounds not extracted in the first extraction step and a portion of the first extraction solvent, depending on the amount used. A second liquid-liquid extraction step may use a second extraction solvent that has lower solubility in water than the first extraction solvent to extract the first extraction solvent and remaining portions of desirable extractable compounds, including remaining light and middle-boiling compounds. The degree of extraction in each step may be configured to extract a major portion of desired compounds, including light and middle boiling compounds and extraction solvent(s) so that further processing of the aqueous phase to recover desired products may be rendered not desirable. For instance, this may be because the amount of recoverable desirable compounds remaining in the aqueous phase renders a subsequent flashing step not economical.
The option of eliminating a subsequent flashing step of an aqueous phase that involves heating or boiling of water may be particularly advantageous. For example, various biofuels process, including those that involve processing cellulosic biomass, require a great deal of energy to process the water generated as an azeotrope byproduct, which contains desirable compounds having a normal boiling similar to or less than that of water. Such azeotrope byproduct is a challenge to handle as recovery of desirable compounds having a normal boiling similar to or less than that of water is not economically feasible by distillation, and discarding the azeotrope water byproduct may not be economically feasible either due to the amount of total organic acid therein. Accordingly, methods and systems described in the present disclosure can address such challenges in handling the water byproduct generated from a biofuel process, particularly one involving cellulosic biomass. In particular, the methods and systems described herein allow for recovery of desirable compounds from the aqueous phase without boiling the water byproduct, which reduces costs by reducing energy requirements and by reducing the total organic content in the water byproduct, making the water byproduct easier and cheaper to treat.
Optionally, if desired compounds are still present in sufficient quantity in the in the aqueous phase after the liquid-liquid extraction, flashing or distillation of the aqueous phase can still be implemented to recover the light compounds. Once separated, the aqueous phase can be subject to flashing with reduced steam stripping effect because it contains a reduced amount of non-water miscible compounds compared to the reaction product with multiple liquid phases because a major portion of the non-water miscible compounds, such as phenols and various oils, are in the non-aqueous phase(s).
The separated non-aqueous phase(s) may be provided to distillation to recover various product fractions. Optionally, the separated non-aqueous phase(s) can be subject to a flashing step prior to distillation to recover an overhead fraction comprising light compounds and a bottom fraction if desired. A first portion of the bottom fraction from flashing of the non-aqueous phase(s) can be recycled to the liquid-liquid extraction step(s) as part of the extraction solvent(s). A second portion of the bottom fraction from flashing of the non-aqueous phase(s) can be provided to distillation. Optionally, to improve product separation in distillation, at least one of the reaction product and non-aqueous phase(s) can be subject to a viscosity reducing reaction prior to distillation, including one or more lignin depolymerization reactions.
Distillation of the non-aqueous phase(s) with reduced water can achieve adequate product separation at a lower temperature where higher temperatures would be needed to achieve similar efficient product separations in distillation of the reaction product without water removal or one that has been subject to flashing prior to distillation. The product fractions from distillation of the non-aqueous phase(s) can include at least a distillate overhead fraction comprising light compounds, a distillate middle fraction comprising lignin and lignin-derived products, including phenols, and a bottom fraction comprising heavy compounds with normal boiling points above about 350° C. The distillation can be performed to provide more than one distillate middle fraction. For instance, distillation can be operated to provide a first distillate middle fraction with a normal boiling point of about 150 to 250 degrees C. and a second distillate middle fraction with a higher normal boiling point of 200 to 350 degrees C. Distillation can also be operated to provide a distillate middle fraction with a normal boiling point of about 150 to 350 degrees C. A distillate middle fraction recovered from the non-aqueous phase(s) can be recycled in the process in various manners, including for use as solvent or for further conversion to other intended products. For instance, a distillate middle fraction can be provided to the liquid-liquid extraction step(s) for use as part of the extraction solvent(s).
The light compounds recovered from the aqueous phase and the non-aqueous phase(s) can optionally be combined for further processing into a higher hydrocarbon products that may be useful for fuels application. Such higher hydrocarbons can be provided to the liquid-liquid extraction step(s) for use as part of the extraction solvent(s).
In particular, the current disclosure provides a method comprising: (a) heating cellulosic biomass solids, molecular hydrogen, a catalyst capable of activating molecular hydrogen, and a digestion solvent in a reactor in a first reaction zone to produce a first reaction product; (b) providing a first extraction solvent and at least a portion of the first reaction product to a first liquid-liquid extraction unit in a separation zone to recover a first aqueous stream and a first non-aqueous stream, wherein the first aqueous stream comprises a major portion of water in said portion of the first reaction product; (c) providing the first aqueous stream and a second extraction solvent to a second liquid-liquid extraction unit in the separation zone to recover a second aqueous stream and a second non-aqueous stream; (d) optionally providing at least a portion of the first reaction product to a gas separator unit to recover a vapor fraction comprising compounds with a normal boiling point of 100 degrees C. or lower before providing the first reaction product to the separation zone; (e) providing the first and second non-aqueous streams to a distillation unit to recover a distillate overhead fraction, a distillate middle fraction, and a distillate bottom fraction; (f) providing at least a portion of the distillate middle fraction to the first liquid-liquid extraction unit, wherein the first extraction solvent comprises said portion of the distillate middle fraction; (g) providing to a further processing zone at least one of at least a portion of the vapor fraction and at least a portion of the distillate overhead fraction to generate a higher hydrocarbon product; (h) providing at least a portion of the higher hydrocarbon product to the second liquid-liquid extraction unit, wherein the second extraction solvent comprises said portion of the higher hydrocarbon product.
In addition, the current disclosure provides another method comprising: (a) heating cellulosic biomass solids, molecular hydrogen, a catalyst capable of activating molecular hydrogen, and a digestion solvent in a reactor in a first reaction zone to produce a first reaction product; (b) heating at least a portion of the first reaction product, molecular hydrogen, and a catalyst capable of activating molecular hydrogen in a reactor in a second reaction zone to produce a second reaction product; (c) providing a first extraction solvent and at least a portion of the second reaction product to a first liquid-liquid extraction unit in a separation zone to recover a first aqueous stream and a first non-aqueous stream, wherein the first aqueous stream comprises a major portion of water in said portion of the first reaction product; (d) providing the first aqueous stream and a second extraction solvent to a second liquid-liquid extraction unit in the separation zone to recover a second aqueous stream and a second non-aqueous stream; (e) optionally providing at least a portion of the second reaction product to a gas separator unit to recover a vapor fraction comprising compounds with a normal boiling point of 100 degrees C. or lower before providing the second reaction product to the separation zone; (f) providing the first and second non-aqueous streams to a distillation unit to recover a distillate overhead fraction, a distillate middle fraction, and a distillate bottom fraction; (g) providing at least a portion of the distillate middle fraction to the first liquid-liquid extraction unit, wherein the first extraction solvent comprises said portion of the distillate middle fraction; (h) providing to a further processing zone at least one of at least a portion of the vapor fraction and at least a portion of the distillate overhead fraction to provide a higher hydrocarbon product; (i) providing at least a portion of the higher hydrocarbon product to the second liquid-liquid extraction unit, wherein the second extraction solvent comprises said portion of the higher hydrocarbon product.
The features and advantages of embodiments provided by the present disclosure will be readily apparent to one having ordinary skill in the art upon a reading of the description of the embodiments that follows.
The following figures are included to illustrate certain aspects of the present disclosure, and should not be viewed as an exclusive embodiment. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to one having ordinary skill in the art and the benefit of this disclosure.
The present disclosure generally provides methods for processing cellulosic biomass into a fuel product, particularly processing of a reaction product obtained from hydrothermal digestion of cellulosic biomass solids. Cellulosic biomass is particularly advantageous because of the versatility of the abundant carbohydrates found therein in various forms. As used herein, the term “cellulosic biomass” refers to a living or formerly living biological material that contains cellulose. The lignocellulosic material found in the cell walls of higher plants is one of the world's largest sources of carbohydrates.
Unless otherwise specified, it is to be understood that use of the terms “biomass” or “cellulosic biomass” may be synonymous. The cellulosic biomass may be in any size, shape, or form. The cellulosic biomass may be natively present in any of these solid sizes, shapes, or forms, or they may be further processed prior to digestion. The cellulosic biomass may be chopped, ground, shredded, pulverized, and the like to produce a desired size prior to hydrothermal digestion. The cellulosic biomass may be washed (e.g., with water, an acid, a base, combinations thereof, and the like) prior to digestion taking place.
Any type of suitable cellulosic biomass source may be used. Suitable cellulosic biomass sources may include, for example, forestry residues, agricultural residues, herbaceous material, municipal solid wastes, waste and recycled paper, pulp and paper mill residues, and any combination thereof. Thus, in some embodiments, a suitable cellulosic biomass may include, for example, corn stover, straw, bagasse, miscanthus, sorghum residue, switch grass, bamboo, water hyacinth, hardwood, hardwood chips, hardwood pulp, softwood, softwood chips, softwood pulp, duckweed and any combination thereof. Leaves, roots, seeds, stalks, husks, and the like may be used as a source of the cellulosic biomass. Common sources of cellulosic biomass may include, for example, agricultural wastes (e.g., corn stalks, straw, seed hulls, sugarcane leavings, nut shells, and the like), wood materials (e.g., wood or bark, sawdust, timber slash, mill scrap, and the like), municipal waste (e.g., waste paper, yard clippings or debris, and the like), and energy crops (e.g., poplars, willows, switch grass, alfalfa, prairie bluestream, corn, soybeans, and the like). The cellulosic biomass may be chosen based upon considerations such as, for example, cellulose and/or hemicellulose content, lignin content, growing time/season, growing location/transportation cost, growing costs, harvesting costs, and the like.
Plants have primary cell walls and secondary cell walls. The primary cell wall contains three major polysaccharides (cellulose, pectin, and hemicellulose) and one group of glycoproteins. The secondary cell wall also contains polysaccharides polymeric lignin that is covalently crosslinked to hemicellulose. The complex mixture of constituents that is co-present with the cellulose can make its processing difficult, as discussed hereinafter. Lignin, in particular, may be an especially difficult constituent to deal with.
When converting cellulosic biomass into fuel blends and other materials, cellulose and other complex carbohydrates therein can be extracted and transformed into simpler organic molecules, which can be further processed thereafter to higher hydrocarbons. The higher hydrocarbons produced are useful in forming transportation fuels, such as synthetic gasoline, diesel fuel, and jet fuel, as well as industrial chemicals. As used herein, the term “higher hydrocarbons” refers to hydrocarbons having an oxygen to carbon ratio less than the oxygen to carbon ratio of at least one component of the biomass feedstock. The higher hydrocarbon predominantly contains C4 to C30 hydrocarbons, more preferably C6 to C18 hydrocarbons. Higher hydrocarbons may contain aromatics and alkanes. As used herein the term “hydrocarbon” refers to an organic compound comprising primarily hydrogen and carbon atoms, which is also an unsubstituted hydrocarbon. In certain embodiments, the hydrocarbons of the invention also comprise heteroatoms (i.e., oxygen sulfur, phosphorus, or nitrogen) and thus the term “hydrocarbon” may also include substituted hydrocarbons.
Digestion is one way in which cellulose and other complex carbohydrates may be converted into a more usable form. Digestion processes can break down cellulose and other complex carbohydrates within cellulosic biomass into simpler, soluble carbohydrates that are suitable for further transformation through downstream further processing reactions. As used herein, the term “soluble carbohydrates” refers to monosaccharides or polysaccharides that become solubilized in a digestion process. Illustrative carbohydrates that may be present in cellulosic biomass solids include, for example, sugars, sugar alcohols, celluloses, lignocelluloses, hemicelluloses, and any combination thereof.
The issues associated with converting cellulosic biomass into fuel blends (biofuels) in an energy- and cost-efficient manner using digestion are not only complex, but they are entirely different than those that are encountered in the digestion processes commonly used in the paper and pulpwood industry. Since the intent of cellulosic biomass digestion in the paper and pulpwood industry is to retain a solid material (e.g., wood pulp), incomplete digestion is usually performed at low temperatures (e.g., less than about 200° C.) for a fairly short period of time (e.g., between two to four hours). In contrast, digestion processes suitable for converting cellulosic biomass into fuel blends and other materials are ideally configured to maximize yields by solubilizing as much of the original cellulosic biomass charge as possible in a high-throughput manner. Paper and pulpwood digestion processes also typically remove lignin from the raw cellulosic biomass prior to pulp formation. Although digestion processes used in connection with forming fuel blends and other materials may likewise remove lignin prior to digestion, these extra process steps may affect the energy efficiency and cost of the biomass conversion process. The presence of lignin during high-conversion cellulosic biomass digestion may be particularly problematic.
Production of soluble carbohydrates for use in fuel blends and other materials via routine modification of paper and pulpwood digestion processes is not believed to be economically feasible for a number of reasons. Simply running the digestion processes of the paper and pulpwood industry for a longer period of time to produce more soluble carbohydrates is undesirable from a throughput standpoint. Use of digestion promoters such as strong alkalis, strong acids, or sulfites to accelerate the digestion rate can increase process costs and complexity due to post-processing separation steps and the possible need to protect downstream components from these agents. Accelerating the digestion rate by increasing the digestion temperature can actually reduce yields of biofuels due to thermal degradation of soluble carbohydrates that can occur at elevated digestion temperatures, particularly over extended periods of time. Once produced by digestion, soluble carbohydrates are very reactive and can rapidly degrade to produce caramelans and other heavy ends degradation products or byproducts, especially under higher temperature conditions, such as above about 150 degrees C. Use of higher digestion temperatures can also be undesirable from an energy efficiency standpoint. Any of these difficulties can defeat the economic viability of fuel blends derived from cellulosic biomass.
A particularly effective manner in which soluble carbohydrates may be formed is through hydrothermal digestion, and in which the soluble carbohydrates may be converted into more stable compounds is through subjecting them to one or more catalytic reductions, which may include hydrogenation and/or hydrogenolysis reactions. Stabilizing soluble carbohydrates through conducting one or more catalytic reduction reactions may allow digestion of cellulosic biomass to take place at higher temperatures than would otherwise be possible without unduly sacrificing yields. Depending on the reaction conditions and catalyst used, reaction products formed because of conducting one or more catalytic reduction reactions on soluble carbohydrates may comprise one or more alcohol functional groups, particularly including triols, glycol, monohydric alcohols, and any combination thereof, some of which may also include residual carbonyl functionality (e.g., an aldehyde or a ketone). The compounds in the alcoholic component can be described as oxygenates where the compounds comprise one or more oxygen-containing functional groups, such as a hydroxyl group or a carbonyl group. Non-limiting examples of oxygenates include an aldehyde, a ketone, an alcohol, furan, an ether, or any combination thereof. Such reaction products are more thermally stable than soluble carbohydrates and may be readily transformable into fuel blends and other materials through conducting one or more downstream further processing reactions. In addition, the foregoing types of reaction products are good solvents in which a hydrothermal digestion may be performed, thereby promoting solubilization of soluble carbohydrates as their reaction products.
Such reaction products, however, also form carboxylates salts that are lost for further processing as products and are eliminated as salts. Examples of such carboxylate salts may include any of C1-C6 carboxylic acids salts such as formates, acetates, lactates, propionate, levulinates salts. An option to address the problem of loss of yield from salt formation is by reverting at least a portion of the carboxylate salts to form free organic acids by adding inorganic acids to the process streams at certain locations thus recovering carboxylic acids and forming inorganic salt and thereby prevent loss of yield. If acid is added, free organic acids may be recovered in part during at least one of the liquid-liquid extraction step. The acid solution may contain sulfuric acids, nitric acids, phosphoric acids and hydrochloric acids. Optionally, acid solution from the wash unit from washing the biomass can be used in this process particularly since any contaminants in the acid wash solution will bypass the catalysts capable of activating hydrogen. Such acid solutions and wash methods and systems are described in detail in co-pending U.S. patent application Ser. Nos. 14/574,438, 14/574,426, 14/574,971, 14/574,661 filed Dec. 18, 2014, each disclosure is herein incorporated by reference in its entirety. Preferably the inorganic acid is added to the process stream so the process stream is acidified to a pH of 3 or less.
The acid addition should be conducted after the first hydrothermal reaction and optional second hydrothermal reaction and before an aqueous stream enters an optional aqueous stream separation zone for recovery of desirable compounds in the aqueous stream. For instance, the acid addition can be conducted at least at one of the following: (i) before the first reaction product enters the optional second hydrothermal reaction step, (ii) before the first reaction product enters the excess gas removal step, (iii) before the second reaction product enters the excess gas removal step, and (iv) before an aqueous stream enters an optional aqueous stream separation zone. By addition of an inorganic acid, it helps to revert some carboxylate salts to form free organic acids and thereby prevent loss of yield. The carboxylates salts can be any of C1-C6 carboxylic acids salts such as formates, acetates, lactates, propionate, and/or levulinates salts. The acids may be any inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid and the like. For example, by addition of hydrochloric acid, acetate salt (such as sodium acetate) may be converted to acetic acid that may be taken by overhead to further processing unit to be reacted to produce higher hydrocarbon products and form sodium chloride. Additional details regarding the acid addition are in U.S. Provisional Application No. 62/097,744, the disclosure of which are incorporated herein by reference.
Hydrothermal digestion of a cellulosic biomass can include heating of the cellulosic biomass and a digestion solvent in the presence of molecular hydrogen and a catalyst capable of activating the molecular hydrogen (which can also be referred to herein as a “hydrogen-activating catalyst” or “hydrocatalytic catalyst”). In such approaches, the hydrothermal digestion of cellulosic biomass and the catalytic reduction of soluble carbohydrates produced therefrom may take place in the same vessel, which can be referred to as “in situ catalytic reduction reaction processes.” As such, digestion processes suitable for converting cellulosic biomass into fuel blends and other materials are preferably configured to maximize yields by solubilizing as much of the original cellulosic biomass charge as possible in a high-throughput manner. In situ catalytic reduction reaction processes may also be particularly advantageous from an energy efficiency standpoint, since hydrothermal digestion of cellulosic biomass is an endothermic process, whereas catalytic reduction reactions are exothermic. Thus, the excess heat generated by the in situ catalytic reduction reaction(s) may be utilized to drive the hydrothermal digestion with little opportunity for heat transfer loss to occur, thereby lowering the amount of additional heat energy input needed to conduct the digestion.
Typically, hydrothermal reactions of cellulosic biomass, including hydrothermal digestion and catalytic reduction, generates a reaction product that contains a variety of components, ranging from lighter compounds, such as an alcoholic component, to heavier compounds, including lignin and lignin-derived compounds, such as phenolics, and various compounds in between. The reaction product can also exist in more than one phase, depending on certain conditions, such as temperature and pressure. Because the reaction product is a mixture of compounds, further processing certain compounds to desired products can be challenging. For instance, further processing of certain light compounds in the reaction product to desired fuel products can be challenging, at least from an economics point of view, because other middle-boiling compounds, such as lignin and lignin-derived compounds also present, can limit further processing options of the components in the reaction product.
For example, the lignin present in the reaction product may lead to fouling of processing equipment, potentially leading to costly system down time. The reaction product is a mixture of various compounds and typically in more than one liquid phase. One phase of the reaction product is usually water. While feasible, distillation of a reaction product containing water into various product fractions typically requires higher temperatures and pressures compared to one with reduced water. The extra energy needed for the higher temperatures and pressures can translate into additional costs. While the water in the reaction product can be removed through flashing prior to distillation into product fractions, doing so can result in steam stripping where water vapors carry some phenols into the overhead fraction. Removal of phenols during flashing can result in less efficient product separation in a subsequent distillation process.
The methods and systems provided in the present disclosure address the foregoing issues by providing liquid-liquid extraction to isolate the phases so that the phases can be further processed independent of each other. The reaction product can comprise an aqueous phase and one or more non-aqueous phases, which can be mixed with one another in an emulsion. In liquid-liquid separation, an extraction solvent is added to the reaction product extract various compounds from the aqueous phase. Two streams that result from the liquid-liquid extraction process include: (i) a non-aqueous stream that contains a major portion of the non-aqueous phase(s) and a major portion of the extraction solvent, which contains the extracted compounds, and (ii) an aqueous stream that contains a major portion of the aqueous phase. Accordingly, the aqueous stream comprises a major portion of water present in the reaction product, while the non-aqueous stream comprises a minor portion of water present in the reaction product. The term “major” or grammatical equivalents thereof refers to greater than 50 wt %, including 55 wt % or greater, 60 wt % or greater, 70 wt % or greater, 75 wt % or greater, 80 wt % or greater, 85 wt % or greater, 90 wt % or greater, and 95 wt % or greater. The term “minor” or grammatical equivalents thereof means up to 50 wt %, including an amount in a range of 0.1 wt % and up to 50 wt %, up to 45 wt %, up to 40 wt %, up to 35 wt %, up to 30 wt %, up to 25 wt %, up to 20 wt %, up to 15 wt %, up to 10 wt %, or up to 5 wt %.
More than one liquid-liquid extraction step may be used to extract a major portion of desired compounds in the aqueous phase such that a flashing or distillation of the aqueous phase to recover these compounds may be eliminated. For instance, a first liquid-liquid extraction step may use a first extraction solvent that can extract from the aqueous phase desirable compounds including certain light compounds that can be further processed into a fuels product, such as those with a normal boiling point of less than about 150 degrees C., including but not limited to monohydric alcohols (e.g., mono-oxygenates), aldehydes, ketones, acids, and any combination thereof. The first liquid-liquid extraction step can also extract middle-boiling compounds, as described herein including but not limited to certain phenols and alcoholic compounds (e.g., tetrahydrofurfuryl alcohol (THFA) and hexanol). The middle-boiling compounds present in the aqueous stream include those that have a normal boiling point in a range of 150 to 350 degrees C. or greater, which can include glycols and phenols. The heavy compounds include those that have a normal boiling point of greater than 350 degrees C. The terms “light,” “middle-boiling,” and “heavy,” or grammatical variations thereof, refer to various compounds relative to one another based on their normal boiling points. The extraction provides non-aqueous phase(s) containing extracted light and middle-boiling compounds and an aqueous phase containing residual desirable compounds not extracted in the first extraction step and a portion of the first extraction solvent, depending on the amount used. In particular, an example of a suitable first extraction solvent is one that has moderate polarity, such as at least one of phenols and certain alcohols (including cyclic alcohols and longer chain alcohols of C5 or greater), to allow dissolution of the light compounds in the first extraction solvent for extraction purposes. If the first extraction solvent used has moderate polarity, some portion of the first extraction solvent would be dissolved in water due to the moderate polarity. The first extraction solvent contains desirable compounds, which can be recovered. A moderately polar extraction solvent is oxygenated and not fully miscible with water at room temperature, as typical of an extraction solvent in a liquid-liquid extraction process.
A second liquid-liquid extraction step may use a second extraction solvent that has lower solubility in water than the first extraction solvent to extract the first extraction solvent and remaining portions of desirable extractable compounds, including remaining light and middle-boiling compounds. The second liquid-liquid extraction step can generate a second aqueous stream containing a minor portion of desired compounds that have been extracted into the non-aqueous stream, and a second non-aqueous stream containing a major portion of the extracted compounds, including light and middle boiling compounds, including the first and second extraction solvents. An example of a suitable second extraction solvent is one that has lower solubility in water than the first extraction solvent, such as higher hydrocarbons (including aromatic compounds or C4 to C30 alkanes). By having a lower miscibility than the first extraction solvent, the second extraction solvent allows for dissolution therein of a major portion of the first extraction solvent and residual desired compounds that remained in the first aqueous stream, while limiting the amount of the second extraction solvent being dissolved the aqueous phase.
The recovery of the light compounds with the first extraction solvent and the subsequent recovery of the first extraction solvent with a second extraction solvent may be configured to recover a major portion of desired compounds from the first and second aqueous streams to an extent that can render a subsequent flashing step of the second aqueous stream for further product recovery not economical due to the minimal amount of recoverable desirable compounds remaining in the aqueous stream after liquid-liquid extraction. As such, a subsequent flashing step of the second aqueous stream may be eliminated.
Elimination of steps involving the boiling or vaporization of substantial portions of water following the first or second extraction steps can result in considerable energy savings and improved efficiency, given the high heat needed vaporization of water, per mass of water vaporized. Most biofuels processes typically require input of energy to remove water from feed or product streams. Accordingly, the methods and systems described herein provides for an option that does not require the boil up or vaporization of a substantial portion of the water present in the process, which may be particularly advantageous.
If a subsequent flashing or distillation step is eliminated, the second aqueous phase may be recycled to at least one of the first hydrothermal digestion step and the second hydrothermal digestion step with a small amount of purge to maintain the levels of undesirable compounds to a certain level, such as those that can be detrimental to the reactions in hydrothermal digestion unit 2 and/or phenolics conversion unit 16. This is because the second aqueous phase can still contain certain glycols, including ethylene glycol and propylene glycol that are not readily extracted during the liquid-liquid extraction process. The glycols may serve as part of the digestion solvent in the first hydrothermal digestion step. The glycols can be further converted to mono-oxygenates in the second hydrothermal digestion step. For example, 9 parts of the second aqueous phase can be recycled to at least one of the first hydrothermal digestion step and the second hydrothermal digestion step, while 1 part of the second aqueous phase is purged. The 1 part that is purged may be sent to a biotreater.
Alternatively, the glycols in the second aqueous phase may be recovered by one or more flashing or distillation steps of the second aqueous phase. For instance, the second aqueous phase can be provided to a first flasher to recover a first overhead fraction comprising a major portion of water and a first bottom fraction. The first overhead fraction may be sent to a biotreater. The first bottom fraction can be provided to a second flasher to recover the glycols in a second overhead fraction and a second bottom fraction. The second overhead fraction can be provided to at least one of the first and second hydrothermal reaction steps as described above. Optionally the first bottom fraction from a single flash containing glycols can be similarly recycled back to at least the first and second hydrothermal reaction steps with a small amount of purge to maintain the levels of undesirable compounds to a certain level tolerable by the system.
Selection of solvent, operating conditions, and the mechanism of contacting the solvent and reaction product permit control over the level or degree of compound extraction. In particular, the amount of extraction solvent added to the reaction product correlates to the amount of compounds extracted into the solvent phase from the aqueous phase. For instance, in a mixture of reaction product and extraction solvent that contains a relatively small amount of solvent, such as about 1 part solvent phase per 9 parts of aqueous phase, the extraction of compounds into the solvent is small as compared to when a larger amount of solvent is contacted with the aqueous phase, such as a mixture with about 9 parts solvent per one part of aqueous phase. That is, the degree of extraction increases with increasing amounts of extraction solvent used in the liquid-liquid extraction process. As such, it is possible to configure the liquid-liquid extraction process to extract a major portion of compounds from the aqueous phase to a degree where further handling of the aqueous phase for additional product recovery, such as flashing to recover light compounds, may not be needed. The addition of an extraction solvent can also facilitate coalescing of the phases of the reaction product by assisting with the breaking of the emulsion.
At least a portion of the first extraction solvent can come from a distillation product of the non-aqueous stream. The product fractions from distillation of the non-aqueous stream may also be referred to as a distillate fraction, including but not limited to a distillate overhead fraction, a distillate middle fraction, and a distillate bottom fraction. The non-aqueous stream with reduced water can be subject to full distillation to obtain various product fractions with a similar degree of product separation at lower temperatures and pressures compared to distillation of the reaction product containing more water or a reaction product that has been subject to flashing for water removal prior to distillation. The product fractions from the non-aqueous stream can include at least an overhead fraction comprising light compounds, a middle fraction comprising lignin and lignin-derived products, including phenols, and a bottom fraction comprising waste, which can be discarded as waste or processed as a byproduct stream for use in biogas generation, or as fuel for a utility boiler. The non-aqueous stream can also comprise an amount of longer diols and mono-oxygenates (such as those with greater than C4) formed from carbohydrates, which can be recovered in the middle fraction. The distillation can be performed to provide more than one middle fractions. For instance, distillation can be operated to provide a first middle fraction with a normal boiling point of about 150 to 250 degrees C. and a second middle fraction with a higher normal boiling point of 200 to 350 degrees C. Distillation can also be operated to provide a middle fraction with a normal boiling point of about 150 to 350 degrees C.
As known to one of ordinary skill in the art, the overlap in the range of normal boiling point of the middle fractions is at least due to the distribution of compounds during the distillation process. For instance, trace amounts of light compounds may be found in a middle fraction and/or a bottom fraction, and vice versa, trace amounts of heavy compounds may be found in the overhead fraction and/or middle fraction. Likewise, there would be an overlap of compounds in the more than one middle fractions, if present, which leads to an overlap of normal boiling point of the middle fractions. In general, the first middle fraction may be referred to as the phenols fraction because it tends to capture compounds with normal boiling points around that of phenolic compounds. It is understood that the first middle fraction can contain other compounds from the second middle fraction as well as those with normal boiling points falling outside of about 150 to 250 degrees C. as discussed above. Similarly, the second middle fraction may be referred to as the lignin oligomers fraction because it tends to capture heavier compounds with normal boiling points around that of lignin oligomers. It is understood that the second middle fraction can contain other compounds from the first middle fraction as well as those with normal boiling points falling outside of about 200 to 350 degrees C. as discussed above. The middle fraction, whether or not it is in one fraction or more than one fraction, contains a major portion of the phenols in the reaction product fed to the distillation process.
A middle fraction recovered from distillation of the non-aqueous stream can be recycled in the process. For instance, a middle fraction can be provided to the liquid-liquid extraction unit for use as part of the extraction solvent. The middle fraction can comprise cyclic alcohols and phenols, particularly at least one of cyclohexanols, alkyl cyclohexanols, cyclopentanols, and alkyl cyclopentanols, and alkyl phenols. At least a portion of the cyclohexanols and cyclopentanols can be derived from sugars, at least a portion of the alkyl cyclohexanols and alkyl cyclpentanols can be derived from lignin, and at least a portion of the alkyl phenols is derived from lignin. The middle fraction may further comprise lignin oligomers. While the application may mention phenols more than cyclic alcohols, it is understood that cyclic alcohols, including cyclohexanols and alkyl cyclohexanols may be present in fractions or recycled solvents that contain phenols.
Optionally, to improve product separation of the non-aqueous stream in distillation, at least one of the reaction product and the non-aqueous stream can be subject to a viscosity reducing reaction prior to distillation, including one or more lignin depolymerization reactions. Accordingly, the methods and systems described in the present disclosure can provide for improved yields and lower costs, including reducing or minimizing the need to employ expensive high-pressure distillation and separations to process the reaction product.
The term “distillation” has its ordinary meaning, which refers to a method of recovering volatile compounds based on their normal boiling points. Distillation can be done in one stage or multiple stages. A one-stage of single stage distillation may be referred to as “flashing” or a grammatical equivalent, including “flash” or “flasher.” Flashing produces an overhead fraction and a bottom fraction and typically does not produce a middle product fraction. Multi-stage distillation produces various product fractions, including an overhead fraction and a bottom fraction, as well as one or more middle fractions. The manner in which flashing or multi-stage distillation can be carried out is known to one of ordinary skill in the art.
The light compounds recovered from reaction product, particularly the non-aqueous stream, can optionally be combined for further processing into a fuels product or used in one or more fuels applications. Additionally or alternatively, at least a portion of the second extraction solvent can come from a higher hydrocarbon product from further processing of at least one of a portion of light compounds recovered from the non-aqueous stream, and optionally from the aqueous stream, to provide a higher hydrocarbon product in a further processing zone.
Recovery of light compounds can occur at several locations as discussed further below. First, the reaction product—prior to entering the liquid-liquid extraction step—may be subject to an optional excess gas removal step, where the excess gas removed can contain light compounds. Second, the non-aqueous stream—prior to full distillation—may be subject to an optional flashing step that produces an overhead fraction and a bottom fraction, where the overhead fraction can contain light compounds. Third, full distillation of the non-aqueous stream can produce a distillate overhead fraction that contains light compounds.
If the non-aqueous stream is subject to the optional flashing step prior to full distillation, at least a portion of the bottom fraction from the flashing may be recycled as part of the first extraction solvent. The bottom fraction comprises cyclic alcohols and phenols that can serve as an effective first extraction solvent. In particular, a first portion of the bottom fraction from flashing of the non-aqueous stream is provided to the first liquid-liquid extraction step so that the first extraction liquid comprises this first portion of the bottom fraction. A second portion of the bottom fraction from flashing continues on to full distillation, including being optionally combined with the second non-aqueous stream and subject to additional optional treatment, such as lignin depolymerization. Additional details of this optional flashing step are provided in co-filed U.S. Provisional Application No. 62/097,919, the disclosure of which is incorporated herein by reference in its entirety.
Unless otherwise specified, it is understood that the mention of various components, such as compounds, products, phases fractions, portions, streams, etc., in this disclosure refers to “at least a portion of” such component, whether or not the phrase “at least a portion of” is included therewith. The term “hydrocarbon compounds” in the second reaction product refers to compounds comprising hydrogen and carbon atoms that do not have a phenolic functional group, which is a hydroxyl group (—OH) bonded to an aromatic hydrocarbon group. Illustrative, non-limiting hydrocarbon compounds include alkanes, alkenes, cycloalkanes and their alkyl substituents or derivatives, and cycloalkenes and their alkyl substituents or derivatives, which can be suitable for use in fuel composition, for instance gasoline or diesel. For instance, illustrative hydrocarbon compounds can include but are not limited to any one of cyclohexane, cyclohexene, propyl cyclopentane, propyl cyclopentene, propyl cyclohexane, propyl cyclohexene, anisole, propyl benzene, methyl propyl benzene, and oxygenated hydrocarbons such as cyclohexanone or methyl cyclohexanone.
Methods and systems described in this disclosure can provide for lignin reversion, e.g., reversion of lignin to phenols and conversion of phenolics derived from lignin to hydrocarbons. As mentioned, processing of cellulosic biomass can include hydrothermally digesting cellulosic biomass and carrying out a catalytic reduction reaction of soluble carbohydrates, including in one reactor. This can be achieved via in situ catalytic reduction reaction, which involves heating the cellulosic biomass and a digestion solvent in the presence of molecular hydrogen and a catalyst capable of activating molecular hydrogen. The hydrothermal digestion and catalytic reduction can generate a first reaction product comprising phenolics derived from lignin in the cellulosic biomass and an alcoholic component formed from a catalytic reduction reaction of soluble carbohydrates derived from the cellulosic biomass.
The term “alcoholic component” refers to an oxygenate where the oxygenate can be a monohydric alcohol, a glycol or diol, a triol, or any combination thereof. As used herein, the terms “glycol” or diol will refer to compounds containing two alcohol functional groups, two alcohol functional groups and a carbonyl functionality, or any combination thereof. It is understood that the alcoholic component also includes carbonyls that have carbonyl functionality. As used herein, the term “carbonyl functionality” will refer to an aldehyde functionality or a ketone functionality. In some embodiments, a glycol may comprise a significant fraction of the reaction product. Although a glycol may comprise a significant fraction of the reaction product, it is to be recognized that other alcohols, including triols and monohydric alcohols, for example, may also be present, as well as other oxygenates such as the ketone equivalent of the alcohol. Further, any of these alcohols may further include a carbonyl functionality.
As used herein, the term “triol” will refer to compounds containing three alcohol functional groups, three alcohol functional groups and a carbonyl functionality, and any combination thereof. As used herein, the term “monohydric alcohol” will refer to compounds containing one alcohol functional group, one alcohol functional group and a carbonyl functionality, and any combination thereof. The term “phenolics” or “phenols” has its ordinary meaning, which generally refers to a class of compounds that contain a hydroxyl group (—OH) bonded to an aromatic hydrocarbon group. The term “lignin oligomers” refers to a class of compounds with more than one lignin monomer, two or more aromatic rings, and a molecular weight of up to 300,000 Daltons. It is understood that lignin is a complex, amorphous, three-dimensional polymer having a structure based on phenylpropane. The molecular structure of lignin varies according to the source (e.g., type of plant) and is so complex and varied that its molecular structure has never been completely described. As such, lignin monomers and polymers can have various molecular structures. Commonly known lignin monomers include p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol.
The in situ catalytic reduction reaction can be considered a first hydrothermal reaction step, which produces a first reaction product that may also be referred to as a digestion product. At least a portion of the phenolics in the first reaction product can optionally be converted to hydrocarbon compounds by a second hydrothermal reaction step where the first reaction product is heated in the presence of molecular hydrogen and catalyst capable activating molecular hydrogen. The reaction product from the second hydrothermal reaction step can be referred to as a second reaction product. Unless otherwise specified, the term “reaction product” can refer to the first reaction product or the second reaction product. Optionally, at least some of the alcoholic component in the first reaction product, such as glycol or triol, including carbonyls, can also be converted to monohydric alcohol in the second hydrothermal reaction step.
Unconverted phenolics—phenolics that have not been converted to hydrocarbons (meaning compounds that still contain a hydroxyl group bonded to an aromatic hydrocarbon group)—may be recycled or returned to at least one of the first hydrothermal reaction step and the second hydrothermal reaction step. The phenols may serve as part of the digestion solvent in the first hydrothermal reaction step, and/or the phenols may be further converted to hydrocarbons in the second hydrothermal reaction step. It has been found that, if employed, a second hydrothermal reaction step having a low phenolics concentration provides better yields of hydrocarbons from phenols, than one with a high concentration of phenolics, which limits the amount of water and other mono-oxygenated compounds available in the reaction. That is, lignin reversion is better when the concentration of phenolics in the reaction content of the second hydrothermal reaction step is low versus when the phenolics concentration is high. For instance, low phenolics concentration in the second hydrothermal reaction step is a concentration of up to 50% by weight based on the total weight of the content of the second hydrothermal reaction step. Non-limiting illustrative phenolics concentrations of the reaction content in the second hydrothermal reaction step can be in a range of about 0.1% and up to 50% by weight, and any amount in between, including up to 45%, up to 40%, up to 35%, up to 30%, up to 25%, up to 20%, up to 15%, up to 10%, or up to 5% by weight, based on the total content weight of the second hydrothermal reaction step. It is understood that the referenced any phenolics concentration amount in between 0.1 wt % to 50 wt % includes at least 5 wt %, at least 10 wt %, at least 15 wt %, at least 20 wt %, at least 25 wt %, at least 30 wt %, at least 35 wt %, at least 40 wt %, at least 45 wt %, or at least 50 wt %.
Lignin reversion, including conversion of lignin to phenols and/or conversion of phenolics to hydrocarbon compounds, can be improved if the conversion is accomplished in the presence of water. That is the overall phenolics concentration in the second hydrothermal reaction step of 50% or less by weight of the content of the second hydrothermal reaction step can be achieved at least in part with water. For instance, the concentration of water in the second hydrothermal reaction step can be at least 10% by weight based on the total weight of the content of the second hydrothermal reaction step. Non-limiting illustrative water concentration of the reaction content in the second hydrothermal reaction step can be at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, or at least 40% by weight, based on the total content weight of the second hydrothermal reaction step. It is realized that the concentrations mentioned for the first or second hydrothermal reaction content are not limited to single liquid phase. Instead, the concentrations provided correspond to the concentrations of water averaged over all phases present in the respective reactor, where two or sometimes three or more liquid phases may be observed. Additional details regarding systems and methods related to lignin reversion can be found in U.S. application Ser. No. 14/868,426 filed on Sep. 29, 2015, claiming priority to application No. 62/058,440, filed on Oct. 1, 2014, entitled METHODS AND SYSTEMS FOR PROCESSING CELLULOSIC BIOMASS, the disclosure of which is incorporated by reference in its entirety.
At least a portion of the first and/or second reaction product can be provided to a separation zone that provides for liquid-liquid extraction of the reaction product and product recovery of the phases independent of each other. Optionally, prior to being provided to the separation zone, excess gas in the reaction product can be removed. In general, liquid-liquid extraction employs an extraction solvent to extraction various compounds from the aqueous phase to provide an aqueous stream containing the aqueous phase and a non-aqueous stream containing the extracted compounds, solvent, and remaining portion of the reaction product not in the aqueous stream. At least a portion of the first extraction solvent can comprise a distillate the non-aqueous stream of the reaction product from at least one of the first and second hydrothermal reaction. At least a portion of the second extraction solvent can comprise a higher hydrocarbon product generated from further processing of certain light compounds recovered from at least one of the first and second reaction products.
In particular, the liquid-liquid extraction process can employ more than one liquid-liquid extraction step. A first liquid-liquid extraction step may use a first extraction solvent that comprises at least a portion of a middle distillate fraction of a non-aqueous stream. The first liquid-liquid extraction step produces a first aqueous stream and a first non-aqueous stream. The first non-aqueous stream can contain extracted light compounds, and the first aqueous stream contains a portion of the first extraction solvent, depending on the amount used.
A second liquid-liquid extraction step may be used to recover the portion of the first extraction solvent in the first aqueous stream, where the second extraction solvent comprises at least a portion of a higher hydrocarbon product generated from further processing of light compounds recovered from the reaction product. The second liquid-liquid extraction step generates a second aqueous stream and a second non-aqueous stream. The first and second non-aqueous streams may be combined for full distillation, including additional optional treatment such as flashing to recover light compounds and lignin depolymerization.
Any suitable liquid-liquid extraction methods and systems capable of partitioning the reaction product and subsequent first aqueous stream into an aqueous stream and a non-aqueous stream can be used. These methods can be operated in batch mode, semi-batch mode, continuous mode, or any combination thereof. Suitable types of apparatus that can be employed in the liquid-liquid extraction include stage-type extractors or differential extractors. An example of a stage-type extractor is a mixer-settler apparatus that typically includes a mixing tank coupled to a settling vessel to allow the phases to coalesce. In general, a mixer-settler apparatus can be used in batch mode, or a plurality of mixer-settler apparatus can be staged to operate in a continuous or semi-continuous mode. Another stage-type extractor is a centrifugal contactor. Various types of differential extractors (also known as “continuous contact extractors,”) that are also suitable include, but are not limited to, centrifugal contactors and contacting columns such as tray columns, spray columns, packed towers, rotating disc contactors and pulse columns.
The liquid-liquid extraction process can also involve apparatus that allows or facilitates coalescing of the phases, including a horizontal settling tank, one or more weirs, centrifuge- or hydroclone-type device, a fiber coalesce mat or a packed bed coalescer.
The content of the aqueous stream (which may also be referred to as the raffinate) exiting the liquid-liquid extraction depends on the level or degree of extraction, ranging from low to high. It is understood that the level of extraction can range anywhere between the low and high extremes.
Liquid-liquid extraction typically does not provide sharp cut-offs between the water-miscible compounds in the aqueous stream and non-water miscible compounds in the non-aqueous stream. The amount of compounds extracted from the aqueous phase depends on various factors as will be apparent to one of ordinary skill in the art, including the type of extraction and the type of extractor apparatus, the type of solvent and the solvent ratio.
If the level of extraction is relatively high, the aqueous stream may comprise only trace amounts of these compounds because the compounds have been extracted from the aqueous phase, and they exit the liquid-liquid extraction in the non-aqueous stream. As such, the extracted compounds may be recovered in subsequent handling of the non-aqueous stream, such as distillation. In such a circumstance, it may not be cost effective to subject the aqueous phase to a product recovery step, such as flashing. Consequently, the aqueous phase may be treated as waste or byproduct in various manners known to one of ordinary skill, including those mentioned in the present disclosure, including processing as a byproduct stream for use in biogas generation, or as fuel for a utility boiler.
As described, at least a portion of the extraction solvent in the liquid-liquid extraction process can come from products recovered from the reaction product and/or a product generated from further processing of products recovered from the reaction product. Any suitable amount of recycled extraction solvent can be provided. In some circumstances, the amount of extraction solvent used in the liquid-liquid extraction process is a ratio of the reaction product in the liquid-liquid extraction process. For instance, in the first liquid-liquid extraction step, the first extraction solvent can be provided at a ratio in a range of 1 part solvent to 9 parts reaction product to 9 parts solvent to 1 part reaction product. Non-limiting illustrative ratios include 1 part solvent to 9 parts reaction product (1:9), 1 part solvent to 8 parts reaction product (1:8), 1 part solvent to 7 parts reaction product (1:7), 1 part solvent to 6 parts reaction product (1:6), 1 part solvent to 5 parts reaction product (1:5), 1 part solvent to 4 parts reaction product (1:4), 1 part solvent to 3 parts reaction product (1:3), 1 part solvent to 2 parts reaction product (1:2), 1 part solvent to 1 part reaction product (1:1), 2 parts solvent to 1 part reaction product (2:1), 3 parts solvent to 1 part reaction product (3:1), 4 parts solvent to 1 part reaction product (4:1), 5 parts solvent to 1 part reaction product (5:1), 6 parts solvent to 1 part reaction product (6:1), 7 parts solvent to 1 part reaction product (7:1), 8 parts solvent to 1 part reaction product (8:1), 9 parts solvent to 1 part reaction product (9:1), 10 parts solvent to 1 part reaction product (10:1), and any combination thereof.
In some circumstances, the amount of extraction solvent used is a ratio of the first extraction solvent in the first aqueous stream. For instance, in the second liquid-liquid extraction step, the second extraction solvent can be provided at a ratio in a range of 1 part second solvent to 9 parts first solvent to 9 parts second solvent to 1 part first solvent and residual desired compounds in the first aqueous stream. Non-limiting illustrative ratios include 1 part second solvent to 9 parts first solvent and residual desired compounds (1:9), 1 part second solvent to 8 parts first solvent and residual desired compounds (1:8), 1 part second solvent to 7 parts first solvent and residual desired compounds (1:7), 1 part second solvent to 6 parts first solvent and residual desired compounds (1:6), 1 part second solvent to 5 parts first solvent and residual desired compounds (1:5), 1 part second solvent to 4 parts first solvent and residual desired compounds (1:4), 1 part second solvent to 3 parts first solvent and residual desired compounds (1:3), 1 part second solvent to 2 parts first solvent and residual desired compounds (1:2), 1 part second solvent to 1 part first solvent and residual desired compounds (1:1), 2 parts second solvent to 1 part first solvent and residual desired compounds (2:1), 3 parts second solvent to 1 part first solvent and residual desired compounds (3:1), 4 parts second solvent to 1 part first solvent and residual desired compounds (4:1), 5 parts second solvent to 1 part first solvent and residual desired compounds (5:1), 6 parts second solvent to 1 part first solvent and residual desired compounds (6:1), 7 parts second solvent to 1 part first solvent and residual desired compounds (7:1), 8 parts second solvent to 1 part first solvent and residual desired compounds (8:1), 9 parts second solvent to 1 part first solvent and residual desired compounds (9:1), 10 parts second solvent to 1 part first solvent and residual desired compounds (10:1), and any combination thereof.
As described, phenols serving as solvent in the first hydrothermal reaction step can come from products recovered from the reaction product. Any suitable amount of recycled phenols—phenols coming from the reaction product—can be provided. In some circumstances, the amount of phenols provided to the first hydrothermal reaction step is a ratio of the amount of lignin provided thereto. For instance, phenols can be provided at a ratio of at least 1 part phenols to 2 parts lignin (1:2), including a ratio in a range of 1 part phenols to 2 parts lignin (1:2) to 10 parts phenols to 1 part lignin (10:1), or any ratio in between. Non-limiting illustrative ratios include at least 1 part phenols to 1 part lignin (1:1), 2 parts phenols to 1 part lignin (2:1), 3 parts phenols to 1 part lignin, 4 parts phenols to 1 part lignin (4:1), 5 parts phenols to 1 part lignin (5:1), 6 parts phenols to 1 part lignin (6:1), 7 parts phenols to 1 part lignin (7:1), 8 parts phenols to 1 part lignin (8:1), 9 parts phenols to 1 part lignin (9:1), 10 parts phenols to 1 part lignin (10:1), and any combination thereof. It is understood that lignin is provided as a component of the biomass feed, or via recycle of a process stream containing lignin.
If a second hydrothermal reaction step is present, glycols, phenols, and/or lignin oligomers recovered from the reaction product can be provided to it. Any suitable amount of recycled phenols and/or lignin oligomers can be provided consistent with the low phenolics concentration of up to 50% by weight based on the total weight of the content of the second hydrothermal reaction step discussed above. The term “recycled” refers to compounds recovered from the reaction product.
Optionally, at least one of the reaction product and the non-aqueous stream can be subject to one or more lignin depolymerization reactions prior to distillation to reduce the viscosity of the non-aqueous stream, thereby improving the separation of the product fractions during distillation. Any suitable lignin depolymerization reaction can be used. In general, lignin depolymerization reactions revert high molecular weight lignin oligomers to lower molecular weight compounds, such as lighter lignin oligomers and/or lignin monomers, which results in viscosity reduction. For instance, the reaction product may be subject to a base catalyzed depolymerization reaction prior to being subject to the liquid-liquid extraction process. Base catalysis for the depolymerization of lignin can break down the lignin for the recovery of phenols and other aromatic compounds. Any suitable method and system of carrying out base-catalyzed depolymerization can be employed with the reaction product prior to the liquid-liquid phase separation or extraction step. Descriptions of suitable base catalyzed depolymerization reactions are described in co-filed U.S. Provisional Application No. 62/098,004, the disclosure of which is incorporated herein by reference in its entirety.
In general, if employed, base catalyzed depolymerization can take place in at least one of the following scenario: (i) before the first reaction product enters the optional second hydrothermal reaction step, (ii) before the first reaction product enters the excess gas removal step, (iii) before the second reaction product enters the excess gas removal step, (iv) before the first extraction solvent is added to the reaction product, and (v) when the first extraction solvent is added to the reaction product, if the first extraction solvent is added before entering the first liquid-liquid extraction unit. In general, the base catalyzed depolymerization step may be carried out by contacting the reaction product with a base catalyst for an amount of time. Any suitable base catalyst may be used. Non-limiting suitable base catalysts include NaOH, KOH, Ca(OH)2, Mg(OH)2, solid base catalysts, and any combination thereof. The amount of base catalyst added may be in a range of about 0.5 wt % and 10 wt %, based on the weight of the reaction product. For instance, the amount may be about 0.5 wt %, 1.0 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 3.5 wt %, 4.0 wt %, 4.5 wt %, 5.0 wt %, 5.5 wt %, 6.0 wt %, 6.5 wt %, 7.0 wt %, 7.5 wt %, 8.0 wt %, 8.5 wt %, 9.0 wt %, 9.5 wt %, 10.0 wt %, and any combination thereof. The base catalyst and reaction product is provided a minimum residence time for contact at a certain temperature before the reaction product proceeds to the next step in the process, including a second hydrothermal reaction step or a liquid-liquid phase separation or extraction step. In general, the residence time for contact can be at least about 5 minutes and can be up to about 240 minutes. For instance, non-limiting residence time for contact before the reaction product proceeds to the next step in the process includes at least 15 minutes, at least 30 minutes, at least 45 minutes, at least 60 minutes, at least 75 minutes, at least 90 minutes, at least 105 minutes, at least 120 minutes, at least 135 minutes, at least 150 minutes, at least 165 minutes, at least 180 minutes, at least 195 minutes, at least 210 minutes, at least 225 minutes, at least 240 minutes, and any combination thereof. In general, the resident temperature can be greater than 100 degrees C. and can be up to about 275 degrees C. For instance, non-limiting residence temperature is at least 110 degrees C., at least 120 degrees C., at least 130 degrees C., at least 140 degrees C., at least 150 degrees C., at least 160 degrees C., at least 170 degrees C., at least 180 degrees C., at least 190 degrees C., at least 200 degrees C., at least 210 degrees C., at least 220 degrees C., at least 230 degrees C., at least 240 degrees C., at least 250 degrees C., at least 260 degrees C., at least 270 degrees C., at least 275 degrees C. and any combination thereof. Additional information regarding base catalyzed depolymerization using a solid catalyst (or insoluble catalysts) are described in U.S. Application Publication No. 2012/0302796, the disclosures of which are incorporated by reference in its entirety. Additional details regarding base catalyzed depolymerization using soluble base catalysts can be found in Pandey & Kim, “Lignin Depolymerization and Conversion: A Review of Thermochemical Methods,” Chem. Eng. Technol., 2011, No. 1, 29-41, the disclosure of which is incorporated by reference in its entirety.
Additionally or alternatively, the non-aqueous stream may be subject to lignin depolymerization, which may provide lignin monomers that facilitate phenolics separation from the lignin oligomers and even heavier compounds. The lignin monomers can become a cutting agent to reduce the viscosity of the high molecular weight lignin oligomers. The middle fraction comprising phenols and/or lignin oligomers distilled from the non-aqueous stream can also be provided to the lignin depolymerization reactions to further reduce the viscosity of the feed into the distillation unit, thereby enhancing product separation. It is recognized that this step may necessarily involve use of less water and optionally can be conducted in the absence of catalyst, such that higher temperatures (in excess of 300° C.) may be required for effective conversion of lignin to smaller fragments of lower viscosity via this step.
The following paragraphs provide additional details of the provided methods and systems for processing cellulosic biomass into a fuel product, particularly processing of a reaction product obtained from hydrothermal reaction of cellulosic biomass solids. As mentioned above, hydrothermal reaction of a cellulosic biomass can include in situ catalytic reduction, which involves heating of the cellulosic biomass and a digestion solvent in the presence of molecular hydrogen and a catalyst capable of activating the molecular hydrogen. Any type of suitable catalyst capable of activating hydrogen can be used in any reactor suitable for use with the selected catalyst(s) for the first and/or second hydrothermal reaction step. For example, at least one of the first and second hydrothermal reaction steps can be carried out using fluidly mobile catalyst particles that can be at least partially suspended in a fluid phase via gas flow, liquid flow, mechanical agitation, or any combination thereof in a reactor. Various conditions can be implemented so that the fluidly mobile catalyst particles do not get carried out of the reactor by the fluid flowing through the reactor. A reactor operating under these circumstances can be called an ebullating bed reactor in part because the catalyst particles remain in the reactor to form a catalytic bed. It is understood that one of ordinary skill in the art can select the various conditions to achieve an ebullating bed reactor. For instance, a suitable concentration of catalyst and/or catalyst size can be selected to obtain the desired reactor conditions.
On the other hand, the conditions can be modified so that the fluidly mobile catalyst particles flow with the biomass solids through the reactor. A reactor operating under these circumstances can be called a slurry reactor. Adequate catalyst distribution is desirable in a slurry reactor so that soluble carbohydrates formed during hydrothermal digestion may be intercepted and converted into more stable compounds before they have had an opportunity to significantly degrade, even under thermal conditions that otherwise promote their degradation.
If present, the second hydrothermal reaction step can also be carried out using a catalyst that does not comprise fluidly mobile catalyst particles. For example, the second hydrothermal reaction step can be carried out in a fixed bed reactor or a trickle bed reactor, which are known by one of ordinary skill in the art. For instance, during operation of a fixed bed or trickle bed reactor and fluid is flowing through the reactor, the height of the bed does not increase to greater than 10% as compared to when fluid is not flowing through the reactor.
If a reactor with a catalyst that does not comprise fluidly mobile catalyst particles is used in the second hydrothermal reaction step, a possible issue may be clogging of the bed by cellulosic particulates in the first reaction product from the digestion. As cellulosic biomass breaks apart during digestion, smaller and smaller particulates may be produced until only insoluble materials remain. Cellulosic particulates may also be present in native cellulosic biomass before digestion takes place. One way of handling cellulosic particulates can be use of a screen at a fluid outlet of the hydrothermal digestion unit to assist in maintaining the cellulosic fines therein. Periodic backflow or “backflush” of liquid or gas may be necessary to flush solids from this screen, to maintain fluid outflow. At a certain size, the cellulosic particulates may pass through the screen of the hydrothermal digestion unit and enter at least the reactor in the second reaction zone.
Another way to address cellulosic particulates, particularly ones that are sufficiently small to pass through screens, is the methods and systems disclosed in commonly owned U.S. Application Publication No. 2013/0152456 (“the '456 publication”), the disclosure of which is incorporated herein in its entirety. In general, the '456 publication discloses a solids separation unit to which the first reaction product can be routed to have at least a portion of the cellulosic particulates removed before it enters a reactor in the second reaction zone. The solids separation unit can comprise one or more filters, where at least one of the filters can be backflushed to remove cellulosic fines therefrom, while one or more of the other filters remain in fluid communication with an inlet of the reactor in the second reaction zone.
In some embodiments, catalysts capable of activating molecular hydrogen may comprise a metal such as, for example, Cr, Mo, W, Re, Mn, Cu, Cd, Fe, Co, Ni, Pt, Pd, Rh, Ru, Ir, Os, and alloys or any combination thereof, either alone or with promoters such as Au, Ag, Cr, Zn, Mn, Sn, Bi, B, O, and alloys or any combination thereof. In some embodiments, the catalysts and promoters may allow for various hydrothermal reactions, such as hydrogenation and hydrogenolysis reactions, to occur at the same time or in succession of one another. In some embodiments, such catalysts may also comprise a carbonaceous pyropolymer catalyst containing transition metals (e.g., Cr, Mo, W, Re, Mn, Cu, and Cd) or Group VIII metals (e.g., Fe, Co, Ni, Pt, Pd, Rh, Ru, Ir, and Os). In some embodiments, the foregoing catalysts may be combined with an alkaline earth metal oxide or adhered to a catalytically active support. In some or other embodiments, the catalyst capable of activating molecular hydrogen may be deposited on a catalyst support that is not itself catalytically active.
In some embodiments, the catalyst used in the first and/or second hydrothermal reaction step may comprise a poison-tolerant catalyst. As used herein the term “poison-tolerant catalyst” refers to a catalyst that is capable of activating molecular hydrogen without needing to be regenerated or replaced due to low catalytic activity for at least about 12 hours of continuous operation. Use of a poison-tolerant catalyst may be particularly desirable when reacting soluble carbohydrates derived from cellulosic biomass solids that have not had catalyst poisons removed therefrom. Catalysts that are not poison tolerant may also be used to achieve a similar result, but they may need to be regenerated or replaced more frequently than does a poison-tolerant catalyst.
Suitable poison-tolerant catalysts may include, for example, sulfided catalysts. In some or other embodiments, nitrided catalysts may be used as poison-tolerant catalysts. Sulfided catalysts suitable for activating molecular hydrogen are described in commonly owned U.S. patent application Ser. No. 13/495,785, and 61/553,591, each of which is incorporated herein by reference in its entirety.
The catalyst particles may have a particulate size of about 250 microns or less, about 100 microns or less, or about 10 microns or less. The minimum particulate size of the catalyst particles may be about 1 micron. The catalyst particles may comprise catalyst fines. As used herein, the term “catalyst fines” refers to solid catalysts having a nominal particulate size of about 100 microns or less. Catalyst fines may be generated from catalyst production processes, for example, during extrusion of solid catalysts. Catalyst fines may also be produced by grinding larger catalyst solids or during regeneration of catalyst solids. Suitable methods for producing catalyst fines are described in U.S. Pat. Nos. 6,030,915 and 6,127,229, each of which is incorporated herein by reference in its entirety. In some instances, catalyst fines may be intentionally removed from a solid catalyst production run, since they may be difficult to sequester in some catalytic processes. Techniques for removing catalyst fines from larger catalyst solids may include, for example, sieving or like size separation processes. When conducting in situ catalytic reduction reaction processes, such as those described herein, catalyst fines may be particularly well suited, since they can be easily fluidized and distributed in the interstitial pore space of the digesting cellulosic biomass solids.
Catalysts that are not particularly poison-tolerant may also be used in conjunction with the techniques described herein. Such catalysts may include, for example, Ru, Pt, Pd, or compounds thereof disposed on a solid support such as, for example, Ru on titanium dioxide or Ru on carbon. Although such catalysts may not have particular poison tolerance, they may be regenerable, such as through exposure of the catalyst to water at elevated temperatures, which may be in either a subcritical state or a supercritical state.
The catalysts used in conjunction with the processes described herein may be operable to generate molecular hydrogen. For example, in some embodiments, catalysts suitable for aqueous phase reforming (i.e., APR catalysts) may be used. Suitable APR catalysts may include, for example, catalysts comprising Pt, Pd, Ru, Ni, Co, or other Group VIII metals alloyed or modified with Re, Mo, Sn, or other metals. Thus, in some embodiments described herein, an external hydrogen feed may not be needed in order to effectively carry out the stabilization of soluble carbohydrates by a catalytic reduction reaction. However, in other embodiments, an external hydrogen feed may be used, optionally in combination with internally generated hydrogen. In yet other embodiments, the molecular hydrogen needed may be externally supplied to the cellulosic biomass solids. If external hydrogen is provided, the molecular hydrogen may be supplied as an upwardly directed fluid stream. Benefits of supplying an upwardly directed fluid stream are described herein.
The digestion solvent provided to the first reaction zone may comprise an organic solvent. In various embodiments, the digestion solvent may comprise an organic solvent and water. Although any organic solvent that is at least partially miscible with water may be used in the digestion solvent, particularly advantageous organic solvents are those that can be directly converted into fuel blends and other materials without being separated from the alcoholic component. That is, particularly advantageous organic solvents are those that may be co-processed during downstream further processing reactions with the alcoholic component being produced. Suitable organic solvents in this regard may include, for example, ethanol, ethylene glycol, propylene glycol, glycerol, phenols, and any combination thereof. Other suitable organic solvents may include sugar alcohols, for example.
In some embodiments, the digestion solvent may further comprise a small amount of a monohydric alcohol. The presence of at least some monohydric alcohols in the digestion solvent may desirably enhance the digestion and/or the catalytic reduction reactions being conducted therein. For example, inclusion of about 1% to about 5% by weight monohydric alcohols in the digestion solvent may desirably maintain catalyst activity due to a surface cleaning effect. At higher concentrations of monohydric alcohols, bulk solvent effects may begin to predominate. In some embodiments, the digestion solvent may comprise about 10 wt. % or less monohydric alcohols, with the balance of the digestion solvent comprising water and another organic solvent. In some embodiments, the digestion solvent may comprise about 5 wt. % or less monohydric alcohols, or about 4% or less monohydric alcohols, or about 3% or less monohydric alcohols, or about 2% of less monohydric alcohols, or about 1% or less monohydric alcohols. Monohydric alcohols present in the digestion solvent may arise from any source. In some embodiments, the monohydric alcohols may be formed as a co-product with the alcoholic component being formed by the catalytic reduction reaction. In some or other embodiments, the monohydric alcohols may be formed by a subsequent catalytic reduction of the initially produced alcoholic component and thereafter returned to the cellulosic biomass solids. In still other embodiments, the monohydric alcohols may be sourced from an external feed that is in flow communication with the cellulosic biomass solids.
In some embodiments, the digestion solvent may comprise between about 1% water and about 99% water, with the organic solvent comprising the balance of the digestion solvent composition. Although higher percentages of water may be more favorable from an environmental standpoint, higher quantities of organic solvent may more effectively promote hydrothermal digestion due to the organic solvent's greater propensity to solubilize carbohydrates and promote catalytic reduction of the soluble carbohydrates. In some embodiments, the digestion solvent may comprise about 90% or less water by weight. In other embodiments, the digestion solvent may comprise about 80% or less water by weight, or about 70% or less water by weight, or about 60% or less water by weight, or about 50% or less water by weight, or about 40% or less water by weight, or about 30% or less water by weight, or about 20% or less water by weight, or about 10% or less water by weight, or about 5% or less water by weight.
Various illustrative embodiments will be further described with reference to
Referring to
The reaction content in hydrothermal digestion unit 2 is heated to form a first reaction product comprising phenols and an alcoholic component. The phenols are derived from lignin in the cellulosic biomass, and the alcoholic component is formed from soluble carbohydrates derived from cellulosic biomass. Heating of the first reaction content provides for in situ catalytic reduction where digestion of the cellulosic biomass and catalytic reduction of soluble carbohydrates takes place in the same reactor. The reaction content in hydrothermal digestion unit 2 is heated to a temperature that may be in a range of about 190 to 260 degrees C., such as in a range of about 225 to 245 degrees C. For instance, the reaction content in hydrothermal digestion unit 2 can be heated to about 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, or 260 degrees C.
The heating of the first reaction content in hydrothermal digestion unit 2 is preferably performed under a pressurized state. As used herein, the term “pressurized state” refers to a pressure that is greater than atmospheric pressure (1 bar). For example, hydrothermal digestion unit 2 may have a pressure of at least about 30 bar, such as at least about 45 bar, at least about 60 bar, at least about 75 bar, at least about 90 bar, at least about 100 bar, at least about 110 bar, at least about 120 bar, or at least about 130. Hydrothermal digestion unit 2 may have a pressure of at most about 450 bar, such as at most about 330 bar, at most about 200 bar, at most about 175 bar, at most about 150 bar, or at most about 130 bar. As such, hydrothermal digestion unit 2 may have a pressure in a range of about 30 to 450 bar, such as a range of about 45 and 330 bar or in a range of about 75 to 130 bar. Hydrogen is preferably added to achieve the desired total pressure of hydrothermal digestion unit 2. For instance, hydrogen partial pressure of greater than 5 bar, greater than 10, or greater than 25 bar can be provided to hydrothermal digestion unit 2 to achieve the desired total pressure. Additional pressure may occur from vaporization of a portion of the water and volatile compounds of the reaction content. Heating of the digestion solvent in hydrothermal digestion unit 2 in a pressurized state may allow the normal boiling point of various compounds of the digestion solvent to be exceeded, thus allowing a predominately liquid state to be maintained, thereby allowing the rate of hydrothermal digestion to be increased relative to lower temperature digestion processes.
The reaction content in hydrothermal digestion unit 2 may be heated for at least 30 minutes and up to 10 hours, most typically between 120 minutes to 300 minutes. For example, digestion may be carried out for at least 30 minutes, at least 60 minutes, at least 120 minutes, at least 180 minutes, at least 240 minutes, at least 300 minutes, at least 360 minutes, at least 420 minutes, at least 480 minutes, at least 540 minutes, or at least 600 minutes. Digestion may be carried out at most 600 minutes, at most 540 minutes, at most 480 minutes, at most 420 minutes, at most 360 minutes, at most 300 minutes, at most 240 minutes, at most 180 minutes, at most 120 minutes, at most 60 minutes, or at most 30 minutes.
Referring to
Solids introduction mechanism 4 may comprise loading mechanism 6 and pressure transition zone 8, which may continuously or periodically elevate the cellulosic biomass from atmospheric pressure to a pressure near that of the operating pressure of hydrothermal digestion unit 2, particularly when hydrothermal digestion unit 2 is in a pressurized state. This allows for continuous or semi-continuous introduction of cellulosic biomass to take place without fully depressurizing hydrothermal digestion unit 2. That is, the cellulosic biomass solids may be continuously or semi-continuously added to the hydrothermal digestion unit while the hydrothermal digestion unit is in a pressurized state. Without the ability to introduce fresh cellulosic biomass to a pressurized hydrothermal digestion unit, depressurization and cooling of the hydrothermal digestion unit may take place during biomass addition, significantly reducing the energy- and cost-efficiency of the biomass conversion process.
Pressure transition zone 8 may comprise one or more suitable pressurization zones for pressurizing and introducing cellulosic biomass solids to hydrothermal digestion unit 2. Such suitable pressurization zones are described in more detail in commonly owned United States Patent Application Publications 2013/0152457 and 2013/0152458, and incorporated herein by reference in their entirety. Another suitable example of an illustrative pressure transition zone is described in more detail in commonly owned U.S. patent application Ser. No. 14/868,448, which claims priority to Application No. 62/058,177, filed on Oct. 1, 2014, entitled SYSTEMS AND METHODS FOR PROVIDING FEED MATERIAL TO A PRESSURIZED SYSTEM, which is incorporated herein by reference in its entirety. Suitable pressurization zones described therein may include, for example, pressure vessels, pressurized screw feeders, one or more pumps capable of pumping solids and solids slurries, and the like. Multiple pressurization zones may be connected in series to increase the pressure of the cellulosic biomass solids in a stepwise manner.
In various embodiments, soluble carbohydrates produced from cellulosic biomass solids may be converted into a reaction product comprising a glycol via a catalytic reduction reaction mediated by a catalyst that is capable of activating molecular hydrogen. As described in commonly owned U.S. Patent Applications 61/720,704 and 61/720,714, entitled “Methods for Production and Processing of a Glycol Reaction Product Obtained from Hydrothermal Digestion of Cellulosic Biomass Solids” and “Methods for Conversion of a Glycol Reaction Product Obtained from Hydrothermal Digestion of Cellulosic Biomass Solids Into a Dried Monohydric Alcohol Feed,” each filed Oct. 31, 2012 and incorporated herein by reference in its entirety, production of glycols may present several process advantages, particularly with regard to downstream further processing reactions. In other aspects, formation of monohydric alcohols may be more desirable.
Referring to
Catalyst particulates 10 may be conveyed into the cellulosic biomass solids in hydrothermal digestion unit 2 for distribution using fluid flow from any direction. In particular, at least a portion of catalyst particulates 10 may be conveyed by upwardly directed fluid flow, or at least that upwardly directed fluid flow is present. For instance, catalyst particulates 10 may be supplied through fluid inlet line 9 as shown in
Suitable techniques for using fluid flow to distribute catalyst particulates 10 within cellulosic biomass solids are described in commonly owned U.S. Patent Applications 61/665,727 and 61/665,627, each filed on Jun. 28, 2012 (PCT/US2013/048239 and PCT/US2013/048248) and incorporated herein by reference in its entirety. As described therein, cellulosic biomass solids may have at least some innate propensity for retaining catalyst particulates 10 being conveyed by fluid flow, and at least a portion of the cellulosic biomass solids may be sized to better promote such retention. In addition, using fluid flow, particularly upwardly directed fluid flow, to force catalyst particulates 10 to actively circulate through a charge of digesting cellulosic biomass solids may ensure adequate catalyst distribution as well as advantageously reduce thermal gradients that may occur during hydrothermal digestion. As a further advantage, active circulation of catalyst particulates 10 may address the problem created by the production of cellulosic biomass fines, since they may be co-circulated with catalyst particulates for continued digestion to take place in hydrothermal digestion unit 2.
The upwardly directed fluid flow may comprise a gas stream, a liquid stream, or any combination thereof. Also, the upwardly directed fluid flow may comprise one upwardly directed fluid stream, or two upwardly directed fluid streams, or three upwardly directed fluid streams, or four upwardly directed fluid streams, or five upwardly directed fluid streams.
At least some of the one or more upwardly directed fluid streams may contain catalyst particulates at its source. That is, the fluid stream(s) may comprise a stream of catalyst particulates. The one or more upwardly directed fluid streams may convey catalyst particulates therein. In other circumstances, the one or more upwardly directed fluid streams may not contain catalyst particulates at its source, but they may still fluidize catalyst particulates located in or near the cellulosic biomass solids.
The one or more upwardly directed fluid streams may comprise a gas stream. For example, a gas stream being used for upwardly directed fluid flow may comprise a stream of molecular hydrogen. Steam, or an inert gas such as nitrogen, for example, may be used in place of or in addition to a stream of molecular hydrogen. Up to about 40% steam may be present in the fluid stream.
The one or more upwardly directed fluid streams may comprise a liquid stream, particularly when it is not necessarily desired to maintain catalyst particulates in the cellulosic biomass solids and/or a gas stream alone is insufficient to distribute catalyst particulates, for example. Unlike a gas stream, a liquid stream may convey catalyst particulates through the cellulosic biomass solids, add to the liquid head surrounding the cellulosic biomass solids, and eventually spill over. In other circumstances, catalyst fluidization may be incomplete, and a liquid stream may still not convey catalyst particulates completely through the cellulosic biomass solids before the liquid head spills over.
As such, in certain instances, at least a portion of the liquid head may be circulated through the cellulosic biomass solids. Suitable hydrothermal digestion units configured for circulating a liquid phase therethrough, such as hydrothermal digestion unit 2 depicted in
Another way to distribute catalyst particulates 10 is to convey at least a portion comprising phenols in hydrothermal digestion unit 2 to a point above at least a portion of the cellulosic biomass solids and release that portion. Catalyst particulates 10 can have the tendency to accumulate and agglomerate in larger particles in presence of phenols, particularly if the phenols aggregate to form a phenols-rich liquid phase, which contains a major portion of the phenols in unit 2. The formation of the phenols-rich liquid phase provides a catalyst-rich fraction, which contains a major portion of catalyst in unit 2, above cellulosic biomass solids in hydrothermal digestion unit 2, which can act to release catalyst particulates for downward percolation through the cellulosic biomass solids. Techniques for downward percolation of catalyst particulates and phenols are described in commonly owned U.S. Patent Application No. 61/720,757 filed Oct. 31, 2012, entitled “Methods and Systems for Distributing a Slurry Catalyst in Cellulosic Biomass Solids” and U.S. Patent Publication No. 20140174432, filed on Dec. 17, 2013, the disclosures of which are incorporated herein by reference in their entirety.
In the embodiment of system 1 shown in
As shown in
Referring to
In
Referring to
The hydrothermal reaction carried out in phenolics conversion unit 16 can provide for conversion of lignin-derived phenolics into desirable hydrocarbons that can be used in a fuel blends, such as gasoline. Illustrative, non-limiting hydrocarbon compounds include alkanes, alkenes, cycloalkanes and their alkyl substituents or derivatives, and cycloalkenes and their alkyl substituents or derivatives, which can be suitable for use in fuel composition, for instance gasoline or diesel. For instance, illustrative hydrocarbon compounds can include but are not limited to any one of cyclohexane, cyclohexene, propyl cyclopentane, propyl cyclopentene, propyl cyclohexane, propyl cyclohexene, anisole, propyl benzene, oxygenated hydrocarbons cyclohexanone or methyl cyclohexanone, and methyl propyl benzene. The conversion of lignin derived phenolics into desirable hydrocarbons may not be complete, which can leave unconverted phenolics still remaining in the second reaction product. Optionally, the hydrothermal reaction carried out in phenolics conversion unit 16 can also provide for hydrodeoxygenation where triols and glycol of the alcoholic component are converted to monohydric alcohol. The hydrodeoxygenation may not be complete, which can leave triols and glycol still remaining in the second reaction product. As such, the second reaction product can comprise unconverted phenolics, hydrocarbons converted from phenolics, and at least a portion of the alcoholic component.
In phenolics conversion unit 16, phenols can also be converted to a cyclic alcohol, including at least one of alkyl cyclohexanols and alkyl cyclopentanols, which can similarly serve as a portion of the first extraction solvent. Operating conditions of phenolics conversion unit 16 can be selected to generate relatively more of certain phenols-derived cyclic alcohols, thereby leaving less phenols in the second reaction content in unit 16. At least one of cyclohexanol and cyclopentanol can also be formed from carbohydrates in hydrothermal digestion unit 2 and phenolics conversion unit 16, if present, via hydrodeoxygenation reactions in the presence of a catalyst capable of activating molecular hydrogen.
As mentioned, it has been found that a second hydrothermal reaction step, which takes in reaction zone 17, such as in phenolics conversion unit 16 of
Also mentioned was that conversion of lignin to phenols and/or conversion of phenolics to hydrocarbon compounds can be improved if the conversion is accomplished in the presence of water. Referring to
As mentioned, gas separator unit 18 is optional so the first reaction product or the second reaction product can be provided to separation zone 13 from hydrothermal digestion unit 2 or phenolics conversion unit 16, respectively, without going through gas separator unit 18. Referring to
Liquid-liquid extraction units 20 and 53 allow for extraction of various compounds from the respective aqueous phase by a respective first and second extraction solvents. This may be achieved by using an extraction solvent in which the compounds targeted for extraction have a higher solubility than in the aqueous phase. At least a portion of the extraction solvent comes from the reaction product, particularly a distillate fraction of the non-aqueous stream or a higher hydrocarbon product generated therefrom, In particular, the first extraction solvent used in unit 20 can comprise a distillate fraction comprising at least one of cyclic alcohols, including but not limited to cyclopentanols and/or cyclohexanols, and phenols, including but not limited to methoxypropylphenol. The second extraction solvent used in unit 53 can comprise a higher hydrocarbon products, including aromatics (which may also be a distillation fraction thereof that is collectively referred to as “higher hydrocarbon products”). The higher hydrocarbon products can be a reaction product from further processing zone 58, including from further processing unit 22 and/or a distillation fraction of a reaction product of further processing unit 22. U.S. Provisional Application Nos. 62/097,728 and 62/097,919 provide disclosures regarding an extraction solvent comprising a distillate fraction of the non-aqueous stream, the disclosures of which are incorporated by reference herein in their entirety. An extraction solvent can also comprise a product from further processing of light compounds recovered from the reaction product, including the aqueous stream and/or non-aqueous stream. U.S. Provisional Application No. 62/097,683 provides disclosures regarding an extraction solvent comprising such product from further processing of recovered light compounds, the disclosure of which is incorporated by reference in its entirety.
As shown in
The first extraction solvent can be provided at a ratio in a range of 1 part first solvent in line 46A and/or 46B to 9 parts reaction product in line 26 to 9 parts first solvent in line 46A and/or 46B to 1 part reaction product in line 26. Non-limiting illustrative ratios include 1 part solvent to 9 parts reaction product (1:9), 1 part solvent to 8 parts reaction product (1:8), 1 part solvent to 7 parts reaction product (1:7), 1 part solvent to 6 parts reaction product (1:6), 1 part solvent to 5 parts reaction product (1:5), 1 part solvent to 4 parts reaction product (1:4), 1 part solvent to 3 parts reaction product (1:3), 1 part solvent to 2 parts reaction product (1:2), 1 part solvent to 1 part reaction product (1:1), 2 parts solvent to 1 part reaction product (2:1), 3 parts solvent to 1 part reaction product (3:1), 4 parts solvent to 1 part reaction product (4:1), 5 parts solvent to 1 part reaction product (5:1), 6 parts solvent to 1 part reaction product (6:1), 7 parts solvent to 1 part reaction product (7:1), 8 parts solvent to 1 part reaction product (8:1), 9 parts solvent to 1 part reaction product (9:1), 10 parts solvent to 1 part reaction product (10:1), and any combination thereof.
As shown in
The second extraction solvent can be provided at a ratio in a range of 1 part second solvent in line 45A to 9 parts first solvent and residual desired compounds in the first aqueous stream in line 28 to 9 parts second solvent in line 45A to 1 part first solvent and residual desired compounds in the first aqueous stream in line 28. Non-limiting illustrative ratios include 1 part second solvent to 9 parts first solvent and residual desired compounds (1:9), 1 part second solvent to 8 parts first solvent and residual desired compounds (1:8), 1 part second solvent to 7 parts first solvent and residual desired compounds (1:7), 1 part second solvent to 6 parts first solvent and residual desired compounds (1:6), 1 part second solvent to 5 parts first solvent and residual desired compounds (1:5), 1 part second solvent to 4 parts first solvent and residual desired compounds (1:4), 1 part second solvent to 3 parts first solvent and residual desired compounds (1:3), 1 part second solvent to 2 parts first solvent and residual desired compounds (1:2), 1 part second solvent to 1 part first solvent and residual desired compounds (1:1), 2 parts second solvent to 1 part first solvent and residual desired compounds (2:1), 3 parts second solvent to 1 part first solvent and residual desired compounds (3:1), 4 parts second solvent to 1 part first solvent and residual desired compounds (4:1), 5 parts second solvent to 1 part first solvent and residual desired compounds (5:1), 6 parts second solvent to 1 part first solvent and residual desired compounds (6:1), 7 parts second solvent to 1 part first solvent and residual desired compounds (7:1), 8 parts second solvent to 1 part first solvent and residual desired compounds (8:1), 9 parts second solvent to 1 part first solvent and residual desired compounds (9:1), 10 parts second solvent to 1 part first solvent and residual desired compounds (10:1), and any combination thereof.
The reaction product generated by either hydrothermal digester 2 in
Referring to
Suitable types of apparatus that can be employed in the liquid-liquid extraction units 20 and 53 include stage-type extractors or differential extractors. An example of a stage-type extractor is a mixer-settler apparatus that typically includes a mixing tank coupled to a settling vessel to allow the phases to coalesce. In general, a mixer-settler apparatus can be used in batch mode, or a plurality of mixer-settler apparatus can be staged to operate in a continuous or semi-continuous mode. Another stage-type extractor is a centrifugal contactor. Various types of differential extractors (also known as “continuous contact extractors,”) that are also suitable include, but are not limited to, centrifugal contactors and contacting columns such as tray columns, spray columns, packed towers, rotating disc contactors and pulse columns.
In general, a mixer-settler apparatus useful in liquid-liquid extraction unit 20 includes a mixer vessel with an agitator to provide mixing of the solvent provided by line 45 and reaction product provided by line 26. The mixed contents can be provided to a settling tank where the phases can coalesce and separate so an aqueous stream can be withdrawn via line 28 and a non-aqueous stream can be withdrawn via line 24.
In general, centrifugal contactors are high-speed, rotary machines characterized by relatively low residence time. The number of stages in a centrifugal device is usually one, however, centrifugal contactors with multiple stages can also be used. Centrifugal contactors utilize mechanical devices to agitate the mixture to increase the interfacial area and decrease the mass transfer resistance. Various types of differential extractors (also known as “continuous contact extractors,”) that are also suitable for use as unit 20 include, but are not limited to, centrifugal contactors and contacting columns such as tray columns, spray columns, packed towers, rotating disc contactors and pulse columns.
Contacting columns are suitable for various liquid-liquid extraction operations. Packing, trays, spray or other droplet-formation mechanisms or other apparatus are used to increase the surface area in which the two liquid phases (i.e., a solvent phase and a hydrocarbon phase) contact, which also increases the effective length of the flow path. Changes in flows and physical properties along the length of an extractor can also be considered in selecting the type of extractor and/or the specific configuration, materials or construction, and packing material type and characteristics (i.e., average particle size, shape, density, surface area, and the like). For instance, the extraction solvent in line 45 may be provided in unit 20 in a counter-current flow direction relative to the flow of reaction product in line 26.
In particular, liquid-liquid separation unit 20 may include a tray column where the reaction product in line 26 is provided to the bottom of the column and the extraction solvent is provided at or near the top of the column. In addition, the column can be a multi-stage counter-current contractor having a plurality of trays and associated down comers as known to one of ordinary skill.
An additional type of unit operation suitable as liquid-liquid extraction unit 20 is a packed bed column, which typically comprises suitable packing material including, but not limited to, Pall rings, Raschig rings, Kascade rings, Intalox saddles, Berl saddles, super Intalox saddles, super Berl saddles, Demister pads, mist eliminators, telerrettes, carbon graphite random packing, other types of saddles, and the like, including combinations of one or more of these packing materials. Packing material provides large interfacial areas for phase contacting, causing the droplets to coalesce and reform.
Further types of apparatus suitable for liquid-liquid extraction include rotating disc contactors. The rotating disc contactor is a mechanically agitated, counter-current extractor. Agitation is provided by a rotating disc mechanism.
An additional type of apparatus suitable for aromatic extraction in the system and method of the present invention is a pulse column, which has a plurality of packing or sieve plates lacking down comers. The perforations in the sieve plates typically are smaller than those of non-pulsating columns. A pulse-producing device, such as a reciprocating pump, pulses the contents of the column at frequent intervals. The rapid reciprocating motion, of relatively small amplitude, is superimposed on the usual flow of the liquid phases. The pulsation causes the contact between the phases to affect extraction.
The liquid-liquid extraction process can also involve apparatus that allows or facilitates coalescing of the phases, including a horizontal settling tank, one or more weirs, centrifuge- or hydroclone-type device, a fiber coalesce mat or a packed bed coalescer. As mentioned, liquid-liquid extraction unit 20 provides aqueous stream in line 28 and non-aqueous stream in line 24.
The first aqueous stream in line 28 comprises a major portion of the water present in the reaction product in liquid-liquid extraction unit 20. The second aqueous stream in line 55 also comprises a major portion of the water present in the first aqueous stream in liquid-liquid extraction unit 53. For instance, the first or second aqueous stream comprises greater than 50 wt %, including 55 wt % or greater, 60 wt % or greater, 70 wt % or greater, 75 wt % or greater, 80 wt % or greater, 85 wt % or greater, 90 wt % or greater, and 95 wt % or greater of the water in the reaction product in unit 20 or in the first aqueous stream in unit 53, respectively. Correspondingly, the first non-aqueous stream in line 24 comprises a minor portion of the water in the respective reaction product in liquid-liquid extraction unit 20. The second non-aqueous stream in line 56 comprises a minor portion of the water in the first aqueous stream in liquid-liquid extraction unit 53. For instance, the first or second non-aqueous stream comprises up to 50 wt %, including an amount in a range of 0.1 wt % and up to 50 wt %, up to 45 wt %, up to 40 wt %, up to 35 wt %, up to 30 wt %, up to 25 wt %, up to 20 wt %, up to 15 wt %, up to 10 wt %, or up to 5 wt % of water in the reaction product in unit 20 or in the first aqueous stream in unit 53. The first non-aqueous stream comprises the remaining portion of the reaction product not in the first aqueous stream. Similarly, the second non-aqueous stream comprises the remaining portion of the first aqueous stream not in the second aqueous stream. For instance, the first or second non-aqueous stream may have more than one phase.
If the relative amount of extraction solvent employed is low, such as when the extraction solvent is provided at less than 50% by weight relative to the reaction product in line 26, the extent of the extraction may be minimal so the aqueous stream can also comprise a major portion of compounds at least partially miscible with water in the reaction product line 26 and provided to unit 20, including light compounds, middle-boiling compounds, heavy compounds, in addition to water-soluble salts, and ash. The light compounds include those that have a normal boiling point of less than 150 degrees C. Non-limiting illustrative examples of light compounds include monohydric alcohols, aldehydes, ketones, acids, and any combination thereof. The middle-boiling compounds present in the aqueous stream include those that have a normal boiling point in a range of 150 to 350 degrees C. or greater, which can include glycols and phenols. The heavy compounds include those that have a normal boiling point of greater than 350 degrees C.
If the relative amount of extraction solvent provided is high, such as when the extraction solvent is provided at greater than 50% by weight relative to the reaction product in line 26, the first aqueous stream in line 28 may be largely depleted of light compounds targeted for extraction, including at least one of mono-oxygenates (such as C1-C4), certain diols, and free acids (such as acetic acid or higher). That is, in these circumstances, the first aqueous stream in line 28 may contain a minor portion of light compounds targeted for extraction in the reaction product in line 26 and provided to unit 20, where these light compounds include at least one of mono-oxygenates (such as C1-C4), certain diols, and free acids (such as acetic acid or higher). In these circumstances, the first aqueous stream in line 28 may still comprise glycols, including ethylene glycol and propylene glycol, as well as some amount of the first extraction solvent. The first aqueous stream in line 28 can also contain water soluble salts, including acid salts and ash.
The first aqueous stream in line 28 is provided to a second liquid-liquid extraction unit, unit 53, to recover a major portion of the first extraction solvent. As with liquid-liquid extraction unit 20, the extraction conditions in unit 53 can be configured to achieve the desired degree of extraction of the first extraction solvent. For instance, the amount of second extraction solvent provided to unit 53, including the amount in line 45A, can be adjusted so that the second aqueous stream in line 55 is largely depleted of the first extraction solvent. The liquid-liquid extraction in units 20 and 53 may be conducted so that the second aqueous stream in line 55 contains a minor portion of desired compounds, including light compounds, glycols, and/or extraction solvents, where it may not be economical to subject the second aqueous stream in line 55 to a flashing step for products recovery. In such circumstances, a first portion of the second aqueous stream in line 55 may be recycled to at least one of hydrothermal digestion unit 2 and phenolics conversion unit 16 via line 55A, as shown in
It is understood that an external solvent may be used in system 1. For instance, an external extraction solvent (i.e., one that is not recycled) may be provided to liquid-liquid extraction unit 20 and/or an external digestion solvent may be provided to hydrothermal digestion unit 2. In particular, external solvent(s) may be needed at start up when system 1 has not produced any product fractions that can be recycled as described herein. External solvent(s) may also be used after start up to supplement as needed or desired.
Referring to
Aqueous stream separation zone 25 can comprise any suitable method known to one of ordinary skill in the art used to separate these light compounds. For instance, zone 25 can comprise one or more flashers. In one circumstance, zone 25 can comprise one flasher to flash the aqueous stream to remove a major portion of water in the flasher and providing a bottom fraction comprising glycols, which can also be provided to at least one of unit 2 and unit 16 as described above, via line 33, with a small amount of purge. The water removed, represented in line 32, and the purge (not shown) can be provided to a biotreater. The glycols can be used as part of the digestion solvent in zone 3. Additionally or alternatively, in phenolics conversion unit 16, the glycols can be further converted to monooxygenated intermediates, such as certain light compounds, including monohydric alcohols. Contaminants such as salts, ash, caramel, and tar remaining can be disposed of as waste and/or byproduct via line 34.
Additionally or alternatively, the glycols in the bottom fraction from a single flash can be recovered with a second flasher, where the overhead fraction of the second flasher comprises a major portion of the glycols in the second flasher. The second overhead fraction can be provided to digestion zone 3 and/or reaction zone 17 via line 33. Contaminants exit as waste or byproduct via line 34. Other suitable separation methods that may be employed in aqueous separation zone 25 includes use of membranes for separation of organics and salts from water.
Referring to
Suitable lignin depolymerization reactions are known in the art. Non-limiting illustrative lignin depolymerization reactions include thermal reactions, which can be performed with or without catalysts. Generally, thermal lignin depolymerization reactions performed without catalysts typically take place in a temperature of greater than 300 degrees C. Catalysts and hydrogen can be added to reduce the reaction to below 300 degrees C. Any suitable catalyst can be employed, including acid or basic catalysts, in solid or liquid form. For example, methods relating to lignin depolymerization catalysts using a solid catalyst are described in U.S. Application Publication No. 2012/0302796, the disclosures of which are incorporated by reference in its entirety. Other disclosures relating to using catalysts in lignin depolymerization include U.S. Pat. Nos. 6,100,385 and 7,964,761, the disclosures of which are incorporated by reference in their entirety. Other methods to depolymerize lignin in the non-aqueous stream include pyrolysis (thermolysis), gasification, hydrogenolysis, chemical oxidation, and hydrolysis under supercritical conditions. Additional details regarding these methods can be found in Pandey & Kim, “Lignin Depolymerization and Conversion: A Review of Thermochemical Methods,” Chem. Eng. Technol., 2011, No. 1, 29-41, the disclosure of which is incorporated by reference in its entirety. If lignin is still present in the non-aqueous stream prior to full distillation, it may become precipitated and form a slurry of lignin. In this circumstance, optionally, a lignin removal mechanism may be used to capture at least a portion of this lignin in the non-aqueous stream prior to full distillation. Any suitable lignin removal mechanism may be used. Non-limiting suitable lignin removal mechanism includes a filter, a press, a hydroclone apparatus, or any combination thereof. The lignin captured by the lignin removal mechanism may be provided to lignin depolymerization unit 29 for further depolymerization or any other depolymerization step.
Referring to
An overhead fraction separated from the non-aqueous stream, which is depicted as line 38, includes a major portion of light compounds in the non-aqueous stream provided to distillation unit 27. For instance, more than 50 wt %, particularly at least 75 wt %, at least 80 wt %, at least 85 wt %, at least 90 wt %, or at least 95 wt % of compounds with a normal boiling point of less than 150 degrees C. present in the non-aqueous stream in distillation unit 27 is in the overhead fraction in line 38.
The middle fraction can comprise compounds heavier than the light compounds, particularly those with a normal boiling point of 150 degrees C. or greater. Distillation unit 27 can be operated to provide more than one middle fraction. For instance, distillation can be operated to provide a first middle fraction, depicted as line 39, with a normal boiling point of about 150 to 250 degrees C., which typically captures phenolic compounds, and a second middle fraction, depicted as line 40, with a higher normal boiling point of 200 to 350 degrees C., which typically captures lignin oligomers. Distillation can also be operated to provide a middle fraction with a normal boiling point of about 150 to 350 degrees C. As mentioned above, there is an overlap in the normal boiling point of the middle fractions, which is at least due to the distribution of compounds during the distillation process. Accordingly, the first middle fraction in line 39 can include compounds with a normal boiling point in a range of about 150 to 300 degrees C. The second middle fraction, which is depicted as line 40, can include compounds with a normal boiling point of 200 to 350 degrees C., which typically captures lignin oligomers. The bottom fraction depicted as line 41 has compounds with a normal boiling point of greater than 350 degrees C., which typically capture the heaviest of compounds regarded as waste or byproducts, such as caramel and/or tar. While the first middle fraction may be referred to as the phenols fraction and the second middle fraction may be referred to as the lignin oligomers fraction, it is understood that the phenols fraction may contain lignin oligomers, and the lignin oligomers may contain phenols. It is understood that a middle fraction distilled from the non-aqueous stream can be the phenols fraction, the lignin oligomers fraction, or a combination thereof. As described, separation zone 13 provides one or more middle fraction that contains a major portion of phenolics in the reaction product provided to separation zone 13.
Referring to
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Referring to
Additionally or alternatively, in
Referring to
As shown in
Some or all of material in at least one of line 39 and line 40 may be provided to lignin depolymerization unit 29. For instance, at least 10 wt % of the material in a middle fraction distilled from the non-aqueous stream is provided to lignin depolymerization unit 29, particularly, at least 20 wt %, at least 30 wt %, at least 40 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt %, or at least 90 wt %. The amount may be selected by one of ordinary skill in the art by balancing different factors, including the use of phenols as solvent in liquid-liquid extraction unit 20, hydrothermal digestion unit 2, and further lignin reversion and conversion to hydrocarbons in phenolics conversion unit 16. Recycling more material to one location leaves less material for recycling to other locations. An external solvent (i.e., one that is not recycled) may be provided to system 1, particularly in hydrothermal digestion unit 2 and extraction units 20 and 53, at start up or as needed.
Referring to
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Although a number of different types of catalysts may be used for mediating condensation reactions, zeolite catalysts also may be particularly advantageous in this regard. One zeolite catalyst that may be particularly well suited for mediating condensation reactions of alcohols is ZSM-5 (Zeolite Socony Mobil 5), a pentasil aluminosilicate zeolite having a composition of NanAlnSi96-nO192.16H2O (0<n<27), which may transform an alcohol feed into a condensation product. Other suitable zeolite catalysts may include, for example, ZSM-12, ZSM-22, ZSM-23, SAPO-11, and SAPO-41.
In various embodiments, the condensation reaction may take place at a temperature ranging between about 275 degrees C. and about 450 degrees C. The condensation reaction may take place in a condensed phase (e.g., a liquor phase) or in a vapor phase. For condensation reactions taking place in a vapor phase, the temperature may range between about 300 degrees C. and about 400 degrees C., such as 350 degrees C. or above. The condensation reaction may take place at a pressure in a range of about 5 bar to 50 bar, such as 10 bar to 30 bar, including about 15 bar to 20 bar.
The alcoholic component, particularly when it includes methanol and an oxygenate, such as such as at least one of ketones, aldehydes, furans, and ethers, can provide for improved conversion of methanol over to a fuel compound, such as gasoline or diesel, as compared to other conventional methanol conversion processes. An example of such a conventional methanol conversion process is the methanol-to-gasoline process.
The higher molecular weight compound produced by the condensation reaction may comprise >C4 hydrocarbons, such as C4-C30 hydrocarbons, C4-C24 hydrocarbons, C4-C18 hydrocarbons, or C4-C12 hydrocarbons; or >C6 hydrocarbons, such as C6-C30 hydrocarbons, C6-C24 hydrocarbons, C6-C18 hydrocarbons, or C6-C12 hydrocarbons. As used herein, the term “hydrocarbons” refers to compounds containing both carbon and hydrogen without reference to other elements that may be present. Thus, heteroatom-substituted compounds are also described herein by the term “hydrocarbons.” The particular composition of the higher molecular weight compound produced by the condensation reaction may vary depending on the catalyst(s) and temperatures used for both the catalytic reduction reaction and the condensation reaction, as well as other parameters such as pressure.
A single catalyst may mediate the transformation of the alcoholic component into a form suitable for undergoing a condensation reaction as well as mediating the condensation reaction itself. Zeolite catalysts are one type of catalyst suitable for directly converting alcohols to condensation products in such a manner. A particularly suitable zeolite catalyst in this regard may be ZSM-5, although other zeolite catalysts may also be suitable.
On the other hand, a first catalyst may be used to mediate the transformation of the alcoholic component into a form suitable for undergoing a condensation reaction, and a second catalyst may be used to mediate the condensation reaction. Unless otherwise specified, it is to be understood that reference herein to a condensation reaction and condensation catalyst refers to either type of condensation process. Further disclosure of suitable condensation catalysts now follows. Zeolite catalysts may be used as either the first catalyst or the second catalyst. Again, a particularly suitable zeolite catalyst in this regard may be ZSM-5, although other zeolite catalysts may also be suitable.
Various catalytic processes may be used to form higher molecular weight compounds by a condensation reaction. In some embodiments, the catalyst used for mediating a condensation reaction may comprise a basic site, or both an acidic site and a basic site. Catalysts comprising both an acidic site and a basic site will be referred to herein as multi-functional catalysts. In some or other embodiments, a catalyst used for mediating a condensation reaction may comprise one or more metal atoms. Any of the condensation catalysts may also optionally be disposed on a solid support, if desired. Additional details regarding suitable catalysts are described in commonly owned U.S. patent application Ser. No. 14/067,330, filed Oct. 30, 2013, and entitled Methods and Systems for Processing Lignin During Hydrothermal Digestion of Cellulosic Biomass Solids,” the entire disclosure of which is incorporated herein by reference.
For example, the condensation catalyst may also include a zeolite and other microporous supports that contain Group IA compounds, such as Li, Na, K, Cs and Rb. Preferably, the Group IA material may be present in an amount less than that required to neutralize the acidic nature of the support. A metal function may also be provided by the addition of group VIIIB metals, or Cu, Ga, In, Zn or Sn. In some embodiments, the condensation catalyst may be derived from the combination of MgO and Al2O3 to form a hydrotalcite material. Another condensation catalyst may comprise a combination of MgO and ZrO2, or a combination of ZnO and Al2O3. Each of these materials may also contain an additional metal function provided by copper or a Group VIIIB metal, such as Ni, Pd, Pt, or combinations of the foregoing.
The condensation reaction mediated by the condensation catalyst may be carried out in any reactor of suitable design, including continuous-flow, batch, semi-batch or multi-system reactors, without limitation as to design, size, geometry, flow rates, and the like. The reactor system may also use a fluidized catalytic bed system, a swing bed system, fixed bed system, a moving bed system, or a combination of the above. In some embodiments, bi-phasic (e.g., liquid-liquid) and tri-phasic (e.g., liquid-liquid-solid) reactors may be used to carry out the condensation reaction.
As shown in
To facilitate a better understanding of the present invention, the following examples of preferred embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.
A 450-ml Parr reactor was charged with 20.02 grams of 2-methoxy-4-propylphenol (MPP), 190.01 grams of deionized water, 0.4192 grams of potassium hydroxide buffer, and 7.2522 grams of nickel-oxide promoted cobalt molybdate catalyst (DC-2534, containing 1-10% cobalt oxide and molybdenum trioxide (up to 30 wt %) on alumina, and less than 2% nickel), obtained from Criterion Catalyst & Technologies L.P., and sulfided by the method described in US2010/0236988 Example 5.
The reactor was then charged with 14.02 grams of southern pine mini-chips (10% moisture), of nominal size 3×5×5 mm in dimension, before pressuring with 52 bar of hydrogen, and heating to 190° C. for 1 hours, then ramping to 245° C. for 2.5 hours. After the reaction completed, the reactor was cooled and depressurized. A nominal 14 grams of wood chips were added, followed by repressurization with 52 bar of hydrogen (H2), and a second reaction cycle using the same heating profile was conducted. The sequence was continued through 8 cycles of wood addition, which added 100.8 grams of dry wood. Following the 8-cycle reaction sequence, the reactor was heated at 270° C. overnight (15 hours) to further hydrogenate and hydro-deoxygenate intermediates formed from the digestion of wood. This simulated a second hydrothermal reaction step, which may take place in phenolics conversion unit 16.
After separation of catalyst by filtration, the reactor contents were distilled in a 500-ml 3-necked flask using a short path Vigreux column (approximately 4 stages) with vacuum adapter isolation for sample removal.
An initial distillation cut of 230.5 grams was produced via distillation at atmospheric pressure under a protective N2 blanket, wherein distillation and bottoms temperature were both 100+/−1° C., indicative of boil off and condensation of the large water fraction. The initial cut of overhead distillation product separated however into two phases while hot, entailing a 16.74 gram upper or tops layer, and a 217.65 gram lower layer. When the distillation abated, vacuum was applied at nominal 100 Torr), and the distillation was continued with ramping of the bottoms kettle temperature to 325° C. Another 18.03 grams of overhead distillation product was produced. Final bottoms product entailed 28.75 grams, for a mass balance of 95.98%.
Distillation products were analyzed by gas chromatography using a 60-m×0.32 mm ID DB-5 column of 1 micrometer thickness, with 50:1 split ratio, 2 ml/min helium flow, and column oven at 40° C. for 8 minutes, followed by ramp to 285° C. at 10° C./min, and a hold time of 53.5 minutes. The injector temperature was set at 250° C., and the detector temperature was set at 300° C. A range of alkanes, ketone and aldehyde mono-oxygenates as well as residual glycol intermediates including ethylene glycol (EG), 1,2-propylene glycol (PG) and glycerol were observed, along with phenolic components from the initial charge of solvent, and those formed in reaction.
Analysis of overheaded products indicated 31.9 wt % of propylphenol (derived from MPP) and methoxypropylphenol (MPP) in the upper layer from overhead distillation cut #1, comprising 5.35 grams of phenols Only 0.051 wt % was observed in the lower aqueous fraction, entailing only 0.11 grams of phenolics. For distillation cut #1, the sum of propylphenol and MPP was 16.01 wt %, comprising 2.89 grams. 64% of the total overhead distilled phenols appeared in the initial cut (No. 1) collected at a boiling and condensation temperature of 100° C., despite the normal boiling point in excess of 200° C. for these components. This anomaly can be explained by formation of a second, no-water-miscible and phenolic-rich liquid phase during distillation, such that be boil off of water “steam stripped” these components into the overhead distillate. The overhead distillate thus produced 5.47 grams of phenols, in addition to the light monooxygenates (ethanol, 1-propanol) of 3.82 grams, and other intermediates from the hydrodeoxygenation of wood. Bottoms product formed a solid tar phase upon cooling, and could not be remelted or poured upon reheating to 200° C.
This comparative example shows that direct distillation of reactor product from hydrothermal digestion of wood, results in substantial steam stripping of heavy components into the overhead product, such that separation on the basis of boiling point is not efficient or effective.
Example 1 was repeated using 5.0035 grams of Raney™ cobalt catalyst (WR Grace 2724), and a solvent comprising of 21.1 grams of 2,6-xylenol as the phenolic solvent, solubilized first into 7.00 grams of methylisobutylcarbinol, and added together with 182.01 grams of deionized water to the 450-ml reactor. Reaction cycles entailed 1 hour at 160° C., followed by 1 hour at 190° C., followed by 3 hours at 240° C. Six cycles of wood addition were effected, which simulated the first hydrothermal reaction. This was followed by heating overnight at 270° C. under 52 bar of H2, which simulated the second hydrothermal reaction to further hydrotreat and complete conversion of various compounds in the first reaction product, which the examples may refer to as intermediates.
At the end of the reaction sequence, 87.03 grams of toluene (simulated aromatics gasoline product) were added to the reactor, and the reactor was stirred at 150° C. for 2 hours to effect extraction. Stirring was then stopped, and the reactor allowed to cool. An upper toluene-rich phase of 127.39 grams was decanted, followed by 220.65 grams of a lower aqueous-rich phase. Catalyst was left on the reactor bottom.
Table 1 shows partitioning of reaction intermediates and solvents between upper organic and lower aqueous phases. Phenolics xylenol and methoxypropylphenol (MPP) highly favored the upper organic-rich phase. Some of the reaction intermediates could also be extracted into this phase.
The upper layer was distilled in a 250-ml 3-necked flask equipped with short-path Vigreux column and vacuum draw off adapter. An initial distillation Cut #1 entailing 79.71 grams was produced via distillation at atmospheric pressure under a N2 blanket with a bottoms temperature ranging from 105-120° C. This cut contained approximately 89% toluene, but only 0.14% xylenol, and undetectable methoxypropylphenol (formed during reaction). 2.45 wt % light mono-oxygenate products were present.
A second distillation cut was obtained after applying vacuum at nominal 100 torr, and continuing the distillation from a bottoms temperature of about 120° C. to 205° C. Cut #2 comprised 10.01 grams. Concentration of xylenol was only 0.04 wt %, light monooxygenates were only 0.159 wt %. Toluene was estimated as 87%, and MPP was undetectable. A number of oxygenated intermediates of boiling point greater than 1-butanol, but less than xylenol, were observed as reaction intermediates.
The distillation was continued with further increase in bottoms temperature under the nominal 100 Torr vacuum, to produce a 3rd cut comprising 22.33 grams of product, at a bottoms temperature ranging from 205 to 340° C. The concentration of xylenol in this cut was analyzed as 47.9 wt %, and propyl phenol plus MPP formed via digestion and reaction of wood, comprised 10.1 wt %. Light ends (volatility less than 1-butanol) were less than 0.1 wt %, and toluene was less than 7 wt %. Greater than 98% of the xylenol and phenols produced in distillation products, were produced in this final high temperature cut.
Bottoms from distillation was only 12.09 grams, and contained only 0.42 wt % xylenol. A majority of xylenol was thus distilled overhead for recycle as solvent, appearing in the distillation cut #3. The final bottoms remained fluid and could be poured out of the flask upon reheating to 200° C.
The 217.84 gram aqueous fraction from reaction was distilled in the same apparatus via a separate distillation. 194.2 grams were distilled overhead as a water cut boiling at 100° C. under atmospheric pressure. Xylenol content was only 0.118 wt %. The distillation was continued to produce a cut #2 of 9.33 grams under 100 Torr vacuum with increase in bottoms temperature to 200° C., and a cut #3 comprising 5.76 grams upon an increase in bottoms temperature to 325° C. Final bottoms product of 6.86 grams was a dull solid, and could not be remelted upon reheating to 200° C.
Xylenol and MPP were undetectable in Cuts #1 and #2, but comprised 1.00% and 0.417% of Cut #3. 99.5% of xylenol was collected in the upper layer (toluene phase) distillation, relative to the bottom phase distillation, reflecting preferential partitioning of phenolics into toluene during extraction.
This result shows that phenolics are primarily extracted into an upper aromatics rich phase via liquid-extraction. Use of extraction and separation prior to distillation of separate organic and aqueous rich phases, leads to efficient separation of components on the basis of boiling points. High boiling phenolics are almost exclusive (greater than 99%) recovered with the high boiling fraction from distillation, and not distributed over all produced cuts as occurred with immiscible liquid phase were distilled together as per Example 1.
Moreover, the heavy ends phase produced form toluene extraction exhibited improved flowability relative to that produced form the total distillation or aqueous distillation. This flowable phase can be readily fed as fuel to a recovery boiler, or used as an asphalt coproduct.
Example 2 was repeated, with use of 75.01 grams of methylisobutycarbinol (MIBC) instead of toluene as extractant.
Partition coefficients for the concentration by weigh in the upper MIBC-rich organic layer, vs. the lower aqueous layer, are reported in Table 2. Phenolics favorably partition into the organic layer. However, monooxygenates and even glycols exhibited a partition coefficient greater than 0.25, indicating that excess solvent with recycle could be used to extract the desired reaction intermediates away from the aqueous phase, with separation of the extracted solution by distillation, and recycle of extraction solvent. This, a moderate polarity lipophilic alcohol like MIBC can be used to extract all target reaction intermediates and solvents from aqueous solution, without the need for boil up of water.
The distillation of the upper layer organic-rich phase was conducted as before, with results shown in Table 3. The initial distillation cut separated into two phases, as a result of the higher concentration of water solubilized into this phase relative to the toluene layer of example 2. Very little xylenol or MPP appeared in the overheads until bottoms temperature was increased for the final vacuum distillation cut #3. More than 90% of phenolic startup solvent (xylenol) and generated phenols (MPP and propyl phenol) was isolated in cut #3, affording easy recycle of solvent. This contrasts example #1, where the entire reactor product was distilled together without prior phase separation or extraction, and phenolic components were produced at significant concentrations in the very first distillation cuts.
One part of the upper organic-rich upper layer from Example 3 was removed prior to distillation, extracted with one part by weight of MIBC solvent, by shaking for 3 minutes in a vial via mechanical shaker, followed by allowing to phase separate overnight at 25° C.
GC results show extraction of light alcohols C1-C3 from the aqueous lower layer to less than about 0.15 wt %. Extraction efficiency as measured by the partition coefficient K increased with increasing carbon number for the light alcohol. Glycols, including ethylene glycol (EG) and propylene glycol (PG) were not extracted.
Methanol (64.7° C.), ethanol (78.4° C.), and 1-propanol (97.2° C.) have boiling points more than 10° C. less than MIBC (131.6° C.). It is therefore feasible to liquid extract the light alcohols from water using MIBC, and flash distil to preferentially remove the extracted light alcohols, with recycle of the MIBC extraction solvent as a bottoms, unboiled fraction. An efficient process for removal of water soluble light alcohols is this revealed.
EG and PG are not extracted due to high polarity. The aqueous phase containing residual EG and PG can be routed back to a hydrodeoxygenation reaction step, for conversion to light alcohols such as ethanol and propanol which can be extracted. By preferentially recycling EG and PG to the second hydrothermal reaction step after extraction of a majority of the ethanol and propanol, loss of ethanol and propanol to undesired ethane and propane by excessive hydrogenation, is avoided.
A simulated reaction product mixture was prepared as 2 weight percent each of ethanol, 2-propanol, ethylene glycol (EG), and propylene glycol (PG) in deionized water. The reaction product mixture was extracted with one part of by weight solvent, with mixing for a minimum of three minutes, followed by phase separation overnight at 25° C. For Example 5A, toluene was used as the extraction solvent. For Example 5B, methoxypropylphenol (MPP) was used as the extraction solvent. For Example 5C, a 1:1 mixture of MPP and methylisobutylcarbinol (MIBC) was used as the extraction solvent. For Example 5D, meta-cresol was used as extraction solvent.
For Example 5E, a 1 wt % solution of MPP in deionized water was prepared, with turbidity indicating only partial solubility at room temperature. This solution was extracted with one part toluene, and gave a partition coefficient of 161.7 for the weight percent in organic layer extract, vs. remaining lower layer aqueous fraction, where the remaining MPP was reduced to only 0.0079 wt %. Comparison with the toluene extraction results for Example 5A in Table 5 reveals selective extraction of phenols (MPP) relative to light alcohols and diols, with use of toluene as extractant. Toluene or other aromatic gasoline fractions can be used to selectively remove phenolic components from aqueous reaction intermediate streams, such that phenolic solvent components can be effectively recycled, and phenol contamination of streams further processed to liquid biofuels is minimized.
The amount of toluene lost to the lower layer sample was less than 0.12 wt %, representing less than 1% loss of toluene extraction solvent.
For Example 5B, MPP was used as extraction solvent, representing use of the phenolic components generated during the first hydrothermal reaction (digestion) and second hydrothermal reaction as an extraction solvent. Removal of light alcohol monooxygenates ethanol and 2-propanol was greatly improved vs. that obtained with toluene as extractant. Partition coefficients for ethanol and propanol are greater than 0.25, allowing feasible use of extraction plus flash separation to recycle MPP phenolic solvent, as a method for recovery of light alcohols in the absence of boiling water. The amount of MPP lost to the aqueous phase was 0.15 wt %, for an apparition partition coefficient of 612 for the distribution of MPP between organic and aqueous layers.
For Example 5C, a mixture of phenolic (MPP) and lipophilic longer chain alcohol (MIBC) extraction solvent was used, as would occur with incomplete separation by flash distillation of phenolic and longer-chain alcohol components made during first hydrothermal reaction (digestion) and second hydrothermal reaction. Extraction of light alcohols ethanol and propanol was further improved via increase in observed partition coefficients between organic and aqueous layers. While again only 0.12 wt % MPP extractant was lost to the aqueous phase versus measured 55 wt % in the final organic extract (462 oil/water partition coefficient), the MIBC co-solvent was lost at a higher fraction (1% lost to aqueous, or a partition coefficient of 48 between oil and water fractions). Thus, recovery of MIBC lost to aqueous may be required for an effective process.
For example 5D, m-cresol was used as extraction solvent, representing a phenolic with only a C1 side chain, vs. C3 methoxy present for MPP. Extraction of ethanol and propanol was further improved, but 2.7 wt % cresol was lost to the aqueous layer, at an apparent partition coefficient of 39 between oil and water. This example shows than methoxyphenols are not required for extraction recovery, and exhibit extraction performance similar to alkylphenols without the methoxy appendage. This is important, because methoxy groups are often lost form phenols generated from biocomponents during thermocatalytic processing under the conditions described herein.
Example 5E (previously described) also describes the recovery of phenols lost to the aqueous phase, via extraction with toluene. More than 99% of MPP lost to the aqueous phase as a 1% solution, was recovered by extraction with toluene as solvent to give a residual aqueous concentration of less than 0.007 wt %, with loss of less than 0.15 wt % toluene solvent to the aqueous phase. Thus, total organics were diminished by 99% in the aqueous extract, by use of aromatic toluene solvent to extract the phenol component from an aqueous mixture. In comparison with Examples 5B through 5D, one can use a phenol or combination of phenol and lipophilic alcohol of carbon number greater than 4 to effectively extract light alcohols ethanol and propanol from the aqueous product mixture, then extract the remaining extractant solvent with and aromatic rich solvent such as toluene, leaving an aqueous coproduct that contains only less than 1% of monooxygenate and phenolic solvents. This combined with a process scheme to recycle glycol components which do not extract, and produce an aqueous product stream with low levels of dissolved organics without requiring boiling of water (with its high heat of vaporization and thermal energy requirement) for separation.
For Example 5F, heptane was used as extraction solvent for recovery of 1% MPP from water, in contrast to toluene used in the previous example. MPP was removed down to 0.08 wt %, for an apparent partition coefficient of 76. Only 0.07 wt % heptane was lost to the aqueous phase, presumably in part emulsified basis turbidity in the final sample. This example shows than and alkane gasoline or diesel cut can be used in place of an aromatics rich cut (toluene), to extract phenolic solvent MPP from aqueous solution.
For Example 5G, a 1% solution of m-cresol was extracted with toluene, to show the extraction of an alkylphenols, as opposed to the methoxyphenol MPP examined in Example 5E. Residual cresol left in the aqueous layer was only 0.05 wt %, which was more than 4-fold higher than extraction with toluene, but still quite low. An apparent partition coefficient of 20.8 was observed for cresol partitioning between organic and aqueous phases. Amount of toluene lost to the aqueous phase was 0.04 wt %. This example confirms that alkylphenols with no methoxy groups follow similar extraction behavior as methoxyphenols, which is important because a fraction of the methoxyphenols formed from thermocatalytic digestion and hydrodeoxygenation reaction of biomass lose their methoxygroups to form alkylphenols in the process.
For Example 5H, a 1% m-cresol solution was extracted with heptane, to show the extraction behavior of alkylphenols with no methoxy group, in the presence of alkane solvent representative of alkane-rich diesel or gasoline fractions. In this case, 0.56 wt % remained with the aqueous layer, for an extraction recovery of only 44%. Heptane lost to the aqueous layer was 0.015%. While effective if used in recycle mode, the alkane extractant appeared to be less efficient than the aromatic extraction of Example 5G, in removal of phenolic components from aqueous solution.
Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods may also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.
This application claims the benefit of U.S. Provisional Application No. 62/098,023, filed on Dec. 30, 2014, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62098023 | Dec 2014 | US |
