Patent Application
20240025871
The present invention relates to methods and systems for production of furfural from a xylose-containing solution.
Furfural plays an important role in the chemical industry as a precursor of furan and derivatives of furan, including furfuryl alcohol. Also, furfural is used for the production of resins by condensation reaction of furfural with formaldehyde, phenol, acetone or urea. In addition, furfural can be used as a solvent, vulcanization enhancer, insecticide, fungicide, germicide, or in the production of such compounds, as well as for use as a potential fuel.
Furfural is an attractive compound because it can be produced from renewable resources. One potential source of renewable (non-fossil) feedstock for the production of furfural are substances selected from the group consisting of xylose, oligosaccharides comprising xylose units and polysaccharides comprising xylose units originating from cellulose-containing biomass.
Xylose is a monosaccharide also referred to as wood sugar which belongs to the group of pentoses. Oligo- and polysaccharides which comprise xylose units typically occur in plants, especially in woody parts of plants, in straw, and in the seeds or the shells of the seeds of several plants. Oligo- and polysaccharides which consist of xylose units are generally referred to as xylans. Oligo- and polysaccharides which consist of xylose units and other monosaccharide units are generally referred to as heteroxylans. Xylans and heteroxylans belong to the group of polyoses. Polyoses (earlier also referred to as hemicellulose) are polysaccharides which in plant biomass typically occur in a composite wherein said polyoses and lignin are incorporated between cellulose fibres. Dry plant biomass (water content below 15 wt.-%) which comprises cellulose, polyoses and lignin is also referred to hereinabove and hereinbelow as lignocellulose.
One general process to produce furfural from xylose in biomass material is “aqueous dehydration” using batchwise or continuous acid-catalysed dehydration. This type of aqueous dehydration process provides a yield of about 30-50 mol % furfural (meaning only 30-50% of the total moles of xylose is converted to furfural) (Furfural—a promising platform for lignocellulosic biofuels by J.-P. Lange, E. van der Heide, J. van Buijtenen, R.J. Price, ChemSusChem 2012, 5, 150-166). With such low yields, it degrades 50-70 mol % of the valuable xylose into undesirable by-products that foul equipment and contaminate the water stream.
Another general process which has improved yields over aqueous dehydration is “biphasic dehydration,” which adds a water-insoluble solution to the aqueous dehydration to extract the furfural into an organic phase to protect it from further degradation, and optionally a salt in the aqueous phase to further assist the extraction of furfural into the water-insoluble solution (Lange et al. 2012). While biphasic dehydration can increase the yield to 60 to 70 mol %, it still degrades 30 to 40 mol % of the valuable xylose into undesirable by-products that foul equipment and build up in the solvent recycle stream.
Yet another process with improved yields over biphasic dehydration is to extract and recover xylose as a solid product from hydrolysis of biomass and subjecting the recovered xylose in a dehydration reaction (B. R. Caes, R. T. Raines, ChemSusChem 2011, 4, 353-356; L. Shuai, J. Luterbacher, ChemSusChem 2016, 9,133-155). Because the xylose is not in solution, the dehydration reaction can be carried out in a single phase under conditions favourable to the furfural conversion, such as using polar aprotic solvents which can provide furfural yields of 90 mol %. However, this process requires isolation of the xylose from the hydrolysate, e.g., by distilling out all the water, which can be highly energy demanding. Such isolation process to recover the xylose in solid form can further concentrate contaminants of the xylose streams in the solid xylose end product.
Although there are processes to provide improved isolation xylose from hydrolysate, such as (U.S. Ser. No. 10/407,453), these processes nonetheless, are directed to providing the xylose in dry form to allow the xylose to then be converted and/or used in the production of a C5 sugar-platform of biochemical and biofuels.
It would, therefore, be advantageous to provide a process for the production of furfural from a xylose-containing aqueous solution with a relatively higher yield without expensive isolation of xylose in dry form.
Accordingly, the present invention provides a process for a method for producing furfural comprising:
The present disclosure also provides for a method for producing furfural comprising:
Optionally, step (i) comprises providing at least a portion of the second non-aqueous phase from (h) to a distillation process to recover an overhead product comprising furfural and a bottom product comprising water-insoluble solvent and water-insoluble boronic acid. Optionally, the method further comprises providing at least a portion of the bottom product for use as part of the extraction solution. Optionally, at least a portion of the first aqueous phase in (c) comprises water-soluble solvent, water-insoluble solvent, and water-insoluble boronic acid, said method further comprising: separating at least a portion of the first aqueous phase in (c) from the first combined solution; and further processing at least a portion of the separated first aqueous phase to recover at least one of water-soluble solvent, water-insoluble solvent, and water-insoluble boronic acid.
Optionally, the method further comprises performing at least a portion of steps (c) and (d) in a liquid-liquid extraction unit in counter-current operation, wherein the xylose-containing solution is provided at a higher temperature than the temperature of the extraction solution.
Optionally, the method further comprises providing at least a portion of the second aqueous phase from (h) to a distillation process to recover an overhead product comprising water and furfural and an acidic bottom product comprising water and water-soluble solvent, wherein the bottom product has a pH of less than 7. Optionally, the method further comprises providing at least a portion of the acidic bottom product for use as part of the conversion solution.
Optionally, the method further comprises providing at least a portion of the second aqueous phase from (h) to a solvent-extraction process to recover furfural, wherein at least a portion of solvent used in the extraction process comprises the distillation bottom product comprising water-insoluble solvent and water-insoluble boronic acid.
Optionally, the xylose-containing solution is a hydrolysate. Optionally, the water-insoluble boronic acid has up to 5 wt. % solubility in water at 20° C. Optionally, the water-insoluble boronic acid is selected from the group consisting of phenylboronic acid, 4-biphenylboronic acid, 4-butylphenyl boronic acid, 4-tert-Butylphenyl boronic acid, 4-ethylphenyl boronic acid, 2-naphthylboronic acid, naphthalene-1-boronic acid, o-tolylboronic acid, m-tolylboronic acid, (2-methylpropyl) boronic acid, butylboronic acid, octylboronic acid, phenethyl boronic acid, cyclohexyl boronic acid, and any combination thereof. Optionally, the water-insoluble solvent has up to 5 wt. % solubility in water at 20° C. Optionally, the water-insoluble solvent is selected from the group consisting of benzoic acid, cresol (m), di-isopropyl ether, terephthalic acid, diethylene glycol diethyl ether, anisole, salicylic acid, 2,6 xylenol, 4Et-phenol, toluene, benzofuran, ethylbenzene, octanoic acid, 1-methylnaphtalene, nitrobenzene, guaiacol, heptane, 1-octanol, and methyl-isobutyl ketones, an any combination thereof. Optionally, at least one of the water-insoluble boronic acid and water-insoluble solvent has a boiling point higher than that of furfural, preferably at least 5° C. higher. Optionally, the water-soluble solvent has a logP (octanol-water partition co-efficient) in a range from (−3) to 0. Optionally, the water-soluble solvent is selected from the group consisting of dimethyl sulfoxide, diglyme, sulfolane, gamma butyrolactone, succinic acid, nMe-acetamide, dioxane, nMe-pyrrolidone, gamma valerolactone, acetone, Acetic acid, and any combination thereof. Optionally, the water-soluble solvent has a boiling point higher than that of water, preferably at least 5° C. higher.
The present invention will now be described in detail with reference to embodiments thereof as illustrated in the accompanying drawings. References to “one embodiment”, “an embodiment” “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the art, are within the spirit and scope of the invention.
Although the description herein provides numerous specific details that are set forth for a thorough understanding of illustrative embodiments, it will be apparent to one skilled in the art that embodiments may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. The features and advantages of embodiments may be better understood with reference to the drawings and discussions that follow.
In addition, when like elements are used in one or more figures, identical reference characters will be used in each figure, and a detailed description of the element will be provided only at its first occurrence. Some features or components of the systems or processes described herein may be omitted in certain depicted configurations in the interest of clarity. Moreover, certain features such as, but not limited to pumps, valves, gas bleeds, gas inlets, fluid inlets, fluid outlets and the like have not necessarily been depicted in the figures, but their presence and function will be understood by one having ordinary skill in the art. Similarly, the depiction of some of such features in the figures does not indicate that all of them are depicted.
The present inventors have surprisingly found that xylose in an aqueous solution can be extracted as xylose-diboronate ester (BA2X) into the non-aqueous phase of an extraction solution comprising a water-insoluble solvent and a water-insoluble boronic acid, and the non-aqueous phase can be separated for conversion or dehydration of the xylose-diboronate ester (BA2X) into furfural with an acidic conversion solution comprising water and a water-soluble solvent. The furfural can then be recovered using any suitable methods. Optionally, instead of or in addition to making furfural, the xylose-diboronate ester (BA2X) in the separated non-aqueous phase can be back-extracted into xylose to recover the xylose away from impurities or other undesired compounds that may be present in the initial xylose solution.
As used herein, “aqueous solution” has its ordinary meaning, which is a solution in which a solute is dissolved in a solvent, and the solvent is water. “Water-insoluble” also has its ordinary meaning, which describes the low solubility of a substance in water. Low solubility means preferably up to 5 wt. % solubility at 20° C., including up to 2 wt. % solubility, up to 1 wt. % solubility, up to 0.5 wt. % solubility, or up to 0.1 wt. % solubility. Alternatively, “water-insoluble” as used herein describes a substance with an octanol-water partition coefficient LogP (also called LogKow) of at least 1, including at least 2, or at least 3. “Water-soluble” as used herein describes a substance with a LogP in a range from (−3) to 0, preferably from (−2.5) to (−0.5), more preferably (−2.0) to (−1.0). “Aqueous phase” has its ordinary meaning, which describes a liquid phase in which the concentration of water is greater than the concentration of water-insoluble liquid component(s). “Non-aqueous” has its ordinary meaning, which describes a liquid phase in which the concentration of water-insoluble liquid component(s) is greater than the concentration of water.
The present disclosure provides for a process for producing furfural comprising:
In addition, the present disclosure also provides for a method for producing furfural comprising:
Referring to
The process described herein can be suitable for use with a xylose-containing aqueous solution with any pH, from 1 to 14. That is, the process described herein can be used with xylose-containing aqueous solution 102 that is acidic with a pH in a range from 1 to 6, xylose-containing aqueous solution 102 that is basic with a pH in a range of 8 to 14, or xylose-containing aqueous solution 102 that is neutral with a pH from greater than 6 to less than 8.
While any xylose-containing solution as described herein may be provided for use in the process, a suitable xylose-containing solution 102 can include one that is derived from a pre-treatment step in which a cellulosic biomass is hydrolysed by methods known by one of ordinary skill in the art, including hot water at neutral pH (e.g. steam explosion), hot water at acidic pH e.g. by addition of organic or inorganic acids (e.g. dilute acid and reversible-acid pre-treatment), or hot water at basic pH e.g. by addition of organic or inorganic base (e.g. kraft pulping), as described e.g. by Steinbach, Kruse, Sauer, Biomass Cony. Bioref. (2017) 7:247-274, as well as those methods that employ ionic liquids.
In a preferred embodiment the term “cellulosic biomass” refers to biomass comprising a) cellulose as well as b) one or more substances selected from the group consisting of polyoses and other sources of xylose units. For example, lignocellulose is cellulosic biomass that can serve as a source of xylose units. Suitable cellulosic biomass, particularly lignocellulose, includes any material and/or agricultural biomass having a lignocellulose (or hemicellulose) concentration of at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, or at least 50%. Exemplary lignocellulosic biomasses that can be used in this regard include, but are not limited to: corn cobs, crop residues such as corn husks, corn stover, grasses, wheat, wheat straw, barley straw, hay, rice straw, switchgrass, waste paper, sugar cane bagasse, sorghum, components obtained from milling of grains, trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes, vegetables, fruits, flowers and animal manure, soy hulls from soybean processing, rice hulls from rice milling, corn fibre from wet milling or dry milling, bagasse from sugarcane processing, pulp from sugar beets processing, distillers grains, and the like.
Suitably, the pretreatment step as described in WO2016025678 and WO2016025679 can be used to hydrolyse cellulosic biomass to produce a xylose-containing solution that may be used in the process described herein. As noted above, such product of hydrolysis may be referred to as a hydrolysate, which comprises xylose in an amount of at least 0.5 wt. %, including preferably at least 1.0 wt. %, at least 2.0 wt. %, or most preferably at least 3.0 wt. %.
Preferably, xylose-containing aqueous solution 102 may be a product of an acidic pre-treatment based on diluted H2SO4 or concentrated HESA as acid, as described in U.S. Pat. No. 9,290,821, the content of which is incorporated by reference in its entirety.
Xylose-containing solution 102 is an aqueous solution, which means it is a solution in which the solvent is liquid water.
Referring to
A suitable water-insoluble boronic acid is one with low water solubility, preferably up to 5 wt. % solubility (meaning the selected water-insoluble boronic acid is soluble up to 5 wt. % in water at 20° C.), including up to 2 wt. % solubility, up to 1 wt. % solubility, up to 0.5 wt. % solubility, or up to 0.1 wt. % solubility. Alternatively, a suitable water-insoluble boronic acid is one with an octanol-water partition coefficient LogP (also called LogKow) of at least 1, including at least 2, or at least 3.
In a preferred embodiment, a suitable water-insoluble boronic acid has an atmospheric boiling point that is higher than the atmospheric boiling point (Tb) of furfural, which is 162° C., to allow for use of distillation as an option for recovery of furfural as an overhead product. Preferably, the suitable water-insoluble boronic acid has an atmospheric boiling point that is at least 2° C. higher (i.e., atmospheric boiling point of at least 164C), more preferably at least 5° C. (i.e., atmospheric boiling point of at least 167C).
For instance, one exemplary suitable water-insoluble boronic acid is phenyl boronic acid, which has a water solubility of 1 wt. % at 20° C. and a logP of 1.59 and an atmospheric boiling point Tb of 265° C. Other substituted phenyl boronate compounds are also suitable, such as alkyl phenyl boronate, naphthanyl boronate and substituted naphthanyl boronate, and any combination thereof. For example, one suitable example is 2-napthyl boronic acid, which has a water solubility of 0.03 wt. % at 20° C. and a logP of 2.82 and a Tb of 382° C. Another example is octylboronic acid which is reported as water-insoluble and has a logP of 3.56 and a Tb of 262° C.
Table 1 below shows examples of suitable water-insoluble boronic acid that can be used in extraction solution 104, along with their solubility description and/or LogP, and atmospheric boiling point (Tb).
One or more (such as two or more) suitable water-insoluble boronic acid as described here can be used in extraction solution 104 as described herein based on design choices by one of ordinary skill in the art. While certain descriptions may refer to “a water-insoluble boronic acid,” “the water-insoluble boronic acid,” or “the boronic acid,” it is understood that such reference can include more than one (such as two or more) water-insoluble boronic acids, as applicable.
Referring to
In a preferred embodiment, a suitable water-insoluble solvent has an atmospheric boiling point that is higher than the atmospheric boiling point of furfural, which is 162° C., to allow for use of distillation as an option for recovery of furfural as an overhead product. Preferably, the suitable water-insoluble boronic acid has an atmospheric boiling point that is at least 2° C. higher (i.e., atmospheric boiling point of at least 164° C.), more preferably at least 5° C. (i.e., atmospheric boiling point of at least 167° C.).
In a preferred embodiment, the water-insoluble solvent has a good affinity for the xylose-diboronate ester and a good affinity for furfural. By affinity we mean a high partition coefficient of the BA2X or furfural between extraction solution 104 and water in first combined solution 106 (described further below), including such partition coefficient of at least 0.1, preferably at least 0.5, preferably at least 1.0, and most preferably at least 2.
Examples of suitable water-insoluble solvent that have good affinity for the xylose-diboronate ester and a good affinity for furfural include aromatic hydrocarbons, preferably toluene and most preferably methyl naphthalene or aromatic mixtures rich in alkylbenzene or alkyl-naphthalene components. Water-insoluble solvent also include aromatic components that carry heteroatoms such as nitrobenzene, anisole, guaiacol, cresols, as well as aliphatic components free of heteroatoms (e.g., heptane and other alkanes) or containing heteroatoms (e.g., 1-octanol, methylisobutyl ketones)
Table 2 below shows examples of suitable water-insoluble solvents that can be used in extraction solution 104, along with their solubility (LogP) and atmospheric boiling point (Tb).
One or more (such as two or more) suitable water-insoluble solvents as described here can be used in extraction solution 104 as described herein based on design choices by one of ordinary skill in the art. While certain descriptions may refer to “a water-insoluble solvent” or “the water-insoluble solvent,” it is understood that such reference can include more than one (such as two or more) water-insoluble solvents, as applicable.
Suitably, extraction solution 104 can comprise at least 1 wt. %, including at least 5 wt. %, at least 10 wt. %, or at least 20 wt. % of the water-insoluble boronic acid and up to 99 wt. %, including up to 95 wt. %, up to 90 wt. %, or up to 80 wt. % of the water-insoluble solvent.
Referring to
When xylose-containing solution 102 is combined with extraction solution 104 to form first combined solution 106, at least a portion of the xylose from solution 102 comes into contact with at least a portion of organic boronic acid from solution 104. This contact allows the xylose to be converted to xylose monoboronate and subsequently xylose-diboronate ester, which has low solubility in water, so it has a greater affinity toward the water-insoluble solvent of solution 104 that is in solution 106. As more xylose is converted to xylose-diboronate esters, non-aqueous phase 110 comprising (i) boronic acid and water-insoluble solvent from extraction solution 104 and (ii) xylose-diboronate esters begins to form. Correspondingly, aqueous phase 108 with less xylose than xylose-containing solution 102 begins to form as well.
After an amount of time, which can be determined or selected by one of ordinary skill to achieve certain desired objectives, first combined solution 106 comprises aqueous phase 108 and a non-aqueous phase 110, said non-aqueous phase comprising at least a portion of the xylose from xylose-containing solution 102 as xylose-diboronate ester (BA2X). Preferably, non-aqueous phase 110 comprises at least 20 mol % of the xylose from xylose-containing solution 102 as xylose-diboronate ester, more preferably at least 50 mol %, including at least 70 mol % or at least 90 mol %.
Preferably, first combined solution 106 is mixed using suitable methods, such as mixing, stirring, static mixer, turbulent flow, jet loop, etc to allow xylose and organic boronic acids molecules to interact, thereby improving the yield of xylose-diboronate-ester that forms. Examples of suitable methods for mixing can additionally or alternatively include internal components of the separation or extraction units noted above. Suitably, the mixing may be performed for at least 30 minutes, preferably at least 60 minutes, and most preferably at least 90 minutes.
Referring to
After at least a portion of the xylose in first combined solution 106 has been allowed to react to form xylose-diboronate esters and first combined solution 106 comprises aqueous phase 108 and non-aqueous phase 110, the phases 108 and 110 can be separated using suitable methods, such as liquid-liquid extraction or separation methods, suitably in co-current flow and preferably counter-current flow. It is understood by one of ordinary skill that aqueous phase 108 can contain an amount of water-insoluble boronic acid and water-insoluble solvent from extraction solution 104 but the concentration of water in aqueous phase 108 is higher than the concentration of water-insoluble components from extraction solution 104. Similarly, it is understood that non-aqueous phase 110 can contain an amount of water but the concentration of water-insoluble boronic acid and water-insoluble solvent in non-aqueous phase 110 is higher than the concentration of water.
Such extraction or separation methods can be performed using a series of mixers-decanters but can also be performed in a unit or series of units that integrates mixing and decanting and is preferably operated in counter current flow. Such unit can optionally contain internal components to facilitate the mixing and decanting, including stationary components (trays, random or structured packings) or agitators (e.g., rotating or oscillating disks).
Referring to
In one embodiment, forming of first combined solution 106 and separating of non-aqueous phase 110 can be performed isothermally (e.g., temperature is the same for both steps). Additionally, or alternatively, they can be performed under a temperature gradient. One suitable way of providing a temperature gradient is to provide xylose-containing solution 102 at a higher temperature than extraction solution 104. For instance, the temperature of xylose-containing solution 102 can be at least 5° C. higher than the temperature of extraction solution 104, preferably at least 10° C. higher, more preferably at least 15° C. higher, and most preferably at least 20° C. higher. Referring to
Referring to
Conversion solution 112 comprises water and a water-soluble solvent. Suitably, the amount of water-soluble solvent in conversion solution is in a range of 1 wt. % to 95 wt. %, preferably from 10 wt. % to 90 wt. %, more preferably from 20 wt. % to 80 wt. %, and most preferably from 30 wt. % to 70 wt. %. Suitably, the water-soluble solvent has a LogP (octanol-water partition co-efficient) in a range from (−3) to 0, preferably from (−2.5) to (−0.5), more preferably (−2.0) to (−1.0), which facilitate solubilizing of the water-insoluble solvent in water.
One or more water-soluble solvents may be used in aqueous conversation solution 112 as described herein based on design choices by one of ordinary skill in the art. While certain descriptions may refer to “a water-soluble solvent” or “the water-soluble solvent,” it is understood that such reference can include more than one (such as two or more) water-insoluble solvents, as applicable. Examples of suitable water-soluble solvent include dioxane, GVL (gamma-valerolactone), dimethyl sulfoxide (DMSO), and sulfolane, and any combination thereof.
Table 3 below shows examples of suitable water-soluble solvents that can be used in conversion solution 112, along with their solubility (LogP).
Conversion solution 112 has a pH of less than or equal to 4, preferably less than or equal to 2. Any suitable acid, preferably inorganic acid (or combination of suitable acids) can be used to lower the pH of conversion solution 112 to the desired acidic pH. Examples of suitable acids include: H2SO4, HCl, H3PO4, methane sulfonic acid, formic acid, acetic acid, trifluoro acetic acid, trichloro acetic acid, and any combinations thereof.
Referring to
Referring to
Preferably at least 20 mol % of the xylose-diboronate ester in second combined solution 114 is converted into furfural, more preferably at least 50 mol %, including at least 70 mol % or at least 90 mol %, of the xylose-diboronate ester is converted into furfural. By heating second combined solution 114 to temperature Th where it consists essentially of a homogenous liquid phase, at least 80 mol % of the xylose-diboronate ester in second combined solution 114 is converted into furfural, preferably at least 90 mol %.
Suitably, second combined solution 114 may be heated at temperature Th for at least 1 minute, preferably at least 10 minutes, more preferably at least 30 minutes, most preferably at least 60 minutes, and preferably up to 10 hours, more preferably up to 5 hours, and most preferably up to 3 hours. For instance, the amount of time second combined solution 114 is preferably heated at temperature Th is in a range from 10 minutes to 10 hours, more preferably from 30 minutes to 5 hours, and most preferably from 60 minutes to 3 hours.
This Th temperature depends at least on (i) the properties and concentration of the water-soluble solvent in conversion solution 112 and the water-insoluble solvent in non-aqueous phase 110 and (ii) the properties and concentration of the boronic acid that is bound to xylose and/or free from xylose in second combined solution 114. As such, it is within the knowledge of one of ordinary skills to determine the Th for the particular conditions of a certain process as designed by such one of ordinary skills in accordance with the disclosures herein, such as composition of second combined solution 114 which depends on composition of upstream elements. Preferably, Th is in a range from at least 160° C., more preferably at least 180° C., and most preferably at least 220 degrees.
Referring to
Referring to
While process 100, particularly heating of second combined solution 114 to temperature Th, may be preferred to provide an optimal rate of conversion of xylose-diboronate ester to furfural, such heating is not necessary to produce furfural in accordance with the processes and systems disclosed herein.
Referring to
Suitably, second combined solution 214 may be heated for at least 1 minute, preferably at least 10 minutes, more preferably at least 30 minutes, most preferably at least 60 minutes, and preferably up to 10 hours, more preferably up to 5 hours, and most preferably up to 3 hours. For instance, the amount of time second combined solution 214 is preferably heated at a temperature of at least 100° C. is in a range from 10 minutes to 10 hours, more preferably from 30 minutes to 5 hours, and most preferably from 60 minutes to 3 hours.
Preferably at least 20 mol % of the xylose-diboronate ester in second combined solution 214 is converted into furfural, more preferably at least 50 mol %, and most preferably least 70 mol % of the xylose-diboronate ester is converted into furfural.
Referring to
It is understood by one of ordinary skill that aqueous phases 116 and 216 can contain an amount of water-insoluble boronic acid and water-insoluble solvent, but the concentrations of water and water-soluble solvent are higher than those in non-aqueous phase 110. Similarly, it is understood that non-aqueous phases 118 and 218 can contain an amount of water and water-soluble solvent but the concentrations of water-insoluble solvent and water-insoluble boronic acid are higher than those in conversion solution 112.
Non-aqueous phase 118 or 218 comprises at least a portion of the produced furfural in second combined solution 114/124 or 214, respectively, including at least 10 wt. %, preferably at least 20 wt. %, more preferably at least 30 wt. %, and most preferably at least 40 wt. %. At least a portion of the furfural in non-aqueous phase 118 or 218 can be recovered by suitable methods, such as distillation where the furfural is part of an overhead product.
Referring to
Referring to
Referring to
In addition to water-insoluble solvent and water-insoluble boronic acid, bottom product 122 or 222 can further comprise an amount of water-soluble solvent (such as, at least 0.1 wt. % to 20 wt. %, preferably 0.5 wt. % to 10 wt. %, and more preferably 1 wt. % to 5 wt. %). If an amount of bottom product 122 or 222 is recycled for use as part of extraction solvent 104, at least some of the water-soluble solvent in bottom product 122 or 222 can be in aqueous phase 108, along with other components from bottom product 122 or 222. That is, aqueous phase 108 can comprise (i) water-soluble solvent, (ii) water-insoluble solvent, and (iii) water-insoluble boronic acid. Optionally, aqueous phase 108 may be further processed (not shown) to recover at least one of such water-soluble solvent, water-insoluble solvent, and water-insoluble boronic acid. Suitable further processing of aqueous phase 108 may include adsorption, such as if the water-soluble solvent comprises sulfolane, then activated carbon may be used to adsorb a portion of the sulfolane. Such adsorption bed may also be used recover a portion of water-insoluble solvent and water-insoluble boronic acid from aqueous phase 108.
Referring to
Aqueous phase 130 comprises (i) water in a range from 50 to 95 wt. %, preferably about 92 wt % and (ii) at least 1 wt. %, preferably at least 5 wt. % and most preferably about 8 wt. % furfural, and non-aqueous phase 132 comprises (i) furfural in a range from 50 to 95 wt. % and (ii) at least 5 wt. % water, preferably 6 wt. %. Aqueous phase 130 and non-aqueous phase 132 may be separated for further furfural recovery using suitable separation methods such as liquid-liquid separation as described herein. Referring to
Alternatively or additionally to providing aqueous phase 116 to a distillation unit for further processing to recover at least a portion of the residual furfural in aqueous phase 116, the residual furfural may be extracted with a water-insoluble solvent as known to one of ordinary skill, including those described herein. Optionally, such water-insoluble solvent may comprise at least a portion of bottom product 122 or 222. That is, at least a portion of bottom product 122 or 222 can be used in extraction of furfural in aqueous phase 116.
As described, referring to
Extraction unit 350 can be operated isothermally for a desired amount of time at a constant temperature. Additionally or alternatively, extraction unit 350 can be operated with a temperature gradient for a desired amount of time by providing xylose-containing solution 102 at a temperature that is at least 5° C., at least 10° C., at least 15° C., or at least ° C., higher than the temperature of extraction solution 104. If extraction unit 350 is operated in counter-current mode with a temperature gradient, such operation can combine a higher extraction rate associated with the warmer section that is in close proximity with the inlet of extraction unit 350 for xylose-containing solution 102 (which translates to higher concentration of xylose in the portion of first combined solution 106 at that location) with low loss of extraction solution 104 in the water-rich effluent in the cooler section in close proximity with an outlet for aqueous phase 108.
Referring to
Referring to
Referring to
Referring to
Further Processing and/or Furfural Recovery Options
Referring to
Referring to
Referring to
Optionally, in addition to or as an alternative to using distillation for unit 356 to remove furfural from aqueous phase 116 to provide bottom product stream 128, unit 356 can comprise a suitable liquid-liquid extraction process using a suitable water-insoluble solvent to extract furfural into the water-insoluble solvent. Such water-insoluble solvent for use in this optional aspect of unit 356 can comprise at least a portion of bottom product stream 122 or 222.
Preferably, embodiments of the processes and systems as described herein are carried out or operated continuously for an amount of time, such as at least 6 hours.
In BA2X-containing solution 514, the xylose-diboronate esters react with water, which converts the xylose-diboronate esters to into boronic acid and xylose, which is more soluble in aqueous phase than non-aqueous phase. As more xylose-diboronate esters dissociate into xylose, an aqueous phase comprising xylose and water and a non-aqueous phase comprising boronic acid and water-insoluble solvent from extraction solution 104 begin to form, wherein the concentrations of water and xylose in such aqueous phase is higher than those in such non-aqueous phase of solution 514. Such aqueous and non-aqueous phases can be recovered from solution 514 as aqueous phase 516 and non-aqueous phase 518 using suitable separation methods, such as those described herein.
Aqueous phase 516 is substantially free of contaminants potentially present in xylose-containing solution 102 which may have presented challenges to isolation of the xylose from solution 102. For instance, if xylose-containing solution 102 were a hydrolysate, evaporation of water from solution 102 would have left a solid product containing xylose along with other contaminants, particularly with the amount of xylose being a small percentage of the solid product. In aqueous-phase 516, however, the amount of xylose would be significantly more than other contaminants from xylose-containing solution 102 because of the selectivity of boronic acid to xylose to form xylose-diboronate esters, which are extracted with extraction solution 104. At least a portion of the xylose in aqueous phase 516 may be recovered in solid or powder form using methods known to one of ordinary skill, including evaporation of water.
If process 500 is selected to recover xylose in addition or as an alternative to furfural production as described with
Embodiments of the processes and systems described herein can be further illustrated by the following exemplary, non-limiting examples
In Example 1, nine experiments were conducted with different water-insoluble solvent and pH as shown in Table 4 below. General experimental conditions for these nine experiments include:
The aqueous phases and non-aqueous phases from Example 1 were analysed by means of 1H-NMR using a 400 MHz Bruker spectrometer. The aqueous phases were measured in a 1:1 H2O/D2O mixture (in which D2O is deuterated water also called heavy water or heavy water used for the analysis) with Trimethylsilyl propanoic acid (TMSP) as the internal standard and the non-aqueous phases were measured in a 1:1 mixture of toluene and toluene-d8 with dioxane as the internal standard. These mixtures of aqueous and non-aqueous phases being analysed are composed by equal volumes (250 μL) of the particular aqueous or non-aqueous phase and the deuterated solvent, containing the standard.
The experiments of Example 1 show recovery of xylose using toluene, 2-methylnaphthalene, n-heptane, and octanol as water-insoluble solution, with PBA as the water-insoluble boronic acid.
In experiments 1 and 4-9, the molar ratio of boronic acid to xylose was 2:1. Experiments 3 and 4 demonstrate a potential correlation between extraction efficiency and ratio of boronic acid to xylose, particularly that a higher molar ratio of boronic acid can produce a higher extraction rate (experiment 3) while a lower molar ratio of boronic acid also results in extraction of xylose but at a lower rate (experiment 4).
In addition, these experiments show that embodiments of the processes and systems described herein allow for xylose extraction from acidic and basic xylose-containing solutions. The experiments also demonstrate that embodiments of the processes and systems described herein allow for xylose extraction using aromatic solvents and aliphatic solvents, although the aromatic solvents (toluene and 2-methylnaphthalene) provide a better rate of extraction than the aliphatic solvents (n-heptane and octanol). The non-aqueous phase of experiments 1-9 of Example 1 can either be back extracted to xylose as described above (particularly with respect to
In Example 2, experiments were conducted under different conditions as set forth in Table 5 below. General experimental conditions for the 12 experiments include:
The various second combined solutions as shown in Table 5 below were provided to a heavy glass wall cylindrical pressure vessel having a total volume 30 mL, which was sealed with a Teflon cap, and heated at 180° C. for various amounts of time shown in Table 5.
The pressure vessel for each experiment was cooled, and the liquid product was separated into a bottom aqueous phase and a top toluene-rich phase. The resulting concentrations of residual xylose diboronate ester (BA2X), xylose (X) and furfural (F) were quantified in each phase using 1H-NMR analysis in the presence of internal standard as described above. The sum of the molar yields of furfural found in the aqueous and organic phase for each experiment are shown below in Table 5. In addition, Table 5 shows the conversion mol %, which indicates the mol % of free xylose or BA2X that was converted to furfural.
The experiments of Example 2 show furfural production in accordance with embodiments of the processes and systems described herein. Such furfural yields can be improved with at least one of (i) using a 1:1:1 volume ratio of water-insoluble solvent: acidic water: water-soluble solvent (see experiments 1 and 2 as compared to experiment 3 in which lower yields were observed with lower ratio of water-soluble solvent), (ii) selecting a longer reaction time (see experiment 3 vs. 4 in which lower furfural yields were observed with shorter reaction time, or experiments 7-9, in which similar correlation between yields and reaction time was observed), and (iii) solvent selection (see experiment 3 vs. 5 in which toluene vs. benzene was used with DMSO, or experiments 10−12 in which the combination of 1-MN and sulfolane is more effective than toluene and GVL dioxane, all of which indicates aromatic water-insoluble solvent can be preferred for use with DMSO or sulfolane as water-soluble solvent (vs. GVL or dioxane).
In Example 2, additional experiments 13-19 as shown in Table 6 were carried out to demonstrate the desirable effect of converting the BA2X to furfural under conditions that allow the formation all the reaction components to merge into a single phase during the reaction (e.g., heating the second combined solution to temperature Th). These experiments were carried out under the same general conditions as described above for experiments 1-12 of Example 2 with the representative second combined solution comprising toluene-water-sulfolane mixture in 1:1:1 volume ratio and PBA but with varying either the reaction temperature or the PBA concentration to switch between mono-phasic and bi-phasic conditions, which was witnessed by visual inspection. The variation in PBA concentration was executed by replacing the xylose-diboronate ester (PBA2X) with an equal molar amount of free xylose and a varying molar amount of free PBA.
Similar to above, experiments 13-19 show furfural production in accordance with embodiments of the processes and systems described herein. Such furfural yield can be improved by heating second combined solution to temperature Tr, at or above which the second combined solution consists essentially of a homogenous phase. For instance, experiments 14−17 show that furfural production yields of at least about 90% were observed under conditions that allow the two liquid phases observed at room temperature fuse into a single liquid phase at reaction temperature as compared to when the representative second combined solution has two phases at reaction temperature.
We first analysed one non-aqueous phase comprising methylnaphthalene (MN) (such as one potential embodiment of non-aqueous phase 118 or 218 of
Table 7 shows that the addition of sulfolane improves the solubility of both MN (water-insoluble solvent) and PBA in the aqueous phase. Accordingly, the aqueous phase that consists essentially of water and sulfolane also contains traces of furfural (<1 wt. %), PBA (<1.3 wt. %) and MN (<0.1 wt %). Optionally, furfural can be recovered as described, for instance as overhead product 126 by providing the polar phase to unit 356 in
The non-aqueous phase that is rich in MN (water-insoluble solvent), meaning greater concentration of MN as compared to the aqueous phase, contained much (41%) of the overall furfural produced and initial PBA (boronic acid). As described, furfural can be recovered from this non-aqueous phase in an overhead product of a distillation process. The remaining bottom product (e.g., 122 or 222) comprising MN and PBA can be recycled as part of the extraction solution. Because the non-aqueous phase also contained some sulfolane (water-soluble solvent, 4 wt %), which may get lost in the aqueous phase of first combined solution if the bottom product comprising MN and PBA is recycled as described. Optional further processing of the aqueous phase of first combined solution (such as aqueous phase 108 of
As described, the present disclosure provides processes and systems to produce furfural from an aqueous xylose-containing solution without isolation of xylose in dry form, which can be costly. In particular, certain embodiments of the processes and systems described herein (such as process 100 and system 300) are capable of and can be designed to produce such furfural at a relatively higher yield of at least 80 mol %, preferably at least 85 mol %, more preferably at least 90 mol %, and most preferably at least mol % (meaning at least 80, 85, 90, or 95 mol % of xylose is converted to furfural) without isolation of xylose in dry form. Although other embodiments (such as process 200 and system 400) may not provide such high yields, they nonetheless can still provide various benefits described herein. One of ordinary skills can design various embodiments as described herein to achieve the desired yields in light of various factors (such as energy demands, equipment costs, etc.).
Embodiments of the processes and systems described herein allow for less formation of undesirable by-products (such as humins) from the various reactants and/or furfural degradation, which allows for furfural production with marginal fouling of equipment and marginal contamination of various product and solvent streams. The selectivity of water-insoluble boronic acid for xylose (in contrast with other sugars such as glucose and mannose) in first combined solution 106 allows for extraction of xylose as described while the majority (greater than 50%) of other sugars remain in solution 108 after non-aqueous phase 110 comprising xylose-diboronate esters is separated. Non-aqueous phase 110 comprising less contaminants (i.e., non-xylose components such as other sugars and lignin) means less contaminants that are subject to dehydration reactions, such as those described for second combined solution 114, 124, and/or 214, and/or carried out in unit 352, which would degrade these contaminants to humins and other fouling components.
Furthermore, various embodiments of the processes and systems describe herein enable recovery of furfural using distillation of water-insoluble components in non-aqueous phase 118 or 218, which is, broadly speaking, simpler as compared to distillation of an aqueous solution containing furfural. For instance, various embodiments described herein allow one of ordinary skill to optionally select a water-insoluble solvent with a boiling point above the boiling point of furfural. Such solvent selection can further reduce energy demands of the corresponding process or system by enabling recovery via distillation of the minor component, furfural, as an overhead product (such as 120 or 220) of the distillation column instead of distilling the major component, the water-insoluble solvent.
Moreover, optional recovery of furfural from aqueous phase 116 or 216 is made possible. It can include post-distillation processing to separate the furfural and water from the water-furfural azeotrope that forms in overhead product 126. However, it can also consist of extraction using at least a portion of bottom product 122 or 222 comprising water-insoluble solvent and boronic acid.
As noted above, the processes and systems described herein can be carried out in solutions without needing the xylose to be in solid form for furfural production, which can allow for a simplified approach of extracting xylose as xylose-diboronate ester into a non-aqueous phase, dehydration of that non-aqueous phase to produce furfural, and recovery of furfural. Nevertheless, embodiments of the processes and systems described herein can be designed to isolate xylose in solid form.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20215448.0 | Dec 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/064132 | 12/17/2021 | WO |
