Patent Application
20250207325
The present invention is directed to a method to separate lignocellulosic biomass into its three main constituents more effectively; more specifically, the method comprises a two-step approach to separate hemicellulose, lignin, and cellulose from one another.
Biofuel is increasingly becoming a necessity in order to wean off the human consumption of fossil fuels in aspects of everyday life; with transport and home heating being the largest two industries of focus. As an alternative energy source to oil and coal, the main feedstock for biofuel production is starch, which can yield its sugar much more readily than cellulose. This is due to the difference in structure as starch links glucose molecules together through alpha-1,4 linkages and cellulose links glucose units with beta-1,4 linkages. The beta-1,4 linkages allow for crystallization of the cellulose, leading to a more rigid structure which is more difficult to break down.
The limitation that comes from solely using the sugars from starch for biofuel production prevents the utilization of the larger portion of biomass, which comes in the form of lignocellulosic biomass (contains lignin, cellulose, and hemicellulose) present in almost every plant on earth. A delignification reaction allows the recovery of cellulose from that lignocellulosic biomass. Once the cellulose is separated from the other two biomass constituents i.e., lignin, and hemicellulose, further degradation of the cellulose generates cellobiose and/or glucose, which can be further processed to bioethanol.
The extraction of hemicellulose from lignocellulosic biomass has been studied under various conditions: acid hydrolysis; alkaline extraction; peroxide extraction; vapor treatment; microwave treatment; ionic liquid extraction, and so on. The most commonly used method, acid hydrolysis, uses either a dilute concentration of acid (0.5%-1% sulfuric acid or hydrochloric acid) at high temperatures or a more concentrated acid at lower temperatures to break down hemicellulose to low molecular weight product. Both low-temperature hydrolysis and high temperature hydrolysis come with advantages and drawbacks. High-temperature extraction at a temperature of 150° C. to 170° C. provided high sugar yields and less degradation product. Moreover, due to the presence of acetate group in hemicellulose, under high temperature extraction, the presence of hydrogen ion in solution increases, which in turn accelerates the hydrolysis reaction, this is referred to as auto-hydrolysis.
When the ultimate goal of the treatment of the lignocellulosic biomass is to obtain bioethanol or other fermentation products, it is preferable to employ the dilute acid hydrolysis of hemicellulose to minimize the formation of decomposition products that are detrimental or toxic to microorganisms. Two-stage pre-treatment of wood chips have been found to maximize hemicellulose recovery in a first step and a subsequent stage of exposing the water-insoluble solids obtained from the first-stage prehydrolysate to dilute sulfuric acid allowed to hydrolyze a portion of the remaining cellulose to glucose and to improve the enzyme digestibility. The total sugar yields obtained after enzymatic hydrolysis was found to be about 10% higher and reduced the net enzyme requirement about 50%.
Seen as a sustainable alternative to gasoline and with the goal of alleviating many countries' dependence on foreign oil, the biofuel industry, in particular the bioethanol industry, is still hampered by its dependence on corn or sugar cane as their primary sources, as they are both rich in starch. It is estimated that about a third of all corn production in the U.S. is directed to the ethanol fuel production. This is a situation which has disastrous consequences when the price of gasoline goes so low as to make corn-based biofuel unsustainable on a price view point.
To pivot from starches to cellulose for the production of glucose is preferable as it will provide near-unlimited amount of feedstock from waste biomass and reduce the competition with food source feedstock to generate glucose. However, the costs to do so are currently prohibitive. Cellulosic ethanol, as it is called, relies on the non-food part of a plant to be used to generate ethanol. This would allow the replacement of the current more widespread approach of making bioethanol by using corn or sugarcane. The diversity and abundance of these types of cellulose-rich plants would allow to maintain food resources mostly intact and capitalize on the waste generated from these food resources (such as cornstalk) to generate ethanol. Other cellulose sources such as grasses, algae, and even trees fall under the cellulose-rich biomass, which can be used in generating ethanol if a commercially viable process is developed.
The hydrolysis of cellulose is, as seen from the above, limited by the structure of cellulose itself but also by the approaches taken to degrade to glucose. The production of a robust, low-cost process from cellulose has not yet been achieved.
The benefits of bioethanol are estimated to have the potential to reduce gas emissions by up to 85% over reformulated gasoline. However, numerous production challenges to generate bioethanol from lignocellulosic biomass rather than from starch have led experts in the field to conclude that, in the near future, cellulosic ethanol will not be produced in sufficient quantities to provide at least a partial gasoline replacement or alternative. It is important that second-generation bioethanol production be based on the use of lignocellulosic biomass as a starting material in order to render it environmentally desirable and economically feasible.
Lignocellulosic biomass is a widely available resource which can be used in bioethanol production. However, the presence of hemicellulose along with the cellulose, either when it is used, unprocessed, as part of the feedstock for bio-ethanol production or when, prior to being added to a fermentation unit to produce ethanol, it is converted to pulp and thus as a result of incomplete removal of hemicellulose causes an inhibition of the microorganism activity in the fermentation of cellulose to ethanol. As such, it is preferable to minimize the amount of hemicellulose remaining in the pulp when the latter is used in the production of bioethanol in order to maximize the value thereof.
Moreover, there is also great value to be derived from lignin if such can be extracted in a fashion which always further processing economically feasible. Lignin is the second most abundant biopolymer in the world (after cellulose). It is a polyphenolic material which is comprised of three phenylpropanoid monomers: p-coumaryl alcohol; coniferyl alcohol; and sinapyl alcohol. The weight average molecular weight (Mw) of isolated lignin (milled wood lignin) is dependent on the biomass source and has been recorder to range from 6700 daltons for Eucalyptus globulus to 23500 daltons for Norway spruce. Lignin has been measured to be present in softwoods in amounts ranging from about 25-35 wt. % to 20-25 wt. % in hardwood. It is also present in herbaceous plants but at much lower concentrations, typically from 15 to 25 wt. %.
U.S. patent application No. 20040244925A1 discloses methods for producing pulp (comprising cellulose) and lignin from lignocellulosic material, such as wood chips. The methods involve acid catalyzed hydrolysis. Lignocellulosic material having a relatively high moisture concentration can be used as the starting material. The lignocellulosic material is impregnated with an acid (preferably nitric acid) and heated. During the heating lignin, is depolymerized at relatively low temperatures, and the acid catalyst is distilled off. The acid catalyst can be collected and recycled after impregnation and heating. The lignocellulosic material is then digested in an alkaline solution under heat, dissolving the lignin and allowing the pulp to be removed. Acid is added to the black liquor to precipitate the lignin which, is then removed. The resultant amber liquor can be further processed into other ancillary products, such as alcohols and/or unicellular proteins.
European patent application no. 2580245A1 discloses a process of fractionation of biomass to obtain lignin, cellulose and hemicelluloses, the process comprises: a. contacting the biomass with 5% to 30% (v/v) aqueous ammonia at a temperature ranging from 50° C. to 200° C. to obtain a first biomass slurry; b. filtering the first biomass slurry to obtain a first filtrate comprising lignin and a first residue comprising cellulose and hemicellulose; c. contacting the first residue with 30% to 90% (v/v) aqueous ammonia at a temperature ranging from 50° C. to 200° C. time to obtain a second biomass slurry; and d. filtering the second biomass slurry to obtain a second filtrate comprising hemicelluloses and a second residue comprising cellulose.
U.S. patent application No. 20210348202A1 discloses a method of processing lignocellulosic biomass comprising: providing soft lignocellulosic biomass feedstock; pretreating the feedstock at pH within the range 3.5 to 9.0 in a single-stage pressurized hydrothermal pretreatment to low severity such that the pretreated biomass is characterized by having a xylan number of 10% or higher; separating the pretreated biomass into a solid fraction and a liquid fraction; hydrolysing the solid fraction with or without addition of supplemental water content using enzymatic hydrolysis catalysed by an enzyme mixture comprising endoglucanase, exoglucanase, B-glucosidase, endoxylanase, xylosidase and acetyl xylan esterase activities; and subsequently mixing the separated liquid fraction, and the hydrolysed solid fraction, whereby xylo-oligomers in the liquid fraction are degraded to xylose monomers by the action of enzyme activities remaining within the hydrolysed solid fraction.
U.S. patent application No. 20100317070A1 discloses a process for converting lignocellulosic materials which are field residues such as cotton stalks and corn stover, process residues such as sugarcane bagasse and sweet sorghum bagasse, woody parts of energy crops such as switchgrass and miscanthus, forest residues or byproducts of the wood processing industries such as sawdust from sawmills to a liquid biofuel by a series of processing steps wherein the feed materials are hydrolysed in three stages and withdrawn as three product streams each consisting of solubilized fragments of one of the three major components of the feed materials and a set of concurrently operating processing steps wherein each of the three product streams is transformed through chemical or biochemical processes into products, such as pure lignin and ethanol, that have a high calorific value and process wherein these products with high calorific value are combined to form a liquid biofuel.
In light of the state-of-the-art with respect to the use of lignocellulosic biomass to generate products for example, biofuels (including but not limited to bioethanol and biodiesel), there still exists a need for a process which is capable of being scaled up efficiently which results in streams of separated lignocellulosic biomass constituents which can then be used, for example, in the manufacturing of such fuels.
As a way to maximize the extraction of the three constituents of lignocellulosic biomass in distinct streams while minimizing the energetic input related to the extraction process, there is proposed a delignification of a lignocellulosic biomass using a modified Caro's acid followed by a post-delignification treatment step using a caustic composition to separate the remaining hemicellulose from the cellulose.
It has been surprisingly and unexpectedly found that by lowering the acid content of modified Caro's acid compositions used in the delignification of lignocellulosic biomass, one could substantially decrease the peroxide consumption while barely impacting the efficiency or the extent of delignification.
Canadian patents CA 3,110,553C, CA 3,110,555C, and CA 3,110,558C are among some of the Canadian patent filings from the Applicant which disclose various modified Caro's acid compositions which are found to be useful in the delignification of lignocellulosic biomass.
However, these prior art documents do not address optimized recovery of three distinct streams of the biomass constituents, namely, cellulose, lignin, and hemicellulose. The present application discloses the use of an additional treatment step following delignification by exposure to modified Caro's acid composition, wherein said additional treatment step comprises an exposure of the remaining solid components (resulting from the above-mentioned delignification step) to a caustic composition adapted to solubilize hemicellulose remaining in the solid components.
It was believed that by reducing the acid concentration in a delignification composition would negatively impact both the extent of delignification as well as the time required for the delignification. This was expected as the three above mentioned Canadian patents which disclose a delignification process using modified Caro's acid and carrying out such process at unconventional temperatures of less than 55° C. The controlled reactivity of those acids provides operators with several advantages, one of which being increased safety of the operators when handling these acids. Another advantage of those modified Caro's acid is that they provide more control to operators during the delignification process. For best results, operators are advised to keep the reaction temperature where the modified Caro's acid delignify a lignocellulosic biomass (or feedstock) at or below 55° C. It was determined that exceeding this temperature can lead to a runaway reaction where the cellulose will be blackened during an increasingly exothermic reaction caused by the increasing temperature. Temperature control allows operators to maintain control on the reaction speed and extent. Presently, operators are performing delignification using modified Caro's acid composition where the sulfuric acid concentration is above 40%. The delignification process provides a cellulose which has a kappa number below 5 all the while using temperatures which do not exceed 55° C.
Surprisingly and unexpectedly, the inventors of the present invention have found that, by reducing the concentration of the acid to below 40%, this would substantially reduce the consumption of the peroxide component in the modified Caro's acid composition. The resulting cellulose has a kappa number of less than 10, preferably, less than 5. Preferably, the resulting cellulose has a kappa number of less than 2. More preferably, the resulting cellulose has a kappa number of less than 1.
As the peroxide component of the modified Caro's acid compositions is the only consumable component, if its consumption can be reduced without significantly affecting the speed or the extent of the delignification reaction, this will lead to considerable financial savings. Moreover, the process according to a preferred embodiment of the present invention allows to optimize the recovery of the three main constituents of lignocellulosic biomass: cellulose, hemicellulose and lignin. Preferably, since the peroxide consumption is lower in the presently disclosed process, it is indicative that the process is more specific and thus undergoes fewer side reactions (which tend to consume peroxide).
According to an aspect of the present invention, there is provided a process which combines a first step of delignification of lignocellulosic biomass with a modified Caro's acid to a point where the Kappa number of the biomass is 10 or less, followed by a second step of caustic treatment of the remaining solids to dissolve hemicellulose and yield a high purity cellulose. Such a process allows for an extremely efficient separation of the three main constituents of lignocellulosic biomass.
The savings from the substantially decreased peroxide consumption are expected to increase the acceptance of the technology using modified Caro's acid to delignify lignocellulosic biomass. This is also expected to increase the various types of biomass being used in such processes rather than relying on wood and wood by-product, more and more fast growing plants and grasses can be employed to generate cellulose, lignin and hemicellulose. It is worth noting that the delignification using modified Caro's acid already provides a number of advantages over other process such as kraft delignification. For one, the process temperatures at which the delignification using modified Caro's acid occurs is so low in terms of energy input since the temperature is preferably maintained at below 55° C.; while the kraft process is routinely carried out at a temperature ranging between 174 and 180° C. and uses large amounts of water. Secondly, the modified Caro's acid process allows recovery of lignin which can be converted into a biofuel or valuable small molecules. The kraft process recovers its lignin but burns it to produce the high temperatures required to delignify the biomass. Third, installations performing the kraft process are large and expensive and require a large amount of water, thereby limiting installations close to rivers which can support such activities, while the modified Caro's acid process does not require large amounts of water. Moreover, with the present discovery that the acid concentration reduction leads to substantial savings in the peroxide consumption, the process is even more advantageous than earlier iterations.
By combining a delignification with a modified Caro's acid having a reduced acid content (below 40%) and following with a caustic treatment of the solids portion remaining after delignification, one is capable of achieving three distinct streams each containing in a major proportion, depolymerized lignin constituents, as well as cellulose and hemicellulose (in its polysaccharide form) respectively.
Initial testing using canola has shown that as the blend is diluted to a final acid concentration of 35% wt., the consumption of peroxide has been reduced by up to 90% all the while leaving a solid product containing less than 1% wt. lignin. This translates into a kappa number of 5. The remaining solids (cellulose and hemicellulose) were subsequently treated to a caustic wash which dissolved the hemicellulose and left cellulose at a purity of over 95%. Given the fact that the liquid portion resulting from the delignification step comprised mainly the modified Caro's acid and the dissolved lignin and that the liquid portion resulting from the caustic treatment step comprised mainly hemicellulose and the caustic component, the process according to a preferred embodiment of the present invention is believed to yield three distinct streams each one mainly comprising one of the three main component of the lignocellulose component which was treated. Moreover, given that each step of the process was low in energy input, it is believed to be a first time such a low energy approach has ever been utilized to generate three distinct streams of the main components of lignocellulosic biomass.
According to an aspect of the present invention, there is provided a method for substantially removing constituents of a lignocellulosic biomass into separate streams, where said method comprises the following steps:
According to a preferred embodiment of the present invention, said modified Caro's acid composition is composition A. According to another preferred embodiment of the present invention, said modified Caro's acid composition is composition B. According to yet another preferred embodiment of the present invention, said modified Caro's acid composition is composition C.
According to an aspect of the present invention, there is provided a method for the delignification by exposure to a modified Caro's acid of a lignocellulosic biomass and separation of said lignocellulosic biomass constituents into separate streams and recovery of hemicellulose in a polysaccharide form, said method comprising the steps of:
Preferably, the removal of hemicellulose from hemicellulose-containing caustic solution comprises an addition of a solvent, such as ethanol, to said caustic liquid phase to precipitate said hemicellulose from said caustic alkali solution and a removal of the resulting precipitated hemicellulose from the caustic solution.
According to an aspect of the present invention, there is provided a method to decrease the consumption of hydrogen peroxide in the delignification of a lignocellulosic material using a modified Caro's acid, wherein said modified Caro's acid selected from the group consisting of: composition A; composition B; composition C; composition D;
Preferably the delignification step is followed by a caustic treatment step of solids resulting from the delignification step, wherein said caustic treatment dissolves the majority of the hemicellulose present in said solids, which can then be separated from the remaining solids comprising substantially pure cellulose of at least 95 wt. % content of the remaining solids.
According to an aspect of the present invention, there is provided a process for the recovery of hemicellulose in its polysaccharide form from a delignification of a lignocellulosic biomass by exposure to a modified Caro's acid, said process comprises the steps of:
Preferably, said modified Caro's acid is selected from the group consisting of: composition A; composition B; composition C; composition D; composition E; composition F; composition G; composition H; composition I; and composition J;
wherein said composition A comprises:
are present in a molar ratio of no less than 1:1;
wherein said composition H comprises:
Preferably, said lignocellulosic biomass is in chips of up to 5 cm in size. More preferably, said lignocellulosic biomass is in chips of up to 3 cm in size. Even more preferably, said lignocellulosic biomass is in chips ranging between 1 and 2 cm in size.
In light of the state-of-the-art with respect to the use of lignocellulosic biomass to generate products for example, biofuels (including but not limited to bioethanol and biodiesel), there is still a need for a process which is capable of being scaled up efficiently which allows the use of lignocellulosic biomass in the manufacturing of such fuels.
Preferably, it is also desirable to overcome at least some of the drawbacks associated with the contamination by the individual constituents (lignin, hemicellulose, and cellulose) in one another's streams. According to a preferred embodiment of the present invention, it is desirable to maintain delignification reaction conditions in a way to minimize hemicellulose decomposition using the modified Caro's acid as much as possible to as to yield a lignin-rich liquid after delignification. Preferably, the lignin-rich liquid obtained after delignification will allow a more efficient conversion to LDO (lignin depolymerized organics) biofuel.
Preferably, the cellulose obtained after delignification will allow a more efficient conversion to bioethanol due to the low amounts of hemicellulose and lignin (or practical absence thereof), which will allow the fermentation of cellulose into bioethanol to be more efficient. The inventors have previously determined that characteristics of the cellulose obtained from a specific type of delignification approach have a substantial impact on the downstream hydrolysis of said cellulose. In that respect, the present invention allows operators to minimize operational costs by implementing a multi-step approach to low-energy delignification to obtain distinct streams of the three main constituents of lignocellulosic biomass.
Features and advantages of embodiments of the present application will become apparent from the following detailed description and the appended figures, in which:
The delignification of biomass according to conventional approaches, such a kraft pulping, yields a pulp which is still high in lignin and hemicellulose.
The most common process for pulp delignification is the kraft process. In the kraft process, wood chips are converted to wood pulp. The multi-step kraft process consists of a first step where wood chips are impregnated with a chemical solution. This is done by wetting wood chips and pre-heating them with steam. This swells the wood chips and expels the air present in them and replaces the air with the liquid. Then the chips are saturated with a black liquor and a white liquor. The black liquor is a resulting product from the kraft process. It contains water, lignin residues, hemicellulose, and inorganic chemicals. White liquor is a strong alkaline solution comprising sodium hydroxide and sodium sulfide. Once the wood chips have been soaked in the different solutions, they undergo cooking. To achieve delignification in the wood chips, the cooking is carried out for a few hours at temperatures reaching up to 176° C. At these temperatures, the lignin and hemicellulose degrade to yield water soluble fragments. The remaining cellulosic fibers are collected and washed after the cooking step.
Biofuel production is another potential application for the kraft process. One of the current drawbacks of biofuel production is that it requires the use of plant parts (such as seeds) in order to transform carbohydrates into fuel in a reasonably efficient process. The carbohydrates could be obtained from cellulosic fibers, by using non-food grade biomass in the kraft process. However, the energy intensive nature of the kraft process for delignification as well as the low delignification efficiencies make this a less commercially viable option. In order to build a plant based chemical resource cycle, there is a great need for energy efficient processes which can utilize plant-based feedstocks that don't compete with human food production.
While the kraft pulping process is the most widely used chemical pulping process in the world, it is extremely energy intensive and has other drawbacks, for example, substantial odours emitted around pulp producing plants.
The applicant has a patented delignification process which produces a bio-crude feedstock that is substantially free of cellulose derivatives and hence its composition is enhanced compared to pyrolysis bio-crude. According to a preferred embodiment of the present invention, this bio-crude feedstock can be achieved by performing a delignification reaction using a modified Caro's acid composition selected from the group consisting of composition A; composition B and Composition C;
According to preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,678) comprises: sulfuric acid; a heterocyclic compound; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, the sulfuric acid and said heterocyclic compound are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12:1 to 6:1. Also preferably, said heterocyclic compound has a molecular weight below 300 g/mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g/mol. More preferably, said heterocyclic compound is a secondary amine. According to a preferred embodiment of the present invention, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; and N-methylimidazole.
According to a preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,677) comprises: sulfuric acid; a modifying agent comprising a compound containing an amine group; and wherein sulfuric acid and said compound containing an amine group; are present in a molar ratio of no less than 1:1. Preferably, the sulfuric acid and said compound containing an amine group are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 12:1 to 6:1. According to a preferred embodiment of the present invention, the modifying agent is selected in the group consisting of: TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; diethylamine; triethylamine; morpholine; MEA-triazine; and combinations thereof. According to a more preferred embodiment of the present invention, the modifying agent is TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; triethylamine.
According to a preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,676) comprises: sulfuric acid; a modifying agent comprising an alkanesulfonic acid; and wherein sulfuric acid and said alkanesulfonic acid are present in a molar ratio of no less than 1:1. Preferably, said alkanesulfonic acid is selected from the group consisting of: alkanesulfonic acids where the alkyl groups range from C1-C6 and are linear or branched; and combinations thereof. Preferably, said alkanesulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. More preferably, said alkanesulfonic acid is methanesulfonic acid. Also preferably, said alkanesulfonic acid has a molecular weight below 300 g/mol. Also preferably, said alkanesulfonic acid has a molecular weight below 150 g/mol. Preferably, the sulfuric acid and said alkanesulfonic acid and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 12:1 to 6:1.
According to preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,675) comprises: sulfuric acid; a substituted aromatic compound; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1:1. Preferably, the substituted aromatic compound comprises at least two substituents. More preferably, at least one substituent is an amine group and at least one of the other substituent is a sulfonic acid moiety. According to a preferred embodiment, the substituted aromatic compound comprises three or more substituent. According to a preferred embodiment of the present invention, the substituted aromatic compound comprises at least a sulfonic acid moiety. According to another preferred embodiment of the present invention, the substituted aromatic compound comprises an aromatic compound having a sulfonamide substituent, where the compound can be selected from the group consisting of: benzenesulfonamides; toluenesulfonamides; substituted benzenesulfonamides; and substituted toluenesulfonamides. Preferably, the sulfuric acid and said substituted aromatic compound and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 12:1 to 6:1.
According to preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,674) comprises: sulfuric acid; a modifying agent comprising an arylsulfonic acid; and optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1:1. Preferably, the compound containing an amine group is selected from the group consisting of: imidazole; N-methylimidazole; triazole; monoethanolamine (MEOA); diethanolamine (DEOA); triethanolamine (TEOA); pyrrolidine and combinations thereof. According to a preferred embodiment of the present invention, sulfuric acid and the peroxide are present in a molar ratio of approximately 1:1. Preferably, the sulfuric acid and said arylsulfonic acid and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 12:1 to 6:1. Also preferably, said arylsulfonic acid has a molecular weight below 300 g/mol. Also preferably, said arylsulfonic acid has a molecular weight below 150 g/mol. Even more preferably, said arylsulfonic acid is selected from the group consisting of: orthanilic acid; metanilic acid; sulfanilic acid; toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.
According to preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,673) comprises: sulfuric acid; a heterocyclic compound; an alkanesulfonic acid; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, said aqueous acidic composition comprising: sulfuric acid; a heterocyclic compound; an arylsulfonic acid; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, the arylsulfonic acid is toluenesulfonic acid.
Preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 28:1:1 to 2:1:1. More preferably, the sulfuric acid the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 24:1:1 to 3:1:1. Preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 20:1:1 to 4:1:1. More preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 16:1:1 to 5:1:1. According to a preferred embodiment of the present invention, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12:1:1 to 6:1:1. Also preferably, said heterocyclic compound has a molecular weight below 300 g/mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g/mol. Even more preferably, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; n-methylimidazole; and combinations thereof. Preferably, the alkanesulfonic acid is selected from the group consisting of:
According to preferred embodiment of the present invention, the modified Caro's acid (as disclosed in Canadian patent application 3,128,672) comprises: sulfuric acid; a carbonyl-containing nitrogenous base compound; and wherein sulfuric acid and said a carbonyl-containing nitrogenous base compound; are present in a molar ratio of no less than 1:1. According to a preferred embodiment of the present invention, the carbonyl-containing nitrogenous base compound is selected from the group consisting of: caffeine; lysine; creatine; glutamine; creatinine; 4-aminobenzoic acid; glycine; NMP (N-methyl-2-pyrrolidinone); histidine; DMA (N,N-dimethylacetamide); arginine; 2,3-pyridinedicarboxylic acid; hydantoin; and combinations thereof. Preferably, the sulfuric acid and said carbonyl-containing nitrogenous base compound and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 12:1 to 6:1.
The pyrolysis of biomass thermally decomposes the liquid portion of the biomass in the absence of air to produce a liquid (bio-crude) through the application of a high heat transfer rate to the biomass particles. The applicant's patented delignification process (using a modified Caro's acid) separates cellulose from the other biomass constituents (lignin and hemicellulose) at a recovery rate of +99% and can depolymerize lignin and hemicellulose into a liquid-rich organic liquid called Lignin-Hemicellulose-Depolymerized-Organics (LHDO). The applicant's LHDO contains virtually no aldehydes, and all carboxylic acids are converted once the LHDO is upgraded using hydrodeoxygenation (HDO). This eliminates the need for bio-crude aldehyde's role in bio-crude stability from thermal application or stability over time. Aldehydes present in pyrolysis bio-crude react with sugars to form higher-molecular-weight resins and oligomers via polymerization and condensation; oligomerization reactions lead to coke formation, which is highly undesirable in bio-crudes. Furthermore, the applicant's LHDO produces minimum and almost negligible char/coke during the HDO process and the upgraded LHDO is completely miscible with Jet and Diesel Fuels without the need for pre-treatment step used for pyrolysis bio-crude by oxidation followed by mild temperature hydrotreating stage to eliminate polymerization that occurred through during hydrocracking process.
It is noteworthy to point out that current pyrolysis of biomass generally yields a large amount of biochar (up to 30-40%). This is highly undesirable as biochar is low in value and the potential to use the remaining bio-crude as a fuel additive, which is the high value product, is greatly diminished due to the large amount of conversion of biomass into bio-char.
Preferably, said lignin-rich feedstock comprises more than 80 wt % of lignin-based compounds obtained from delignification of biomass. More preferably, said lignin-rich feedstock comprises more than 85 wt % of lignin-based compounds obtained from delignification of biomass. Even more preferably, said lignin-rich feedstock comprises more than 90 wt % of lignin-based compounds obtained from delignification of biomass. Yet even more preferably, said lignin-rich feedstock comprises more than 95 wt % of lignin-based compounds obtained from delignification of biomass. According to a preferred embodiment of the method of the present invention, the lignin-rich feedstock comprises more than 97.5 wt % of lignin-based compounds obtained from delignification of biomass.
In an application using a resulting stream obtained from a preferred embodiment of the process of the present invention, one can produce biofuel using a lignin-rich feedstock using a method comprising:
In the context of manufacture of bioethanol, it is to be understood that the presence of a low amount of hemicellulose (including but not limited to xylose) may still yield generally much improved yields in comparison to conventional cellulose which contains larger percentages of hemicellulose (including but not limited to xylose) scattered therein. For instance, since xylose is in general, the second most common sugar found in lignocellulosic biomass, it is expected that it be present in a range of 15-25% in a conventional pulp after delignification.
Preferably, the addition of a substantially free of xylose biomass additive allows for an increase in the generation of ethanol in a fermentation unit when the biomass additive is used as part of the organic waste being fermented or as the entire organic load in the fermentation unit. When converting cellulose to ethanol, it is preferable to have a biomass where the cellulose is substantially free of hemicellulose. Preferably, the biomass contains at most 10% of the original hemicellulose content from harvested lignocellulosic biomass. Preferably, the biomass contains at most 8% of the original hemicellulose content from harvested lignocellulosic biomass. Preferably, the biomass contains at most 6% of the original hemicellulose content from harvested lignocellulosic biomass. Preferably, the biomass contains at most 5% of the original hemicellulose content from said harvested lignocellulosic biomass. Preferably, the biomass contains at most 4% of the original hemicellulose content from said harvested lignocellulosic biomass. Preferably, the biomass contains at most 3% of the original hemicellulose content from said harvested lignocellulosic biomass. Preferably, the biomass contains at most 2% of the original hemicellulose content from the harvested lignocellulosic biomass. Preferably, the biomass additive contains at most 1% of the original hemicellulose content from said harvested lignocellulosic biomass. Preferably, the biomass contains at most 0.5% of said original hemicellulose content from the harvested lignocellulosic biomass.
When resorting to a biomass which was delignified using a modified Caro's acid and performed according to a process described herein, the remaining hemicellulose along with the cellulose can hover as low as 7.5 wt % or even less of the total weight of the pulp being used.
However, it is more desirable to separate out the lignin from the carbohydrate components of the lignocellulosic feedstock and, as such, incorporating a lignocellulosic feedstock post-treatment step using a caustic component adapted to dissolve hemicellulose from a mixture comprising mainly of hemicellulose and cellulose. The resulting hemicellulose content in the final solids content (comprising mainly cellulose) will be below 2 wt. %.
According to a preferred embodiment of the present invention, it has been observed that lowering the acidic content of the modified Caro's acid composition (mainly sulfuric acid, or methanesulfonic acid, depending on the modified Caro's acid blend used) will result in most of the lignin being removed in a first step with a lower removal of hemicellulose compared to a modified Caro's acid. After removal of the dissolved lignin and modified Caro's acid composition, a second step aimed at the removal of hemicellulose, using a caustic composition generates a distinct recoverable liquid stream of hemicellulose and a solid residual cellulose component. Preferably, since the modified Caro's composition has been modified, the chemicals used in the delignification of the lignocellulosic biomass are practically solely used for removing and solubilizing the lignin from the remaining biomass mixture. After the delignification is deemed sufficiently complete for the purposes of the operator, the solids (hemicellulose and cellulose) are separated from the liquid containing the modified Caro's acid as well as lignin fragments.
By using a post-treatment step to remove hemicellulose from the remaining delignified lignocellulosic components (lignin and cellulose), one can maximize the hemicellulose removal from the cellulose and minimize the peroxide consumption in the delignification step. The hemicellulose recovered is also mainly in its polysaccharide form contrary to conventional approaches where a high temperature acidic pre-treatment of lignocellulosic biomass does remove the hemicellulose from the biomass, but degrades it into xylose and its other constituents.
The process according to a preferred embodiment of the present invention uses two low temperature steps, including a low temperature post-treatment step to remove hemicellulose in the manner described herein also allows conventional enzymes or the like to be used to convert the extracted cellulose into ethanol. This also removes the necessity of finding a mixture of various enzymes capable of converting cellulose and xylose into ethanol, thus streamlining the process and ensuring a more efficient conversion of lignocellulosic biomass into ethanol.
According to a preferred embodiment of the present invention, there is provided a process capable of substantially separating out the three main constituents of lignocellulosic biomass.
According to a preferred embodiment of the present invention, there is provided a method capable of substantially separating out the three main constituents of lignocellulosic biomass and thus overcoming many difficulties encountered by previous methods.
Preferably, the process employs steps where the minimum input of energy is required in order to separate out said constituents. Preferably, the separation of the three constituents of biomass allows further processing for a number of applications which benefit from a higher purity of each of the constituents. This higher purity is meant to be understood as the hemicellulose being substantially free of cellulose and lignin; the cellulose being substantially free of hemicellulose and lignin; and lignin the being substantially free of cellulose and hemicellulose. Preferably, substantially free is meant to be understood as the main constituent being present in an amount of at least 90 wt % of total weight of the stream of interest, i.e., hemicellulose which is substantially free of cellulose and lignin would be understood as being a stream of hemicellulose which contains at least 90 wt % of hemicellulose, the same applying to the other streams. Preferably, substantially free is meant to be understood as the main constituent being present in an amount of at least 95 wt % of total weight of the stream of interest. Preferably, substantially free is meant to be understood as the main constituent being present in an amount of at least 96 wt % of total weight of the stream of interest. Preferably, substantially free is meant to be understood as the main constituent being present in an amount of at least 97 wt % of total weight of the stream of interest. Preferably, substantially free is meant to be understood as the main constituent being present in an amount of at least 98 wt % of total weight of the stream of interest. It is understood by those skilled in the art that when referring to hemicellulose, one refers to its polymeric form as well as its sugar constituents (i.e., xylose, arabinose, mannose, etc.).
In an application using a resulting stream obtained from a preferred embodiment of the process of the present invention, adding a cellulose-rich biomass which is essentially devoid of hemicellulose (which contains the xylose residues) enables one to increase the generation of ethanol from the fermentation of cellulose.
According to a preferred embodiment of the present invention, the cellulose obtained after the post-delignification caustic treatment is an unbleached cellulose which has a hemicellulose weight content of 3% wt. or lower. Preferably, the cellulose is obtained by the delignification of a lignocellulosic biomass feedstock through the exposure of such to a modified Caro's acid as per the following processes.
A preferred embodiment of the process to delignify biomass comprises the steps of:
Preferably, the removal of hemicellulose from hemicellulose-containing caustic solution consisting essentially of adding to said alkali solution a sufficient amount of a solvent consisting essentially of ethanol to precipitate said hemicellulose from said caustic alkali solution, removing the resulting precipitated hemicellulose from the caustic solution. Optionally, the caustic composition can be recovered and purified.
According to a preferred embodiment of the present invention, the modified Caro's acid composition must not comprise more than 40% by weight of H2SO4.
Preferably, said lignocellulosic biomass comprising lignin, hemicellulose and cellulose is exposed to a modified Caro's acid composition having a pH of less than 1, said modified Caro's acid composition selected from the group consisting of: composition A; composition B; composition C; composition D; composition E; composition F; composition G; composition H; composition I; and composition J;
wherein said composition A comprises:
According to a preferred embodiment of the present invention, exposing said biomass to said modified Caro's acid composition will allow the delignification reaction to occur and remove over 90 wt % of said lignin from said biomass.
Preferably, the delignification reaction is carried out at a temperature below 55° C. by a method selected from the group consisting of:
Preferably, the streams resulting from the above process according to a preferred embodiment of the present invention include: a stream rich in dissolved hemicellulose depolymerized during the caustic post-treatment; a cellulose stream comprising solid cellulose fibers; and a lignin-rich stream comprising the lignin removed from the remaining biomass.
According to a preferred embodiment of the method of the present invention, one advantage of this approach is that compared to other approaches using the entire biomass to generate biofuel, this approach focuses on the lignin-depolymerized organics (LDO) present within the lignin-rich stream. Consequently, the portion of aromatic carbons (present on lignin and lignin monomers, dimers and oligomers resulting from the delignification) is substantially higher than in the processes which employ the entire biomass (cellulose, lignin and hemicellulose). For example, in softwood trees, the proportion of cellulose is in the range of 40-50%, the percentage of lignin can range from 30-40% and the remaining balance is hemicellulose.
According to another aspect of the present invention, there is provided a process to perform a controlled exothermic delignification of lignocellulosic biomass, said process comprising the steps of:
According to a preferred embodiment of the method of the present invention, the stream of LDO/LHDO is exposed to a pH adjustment prior to undergoing upgrading.
According to a preferred embodiment of the method of the present invention, the stream of LDO/LHDO is substantially free of cellulose (i.e., less than 5 wt % cellulose). More preferably, the stream of LDO/LHDO contains less than 2 wt % cellulose. Even more preferably, the stream of LDO/LHDO contains less than 1 wt % cellulose. Yet even more preferably, the stream of LDO/LHDO contains less than 0.5 wt % cellulose. Yet even more preferably, the stream of LDO/LHDO contains less than 0.1 wt % cellulose.
In terms of hemicellulose removal, a caustic treatment post-delignification using a modified Caro's acid provides significant advantages in terms of energy input as the caustic treatment occurs at ambient temperatures; thus, requiring less energy than a high temperature pretreatment. In addition, the caustic post-treatment is less aggressive to the structural composition of hemicellulose than a conventional delignification using a modified Caro's acid as the reaction conditions of the delignification will cause the depolymerization and further decomposition of hemicellulose in a vast range of products (including but not limited to sugars, furfural derivatives, organic acids, etc.) that are difficult to separate and capitalize on from the stream of LHDO.
It is worthy of mention that almost all efforts for lignocellulosic biomass conversion into fuels have failed due to undesired interactions among the three main biomass constituents; cellulosic ethanol represents a clear example of the aforementioned, beside the undesired properties of pyrolysis bio-oil.
According to yet another aspect of the present invention, there is provided a process to delignify biomass and recover a liquid stream which is substantially pure lignin and/or lignin monomers (i.e. lignin-based compounds make up over 90 wt. % of the liquid stream), said process comprising the steps of:
According to yet another aspect of the present invention, there is provided a process to delignify biomass and recover a substantially hemicellulose free liquid stream of lignin and lignin monomers, said process comprising the steps of:
According to a preferred embodiment of the present invention, the lignocellulosic biomass comprising hemicellulose, lignin and cellulose is exposed to a modified Caro's acid composition selected from the group consisting of: said modified Caro's acid composition selected from the group consisting of: composition A; composition B; composition C; composition D; composition E; composition F; composition G; composition H; composition I; and composition J as described herein.
According to a preferred embodiment of the present invention, the lignocellulosic biomass mixture comprising hemicellulose, lignin, and cellulose is exposed to a modified Caro's acid composition for a period of time sufficient to a delignification reaction to occur and remove over 95 wt % of said lignin and preferably leaving in solid form most of the hemicellulose and cellulose from said biomass. Preferably, the stream of LHDO/LDO is removed upon completion of the delignification reaction for further processing into biofuel. It is highly desirable to improve the separation of the various constituents in such a way as to increase the percent concentration of the targeted constituent (be it cellulose, hemicellulose, lignin) depending on the treatment step. In a delignification step using a modified Caro's acid where the sulfuric acid content is above 40%, approximately 85% of the hemicellulose initially present in the biomass, will be removed during the delignification step and will be present with the lignin-derived products. When performing a delignification of the biomass according to a preferred embodiment of the present invention, it is estimated that only up to 60% of the hemicellulose initially present in the biomass will be dissolved during the delignification step and will end up intermixed with the lignin derived products. Decreasing the hemicellulose content present with the lignin is greatly desirable as the LDO with contain fewer sugars and produce a higher quality bio-oil.
Preferably, said compound comprising an amine moiety and a sulfonic acid moiety is selected from the group consisting of taurine; taurine derivatives; and taurine-related compounds.
Preferably, said taurine derivative or taurine-related compound is selected from the group consisting of: taurolidine; taurocholic acid; tauroselcholic acid; tauromustine; 5-taurinomethyluridine and 5-taurinomethyl-2-thiouridine; homotaurine (tramiprosate); acamprosate; and taurates as well as aminoalkylsulfonic acids, where the alkyl is selected from the group consisting of C1-C5 linear alkyl and C1-C5 branched alkyl. Preferably, said linear alkylaminosulfonic acid is selected from the group consisting of: methyl; ethyl (taurine); propyl; and butyl. Preferably, said branched aminoalkylsulfonic acid is selected from the group consisting of: isopropyl; isobutyl; and isopentyl.
According to a preferred embodiment of the present invention, said compound comprising an amine moiety and a sulfonic acid moiety is taurine.
According to a preferred embodiment of the present invention, said sulfuric acid and a compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3:1.
According to a preferred embodiment of the present invention, said compound comprising an amine moiety is an alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine; and combinations thereof.
Preferably, said compound comprising a sulfonic acid moiety is selected from the group consisting of: alkylsulfonic acids; arylsulfonic acids; and combinations thereof. Preferably, said alkylsulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from C1-C6 and are linear or branched; and combinations thereof. More preferably, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. According to a preferred embodiment of the present invention, said arylsulfonic acid is selected from the group consisting of: toluenesulfonic acid; benzesulfonic acid; and combinations thereof.
According to a preferred embodiment of the present invention, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is kept below 55° C. for the duration of the delignification reaction. Preferably, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is kept below 50° C. for the duration of the delignification reaction. According to another preferred embodiment of the present invention, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is kept below 45° C. for the duration of the delignification reaction. According to a preferred embodiment of the present invention, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is kept below 40° C. for the duration of the delignification reaction.
According to a preferred embodiment of the present invention, the temperature of the remaining biomass mixture is controlled throughout the delignification reaction to subsequent additions of a solvent (water) to progressively lower the slope of temperature increase per minute from less than 1° C. per minute to less than 0.5° C. per minute.
According to another preferred embodiment of the present invention, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is controlled by an addition of a solvent (water) to reduce the slope of temperature increase per minute of the reaction mass to less than 1° C. per minute.
According to yet another preferred embodiment of the present invention, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is controlled by a second addition of a solvent (water) to reduce the slope of temperature increase per minute of the reaction mass to less than 0.7° C. per minute.
Preferably, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is controlled by a third addition of a solvent (water) to reduce the slope of temperature increase per minute of the reaction mass to less than 0.3° C. per minute.
Preferably, the temperature of the lignocellulosic biomass mixture comprising hemicellulose, lignin and cellulose is controlled by a fourth addition of a solvent (water) to reduce the slope of temperature increase per minute of the reaction mass to less than 0.1° C. per minute.
According to a preferred embodiment of the present invention, the kappa number of the resulting cellulose is below 10, preferably it is below 5.
According to a preferred embodiment of the present invention, there is provided a process to delignify biomass using an aqueous acidic composition comprising:
According to another preferred embodiment of the present invention, there is provided a process to delignify biomass using an aqueous acidic composition comprising:
Preferably, the sulfuric acid and said heterocyclic compound are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12:1 to 6:1.
Also preferably, said heterocyclic compound has a molecular weight below 300 g/mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g/mol. More preferably, said heterocyclic compound is a secondary amine. According to a preferred embodiment of the present invention, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; and N-methylimidazole.
According to an aspect of the present invention, there is provided a process to delignify biomass, such as wood using an aqueous acidic composition comprising:
Preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 1:1:1. Also preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no more than 15:1:1.
According to a preferred embodiment of the present invention, said sulfuric acid and said compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3:1.
According to a preferred embodiment of the present invention, said compound comprising an amine moiety and a sulfonic acid moiety is selected from the group consisting of: taurine; taurine derivatives; and taurine-related compounds.
According to a preferred embodiment of the present invention, said taurine derivative or taurine-related compound is selected from the group consisting of: taurolidine; taurocholic acid; tauroselcholic acid; tauromustine; 5-taurinomethyluridine and 5-taurinomethyl-2-thiouridine; homotaurine (tramiprosate); acamprosate; and taurates; as well as aminoalkylsulfonic acids where the alkyl is selected from the group consisting of C1-C5 linear alkyl and C3-C5 branched alkyl. Preferably, said linear alkylaminosulfonic acid is selected from the group consisting of: methyl; ethyl (taurine); propyl; and butyl.
Preferably, said branched aminoalkylsulfonic acid is selected from the group consisting of: isopropyl; isobutyl; and isopentyl.
According to a preferred embodiment of the present invention, said compound comprising an amine moiety and a sulfonic acid moiety is taurine.
According to a preferred embodiment of the present invention, said sulfuric acid and a compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3:1.
According to a preferred embodiment of the present invention, said compound comprising an amine moiety is an alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine; and combinations thereof.
According to a preferred embodiment of the present invention, said compound comprising a sulfonic acid moiety is selected from the group consisting of: alkylsulfonic acids and combinations thereof.
According to a preferred embodiment of the present invention, said alkylsulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from C1-C6 and are linear or branched; and combinations thereof.
According to a preferred embodiment of the present invention, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof.
According to a preferred embodiment of the present invention, said alkylsulfonic acid; and said peroxide is present in a molar ratio of no less than 1:1.
According to a preferred embodiment of the present invention, said compound comprising a sulfonic acid moiety is methanesulfonic acid.
According to a preferred embodiment of the present invention, in Composition C, said sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1:1:1.
According to a preferred embodiment of the present invention, in Composition C, said sulfuric acid, said compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio ranging from 28:1:1 to 2:1:1.
The following experimentation was conducted using canola straw as the biomass feedstock. The canola straw was characterized to determine the content of acid-insoluble lignin (also known as Klason lignin) as well as carbohydrate composition. The carbohydrate composition gives an indication of cellulose and hemicellulose distribution within the biomass. Results of the characterization of the canola straw are shown in Table 1.
The following experimentation was conducted using canola straw as the biomass feedstock. The canola straw was characterized to determine the content of acid-insoluble lignin (also known as Klason lignin) as well as carbohydrate composition. The carbohydrate composition gives an indication of cellulose and hemicellulose distribution within the biomass. Results of the characterization of the canola straw are shown in Table 1.
The canola biomass was exposed to a delignification reaction according to the method described herein. Different blends comprising a modified Caro's acid composition consisting of H2SO4:H2O2:taurine were prepared. The blends all have the same 10:10:1 molar ratio between the components, but where the acid concentration was varied between 43 and 30% wt. of the blend. Details of the blends are shown in Table 2. As the mixing releases a large amount of heat, the beakers were placed in an ice bath. The pH of the resulting composition was less than 0.5. Canola was then added into each of the blends as 3% wt. solids loading (9 g). The reaction was left stirring at 35° C. for 3 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. Table 2 shows the yield of solid cellulose for the delignification reactions of canola biomass at different acid concentration as % of the initial biomass. Hydrogen peroxide consumption in the reaction is an important metric as it is the only chemical consumed in the reaction and determines chemical consumption in large scale facilities. During these reactions, hydrogen peroxide was monitored. Table 2 shows the hydrogen peroxide consumption for each delignification reaction as % of the cellulose solids recovered. Kappa number or lignin content is typically used to ascertain the efficiency of the delignification. Kappa number is a test method that determines the amount of lignin remaining in a pulp sample and thus provides information as to the degree of delignification. Table 2 shows the Kappa number of the cellulose obtained from each delignification reaction.
Table 2 shows that as the acid concentration decreases, the cellulose yield increases and so does the Kappa number. This is expected since as the acid concentration is reduced, the reactivity of the modified Caro's acid decreases, thus leading to a less efficient delignification. This is further evidenced by the increase in cellulose yield and the increase in Kappa number, which indicates that more lignin and hemicellulose is left behind with the solids. However, there is a point where the peroxide consumption is lowered enough to result in significant financial savings, while the delignification efficiency losses are not significant. This point makes the economics of the process more attractive.
The following experimentation was conducted using hardwood as the biomass feedstock. The hardwood was characterized to determine the content of acid-insoluble lignin (also known as Klason lignin) as well as carbohydrate composition. The carbohydrate composition gives an indication of cellulose and hemicellulose distribution within the biomass. Results of the characterization of the hardwood are shown in Table 3.
The hardwood was exposed to a delignification reaction according to the method described herein. Different blends comprising a modified Caro's acid composition consisting of H2SO4:H2O2:taurine were prepared. The blends all have the same 10:10:1 molar ratio between the components, but where the acid concentration was varied between 43 and 30% wt. of the blend. Details of the blends are shown in Table 4. Hardwood was then added into each of the blends as 3% wt. solids loading (9 g). The reaction was left stirring at 35° C. for 3 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. Table 4 shows the yield of solid cellulose for the delignification reactions of hardwood at different acid concentration as % of the initial biomass, the hydrogen peroxide consumption for each delignification reaction as % of the cellulose solids recovered as well as the Kappa number of the cellulose obtained from each delignification reaction.
Table 4 confirms the trend observed previously for canola, whereas the acid concentration decreases, the cellulose yield increases and so does the Kappa number. More importantly, the hydrogen peroxide consumption decreases significantly where it allows the determination of a more economically viable reaction.
Canola biomass was exposed to two different delignification reaction according to the method described herein using two different acid concentrations 38.0 and 43.4 wt. % in a 1600 and 2700 kg scale reaction, respectively. Details of the blends are shown in Table 5. Canola was added into each of the blends as 3% wt. solids loading. The reaction was left stirring for 24 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. Table 5 shows the yield of solid cellulose for the delignification reactions of canola biomass at different acid concentration as % of the initial biomass as well as hydrogen peroxide consumption as % of the initial biomass and Kappa number for the cellulose solids obtained from each delignification reaction.
Table 5 shows that as the acid concentration decreases, the cellulose yield increases. In terms of peroxide consumption, it decreases by 34% with respect to the modified Caro's acid with 43.4% wt. acid concentration. However, at larger scale, pulping effects are not as significant as indicated by the same Kappa number in both runs, likely due to optimized mixing and longer reaction times. This shows that it is likely that the increase in cellulose yield is due to unreacted hemicellulose remaining with the cellulose solids.
Cellulose solids were characterized before and after being exposed to a caustic solution at 8.5% wt. NaOH at a loading of 3 g oven-dry per 100 mL of caustic. The caustic treatment lasted 1 hour at room temperature, after which the solid portion was separated from the liquid via filtration. The rest of the cellulose characterization are shown in Table 6.
Table 6 highlights that the caustic treatment not only it dissolves the hemicellulose, but it also aids in removing any remaining lignin content within the cellulose solids. The liquid is expected to mostly contain dissolved hemicellulose. It is understood by those skilled in the art that when referring to hemicellulose, one refers to its polymeric form as well as its sugar constituents (i.e., xylose, arabinose, mannose, etc.) and other decomposition products.
The canola straw cellulose solids obtained from Experiment #1 were analyzed to determine their content of undegraded cellulose, degraded cellulose, and hemicellulose respectively, denoted as α-, β-, and γ-cellulose content using TAPPI T203. It was expected that more hemicellulose would be removed with increasing acid concentration in the delignification blend. Table 7 shows the results of the test performed on the dry delignified cellulose solids as well as the calculated hemicellulose recovery, obtained from comparing the actual hemicellulose in the solids with the theorical amount of hemicellulose in the initial biomass and the yield of delignification.
Table 7 shows that as acid concentration in the delignification blend increases, the blend becomes more reactive and it degrades more of the hemicellulose portion in the biomass, as indicated by the lower hemicellulose content remaining in the solid product. This is an important finding as it suggests that the parameters of the delignification described herein can be altered to favour more or less degraded hemicellulose as desired based on the intended application. It is known to those skilled in the art that pulps with higher hemicellulose content are more suitable for applications where higher pulp strength is sought after, such as in paper-marking facilities, while low hemicellulose pulps are desirable for applications where its presence is less desired, such as in the pharmaceutical, food, and textiles industries.
Table 7 also displays a trend in the degradation of pure cellulose. As the acid concentration in the blend increases, more cellulose is being degraded to a lower-molecular weight, more degraded cellulose known as β-cellulose (ratio of α-cellulose to β-cellulose lowers from 16.5 at 35.0° C. to 11.7 at 43.0° C., displaying lower alpha-cellulose in the cellulosic portion). This is understood to be due to the function of increasing acid concentration being more reactive to attack the glycosidic bonds in cellulose and break down the cellulosic polymer at its amorphous regions. Amorphous regions of cellulose are more susceptible to acid hydrolysis. The apparent increase in alpha-cellulose with acid concentration is due to the degradation of hemicellulose and thus lowering of that portion within the solids.
Sugarcane bagasse was exposed to a low acid delignification reaction containing 37.5% wt. acid according to the method described herein. Sugarcane bagasse was added into the reactor as 3% wt. solids loading. The reaction was left stirring for 24 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. After delignification, the cellulose was treated with a caustic treatment that dissolves the degraded cellulose and the hemicellulose content of the cellulose solids. The treatment was conducted by suspending 973.21 g of wet cellulose (18.5% wt. solids) in 9% wt. NaOH for 2 hours at room temperature while stirring at 150 rpm. The solids obtained after neutralization and washing were analyzed cellulose and hemicellulose content using TAPPI T203. The results of this test are summarized in Table 8 along with the analysis of the cellulose prior to caustic treatment.
Table 8 shows that the caustic treatment is able to dissolve more than 80% of the hemicellulose present in the sample and can be used successfully post-delignification to fractionate cellulose and hemicellulose through the dissolution of the hemicellulose, as indicated by the decrease in % wt. in the solids following the caustic treatment. The cellulose obtained was characterized by FT-IR and compared to a standard of microcrystalline cellulose to ascertain purity (
It is known to those skilled in the art that a number of different precipitation and separation techniques may be employed for the isolation of the dissolved hemicellulose from the solvent. By way of example, two different techniques were used herein to demonstrate the ability to separate and isolate the dissolved hemicellulose as a pure separate stream. In a first example, the solution with the dissolved hemicellulose was evaporated under reduced pressure using a rotary evaporator.
In a second example, the solution with the dissolved hemicellulose was concentrated under reduced pressure to increase the concentration of hemicellulose in the sample. Once the sample had been concentrated, a certain amount of ethanol was added to the solution to promote the re-precipitation of the hemicellulose. Ethanol was added stepwise increasing the ethanol concentration of the mixture from 15 to 60% vol. After each ethanol additions, the corresponding hemicellulose solids were collected.
In kraft pulping, about 90% of the lignin present in the processed biomass is dissolved and removed therefrom. Kraft pulp also contains hemicellulose fragments (containing xylose) which are detrimental to the proper performance of a fermentation unit. In fact, Kraft pulping dissolves only between 40 to 60% of the hemicellulose initially present in the lignocellulosic feedstock. Therefore, it is clear that the implementation of a process according to a preferred embodiment of the present invention overcomes some of the shortcomings of the state-of-the art to produce bioethanol on a large scale using lignocellulosic biomass (or feedstock). Moreover, large-scale implementation of a preferred embodiment of the method of the present invention as taught herein will allow large-scale bioethanol production from lignocellulosic biomass rather than from starches (such as corn).
According to a preferred embodiment of the present invention, the lignocellulosic biomass is exposed to the modified Caro's acid when it is in chips ranging in size of up to 5 cm, preferably up to 3 cm and more preferably ranging between 1 and 2 cm. The water content of the biomass can vary greatly from below 10% to close to 50% and while water content does not affect the delignification reaction, operators have to make adjustments to account for the water in said biomass prior to treating such.
While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by those skilled in the relevant arts, once they have been made familiar with this disclosure that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 3224381 | Dec 2023 | CA | national |
