IONIC LIQUID BIOPROCESSING

BACKGROUND

The disclosure relates generally to industrial chemistry and more specifically to processes involving ionic liquids. Ionic liquids (ILs) are salts that melt at low temperatures and can be used as solvents in various processes, including processing of ligno-cellulosic biomass. However, in order to approach industrial applicability, separation strategies for recovering and reusing ionic liquids are needed.

SUMMARY

Methods are provided herein for performing ionic liquid separations.

In an aspect, the present disclosure provides a method for recovering biomass components from an ionic liquid, the method comprising: adding a

kosmotropic salt to a hydrolyzed biomass composition to form a first phase and a second phase, wherein the hydrolyzed biomass composition comprises an ionic liquid, water and one or more biomass components, wherein the first phase comprises the ionic liquid and the second phase comprises water, one or more biomass components, the kosmotropic salt, and optionally some of the ionic liquid.

In another aspect, the present disclosure provides a method for precipitating a solid from an ionic liquid, the method comprising contacting an anti- solvent with an ionic liquid solution to precipitate a solid from the ionic liquid solution.

In another aspect, the present disclosure provides a method for recovering an ionic liquid from a solid, the method comprising washing the solid with an anti-solvent, wherein the solid is substantially insoluble in the anti-solvent and the ionic liquid is miscible with the anti-solvent.

In another aspect, the present disclosure provides a method for drying an ionic liquid, the method comprising: (a) adding an azeotropic agent to a mixture of ionic liquid and water, wherein the azeotropic agent forms an azeotrope with water; and (b) evaporating the azeotrope from the mixture, thereby removing water from the mixture.

In another aspect, the present disclosure provides a method for recovering biomass components from an ionic liquid, the method comprising: adding a volatile salt to a hydrolyzed biomass composition to form a first phase and a second phase, wherein the hydrolyzed biomass composition comprises an ionic liquid, water and one or more biomass components, wherein the first phase comprises the ionic liquid, and wherein the second phase comprises water, one or more biomass

components and optionally some of the ionic liquid.

In another aspect, the present disclosure provides a method for recovering a sugar from an ionic liquid, the method comprising: (a) providing a sugar dissolved in an ionic liquid at an acidic pH; (b) alkylating the sugar with an alcohol to create an alkylglycoside; and (c) recovering the alkylglycoside from the ionic liquid.

In another aspect, the present disclosure provides a method for separating a solute from an ionic liquid, the method comprising: contacting a polyelectrolyte with an ionic liquid solution comprising a solute. In some embodiments, the method further comprises separating the polyelectrolyte from the ionic liquid solution.

In another aspect, the present disclosure provides a method for recovering a solute from an ionic liquid, the method comprising: (a) providing a composition comprising an ionic liquid, water and a solute; (b) mixing the composition with a strong kosmotrope to form a first phase and a second phase, wherein the first phase comprises the ionic liquid and the second phase comprises water, the solute, the strong kosmotrope and optionally some of the ionic liquid; (c) separating the first phase from the second phase; and (d) in the second phase, converting the strong kosmotrope to a weak kosmotrope.

In some embodiments, the method further comprises (e) recovering the weak kosmotrope from the second phase.

In some embodiments, the method further comprises (f) converting the weak kosmotrope into the strong kosmotrope and optionally recycling the strong kosmotrope.

In some embodiments, the method further comprises, in any order: (g) recovering ionic liquid and/or kosmotropic salt from the filtrate and optionally recycling the ionic liquid and/or kosmotropic salt; and/or (h) recovering the anti-solvent from the filtrate and optionally recycling the anti-solvent.

In some embodiments, the strong kosmotrope is K ₂ C0 ₃ . In some embodiments, the weak kosmotrope is KHC0 ₃ . In some embodiments, the composition is obtained by hydrolyzing biomass and/or a biomass component in the ionic liquid. In some embodiments, the solute is a sugar. In some embodiments, the sugar comprises glucose.

In another aspect, the present disclosure provides a method for separating C5 sugars from C6 sugars (sugars containing 5 and 6 carbons, respectively), the method comprising: (a) providing a first solution comprising a lignocellulosic biomass at least partially dissolved in a first ionic liquid; (b) hydrolyzing the first solution to provide a first sugar stream and a non-hydrolyzed biomass; (c) dissolving the non-hydrolyzed biomass in a second ionic liquid; and (d) hydrolyzing the second solution to provide a second sugar stream, wherein the ratio of C6 to C5 sugars is higher in the second sugar stream than in the first sugar stream.

In another aspect, the present disclosure provides a system for recovering a solute from an ionic liquid. The system can comprise (a) an aqueous biphasic system (ABS) formation module capable of forming an ABS, which ABS comprises an ionic liquid phase and an aqueous phase, wherein the aqueous phase comprises a kosmotrope and a solute to be recovered; and (b) a kosmotrope recovery module in fluid communication with the ABS formation module, wherein the kosmotrope recovery module is capable of contacting the aqueous phase with an anti- solvent to precipitate and recover the kosmotrope.

In some embodiments, the system further comprises (c) a kosmotrope conversion module in fluid communication with the kosmotrope recovery module, which kosmotrope conversion module is capable of converting a strong kosmotrope to a weak kosmotrope.

In some embodiments, the system further comprises (d) an ion exchange module in fluid communication with the kosmotrope recovery module, which ion exchange module is capable of recovering residual ionic liquid and/or kosmotrope from the aqueous phase; and (e) a distillation module in fluid communication with the ion exchange module, which distillation module is capable of recovering the anti-solvent from the aqueous phase.

The kosmotrope conversion module can be before or after the kosmotrope recovery module. The kosmotrope conversion module and the kosmotrope recovery module can be performed in a single vessel. The ion exchange module can be before or after the distillation module.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. PCT Patent Application Serial No.

PCT/US2012/054302; PCT Patent Application Serial No. PCT/US2014/20375; Provisional Patent Application No. 62/048,097 and U.S. Provisional Patent Application No. 62/116,884, are incorporated herein by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also referred to as "figures" or "FIGs.") of which:

FIG. 1A shows an example of the extraction of water and a solute away from ionic liquid by a polyelectrolyte;

FIG. IB shows an example of the extraction of water and a solute away from ionic liquid by a polyelectrolyte where the ionic liquid is [BMIMJC1 and the solute is glucose;

FIG. 2 shows an example of two separate phases created between an IL and a polyelectrolyte;

FIG. 3 shows an example of a l-butyl-3-methylimidazolium chloride and sodium polyacrylate interface (Mw ~ 5100);

FIG. 4 shows an example of a separation process for a target solute in an ionic liquid/water solvent;

FIG. 5 shows an example of poplar whole tree hydrolysate extracted with sodium polyacrylate;

FIG. 6 shows an example of a separation process for sugar in an ionic liquid/water solvent;

FIG. 7 shows an example of a column containing [BMIMJC1, potassium phosphate tribasic and water during ABS formation where coalesced drops rich in salt and water can be seen (left), and after a few minutes, an IL-rich phase forms over a salt- rich phase (right);

FIG. 8 shows an example of two binary phase diagrams that illustrate a strong and a weak ABS formed by IL, salt and water where any mixture with a composition inside the upper-right envelope can split into two phases along its tie line, and the length of the tie line can be proportional to the speed of separation and partition coefficients;

FIG. 9 shows an example of partion coefficients (K) for IL and glucose, and selectivity (S) are shown on a semi-log scale with respect to the total concentration of phosphate buffer and IL in the mixture; FIG. 10 shows an example of the influence of pH, where, typically, higher pH drives stronger ABS formed between [BMIMJC1 and kosmotropic salt;

FIG. 11 shows an example of the solubilities of glucose in methanol/water at 40 C and soda ash in methanol/water in 22 C, both on a solute-free basis, where the inset depicts the ratio of glucose to soda ash solubility;

FIG. 12 shows an example of the temperature dependence of glucose and soda ash solubility in pure water;

FIG. 13 shows an example of glucose and xylose recovery after filtration (wash ratio of zero) and wash (wash ratio > zero) in an 80% methanol/water solution;

FIG. 14 shows an example of a soda ash cake after filtration and wash;

FIG. 15 shows an example of poplar whole tree hydrolysate extracted with concentrated potash in a separatory funnel;

FIG. 16 shows an example of a vial (resting on wood chips) with sugar crystals obtained using the method of the present disclosure;

FIG. 17 A shows an example of a system for performing ionic liquid separations using a kosmotropic salt and an anti-solvent;

FIG. 17B shows an example of an engineering process flowsheet for separating a sugar from a biomass hydrolysate using a kosmotropic salt and methanol extractant;

FIG. 18 shows an example of the effect of IL co-solvent on ABS selectivity;

FIG. 19 shows an plot of the solubility of K ₂ C0 ₃ and KHC0 ₃ at various temperatures;

FIG. 20 shows an plot of the solubility of glucose and potassium bicarbonate in various concentrations of methanol in water mixtures;

FIG. 21 shows an example of a chemical process for hydrolyzing biomass in ionic liquid and performing separations using interconversion between a strong kosmotrope and a weak kosmotrope;

FIG. 22 A shows an example of a system for performing ionic liquid separations using interconversion between a strong kosmotrope and a weak kosmotrope followed by an anti-solvent;

FIG. 22B shows an example of a system for performing ionic liquid separations using an anti-solvent followed by interconversion between a strong kosmotrope and a weak kosmotrope; FIG. 22C shows an example of a system for performing ionic liquid separations using an anti-solvent and interconversion between a strong kosmotrope and a weak kosmotrope in a single pot;

FIG. 22D shows an example of an engineering process flowsheet for separating a sugar from a biomass hydrolysate using interconversion between a strong kosmotrope and a weak kosmotrope;

FIG. 23 shows an example of sugar purification with acetonitrile starting from a mixture of 88% glucose and 12% [BMIMJCl, the amounts remaining of both relative to the starting amounts are plotted against ACN wash ratio (ratio of ACN mass to starting solids mass);

FIG. 24A shows an example of a system for performing ionic liquid separations using an anti-solvent;

FIG. 24B shows an example of a sugar purification process where the output from primary sugar extraction is dried and fed to this process where ACN solubilizes and recovers all the remaining [BMIMJCl;

FIG. 25 shows an example of the kinetics of glucose alkylation with normal alcohols in [BMIMJCl, where the alpha and beta gluco-pyranoses are formed;

FIG. 26 shows an example of the kinetics of glucose alkylation with normal alcohols in [BMIMJCl, where the alpha and beta gluco-pyranoses are formed;

FIG. 27 shows an example of the kinetics of IL consumption for glucose alkylation with normal alcohols in [BMIMJCl;

FIG. 28 shows an example of the kinetics of glucose consumption for glucose alkylation with normal alcohols in [BMIMJCl;

FIG. 29A shows an example of a system for azeotropic drying;

FIG. 29B shows an example of an apparatus for azeotropic drying;

FIG. 29C shows a typical azeotropic drying apparatus used in the laboratory;

FIG. 30 shows an example of a process for using differential kinetics of hydrolysis to separate C5 from C6 sugars;

FIG. 31 shows an example of fermentation of sugars produced by the methods described herein with S. cerevisiae; and

FIG. 32 shows an example of fermentation of sugars produced by the methods described herein with E. coli. DETAILED DESCRIPTION

While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed.

The term "invention" or "present invention" as used herein is not meant to be limiting to any one specific embodiment of the invention but applies generally to any and all embodiments of the invention as described in the claims and specification.

As used herein, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, references to "the method" includes one or more methods, and/or steps of the type described herein which will become apparent to those persons skilled in the art upon reading this disclosure.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are described.

Ionic liquids

An "ionic liquid" ("IL") refers to salts (e.g., comprising cations and anions) that are liquid. In some cases, the ionic liquid is a liquid at the conditions (e.g., temperature, presence of materials mixed with the ionic liquid) used in the process. Ionic liquids can have a relatively low melting point (e.g., are liquid at temperatures below a certain low temperature). In some cases, the melting point is below about 300 °C, below about 200 °C, below about 150 °C, below about 130 °C, below about 100 °C, below about 75 °C, below about 50 °C, and the like. In some embodiments, the ionic liquid is a liquid at ambient and/or room temperature. The melting point can refer to the melting point of the pure (e.g., at least 90% pure, at least 95% pure, at least 96%> pure, at least 97%> pure, at least 98%> pure, at least 99%> pure) ionic liquid, or can refer to the melting point of the ionic liquid when mixed with other components as used in the process (e.g., water). Mixtures of one or more ionic liquids can also be used. In some embodiments, a mixture of 1 , 2, 3, 4, 5 or more ionic liquids can be used. For example, l-butyl-3-methylimidazolium chloride, which has an anion, a cation, and a melting point of about 65° C is an ionic liquid. In some cases, the term "molten salt" is used interchangeably with ionic liquid. In some cases, a molten salt is not an ionic liquid (e.g., molten sodium chloride, which has a high melting point).

Herein, for clarity and without limitation, ionic liquids can include for example l-propyl-3-methylimidazo Hum chloride. Many salts exist that are ionic liquids, which are usable in the methods, apparatus, and processes herein. Some further examples of ionic liquids include but are not limited to l-allyl-3-methylimidazolium chloride, l-butyl-3-methylimidazolium chloride, l-ethyl-3-methylimidazolium chloride, 1 -(2-hydroxylethyl)-3 -methy limidazolium chloride, 1 -butyl- 1 -methylpyrrolidinium decanoate. For clarity, additional ionic liquids may be known in the art and can be employed with the methods of the present disclosure.

In some embodiments, the ionic liquid comprises immidazolium-based, pyridinium-based and/or choline -based cations. In various embodiments, the ionic liquid is selected from the group consisting of l-butyl-3-methylimidazolium chloride, l-allyl-3-methylimidazolium chloride, l-propyl-3-methylimidazolium chloride, 1-ethyl- 3 -methy limidazolium chloride, l-(2-hydroxylethyl)-3-methylimidazolium chloride, 1- butyl-1 -methylpyrrolidinium decanoate and any combination thereof.

In some embodiments, the anion component of the ionic liquid includes for example and without limitation chloride, acetate, bromide, iodide, fluoride and nitrate.

Mixtures of ionic liquids can be used, and/or any suitable enhancer, modifier, or the like can be added. In some cases, the ionic liquid comprises a plurality of species of cation and/or anion. In some cases, the overall charge of an ionic liquid is neutral, but this is not required.

Embodiments of the invention also encompass using materials convertible to, and/or converted to an ionic liquid. For example, some ionizable compounds can become more dissociated into ions when mixed with an ionic liquid.

The ionic liquids can be hydrophilic, meaning that they are miscible in any proportion with water. In some cases, the ionic liquids are hydrophobic.

Hydrophobic ionic liquids can contain some water. Hydrophobic ionic liquids are not miscible with water and at certain concentrations, for example, form a water phase and an ionic liquid phase.

In some embodiments, the ionic liquid is a biomass dissolving ionic liquid (e.g., is capable of dissolving biomass). The solubility of biomass in the ionic liquid can be any suitable value including about 1%, about 3%, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 50%, and the like by mass. In some embodiments, the solubility can be about 1% to about 50%>, about 3%) to about 40%>, about 5% to about 35%, about 10%> to about 30%>, or about 15% to about 25% by mass. In some embodiments, the solubility of biomass in the ionic liquid is at least 1%, at least 3%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 50%, and the like by mass.

In some embodiments, the ionic liquid is functionalized, task-specific, protic, aprotic, polymerized, or combinations thereof. In certain embodiments, the ionic liquid is non-toxic, biodegradable, non-flammable, or has other properties that result in a safe and environmentally friendly process.

Biomass and hydrolysis

In some embodiments, the disclosure provides methods for separating biomass and/or biomass components from ionic liquids. The methods can be performed with hydro lysate, also referred to as biomass hydro lysate or a hyrolyzed biomass composition, which can refer to biomass dissolved in an ionic liquid that has undergone a hydrolysis reaction as described in U.S. Patent 8,722,878; PCT Patent Application Serial Number PCT/US2012/054302; and PCT Patent Application Serial Number PCT/US2014/020375, each of which are incorporated herein by reference in their entirety. The hydrolysis reaction can involve dissolving the biomass in ionic liquid in the presence of a catalytic amount of acid and adding water to the hydrolysis reaction as it proceeds.

The biomass can be any suitable material, including mixed material or materials that can change or are changed over time. In some embodiments, the present methods may be practiced in a feedstock-flexible biorefmery.

The biomass can include for example and without limitation plant matter, algae, seaweed, agricultural or forestry residue, industrial or municipal waste, or any other suitable material, as well as any combinations of these materials. As used herein, "biomass" includes any component of the biomass (e.g., lipids, proteins, cellulose, lignin) and/or derivatives of the plant material and/or derivatives of its components (e.g., cellulose hydrolyzed to sugars, sugars dehydrated to furanic compounds).

In some instances the biomass is cellulosic, meaning that it comprises cellulose or derivatives thereof. Cellulose is a polymer of glucose monomers (e.g., beta 1-4 linked, a polysaccharide). In some instances, the cellulose is broken down and/or hydrolyzed (e.g., to sugars).

In some instances, the biomass is lignocellulosic, meaning that it comprises cellulose and lignin. Lignin is a complex chemical compound that forms part of some plants (e.g., cell walls). Lignin is generally heterogeneous and lacks of a defined primary structure. Lignin can comprise biopolymers of p-coumaryl alcohol, coniferyl alcohol and/or sinapyl alcohol. In some instances, the biomass has no lignin or a small amount of lignin (e.g., less than 5%, less than 3%, or less than 1%).

Cellulosic and/or lignocellulosic biomass may also comprise hemicellulose. A hemicellulose can comprise any of several heteropolymers, such as arabinoxylans, present along with cellulose in some plant cell walls. Hemicellulose can contain many different sugar building blocks. In contrast, cellulose generally contains only anhydrous glucose. For instance, besides glucose, sugar building blocks in hemicellulose can include xylose, mannose, galactose, rhamnose, and arabinose. Hemicelluloses can contain pentose (5 carbon) sugars. In some instances, xylose is the sugar monomer present in the largest amount, but mannuronic acid and galacturonic acid may also be present among others. In some instances, hemicellulose is broken down and/or hydrolyzed into sugars.

In some instances, biomass components are removed from ionic liquids. The biomass can optionally be broken down into its components in the ionic liquid, or may be broken down by other means and added to an ionic liquid. In some instances, the biomass components are not only removed from the ionic liquid, but also fractionated. For instance, carbohydrates can be fractionated from lipids and/or proteins (e.g., biomass components are isolated or separated from each other). In some embodiments, various sugars may be isolated from each other, such as for example glucose from other sugars such as arabinose and xylose. Any of these operations and/or combinations of operations can result in a biomass mixture.

Exemplary biomass components in a biomass mixture include, but are not limited to nucleic acids, proteins, lipids, fatty acids, resin acids, waxes, terpenes, acetates (e.g., ethyl acetate, methyl acetate), carbohydrates, polysaccharides cellulose, hemicellulose, alcohols, sugars, sugar acids, glucose, fructose, xylose, galactose, arabinose, mannose, rhamnose, mannuronic acid, galacturonic acid, lignin, alcohols (e.g., methanol, ethanol), phenols, aldehydes, ethers, p-coumaryl alcohol, coniferyl alcohol, sinapyl alcohol, pectin, D -galacturonic acid, amino acids, acetic acid, ash, water, any derivative thereof (e.g., furanic compounds), or any combination thereof. Any suitable biomass component can be recovered from the biomass mixture as described herein. Any of these individual components and/or mixtures thereof can be separated from one another.

In some embodiments, the biomass components include carbohydrates. Carbohydrates have the chemical formula C _m (H ₂ 0) _n , where m and n are integers. In some cases, the biomass component is a carbohydrate derivative (e.g. , chloroglucose (C ₆ Hi i0 ₅ Cl)). Carbohydrates include water-soluble carbohydrates and water-insoluble carbohydrates.

Polysaccharides are also biomass components (e.g. , cellulose, starch, or hemicellulose). In various embodiments, the biomass may comprise polysaccharides of any average degree of polymerization and/or profile or range of degrees of

polymerization. In some instances, cellulose may have 7,000 - 15,000 glucose molecules per polymer and hemicellulose may have about 500 - 3,000 sugar units. In some examples, the degree of polymerization of the polysaccharide is reduced in the ionic liquid. In some embodiments, polysaccharides that have a degree of

polymerization of at most about 20, at most about 5, at most 2, or at most one (i.e. , monosaccharides) are recovered from the ionic liquid as described herein. In some embodiments, the polysaccharides recovered are water-soluble and/or fermentable. In some cases, the recovered polysaccharides comprise between 1 and about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9 or about 10 sugar units. In some embodiments, low molecular weight carbohydrates (e.g., polysaccharides) are continuously removed from the ionic liquid reaction as the polysaccharides are continuously broken down to lower molecular weight carbohydrates (e.g., sugars). As used herein, "continuously" can generally include being performed over repeatedly small time intervals such as about 1 second, 10 seconds, 30 seconds, 1 minute, 5 minutes or 10 minutes.

In some embodiments, the biomass components include sugars. Sugars include monosaccharides, disaccharides and oligosaccharides.

In some instances, the sugars are fermentable. Fermentable sugars are capable of nourishing and/or sustaining a culture of microbes (e.g. , E. coli and/or yeast). Various microorganisms are capable of using various sugars, so while arabinose may be fermentable by one organism it may not be by another. For the purposes of clarity, a sugar is fermentable if there is at least one microorganism known to be capable of growing on the sugar and/or metabolizing the sugar. Exemplary fermentable sugars include but are not limited to glucose, fructose, xylose, or combinations thereof.

Fermentable sugars need not be monosaccharides. As used herein, biomass includes derivatives of biomass and/or derivatives of biomass components. Also, as used herein, biomass components include derivatives of biomass components. In some cases, at least some of the mass of the derivative (e.g., at least some atoms) are traceable back to biomass and/or biomass component (e.g., plant material and/or cellulose). For example, furanic compounds

(e.g., hydroxymethylfurfural, 2,5-dimethylfuran) can be produced by the dehydration of sugars, so are an example of a biomass derivative. A method for producing furanic compounds from biomass is described for example in U.S. Patent Pub. No.

2010/0004437, which is herein incorporated by reference in its entirety. Those of ordinary skill in the art will be aware of many biomass derivatives including polyols, and the like.

Hydrolysis can be performed in one stage or multiple stages. A multiple- stage hydrolysis can involve isolating non-hydrolyzed solids from a first hydrolysis stage and performing an ionic liquid hydrolysis on the isolated solids. Example 9 describes a method for achieving hydrolysis in a single stage.

In some cases, hydrolysis can be performed in a way that results in a first sugar solution enriched in 5 -carbon sugars (C5, such as xylose) and a second sugar solution enriched in 6-carbon sugars (C6, such as glucose). The ratio of C5 to C6 sugars in the first sugar solution and/or the ratio of C6 to C5 sugars in the second sugar solution can be at least about 1.4, at least about 1.6, at least about 1.8, at least about 2, at least about 3, at least about 4, at least about 5, at least about 6, at least about 8, at least about 10, or at least about 20.

In another aspect, the present disclosure provides a method for separating C5 sugars from C6 sugars, the method comprising: (a) providing a first solution comprising a lignocellulosic biomass at least partially dissolved in a first ionic liquid; (b) hydrolyzing the first solution to provide a first sugar stream and a non- hydrolyzed biomass; (c) dissolving the non-hydrolyzed biomass in a second ionic liquid; and (d) hydrolyzing the second solution to provide a second sugar stream, wherein the ratio of C6 to C5 sugars is higher in the second sugar stream than in the first sugar stream.

In some embodiments, the first hydrolysis is performed at a first temperature, the second hydrolysis is performed at a second temperature, and the second temperature is greater than the first temperature.

In some embodiments, the extent of the first hydrolysis and/or the second hydrolysis is controlled by an amount of water added to the hydrolysis. In some embodiments, the first solution comprises a greater fraction of the hemicellulose of the lignocellulosic biomass in solution compared to the fraction of cellulose in solution.

Separate sugar streams can be produced either during the hydrolysis reaction, or at the end of the process. Simulated Moving Bed chromatography (SMB) can be used to separate C5 from C6 sugars following hydrolysis.

As described herein, hydrolysis kinetics can be exploited to create separate C5 and C6 streams within the process (i.e., kinetic separation). The rate law for acid-catalyzed hydrolysis in [EMIMJCl and [BMIMJC1 shows that the activation energy for cellulose hydrolysis is significantly higher than hemicellulose (93 vs 60 kJ/mol). With reference to FIG. 30, the method involves dissolving biomass 3000 and selectively hydrolyzing hemicellulose (C5) in a first reactor 3005, having a lower temperature and optionally higher residence time than a second hydrolysis reactor 3010. The output of the first reactor can flow to a first separations module 3015 where solids 3020 are recovered (containing lignin and cellulose) and introduced into a second hydrolysis reactor 3010. The second reactor can have a higher temperature than the first reactor to hydrolyze cellulose and liberate glucose (C6). The product of the second reactor can be transferred to a second separations module 3025, resulting in an overall process yield of a stream enriched in C5 sugars 3030, a stream enriched in C6 sugars 3035 and residual solids 3040.

In some cases, the process described in FIG. 30 does not alter the capital requirements of the process significantly relative to producing a hydrolysate of mixed C5 and C6 sugars and any additional capital outlay due to the extra vessels and/or increased ionic liquid volume can be offset by higher prices commanded by separate sugar streams.

In some cases, the process described in FIG. 30 is supplemented with additional separation steps to arrive at C5 and C6 streams of the desired amount of purity and yield (i.e., reduce cross-contamination between sugars to a desired level). Having performed a low-purity separation based on differential hydrolysis kinetics can facilitate and reduce the cost of further purification downstream. For instance, kinetic separation can be followed by one or more of a simulated moving bed chromatography, membrane nanofiltration, bio-filtration or ultrafiltration steps to purify sugar streams.

Bio-filtration is a process of separating sugar streams according to their biological activity in a biological process. For instance, a microbe (wild-type or engineered) can be introduced to a mixed C5/C6 sugar stream in order to consume C6 sugars and convert them to a metabolite (e.g., ethanol), which is then more readily separated from solution, resulting in ethanol and C5 sugars. After removal of the microbes and metabolites (e.g., by centrifugation and distillation), the resulting C5 sugar solution can be used for other downstream processes requiring C5 sugars.

Furthermore, simulated moving bed, other chromatographic, or other separation steps may be added to further refine sugar streams into its individual component species, such as sucrose, glucose, fructose, xylose, arabinose, galactose, etc.

In some cases, the kinetics of dissolution can be exploited in order to improve separations. For instance, conditions such as temperature, agitation and the use of co-solvents can be varied in order to promote the dissolution of some biomass fractions over others. In one example, the dissolution of hemicellulose proceeds at a lower temperature (by about 20 degrees Celsius) than the temperature necessary to carry out cellulose dissolution in the ionic liquid. Since, in this case, a lesser amount of cellulose is dissolved, a lesser amount of glucose is formed in the hydrolysis step, thus resulting in some separation of C5 and C6.

The ionic liquid-based process described herein is flexible with respect to the material it can process. The whole plant may be processed instead of specific structures such as grain, trunk, leaves, etc. Some structures can contain polysaccharides that are simpler or easier to deconstruct to sugars. For instance, both corn grain and stover can be processed at once, but corn grain contains simpler starch sugars that are easier to dissolve and hydrolyze than the cellulose of the corn stover. As such, hydrolysis can be tailored to preferentially liberate sugars originating from a given biomass fraction, with those streams achieving a degree of separation between C5 and C6 sugars.

Polyelectrolytes

In an aspect, described herein is a method for separating a solute from an ionic liquid. The method can include contacting a polyelectrolyte with an ionic liquid solution comprising a solute. The solute can migrate into the polyelectrolyte, partially or totally excluding the ionic liquid from the polyelectrolyte as shown in FIG. 1A. The contacting can form two phases {e.g., an IL-rich phase and a polyelectrolyte-rich phase) that can be separated as described herein. The solute can be recovered from the polyelectrolyte and the polyelectrolyte can be re-used. FIG. IB shows an example where the ionic liquid is [BMIMJC1 and the solute is glucose. Water is not shown.

In some cases, the solute is water {i.e., the ionic liquid solution has ionic liquid and water) and the water is separated from the ionic liquid {i.e., the ionic liquid is dried). In some cases, the ionic liquid solution includes water along with one or more solutes and, while the water may also be removed, the non- water solute is the entity that is the target for recovery from the solution (e.g., because it is a valued product). In some instances, the ionic liquid solution does not comprise water. Note that in some cases, the ionic liquid can absorb to the polyelectrolyte rather than the solute.

FIG. 2 shows an example of two separate phases created between an IL and a polyelectrolyte. The top layer 200 is rich in the IL l-butyl-3-methylimidazolium chloride and appears light yellow. The bottom layer 210 is rich in sodium polyacrylate and appears clear. The interface is visible due to a color change, but is not readily apparent in the gray-scale image. FIG. 3 shows an example of a l-butyl-3- methylimidazolium chloride and sodium polyacrylate interface (Mw ~ 5100). Indigo carmine is blue and was added to the mix and is retained preferentially in the IL-rich layer 300 to add contrast with the clear lower layer 310.

As shown in FIG. 4, the polyelectrolyte 400 can be mixed with the ionic liquid solution 405 {e.g., comprising ionic liquid, water and a solute) in a mixer 410 {e.g., with an impeller in a tank). The mixture can be allowed to settle in order to form two phases. The time of mixing and/or settling can be optimized {e.g., to provide the most amount of solute to enter the polyelectrolyte, or to provide the least amount of ionic liquid to enter the polyelectrolyte). The polyelectrolyte can be contacted (mixed and/or settled) with the ionic liquid solution for about 10 seconds (s), about 20 s, about 30 s, about 45 s, about 1 minute (min), about 2 min, about 5 min, about 10 min, about 20 min, about 30 min, about 1 hour (h), about 2 h, about 3 h, about 5 h, or more. The polyelectrolyte can be contacted (mixed and/or settled) with the ionic liquid solution for at least about 10 seconds (s), at least about 20 s, at least about 30 s, at least about 45 s, at least about 1 minute (min), at least about 2 min, at least about 5 min, at least about 10 min, at least about 20 min, at least about 30 min, at least about 1 hour (h), at least about 2 h, at least about 3 h, at least about 5 h, or more. The polyelectrolyte can be contacted (mixed and/or settled) with the ionic liquid solution for at most about 10 seconds (s), at most about 20 s, at most about 30 s, at most about 45 s, at most about 1 minute (min), at most about 2 min, at most about 5 min, at most about 10 min, at most about 20 min, at most about 30 min, at most about 1 hour (h), at most about 2 h, at most about 3 h, at most about 5 h, or more.

As shown in FIG. 4, in some embodiments, the method further comprises separating the polyelectrolyte phase 415 (e.g., poly-electrolyte bound water and solute) from the ionic liquid phase 420 in a separator 425. The polyelectrolyte can be separated from the ionic liquid solution by any suitable method including, but not limited to centrifugation, filtration, nanofiltration, contacting with an acid, contacting with a base, electrical stimulation, changing electrical conductivity, changing electrical charge, electrodialysis, changing counter-ion species or composition, precipitation, changing temperature, changing pressure, or combinations thereof.

As shown in FIG. 4, the solute and/or water 430 can be recovered from the polyelectrolyte 435 in a regenerator 440 {e.g., to provide polyelectrolyte that is regenerated and capable of being re-used). Without limitation, the polyelectrolyte can be regenerated by reducing the pH, increasing the pressure, decreasing the pressure, increasing the temperature, decreasing the temperature, or combinations thereof.

The solute that is recovered from the ionic liquid solution can have a low concentration of ionic liquid. In some embodiments, the solute that is removed from the ionic liquid solution contains about 5%, about 3%, about 1%, about 0.5%, about 0.1%, about 0.05%), about 0.01%, or about 0.005%) ionic liquid by mass.In some

embodiments, the solute that is removed from the ionic liquid solution contains less than about 5%, less than about 3%, less than about 1%, less than about 0.5%>, less than about 0.1%o, less than about 0.05%>, less than about 0.01%, or less than about 0.005%) ionic liquid by mass. The methods of the disclosure can be repeated in series to yield the desired degree of purity (e.g., in 2, 3, 4, 5, 6, 7, 8, 9, 10, or more stages).

Polyelectrolytes are polymers whose repeating units bear an electrolyte group, such as polycations, polyanions and polyampholytes (a polymer having both positive and negative charges). These electrolyte groups can dissociate in aqueous solutions (water), making the polymers charged. Polyelectrolyte properties can be similar to both electrolytes (salts) and polymers (high molecular weight compounds), and are sometimes called polysalts. Like salts, their solutions can be electrically conductive. Like polymers, their solutions can be viscous. Many biological molecules are polyelectrolytes. For instance, polypeptides, glycosaminoglycans, and nucleic acids are polyelectrolytes. Both natural and synthetic polyelectrolytes are used in a variety of industries.

The methods described herein can use any suitable polyelectrolyte. The choice of polyelectrolyte can have an effect on various aspects of the system including the amount of solute absorbed by the polyelectrolyte, the amount of ionic liquid absorbed by the polyelectrolyte, the ability to recover the polyelectroltye from the ionic liquid solution and the ability to recover the solute and/or regenerate the

polyelectrolyte.

The polyelectrolyte can be a polyacid, polybase or polyampholyte. In some cases, the polyelectrolyte is a co-polymer (a polymer having more than one type of monomer), such as a block co-polymer (which alternates sections of a first monomer with sections of a second monomer). The polyelectrolyte can have any suitable morphology including being linear, branched, ring, star or comb topology.

Without limitation, the polyelectrolyte can be polyacrylic acid, polystyrene sulfonate, solfonated tetrafluoroethylene (Nafion), salts thereof, and combinations thereof. The counter-ion of the polyelectrolyte can also be varied. For example, the counter-ion can be ionic forms of sodium, potassium, magnesium, calcium, chlorine, bromine, or combinations thereof. In some cases, the counter-ion is the same as one of the ions comprising the ionic liquid (e.g., a chloride counter-ion when the ionic liquid is l-butyl-3-methylimidazolium chloride). In some cases, the polyelectrolyte comprises monomers of one of the ions comprising the ionic liquid (e.g., a polymerized l-butyl-3 -methyl imidazolium when the ionic liquid is l-butyl-3- methylimidazolium chloride).

The polyelectrolyte can have any suitable modification. In some embodiments, the polyelectrolyte comprises an entity that aids in the separation of the polyelectrolyte from the ionic liquid solution, such as an azide or a ferromagnetic nanoparticle. A magnet can be used to concentrate polyelectrolytes having a

ferromagnetic nanoparticle.

The polyelectrolyte can be in any suitable form. In some cases, the polyelectrolyte is formed into a membrane. The membrane can be a filter membrane that is layered onto a porous support. The membrane can be contacted with the ionic liquid solution and provide selectivity between the ionic liquid and the solute.

The polyelectrolyte can have any suitable molecular weight or degree of polymerization, which can be varied to optimize any aspect of the system, such as the selectivity for absorbing the solute rather than the ionic liquid. In some embodiments, the polyelectrolyte has a molecular weight of about 1,000, about 3,000, about 5,000, about 10,000, about 50,000, about 100,000, about 500,000, about 1,000,000, about 3,000,000, about 5,000,000, about 10,000,000, or more. In some cases, the

polyelectrolyte has a molecular weight of at least about 1,000, at least about 3,000, at least about 5,000, at least about 10,000, at least about 50,000, at least about 100,000, at least about 500,000, at least about 1 ,000,000, at least about 3,000,000, at least about 5,000,000, or at least about 10,000,000, or more. In some cases, the polyelectrolyte has a molecular weight of at most about 1,000, at most about 3,000, at most about 5,000, at most about 10,000, at most about 50,000, at most about 100,000, at most about 500,000, at most about 1,000,000, at most about 3,000,000, at most about 5,000,000, or at most about 10,000,000, or more. The polyelectrolyte can be cross-linked or not cross-linked. The degree of cross-linking can be varied to optimize any aspect of the system, such as the amount of solute that the polyelectrolyte can absorb or the extent to which the polyelectrolyte excludes ionic liquid. In some cases, the degree of cross-linking (i.e., the percentage of monomers that are linked to another polymer chain) is about 0.001%, about 0.005%, about 0.01%, about 0.05%, about 0.1%, about 0.5%, about 1%, about 3%, about 5%, about 10%), or more. In some cases, the degree of cross-linking is at least about 0.001%, at least about 0.005%, at least about 0.01%, at least about 0.05%, at least about 0.1%, at least about 0.5%, at least about 1%, at least about 3%, at least about 5%, at least about 10%), or more. In some cases, the degree of cross-linking is at most about 0.001%, at most about 0.005%, at most about 0.01%, at most about 0.05%, at most about 0.1%, at most about 0.5%, at most about 1%, at most about 3%, at most about 5%, at most about 10%), or more.

Any amount of polyelectrolyte can be added to the ionic liquid solution. In some embodiments, the mass of the polyelectrolyte is about 150%, about 120%, about 100%, about 80%, about 60%, about 50%, about 40%, about 30%, about 20%, about 10%), about 8%, about 6%, about 4%, about 2%, about 1%, or about 0.5% of the mass of the ionic liquid solution. In some embodiments, the mass of the polyelectrolyte is at least about 150%, at least about 120%, at least about 100%, at least about 80%, at least about 60%, at least about 50%, at least about 40%, at least about 30%, at least about 20%), at least about 10%, at least about 8%, at least about 6%, at least about 4%, at least about 2%, at least about 1%, or at least about 0.5% of the mass of the ionic liquid solution. In some cases, the mass of the polyelectrolyte is at most about 150%), at most about 120%, at most about 100%, at most about 80%, at most about 60%, at most about 50%, at most about 40%, at most about 30%, at most about 20%, at most about 10%, at most about 8%, at most about 6%, at most about 4%, at most about 2%, at most about 1%, or at most about 0.5% of the mass of the ionic liquid solution.

The amount of polyelectrolyte added can also be quantified relative to the mass of solute in the ionic liquid solution, rather than the total mass of the ionic liquid solution. In some embodiments, the mass of the polyelectrolyte is about 100%), about 80%, about 60%, about 50%, about 40%, about 30%, about 20%, about 10%, about 8%), about 6%, about 4%, about 2%, about 1%, or about 0.5% of the mass of the solute in the ionic liquid solution. In some cases, the mass of the polyelectrolyte is at least about 100%), at least about 80%, at least about 60%, at least about 50%, at least about 40%, at least about 30%, at least about 20%, at least about 10%, at least about

8%, at least about 6%, at least about 4%, at least about 2%, at least about 1%, or at least about 0.5% of the mass of the solute in the ionic liquid solution. In some cases, the mass of the polyelectrolyte is at most about 100%, at most about 80%, at most about 60%), at most about 50%>, at most about 40%>, at most about 30%>, at most about 20%>, at most about 10%, at most about 8%, at most about 6%, at most about 4%, at most about 2%, at most about 1 %, or at most about 0.5% of the mass of the solute in the ionic liquid solution.

The methods described herein can be used with an ionic liquid solution that is a biomass hydrolysate (e.g., as described in United States Patent Number 8,722,878, which is incorporated herein by reference in its entirety). The biomass can be any ligno-cellulosic biomass as described therein. In some cases, the ionic liquid solution is the IL-phase or aqueous-phase of an Aqueous Biphasic System (ABS) (e.g., as formed from a biomass hydrolysate as described in PCT Patent Application Number PCT/US2014/020375, which is incorporated herein by reference in its entirety). FIG. 5 shows an example of poplar whole tree hydrolysate extracted with sodium polyacrylate. The [BMIMJCI rich phase 500, along with dark color from the hydrolysate, stays above the interface. The bottom phase 510 is rich in sodium polyacrylate. The hydrolysate is an example of a reaction performed in an IL medium. The methods described herein can be used to separate solutes from any reaction performed in an IL medium.

The solute that is removed from the ionic liquid solution can be any compound, chemical solution or mixture. In some cases, the solute is a sugar such as glucose and/or xylose (e.g., when the ionic liquid solution is a biomass hydrolysate). In some cases, the solute is water. In some embodiments, the ionic liquid solution further comrises water and water is removed along with the solute (e.g., water and sugars can be removed from biomass hydrolysate). In some instances, the method is used to purify an ionic liquid that has been made in an ionic liquid production process. In some cases, the methods of the disclosure are used to prepare an ionic liquid for an application (e.g., dry the ionic liquid for use as a battery electrolyte).

FIG. 6 shows an example of a separation process for sugar from an ionic liquid/water solvent (e.g., a biomass hydrolysate). Dry polyelectrolyte 600 is mixed with the ionic liquid solution 605 (comprising water and sugar) in a solid/liquid (S/L) mixer 610. The mixture forms two phases and the ionic liquid phase 615 can be separated from the swollen polyelectrolyte 620 with a filter 625. In some cases, the ionic liquid phase is sent to a drier. The polyelectrolyte (PE) bound water and sugar 630 can be mixed with C0 ₂ 635 in a gas/liquid (G/L) mixer 640. The C0 ₂ can form carbonic acid and liberate some of the water and solute (sugar) from the polyelectrolyte. The liberated solution 645 can be filtered 650 and degassed 655 to produce an aqueous solution of sugar 660. The C0 ₂ 665 can be re -used by a pump or compressor 670. The wet polyelectrolyte 675 that is liberated of some of the solute can exit the filter 650 and be dried 680 (i.e., liberated of water 685) and returned to the beginning of the process.

Kosmotropic Salts

In an aspect, the present disclosure provides a method for recovering biomass components from an ionic liquid. The method can comprise adding a kosmotropic salt to a hydrolyzed biomass composition to form a first phase and a second phase. The hydrolyzed biomass composition can comprise an ionic liquid, water and one or more biomass components. The first phase can comprise the ionic liquid. The second phase can comprise water, one or more biomass components, the kosmotropic salt, and optionally some of the ionic liquid. In some cases, the kosmotropic salt is added to the hydrolyzed biomass composition in a counter-current column. The method can further comprise separating the first phase from the second phase.

The method can further comprise adding a salt anti-solvent to the second phase to precipitate the kosmotropic salt from the second phase. The salt anti-solvent can be, without limitation, an alcohol, a diol, a ketone, an ester, an acid, or an amine. In some cases, the salt anti-solvent is polar and organic. In some embodiments, the salt anti-solvent is methanol, ethanol, propanol, acetone, or any combination thereof. As an alternative, the method can further comprise precipitating the kosmotropic salt from the second phase by altering the pH of the second phase (increasing or lowering the pH).

The method can further comprise filtering or centrifuging the precipitated kosmotropic salt from the second phase to provide a filtrate and optionally recycling the precipitated kosmotropic salt.

The method can further comprise, in any order: (a) recovering ionic liquid and/or kosmotropic salt from the filtrate and optionally recycling the ionic liquid and/or kosmotropic salt; and/or (b) recovering the salt anti-solvent from the filtrate and optionally recycling the salt anti-solvent. In some cases, (a) is performed with ion exchange, electrophoresis, electrofiltration, ion-exclusion chromatography,

dielectrophoresis, electrodialysis, reverse osmosis, nanofiltration, ultrafiltration, microfiltration, membrane pervaporation, simulated moving bed chromatography, or any combination thereof. In some embodiments, (b) is performed by distillation, extractive distillation, azeotropic distillation, high pressure distillation, low pressure distillation, evaporation, flashing, liquid-liquid extraction, or any combination thereof. In some cases, the hydrolyzed biomass composition and/or the kosmotropic salt further comprises a co-solvent. The co-solvent can increase the rate of dissolution of cellulose in a pure ionic liquid when compared with the rate of dissolution of cellulose in the ionic liquid without the co-solvent.

In some cases, the co-solvent increases the concentration of the biomass component in the second phase by at least about 20%, at least about 40%, at least about 60%, at least about 80%, at least about 100%, at least about 150%, at least about 200%, at least about 250%, at least about 300%, at least about 400%, or at least about 500% compared with the concentration of the biomass component in the second phase without the co-solvent.

In some instances, the co-solvent decreases the concentration of the ionic liquid in the second phase by at least about 20%>, at least about 40%>, at least about 60%>, at least about 80%, at least about 100%, at least about 150%, at least about 200%, at least about 250%, at least about 300%, at least about 400%), or at least about 500%) compared with the concentration of the ionic liquid in the second phase without the co- solvent.

The ratio of the concentration of the co-solvent in the second phase to the ratio of the concentration of the co-solvent in the first phase can be at least about 2, at least about 5, at least about 10, at least about 50, at least about 100, at least about 500, or at least about 1000. In some cases, the mass of co-solvent is at least about 20%>, at least about 40%, at least about 60%, at least about 80%, at least about 100%, at least about 150%), at least about 200%), at least about 250%), at least about 300%), at least about 400%), or at least about 500%) compared with the mass of hydrolyzed biomass composition.

The co-solvent can be any species that enhances biomass dissolution, hydrolysis and/or separation. In some cases, the co-solvent is polar and aprotic. The co- solvent can be, without limitation, Ν,Ν-dimethylformamide (DMF), N,N- dimethylacetamine (DMA), pyrrolidinone, valerolactam, caprolactam, N- methylpyrrolidinone (NMP), 1,3-dimethylpropylene urea (DMPU), Ν,Ν,Ν',Ν'- tetramethyl urea, dimethylsulfoxide (DMSO), sulfolane, acetylacetone (ACAC), tert- butanol, tert-pentanol, ethanol, acetonitrile, acetone, propylene carbonate, ethylene carbonate, or any combination thereof.

The kosmotropic salt can be any species that induces phase separation. Without limitation, the kosmotropic salt can comprises: (a) a cation selected from the group consisting of Cs+, Rb+, (NH4)+, K+, Na+, Li+, H+, (UO)2+, Ca2+, Mn+, Mg2+, Fe2+, Zn+, Cu2+, A13+, Th4+, and any combination thereof; and (b) an anion selected from the group consisting of (C104)-, (Tc04)-, (N03)-, I-, Br-, C1-, OH-, (CH3C02)-, (HS04)-, F-, (Cr04)2-, (S04)2-, (C03)2-, (S03)2-, (C6H507)2-, (P04)3-,

(C4H406)2-, and any combination thereof. In some cases, the kosmotropic salt is potassium phosphate, sodium carbonate, potassium carbonate, or any combination thereof.

The mass of kosmotropic salt added to the hydrolyzed biomass composition can be approximately equal to the mass of ionic liquid in the hydrolyzed biomass composition (e.g., within about 1%, 5%, 10%, or 20%>). In some cases, the combined mass of the ionic liquid and the kosmotropic salt is at least 40%, at least 50%, at least 60%, or at least 70% of the mass of the hydrolyzed biomass composition after addition of the kosmotropic salt.

The method is typically performed at a basic pH. In some cases, the pH of the hydrolyzed biomass composition is at least about 7, at least about 8, at least about 9, at least about 10, at least about 1 1 , at least about 12, at least about 13, or at least about 14 after the addition of the kosmotropic salt. The pH can be low enough such that the sugars or other biomass components are not degraded. In some cases, the pH of the hydrolyzed biomass composition is less than about 1 1 after the addition of the kosmotropic salt.

The method can be performed at any temperature, with lower

temperatures being prefered in some cases. The temperature of the hydrolyzed biomass composition can be less than about 50 °C, less than about 40 °C, less than about 30 °C, less than about 20 °C, after the addition of the kosmotropic salt.

The hydrolyzed biomass composition can be obtained by hydrolyzing the biomass and/or biomass component in the ionic liquid. In some embodiments, the biomass component is a sugar (e.g., glucose, xylose).

In some cases, the first phase (e.g., phase having the majority of the ionic liquid of the hydrolyzed biomass composition) further comprises acetic acid, furanic compounds (e.g., compounds having a furan ring, such as

hydroxymethylfurfural), extractives, or any combination thereof. The the extractives can comprise one or more biomass components other than cellulose, hemicellulose, lignin, or derivatives thereof, for example, tannins, proteins, or chlorophyll.

The acetic acid, furanic compounds, or extractives can be separated from the first phase, for example, by distillation or liquid-liquid separation.

Kosmotropes are water-structuring solutes. They typically possess very low free energies of hydration (A _t≠ G), which form stable hydration shells and, in some cases, leads to auto-separation from ILs. For instance, dilute water solutions of potassium phosphate intermix freely with l-butyl-3-methylimidazolium chloride, or [BMIMJCI, but additional dissolution of the salt can eventually lead to macroscopic de- mixing and the formation of an interface separating two distinct liquid phases at equilibrium. Typically, an IL-rich phase forms over a denser, kosmotrope-rich solution.

Potassium phosphate tribasic is an inexpensive and non-toxic salt with a very low free energy of hydration (K ⁺ A _h≠ G = -305 kJ/mol and PGv -A _h≠ G = -2835 kJ/mol, note here that CI from the IL has A _t≠ G = -338 kJ/mol, comparable to K ⁺ ). As shown in FIG. 7, potassium phosphate tribasic can induce an aqueous biphasic system (ABS) with [BMIMJCI. The liquids become immiscible (left) and are allowed to settle into two phases (right). In some cases, a strong ABS requires about equal mass fractions of the salt and IL, but with just enough water to prevent precipitation of the salt. ABS with this salt typically separate and reach equilibrium in only a few minutes.

The IL/water/kosmotropic salt system can have glucose. Although sugar is 100-fold more soluble in water than pure [BMIMJCI at 25 °C, both phases have significant amounts of water. Idealized hydrolysate solutions were prepared containing 5 to 10% glucose or glucose and xylose mixtures, 55 to 60% [BMIMJCI and 30 to 40% water. Also, an extractant solution was prepared consisting of 20%> (w/w) potassium phosphate buffer (PB) at pH = 6.5. Here and elsewhere, PBs were prepared and adjusted to the desired pH by balancing the relative amounts of potassium phosphate mono-, di-, and tribasic, as well as phosphoric acid, as appropriate. Extractant and hydrolysate were mixed at equal volume ratios, vortexed for 1 min and centrifuged for 1 min to ensure equilibrium had been reached. Both top (IL-rich) and bottom (PB-rich) phases were sampled and analyzed by HPLC. Glucose partitioned preferentially into the PB-rich (kosmotrope) phase, with a partition coefficient of 2.2. Simultaneously, IL partitioned with a coefficient of 0.30, giving a selectivity of glucose over IL of 7.5. We remind the reader that partition coefficients (K) and selectivities (S) are equilibrium thermodynamic quantities defined by:

where x and y are chemical species such as glucose and [BMIMJCI.

PB buffer can be used at a higher concentration (30%) and pH (8.0). Other parameters of the experiment remained unchanged and the selectivity increased to 27. In both instances, potassium phosphate buffers were effective in extracting glucose away from IL. As shown in FIG. 8, the strength of the ABS can underlie the magnitude of both partition coefficients and selectivity.

Several factors can affect Aqueous Biphasic Systems. A potassium phosphate buffer (PB) was prepared with pH = 9.4 and 56% (w/w) concentration by dissolving K ₂ HP0 ₄ and adjusting the pH down with H ₃ P0 ₄ . ABS mixtures were prepared with gradually less water and measured glucose and IL partitions, as shown in FIG. 9.

The kosmotropic salts extracted glucose by absorbing most of the water away from the IL phase, which also helped to de-water it towards its re-use dissolving fresh biomass. Also, mixtures containing less water, even though more viscous, underwent faster separations. In some cases, a low glucose concentration was not required in order to achieve good selectivity. A significant effect was not observed when varying the initial glucose concentration between 4 and 15%, a wider range than the starting hydrolysate. In fact, higher glucose concentrations strengthened ABS formation. In one example, a starting composition of 41% [BMIMJC1, 39% glucose and only 3% potassium phosphate tribasic created a partition with a selectivity of 9, whereas the same concentrations of IL and salt in the absence of glucose did not separate.

Conversely, glucose alone was not enough to form an ABS, even at very high concentrations. These results point to an ability to drive favorable separations starting from a wide range of sugar concentrations, which favors multi-stage or counter-current designs.

The pH can be a sensitive parameter in ABS strength, as shown in FIG. 10. In some cases, ABS strength is proportional to the product of hydration free energy (a negative number) and concentration. In some cases, an ion's capacity to structure water is dominated by its valency. For instance, for phosphate the hydration free energy decreases with the successive loss of protons, in the order: FLPCv > HPCv >PO„ ³ Hence, pH modifies ABS strength by varying speciation, with higher pH favoring higher valency, stronger water structuring and ABS. This finding does not preclude the formation of ABS with salts that have cations with very low free energies of hydration, which would be favored by the acidic conditions found in our hydrolysate. In some cases, alkaline conditions are preferred for ABS formation with [BMIMJC1.

Temperature can have an effect on ABS. ABS can be formed between [BMIMJC1 and PB even at fairly elevated temperatures (~50 °C), but generally become stronger at lower temperatures. Two identical vials were prepared with initial compositions matching actual biomass hydrolysates. The first vial remained at ambient temperature (21 °C) and the second vial was chilled to 1°C. Selectivity was improved from 90 to 96 by lowering the temperature. Even though the IL anion, chloride, is both inexpensive and effective in converting lignocellulose, there is some room for tailoring the chemistry of the cation. The IL l-butyl-4-methylpyridinium chloride ([BMPYRJC1) was demonstrated. This IL returned even greater sugar yields than [EMIMJCl in preliminary experiments with cellulose, and is readily synthesized from methylpyridine and chlorobutane, both bulk industrial chemicals. In some cases, the larger aromatic structure at the cation (relative to BMIM) can lower its hydrophilicity and facilitate separations from water and sugar. ABS were prepared with equal compositions of the two IL species and PB. Even though the partition coefficients for glucose and IL were similar, the amount of water in the [BMP YR] C 1-rich phase was significantly less than the [BMIM]Cl-rich phase, 19% vs. 31%, respectively, indicating that some biomass-hydrolyzing ILs may be easier to recycle.

Higher concentration and pH can improve not only the separation efficiency, but also its kinetics. With a potassium phosphate buffer sufficient to impart a glucose/IL selectivity of -100, the concentration of each species was monitored over time, which revealed an inverse-exponential trajectory with a characteristic timescale of τ = 0.65 min, and equilibration time of ~5τ = 3.25 min. At selectivities of 300 or higher equilibration times dropped to < 1 min.

At high pH experiments glucose and xylose can be degraded.

Concentrated xylose and glucose solutions were mixed in concentrated potassium phosphate buffers at pH = 6.5 to 14.1, and monitored at room temperature for a few days. The pH = 14 solutions of xylose and glucose turned pale yellow after two to three days, whereas pH = 6.5 to 11 vials remained clear. HPLC analysis confirmed the appearance of new compounds with concomitant consumption of the initial xylose and glucose at pH = 14. Glucose and xylose can remain intact in the conditions and time durations of the actual separation process. In some cases, heating is preceded by neutralization.

The ABS-forming salts K ₃ P0 ₄ /K ₂ HP0 ₄ (pH = 11), Na ₂ CO, (pH = 12), K ₂ CO, (pH = 14), and NaOH (pH = 14) were used on both simulated and actual hydrolysates. Simulated hydrolysates comprised [BMIMJC1 (68.6%>), water (23%>), glucose (5%), xylose (2%), acetic acid (0.3%), furfural (0.1%) and HC1 (1%). Actual hydrolysates were prepared by dissolution of untreated biomass in [BMIM] CI, followed by HCl-catalyzed hydrolysis under gradual water addition, as done described in Binder and Raines, PNAS 107, 4516-4521 (2010), which is incorporated herein by reference. Sugarcane bagasse and poplar whole trees were used as biomass. Lignin and other solids were filtered out of the mixture, yielding a solution with a similar composition to simulated hydrolysates. All these examples were successful in concentrating the sugar and diluting the IL in the extract phase (S > 1). Moreover, apart from the dark-brown color of the hydrolysate compared to the pale yellow of the simulant, there were no noticeable differences in the partition of solutes in either simulated or actual hydrolysates. For instance, both attained selectivities of -300 in concentrated K ₂ C0 ₃ .

The partition coefficients of other major and some minor hydrolysate species were measured. Regardless of which salt was used, partition coefficients increased (higher concentrations in extract) in the order: furfural <

hydroxymethylfurfural < acetic acid < [BMIMJC1 < 1 < xylose ~ C ₅ -sugars < glucose ~ C ₆ -sugars < kosmotropic salt. Also, partitions became more extreme for all components as ABS strength increased. That is, partition coefficients became either vanishingly small if starting below 1 or very large if above 1. The effect can be related to the larger amounts of water that equilibrate with the salt phase at stronger ABS. Sugars typically partition to the extract (salt) phase. Furanics and acetic acid, which can be poisons to downstream fermenation processes, are typically rejected. This also allows the IL to be cleaned up downstream, since furanics, acetic acid and extractive compounds (fatty acids, terpenes, etc) are either extractable into an organic (low polarity) phase or volatile.

The ABS method for separating sugars can produce an extract stream containing, in the order of decreasing concentration: kosmotropic salt > glucose > xylose > [BMIMJC1. In some cases, complete recovery of the salt extractant and IL at high sugar yields can be accomplished using any one of several methods. As described herein, methanol can precipitate strong kosmotropes such as ash) and K ₂ C0 ₃ (potash) in the presence of large (-25%) sugar concentrations, and without the need to acidify the extract. Methanol has a much higher solubility for glucose and other sugars than most other alcohols. For instance, at 22 °C D-glucose dissolves up to 23.5 g/L in pure methanol, but only 1.96 g/L in ethanol and even less in either isopropanol or 1-propanol. At the same time, the solubility of soda ash or potash in methanol/water systems drop to nearly zero at 80% methanol and above. The large ratio of sugar-to-salt solubility allows methanol to solubilize the sugar and precipitate the salt, whereas ethanol or acetone solubilized sugars only partially, resulting in a separate phase or slurry, and poor extraction. Substituting salt with methanol affords an attractive route to clean sugars because methanol boils at a low temperature (65 °C) and does not form an azeotrope with water. Ternary plots omitting either the salt or glucose (FIG. 11), and the temperature dependence of solubility in pure water (FIG. 12) are presented. The complete method was demonstrated starting from both simulated and actual hydrolysates, and ending with concentrated sugar solutions or sugar crystals. The operations included: i) hydrolysate extraction by soda ash or potash, ii)

kosmotropic salt precipitation by methanol, Hi) salt separation by filtration and wash, iv) pH adjustment (ion exchange), and v) methanol recovery by evaporation.

In one example, about 100 mL of untreated sugarcane bagasse hydrolysate (-40% water) was filtered to remove lignin and extracted with 200 mL of soda ash solution in a 0.5-L separatory funnel. The result was not concentrated and ABS took -55 min to equilibrate, but extracted 55% of xylose and 61 > of glucose in a single step. Then, the bottom (extract) phase was transferred to a stirred beaker and precipitated with an equal amount of methanol. Precipitation was nearly instantaneous, and the resulting slurry was submitted to a standard vacuum filtration and wash with 80% methanol in water. This was performed with a filter paper lined Buchner funnel attached to an Erlenmeyer flask and vacuum pump. A specific cake resistance of 2xl0 ⁸ m/kg was measured at a 75 kPa vacuum and a cake growth rate of -500 cm/hr. Near- quantitative recovery was achieved with a wash ratio of only -1 (FIG. 13). The cake did not crack and was easily discharged from the filter medium afterwards as shown in FIG. 14. The filtrate was alkaline and was neutralized before methanol evaporation to prevent sugar degradation. This operation used a small amount (-1%) of HC1 8 M to reach pH = 7, simulating the neutralization effect of an ion exchanger. Methanol (and some water) was evaporated in a wide beaker at 55 °C under stirring, resulting in concentrated and clean sugars. The discharged cake redissolved in ambient temperature water in a few seconds to reconstitute the concentrated extractant solution. By the end of the method (neutral concentrated sugars), 99.8%> of glucose and 98.6%> of xylose were recovered in the extract. Only trace amounts of sugar were retained in the cake and no sugar degradation products were found in any of the steps. A second extraction from the hydrolysate afforded another -24% of remaining glucose, for a total of -85% yield from the hydrolysate, simulating the first two steps of a multi-stage extraction.

The method was also demonstrated with K ₂ C0 ₃ (potash). Potash can be a stronger kosmotrope and reach higher selectivities and faster separations at equal concentrations. Here, even though the procedure was similar to soda ash, equilibrium was reached in under 10 min at rest and only a few seconds under low-g centrifugation as shown in FIG. 15. A single stage extracted 96%> of glucose and only 4% of IL. Potash can be more water-soluble than soda ash and required a 5 : 1 volumetric ratio of methanol to extract to achieve complete salt precipitation (versus 1 : 1 for soda ash).

However, since the glucose partition coefficient is also about 5 -fold higher, the volume of extractant required is 1/5*, and the amount of methanol used was about the same as with soda ash. As before, the result was neutralized and evaporated until sugar crystals were obtained as shown in FIG. 16. Sugar yields were nearly quantitative.

The process front end is optional (not shown) and can comprise de- ashing and other biomass handling steps leading to the hydrolysis reactor. Hydrolysis can proceed by dissolution in IL and acid-catalyzed hydrolysis by gradual water addition to give high glucose yields (currently 95%). After removal of the lignin, which can achieve a quantitative (-100%) recovery of the IL by simple vacuum filtration and water wash, the result can be fed to the sugar recovery process (FIG. 17 A and FIG. 17B).

With reference to FIG. 17 A, the flow sheet shows an example of a system for performing ionic liquid separations using a kosmotropic salt and an anti- solvent. An ionic liquid solution containing a solute to be recovered (e.g., sugar) 1700 can be mixed with a kosmotropic salt 1702 to form a mixutre in a mixing vessel 1704. The mixture typically contains water. In a settling vessel 1706, an ABS can form having an ionic liquid phase 1708 and an aqueous phase 1710 containing the kosmotropic salt. The ionic liquid phase can be recycled 1712. The solute partitions into the aqueous phase (e.g., by a factor of about 1 : 1, about 1 :5 about 1 : 10 about 1 :50 about 1 : 100 about 1 :500, or more). The aqueous phase can also contain some IL.

The system shown in FIG. 17 A also provides a means for recovering the kosmotrope and solute. The aqueous phase can be contacted with an anti-solvent 1714 (e.g., methanol) to precipitate the kosmotrope 1716 in a vessel 1718 (e.g., a counter- current column). In some cases, additional kosmotrope and/or IL 1720 can be recovered in a secondary recovery unit 1722 (e.g., an ion exchanger). The anti-solvent can be recovered and optionally recycled 1714 from the solution, for example in a distillation column 1724. This leaves a product solution 1726 comprising the solute. The distillation unit 1724 and the secondary recovery unit 1722 can be in either order.

FIG. 17B shows an implementation of the process of FIG. 17 A An this case, hydrolysate without lignin can be fed to the bottom of a counter-current column (1). Mixer-settlers are also applicable, but counter-current operation can minimize the extractant volume and process scale. By varying the flowrates of feed and extractant, complete extraction of sugars can be achieved but with some entrainment of IL in some cases. The extract can be fed to a stirred tank, in which the salt is precipitated with methanol (2). The slurry can be filtered and washed or centrifuged and washed at (3) keeping methanol vapor contained. The filtrate can pass through ion exchangers to remove and recycle entrained [BMIMJC1. The result, which is now neutralized, can be distilled at (5) to recover all of the methanol, yielding concentrated or partially crystalized clean sugars. Soda ash cake can be re-dissolved with makeup water at a stirred tank (6), and pumped (7) back to the column (1).

This sugar recovery process shown in FIG. 17 A and FIG. 17B has a number of noteworthy features. First, it can achieve near-quantitative (-100%) recovery of sugars present in the hydrolysate. Kosmotropic salt extraction rejects not only IL but also fermentation poisons, both the ones already present in biomass {e.g. acetic acid and extractives) and the small amount of furanic side-product generated during hydrolysis (-0.2% of hydrolysate). The extractants soda ash (or potash) and methanol are all inexpensive. The distillation column (5) can be short and inexpensive because the amount of sugar and water are comparable, substantially lowering the vapor pressure of the water fraction relative to methanol. Sugars can be concentrated substantially in the extract phase, therefore the ratio of extractant to hydrolysate required for complete sugar recovery is l/K _^ , typically < 0.1, allowing the sugar recovery process to have a modest scale and cost. Overall, one embodiment of the process process has only 7 unit operations of carbon steel construction. Salt and methanol contamination at the extraction column (1) can be tolerated. In some instances, the method is highly flexible as it can be optimized by using different kosmotropic salt species, salt concentrations, relative flowrates, residence times, and temperatures.

In some embodiments, the method uses co-solvents. Some polar aprotic organics can intermix with cellulose-dissolving ILs without affecting its solubility towards cellulose. For instance, a co-solvent formed by [BMIMJCl and the polar aprotic l,3-dimethyl-2-imidazolidinone dissolves similar amounts of cellulose compared to the pure IL. However, because dissolution can be a mass transport rate limited process and viscosity is now lower, dissolution can take only a few minutes instead of a few hours. This enhancement can be highly beneficial by reducing the size of vessels and amounts of IL being handled within the process.

To evaluate how a co-solvent affects separations, an ABS was created starting from [BMIMJCl dissolved in select co-solvents. A solvatochromic analysis concluded that good co-solvents for cellulose dissolution typically combined a high polarity and hydrogen bonding basicity with a low hydrogen bonding acidity. In some cases, the co-solvent does not interfere with acid catalysis, or react with sugars or other biomass components. Although many other species are applicable, dimethyl sulfoxide or DMSO ($1.0/kg), acetonitrile ($1.0/kg), sulfolane ($0.5/kg), and propylene carbonate ($1.0/kg) were selected for their relatively low cost in this example. Compositions of IL, co-solvent and kosmotropic salt assumed mass ratios of 1 : 1 : 1 or 1 : 1 :2, respectively. Here, we started from a simulated IL hydrolysate solution (5% glucose, 2% xylose) and used a K ₂ HP0 ₄ solution near saturation to drive the ABS. The results are shown in FIG. 18. Compared to pure IL, these co-solvents produced a marked enhancement to selectivity, resulting in higher glucose and lower IL concentrations in the extract. The effect was modulated by composition, with 1 : 1 :2 showing the greatest benefit (except for DMSO). Enhancements in selectivity ranged from 2.3 to 3.0-fold for DMSO to 3.6 to 5.7-fold for acetonitrile, which attained a selectivity of -1500 (K _^ = 0.023 and Κ _∞χ = 34.6). The latter selectivity can be sufficient to achieve a low IL loss (0.1%) without the need for an ion exchanger. In addition, the larger concentration of glucose in the extract phase can reduce the overall scale of the sugar separation process, further reducing cost. Finally, the co-solvent was also strongly rejected from the salt phase, with K _∞ . _∞hta « 0.01 for all tested (Κ _∞Μ ~Κ^ „ _« ,). As a result, additional process steps to recover the co-solvent are not typically required.

The kosmotrope can be a strong kosmotrope or a weak kosmotrope, or have any amount of kosmotropic behavior. An example of a weak kosmotrope is Na ₂ C0 ₃ , which imparts weak liquid separations from ionic liquids, but can be easy to remove from water or water-sugar solutions. For instance, even when saturated, Na ₂ C0 ₃ induces separation only slowly, taking up to 30 minutes or more to segregate and reach equilibrium. In some cases, weak kosmotropes perform poorly in extracting sugars. The efficiency of sugar extraction can be measured thermodynamically by the partition coefficients of the various solutes at equilibrium. For example, the partition coefficient of sugar in a weak kosmotrope can be typically between about 2 and about 5. This means the concentration of sugar in the extract (kosmotrope) phase is 2 to 5 times higher than in the raffmate (ionic liquid) phase at equilibrium. Also, the partition coefficient of ionic liquid is not particularly low (e.g., about 0.1). In other words, the concentration of ionic liquid in the extract is about 10-fold lower than in the raffmate. This gives a selectivity for sugar and against ionic liquid between about 10 and 50, where selectivity is simply the ratio of partition coefficients.

When using a weak kosmotrope, the resulting extract can contain principally water and salt (the weak kosmotrope), as well as significant quantities of sugar and ionic liquid. Both salt and ionic liquid are removed from the sugar stream in some cases. The salt can be precipitated from solution by an anti-solvent such as methanol or ethanol. Because the kosmotrope is weak, removing it from solution requires a relatively small amount of anti-solvent (compared to a strong kosmotrope). For example, to remove Na ₂ C0 ₃ from the extract, typically a 1 : 1 volumetric ratio of methanol to extract is sufficient. The salt can be recovered from the solution by

filtration or centrifugation. However, the anti-solvent does not precipitate the ionic liquid, which is highly miscible in water.

If the methods of the present disclosure are performed with a strong kosmotrope such as K ₂ C0 ₃ , ionic liquid contamination (e.g., in the sugar product stream) is greatly reduced but the kosmotrope may persist, creating similar problems downstream. For example, the strong kosmotrope K ₂ C0 ₃ is far more soluble than

Na ₂ C0 ₃ in water and imparts a much higher pH. When mixed with hydrolysate, K ₂ C0 ₃ auto-separates very quickly and reaches equilibrium in a matter of a few minutes. In addition selectivities for sugar and against ionic liquid can be greater than 100. In some cases, over 90% of glucose can be extracted in a single stage, while co-extracting only 1% or less of the ionic liquid, use of a strong kosmotrope can result in a much cleaner liquid-liquid separation, but can also hinder precipitation of the salt with anti-solvents. For instance, with K ₂ C0 ₃ a volumetric excess of at least 6: 1 of methanol can be

required. The handling of large volumes of anti-solvent can be undesirable at large scale. In addition, even when employing large excess of anti-solvent all the salt cannot be recovered without losing a large amount of the sugar (e.g., about 50%). This

limitation is due to the limited solubility of sugar in a solvent that contains about 95% methanol or more.

In some embodiments, the methods described herein use a strong

kosmotrope that can be reversibly converted into a weak kosmotrope to facilitate its separation and recycle (referred to as a tunable extractant).

One tunable extractant is described in the following reversible reaction:

C0 ₂ + H ₂ 0 + K ₂ C0 ₃ 2KHC0 ₃ (Equation 1)

As described herein, K ₂ C0 ₃ is a strong kosmotrope. Its saturated

solution is over 50%> salt, has a density of over 1.5 g/cm ³ and a pH of at least 14. On the other hand, the bicarbonate form of potassium (KHC0 ₃ ) is a weak kosmotrope. Its saturated solution is only 25% salt and has a pH of 8.6. The forward reaction is favored by low temperatures and C0 ₂ pressure, whereas the reverse reaction can be driven by high temperatures and C0 ₂ removal. Potassium carbonates are non-toxic, relatively cheap, and widely available industrially.

Some key relative solubilities for this strong/weak kosmotrope system (switchable solvent) are shown in FIG. 19 and FIG. 20. As seen in FIG. 19, K ₂ C0 ₃ is more soluble than KHC0 ₃ at all temperatures from 0°C to 60°C, however the difference in solubility is greater at lower temperature than at higher temperature. The solubilities of glucose and potassium bicarbonate are shown in FIG. 20 as a function of the concentration of methanol in water. Methanol can be used as an anti-solvent.

FIG. 21 shows a schematic drawing of a process for hydrolyzing lignocellulosic biomass in ionic liquid and separating the hydrolysate into its component fractions. The ionic liquid and other solvents are recycled in an "ionic liquid cycle" a "carbonate cycle" and an "alcohol cycle". Reactions are shown as squares and separations are shown as circles with the flow of major components through the process designated by arrows. The method can be performed in any suitable process

configuration and/or with any suitable equipment, an example of which follows herein.

The present disclosure provides several options for recovering solutes from ionic liquids using inter-conversion of strong and weak kosmotropes. Some of these systems are shown in FIG. 22 A, FIG. 22B and FIG. 22C. Streams and units that are similar to those in FIG. 1 A share like numerals and are described in detail above. For example, the system for producing the aqueous phase 1710 containing the kosmotrop and solute can be generated in the same or similar way using units and streams 1700 to 1710. From there, options exist for converting the strong kosmotrope to a weak kosmotrope and recovery of the various components.

With reference to FIG. 22A, C0 ₂ 2200 can be contacted with the aqueous phase in a vessel 2202 to convert the strong kosmotrope to a weak kosmotrope (e.g., bicarbonate salt). In some cases, a portion of the weak kosmotrope precipitates and can be recovered 2204. Additional amounts of the weak kosmotrope 2206 can be recovered using an anti-solvent 1714. Compared to using an anti-solvent without conversion to a weak kosmotrope (e.g., as shown in FIG. 17 A), the present embodiment can require less anti-solvent (e.g., by a factor of at least 2, 4, 6, 8, 10, or more).

In the many embodiments described herein, precipitated kosmotrope

(strong and/or weak) can be recovered by a variety of methods including centrifugation, settling, filtration, and the like. In some cases the recovered kosmotrope is washed (e.g., with water). The recovered weak kosmotrope can be converted to a strong kosmotrope by steam stripping to regenerate C0 ₂ (not shown).

Contacting with anti-solvent and conversion to a weak kosmotrope can be performed in any order. With reference to FIG. 22B, some of the strong kosmotrope can be precipitated 1716 with anti-solvent 1714 prior to conversion to a weak kosmotrope. In some cases, the amount of anti-solvent used and/or the amount of strong kosmotrope precipitated can be less than (e.g., by a factor of at least 2, 4, 6, 8, 10, or more) the case for embodiments that do not convert to a weak kosmotrope (e.g., as shown in FIG. 17A). Continuing with FIG. 22B, C0 ₂ 2208 can be used to convert the strong kosmotrope to a weak kosmotrope (in a vessel 2210) and, in some cases, thereby precipitate 2212 the weak kosmotrope. As described above, ion exchange 1722 and distillation 1724 can be performed in either order.

In some cases, contacting with anti-solvent and conversion to a weak kosmotrope can be performed in a single vessel. With reference to FIG. 22C, the single vessel 2214 can be used to contact the aqueous phase with both C0 ₂ 2216 and the anti- solvent 1714, thereby, in some cases, precipitating a weak kosmotrope 2218.

FIG. 22D shows an implementation of the process of FIG. 22C. Here, mixing the carbonate form of the extractant with hydrolysate results in separation proceeding quickly and at high selectivity (1). The extract is then mixed with an anti- solvent such as methanol (2), which can initially result in a two-phase system (both phases being liquids) with relatively little intermixing. This mixture is placed in a reactor and C0 ₂ is loaded (H ₂ 0 is already present) (2). The reactor can be designed to maximize mass transfer. Carbonate anions are converted to bicarbonate, which precipitate from solution with the help of the anti-solvent. The result is a liquid-solid mixture (slurry) which can be easily separated (e.g., using filtration and/or

centrifugation) (3). The solid fraction comprises KHCO ₃ which can be regenerated in a later step (6). The liquid fraction contains mainly anti-solvent, water and sugar, and a much smaller amount of both salt and ionic liquid contaminants. The sugar solution can be polished using ion exchange (4) to remove any residual ionic liquid and distillation to remove the anti-solvent (5).

Note that the anti-solvent is not required to cause precipitation of the salt. That is, since the carbonate form is much more soluble than the bicarbonate, some precipitation occurs regardless. The use of the anti-solvent, however, can be desirable to reduce the salt concentration (e.g., to below about 10%, below about 5%, or below about 1%).

Returning to FIG. 22D, carbonate can be regenerated from bicarbonate by driving the reaction in reverse. One method for accomplishing this is to first dissolve the bicarbonate cake in water. The solution can then be flowed in a stripping column (6). The stripping column can then be fed from the bottom by steam and from the top by the salt solution. The steam and salt flow counter-currently as the steam both heats the salt and removes C0 ₂ , promoting the formation of carbonate. Steam temperature and/or pressure can be low, such as the steam obtained as the output from other unit operations. Generally, any temperature above ambient will promote the reverse reaction. Also, the steam can dip to sub-atmospheric pressures since C0 ₂ removal is an objective. In some cases, other gasses that are not C0 ₂ can be substituted. Aqueous carbonate can be obtained as the bottoms product from the stripping column. This stream may be adjusted to obtain a saturated solution. This solution can then be cooled and used as the extractant to extract sugar from fresh hydro lysate, thus completing the cycle.

The kosmotropic salt can forms a strong kosmotrope or a weak kosmotrope. In another aspect, the present disclosure provides a method for recovering a solute from an ionic liquid, the method comprising: providing a composition comprising an ionic liquid, water and a solute; mixing the composition with a strong kosmotrope to form a first phase and a second phase, wherein the first phase comprises the ionic liquid and the second phase comprises water, the solute, the strong

kosmotrope and optionally some of the ionic liquid; separating the first phase from the second phase; and (in the second phase) converting the strong kosmotrope to a weak kosmotrope. Forming the first phase and the second phase can be performed in a counter-current column.

In another aspect, the present disclosure provides a system for recovering a solute from an ionic liquid. The system can comprise an aqueous biphasic system (ABS) formation module capable of forming an ABS, which ABS comprises an ionic liquid phase and an aqueous phase, wherein the aqueous phase comprises a kosmotrope and a solute to be recovered; and a kosmotrope recovery module in fluid communication with the ABS formation module, wherein the kosmotrope recovery module is capable of contacting the aqueous phase with an anti-solvent to precipitate and recover the kosmotrope.

In some embodiments, the system further comprises a kosmotrope conversion module in fluid communication with the kosmotrope recovery module, which kosmotrope conversion module is capable of converting a strong kosmotrope to a weak kosmotrope.

In some embodiments, the system further comprises an ion exchange module in fluid communication with the kosmotrope recovery module, which ion exchange module is capable of recovering residual ionic liquid and/or kosmotrope from the aqueous phase; and a distillation module in fluid communication with the ion exchange module, which distillation module is capable of recovering the anti-solvent from the aqueous phase.

The kosmotrope conversion module can be before or after the kosmotrope recovery module. The kosmotrope conversion module and the kosmotrope recovery module can be performed in a single vessel. The ion exchange module can be before or after the distillation module. When the solute is a sugar, which can be degraded at high H, it can be preferable to have ion exchange before distillation.

In some embodiments, the strong kosmotrope is converted to the weak kosmotrope in the presence of an anti-solvent. The strong kosmotrope can be converted to the weak kosmotrope by lowering the temperature of the second phase in some cases. In some instances, the strong kosmotrope can be converted to the weak kosmotrope by increasing the partial pressure of C0 ₂ in the second phase. Converting the strong kosmotrope to the weak kosmotrope can precipate the weak kosmotrope from the second phase.

The method can further comprise recovering the weak kosmotrope from the second phase (e.g., by filtration or centrifugation). In some embodiments, the method further comprises (re)converting the weak kosmotrope into the strong kosmotrope (e.g., by dissolving the weak kosmotrope in water and contacting it with steam in a stripping column), and optionally recycling the strong kosmotrope. The weak kosmotrope can be converted to the strong kosmotrope by increasing the temperature and/or decreasing the partial pressure of C0 ₂ .

In some cases, the method further comprises recovering ionic liquid and/or kosmotropic salt from the filtrate and optionally recycling the ionic liquid and/or kosmotropic salt. This can be performed with ion exchange, electrophoresis, electrofiltration, ion-exclusion chromatography, dielectrophoresis, electrodialysis, reverse osmosis, nanofiltration, ultrafiltration, microfiltration, membrane pervaporation, simulated moving bed chromatography, or any combination thereof.

In some cases, the method further comprises recovering the anti-solvent from the filtrate and optionally recycling the anti-solvent. This can be performed by distillation, extractive distillation, azeotropic distillation, high pressure distillation, low pressure distillation, evaporation, flashing, liquid-liquid extraction, or any combination thereof.

In some embodiments, the strong kosmotrope is a carbonate salt (e.g., K ₂ C0 ₃ ). In some cases, the weak kosmotrope is a bicarbonate salt (e.g., KHC0 ₃ ).

In some instances, the selectivity for sugar against ionic liquid in the

ABS is at least about 10, at least about 20, at least about 40, at least about 60, at least about 80, at least about 100, at least about 150, at least about 200, at least about 250, at least about 300, or at least about 500.

In some embodiments, the first phase and the second phase are formed in the ABS in less than about 60 minutes, less than about 40 minutes, less than about 20 minutes, less than about 10 minutes, less than about 5 minutes, less than about 3 minutes, or less than about 1 minute.

In some cases, the ratio of the volume of the anti-solvent to the volume of the second phase is less than about 10, less than about 8, less than about 6, less than about 4, less than about 2, or less than about 1.

After performing the methods described herein, the second phase can comprise at least about 75%, at least about 80%>, at least about 85%, at least about 90%>, at least about 95%, at least about 97%, or at least about 99% of the solute present in the composition. After performing the methods described herein, the second phase comprises at most about 5%, at most about 3%, at most about 1%, at most about 0.5%, at most about 0.1%, at most about 0.05%, or at most about 0.01% of the ionic liquid present in the composition.

The (salt) anti-solvent can be an alcohol, a diol, a ketone, an ester, an acid, or an amine. In some cases, the (salt) anti-solvent is polar and organic. The (salt) anti-solvent can be methanol, ethanol, propanol, acetone, or any combination thereof.

In some embodiments, the composition and/or the strong or weak kosmotrope further comprises a co-solvent. The composition can be obtained by hydrolyzing biomass and/or a biomass component in the ionic liquid. In some cases, the solute is a sugar (e.g., glucose). In some instances, the first phase further comprises acetic acid, furanic compounds, extractives, or any combination thereof. The extractives can comprise one or more biomass components other than cellulose, hemicellulose, lignin, or derivatives thereof. In some cases, the method further comprises separating the acetic acid, furanic compounds, or extractives from the first phase (e.g., by distillation or liquid- liquid separation). Anti-Solvents

Anti-solvents can be used to separate a solid from the ionic liquid. An anti-solvent is a species that causes a previously dissolved species to precipitate from solution. The ionic liquid solution can be a biomass hydrolysate. The solid can be derived from biomass (e.g., is a sugar such as glucose). In some embodiments, the ionic liquid comprises a halide anion (e.g., l-butyl-3-methylimidazolium chloride).

In an aspect, the present disclosure provides a method for precipitating a solid from an ionic liquid. The method can comprise contacting an anti-solvent with an ionic liquid solution to precipitate a solid from the ionic liquid solution. In some cases, the solid is not cellulose and/or the anti-solvent is not water. The method can further comprise washing the precipitated solid with the anti-solvent. In addition to using the anti-solvent to precipitate a solid, the anti-solvent can be used to wash ionic liquid from a solid (whether the solid was precipitated by addition of the anti-solvent or not). In another aspect, the disclosure provides a method for recovering an ionic liquid from a solid, the method comprising washing the solid with an anti-solvent, wherein the solid is substantially insoluble in the anti-solvent and the ionic liquid is miscible with the anti-solvent. In some cases, the solid is not lignin and/or the anti-solvent is not water.

The method for precipitating a solid or washing a solid of ionic liquid can further comprise evaporating the anti-solvent from the solid.

The method can be more effective when the ionic liquid solution has a low amount of water. In some cases, the method further comprises drying the ionic liquid solution prior to contacting the ionic liquid solution with the anti-solvent. In some embodiments, the ionic liquid solution contains less than about 50%, less than about 40%), less than about 30%>, less than about 20%>, less than about 10%>, less than about 5%o, less than about 3%, less than about 1%, less than about 0.5%>, less than about 0.1%), less than about 0.05%>, or less than about 0.01% water by mass.

The solid is typically insoluble or slightly soluble in the anti-solvent. In some embodiments, the solubility of the solid in the anti-solvent is less than about 3%, less than about 1%, less than about 0.5%>, less than about 0.1 %, less than about 0.05%, or less than about 0.01 % by mass.

Any amount of anti-solvent can be added to the ionic liquid solution. In some embodiments, the amount of anti-solvent added to the ionic liquid solution is at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%), at least about 60%, at least about 70%, at least about 80%, at least about 100%, at least about 120%, at least about 150%, at least about 200%, or at least about 500% relative to the mass of ionic liquid solution.

The solid can be washed with any amount of anti-solvent. In some instances, the solid is washed with at least about 50%, at least about 100%, at least about 150%), at least about 200%, at least about 300%), at least about 400%), at least about 500%), at least about 600%), at least about 700%), or at least about 800%) ionic liquid when compared with the mass of solid. In some cases, the solid is washed with the anti-solvent until the mass of ionic liquid remaining on the solid is less than about 3%), less than about 1%, less than about 0.5%, less than about 0.1%, less than about 0.05%), or less than about 0.01% compared to the mass of the solid.

The anti-solvent is typically miscible with the ionic liquid. In some cases, the anti-solvent is polar. In some embodiments, the anti-solvent dissolves less than 3%, less than 1%, less than 0.5%, less than 0.1%, less than 0.05%>, or less than O.O /o the solid by mass.

The anti-solvent can be any suitable species. In some cases, the anti- solvent is acetonitrile (ACN), tetrahydrofuran (THF), propylene carbonate, 1-butanol, ethanol, sulfolane, acetone, or any combination thereof.

The method can be performed at any temperature. In some cases, the temperature of the anti-solvent and/or ionic liquid solution is less than about 20 °C, less than about 15 °C, less than about 10 °C, less than about 50 °C, less than about 0 °C, or less than about -5 °C.

Acetonitrile (ACN), tetrahydrofuran (THF), tetrafluoroethanol (TFE), and other polar substances dissolve very little glucose, but are arbitrarily miscible in [BMIM]C1, [HMIM] HS0 ₄ , [HNEt ₃ ]HS0 ₄ , and other ILs.

In one example, ACN was added to hydrolysate simulant (formula as described above) at a 10: 1 volumetric ratio. After several hours at rest and 0 °C, sugars crystalized out of solution. A direct addition of an anti-solvent to the hydrolysate can accomplish sugar separation, followed by the recovery of ACN by evaporation (BP = 82 °C). However, the large volumetric ratios and long residence times can require large amounts of ACN in some cases. Successive trials started from hydrolysates containing less water, which can improve the rate of crystallization.

In another example, a dry mixture of 88% glucose and 12% [BMIMJC1 was used. The mixture was dissolved in a comparable amount of ACN and centrifuged, resulting in a translucent pale-yellow liquid phase over white crystals. The liquid was decanted and saved, and solids were washed again with fresh ACN. This was repeated two times, followed by a larger third and final wash. HPLC analysis of all washes and final product are summarized in FIG 23. By the end of the wash series the amount of IL in sugar became undetectable, suggesting at most 0.1%>. At the same time, 4%> of the starting sugar amount was washed out. However, the resulting solution of ACN, IL and a small amount of sugar was easily evaporated and condensed to yield pure ACN and a dilute solution of intact sugar in IL accounting for the full amount washed out. The latter can be recovered fully simply by mixing with incoming hydrolysate.

FIG. 24A is shows an example of a system for performing ionic liquid separations using an anti-solvent. The system can include an IL/anti-solvent mixing vessel 2400, a solute recovery unit 2402 and an anti-solvent recovery unit 2404. The ionic liquid solution 2406 can include a solute that is to be recovered. Mixing of the ionic liquid solution with the anti-solvent 2408 can precipitate the solute, which can be recovered 2410 by the solute recovery unit 2402. Since ionic liquids are typically not volatile, the anti-solvent can be recovered by simple evaporation and recycled to the mixing vessel 2400. In some cases, the precipitated solute is also washed with the anti- solvent. The system produces an ionic liquid stream 2412, which can be recycled to the process.

FIG. 24B is a method for recovering IL from sugars, and delivering a clean sugar product. This is accomplished in three operations: i) IL dissolution in ACN (1), ii) sugar filtration (or centrifugation) and wash (2), and Hi) ACN evaporation and condensation (3). Starting samples also can have various amounts of water. In general, the more water, the more ACN was required to achieve similar results. As such, it is likely more economical to dry the material prior to purification.

Other polar species were demonstrated in order to compare and contrast ACN in a broader context. Here, we measured the solubilities of glucose, [BMIMJC1 and [HMIM]HS0 ₄ in 10 other liquids. Even though glucose is only slightly soluble in all but DMSO and methanol, its solubility in ACN is indeed the lowest.

Tetrahydrofuran boils at a low 66 °C and could be used in lieu of ACN. Interestingly, [HMIM]HS0 ₄ is immiscible in most solvents where [BMIMJC1 is miscible, and vice- versa.

Volatile Salts

In an aspect, the present disclosure provides a method for recovering biomass components from an ionic liquid. The method can comprise adding a volatile salt to a hydrolyzed biomass composition to form a first phase and a second phase, where the hydrolyzed biomass composition comprises an ionic liquid, water and one or more biomass components. The first phase can comprise the ionic liquid (e.g., at least about 70%, at least about 80%>, at least about 90%>, at least about 95%, or at least about 99%) of the ionic liquid from the hydrolyzed biomass composition). The second phase comprises water, one or more biomass components and optionally some of the ionic liquid.

In some embodiments, the volatile salt is added to the hydrolyzed biomass composition by dissolution. In some cases, the volatile salt is added to the hydrolyzed biomass composition by pressurization with precursors of an anion and/or a cation of the volatile salt. The pressure of the precursors can be to a pressure of at least about 5 bar, at least about 10 bar, at least about 15 bar, at least about 20 bar, at least about 30 bar, at least about 40 bar, at least about 50 bar, at least about 60 bar, at least about 80 bar, or at least about 100 bar. The precursor can react with water to form the anion and/or cation of the volatile salt. In some instances, the precursor of the anion is carbon dioxide and the anion of the volatile salt is carbonate and/or bicarbonate. In some cases, the precursor of the anion is ammonia and the cation of the volatile salt is ammonium. The volatile salt can be, for example, ammonium hydroxide (NH ₄ OH) or ammonium carbonate

(NH ₄ ) ₂ C0 ₃ .

In some embodiments, the temperature of the hydrolyzed biomass composition, the first phase and/or the second phase is less than about less than about 20 °C, less than about 15 °C, less than about 10 °C, less than about 50 °C, less than about 0 °C, or less than about -5 °C.

The method can further comprise recovering the volatile salt from the first phase and/or the second phase by heating, sparging with an inert gas, or any combination thereof. In some cases, the volatile salt is recovered as a precursor.

Carbonic acid and ammonium hydroxide can be used as volatile kosmotropes to drive ABS. Pressurizing with C0 ₂ up to 66 bar and 12 °C formed ABS in [BMIM]BF ₄ . The method can be effective using ILs with fluorinated anions. Higher pressures can force more C0 ₂ to dissolve in the IL, but it can also lower the pH (via carbonic acid formation), and lowering the pH tends to weaken ABS.

In some cases, ammonium hydroxide is more volatile. NH ₄ OH is similar to NaOH, which creates strong ABS, but can be recovered as NH ₃ by depressurization, heating or sparging. Driving ABS formation with ammonia at higher pressures and lower temperatures can boost the concentration of ammonium hydroxide sufficiently to form ABS. NH ₃ can be sparged from water leaving intact glucose.

Reactive Extraction

In an aspect, the present disclosure provides a method for recovering a sugar from an ionic liquid. The method can comprise: (a) providing a sugar dissolved in an ionic liquid at an acidic pH; (b) alkylating the sugar with an alcohol to create an alkylglycoside; and (c) recovering the alkylglycoside from the ionic liquid. In some cases, the alkylglycoside is recovered by a phase separation. The method can further comprise regenerating the sugar and the alcohol by hydrolysis. The sugar can be glucose.

The pH of the ionic liquid can be acidic. In some embodiments, the pH of the ionic liquid is less than about 7, less than about 6, less than about 5, less than about 4, less than about 3, or less than about 2.

In some cases, the method further comprises drying the ionic liquid prior to alkylating the sugar. The ionic liquid can be dried using pervaporation, evaporation of water, or azeotropic distillation. In some embodiments, the ionic liquid comprises less than about 10%, less than about 5%, less than about 1%, less than about 0.5%, less than about 0.1 %, less than about 0.05%>, or less than about 0.01% water by mass.

In some embodiments, the alcohol is 1 -butanol, 1-hexanol, 1-octanol, or any combination thereof. The alcohol can be in molar excess relative to the sugar.

The alkylation can be performed at about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 120°C, or about 150°C.

Reactive extraction has been reported using boronic acids, which complexed with sugars in IL solution to create structures extractable in an organic phase. Sugars can then be regenerated simply by stripping with dilute acid. This procedure requires an alkaline environment to create the active boronate form. In contrast, the present method exploits the same or similar acid catalyst already present in the hydrolysate to catalyze a reactive extraction method in an acidic environment.

Acid catalysis was used to alkylate glucose with an alcohol, affording alkylglycosides as shown here:

Reaction mixtures comprised dry hydrolysate simulants ([BMIMJC1, glucose and acid at similar proportions) with a molar excess of the linear alcohols 1- butanol, 1-hexanol or 1-octanol. These mixtures were kept at 90 °C without stirring, and composition was monitored over time (FIG. 25 - FIG. 28). All examples show the kinetics of glucose conversion to two products, a and β-alkylated glucopyranosides. Hexylated products elute later from the chromatographic column than butylated ones, as expected from its greater hydrophobicity. In octylation, glucose consumption remains consistent with other reactions, but the product is not detected in the chromatogram, suggesting they are not water-soluble.

The presence of water generally slows down alkylation. In actual hydrolysates, alkylation can proceed during or after drying, for instance by evaporation in the presence of 1-decanol. Alternatively, we have dried the IL azeotropically to < 1% water with a xylene reflux as described below. After transport through an organic phase (e.g. hexane), glucose and alcohol can be regenerated by hydrolysis. Alkylation was reasonably fast and used only common and recyclable reagents. Importantly, no IL was consumed and no side-products were produced. Azeotropic Drying

In an aspect, the present disclosure provides a method for drying an ionic liquid. The method can comprise: (a) adding an azeotropic agent to a mixture comprising ionic liquid and water, wherein the azeotropic agent forms an azeotrope with water; and (b) evaporating the azeotrope from the mixture, thereby removing water from the mixture.

In some embodiments, the method further comprises: (c) condensing the evaporated azeotrope; (d) separating the water from the azeotropic agent; and (e) returning the azeotropic agent to the mixture. In some cases, the method further comprises (f) evaporating the azeotropic agent from the ionic liquid following evaporating the azeotrope from the mixture. In some instances, the method further comprises (g) evaporating at least some of the water from the mixture prior to adding an azeotropic agent to a mixture of ionic liquid and water. The operations of the method (e.g., (a)-(b), (a)-(e) or (a)-(g)) can be performed in a continuous process.

In some cases, the azeotropic agent phase-separates from the water when condensed. The evaporating can be a multi-effect or vapor recompression evaporation. The evaporating can be performed by heating the mixture. The mixture can be heated at least to the boiling point of the azeotrope. The evaporating can be performed at a pressure at which the azeotrope forms.

The azeotropic agent can be any suitable chemical or mixture (e.g. , an organic chemical). In some cases, the azeotropic agent is an aromatic chemical. In some instances, the aromatic chemical is toluene, xylene, or any combination thereof. In some cases, the azeotropic agent is an alkane (e.g., hexane, heptane, or any combination thereof).

The azeotropic agent can be an ionic liquid co-solvent for the dissolution of biomass (i.e., enhances the rate of solubilization or the solubility of biomass in ionic liquid), such as DMSO, acetonitrile, sulfolane, propylene carbonate, ethylene carbonate, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, pyrrolidinone, gamma- valerolactone, ε-caprolactam, N-methylpyrrolidinone, 1,3-dimethylpropylene urea, Ν,Ν,Ν',Ν'-tetramethyl urea, dimethylsulfoxide, acetyl acetone, tert-butanol, tert- pentanol, ethanol, acetone, or any combination thereof.

In some cases, the mixture further comprises a sugar, which can be derived from cellulosic biomass. The method can further comprise dissolving cellulose in the ionic liquid following evaporating the azeotrope from the mixture. The mixture can further comprise volatile components derived from cellulosic biomass and the volatile components are evaporated from the mixture when evaporating the azeotrope from the mixture.

In some embodiments, evaporating the azeotrope from the mixture is continued until the concentration of water in the mixture is at most about 5%, at most about 3%, at most about 1%, at most about 0.5%, at most about 0.1%, at most about 0.05%, or at most about 0.01% by mass as measured by Karl Fischer titration.

FIG. 29A shows an example of a system for azeotropic drying of an ionic liquid using a heterogeneous azeotropic mixture. The system can comprise a counter-current distillation column 2900 and a second distillation column 2902, optionally with reflux. A solution of ionic liquid and water 2904 enters the column and is contacted with an azeotropic agent 2906. The azeotropic agent provides the azeotrope for drying the ionic liquid, but can also extract other components from the ionic liquid {e.g. , organic compounds that are more soluble in the hydrophobic azeotropic agent than in the ionic liquid). After contacting, the azeotrope 2908 emerges from the column, is condensed and the lighter phase comprising the azeotropic agent can be recycled back to the column 2907 and the heavy phase comprising water 2910 is removed.

(Optionally the overhead stream can be separated by other means such as distillation (not show) in the case of a homogeneous azeotrope.) In some cases, compounds more volatile than the ionic liquid azeotropic agent mixture such as acetic acid can be removed from the overhead streams {e.g., using any suitable unit operation such as distillation, not shown). The ionic liquid with residual azeotropic agent 2912 can be distilled in column 2902 to separate the residual azeotropic agent 2914 and the dry ionic liquid 2916.

FIG. 29B shows an example of a process for drying the ionic liquid and recovering furanic and extractive compounds from an ionic liquid that has been used in a biomass hydrolysis process described herein. In this embodiment, solutes {e.g. , sugar) and precipitable solids {e.g., lignin) have been removed from the ionic liquid prior to extraction and azeotropic drying. The ionic liquid solution containing water and extractives can enter a counter-current liquid - liquid extraction column (18) at (9) using any suitable solvent (7) immiscible with the ionic liquid water solution. The overhead solvent stream (14) comprises the extraction solvent, furanics and extractives. The solvent can be separated from the overhead stream by any suitable means such as distillation (not shown) and returned (11) to the extraction step and the extractives are removed at (15). The separated extractive stream can be separated into its components (not shown). The bottoms can be transitioned to a distillation with reflux (19) as described in FIG. 29Λ where azeotropic drying removes water (23) and volatile components such as acetic acid. In column (20), the azeotropic agent (21) can be separated from the dry ionic liquid (25) and returned to the drying column at (31). The extracted dry ionic liquid is returned to the dissolution step.

FIG. 29 C shows a typical azeotropic drying apparatus used in the laboratory. The apparatus comprises a boiling flask 2918, a Dean Stark receiver 2920, and a condenser 2922. A mixture 2922 of ionic liquid, water and azeotropic agent (e.g., xylene) is boiled. The overhead product 2924 forms two phases when a heterogeneous azeotropic agent is used. In this example, heavier phase 2926 is aqueous and can be drawn out below the phase interface 2928. The condensed azeotropic agent is the lighter phase 2930 and can flow back into the boiling flask.

EXAMPLES

Example 1 - Initial Sample Preparation.

A solution is prepared containing water, ionic liquid and glucose. First, a concentrated glucose solution is diluted 20-fold with deionized water. To this, a small amount of ionic liquid is added and vortexed. The result is analyzed by an Agilent Technologies (Santa Clara, CA) 1200 Series HPLC equipped with refractive index and photodiode array detectors for determining phase composition. Elution is driven by an isocratic pump and an Aminex HPX-87H column (300 mm by 7.8 mm) from Bio-Rad (Hercules, CA) using a 5 mM H ₂ SO ₄ mobile phase at a flow rate of 0.6 mL/min at 65 °C. Integration of chromatographic peaks results in areas that can be related to species amounts via calibration curves. This analysis is done in Agilent ChemStation software. Gravimetric measurements are done by a Mettler Toledo analytical balance (Columbus, OH) with ±0.5 mg precision. The result is a solution containing 24 g/L ionic liquid and 57 g/L glucose.

Example 2 - Gel Formation.

A 15-mL centrifuge tube is loaded with 5 mL of the initial sample. The tube contains approximately 122 mg of ionic liquid and 285 mg of glucose. To this, 200 mg of polyacrylic acid partial potassium salt is added. The salt, a polyelectrolyte, are particles of less than 1 mm in size and about 0.1% cross-linking. The mixture is vortexed vigorously for 5 minutes and then centrifuged at 4000 g for another 5 minutes. The result show a liquid phase over a gel phase. The liquid phase is transferred to a separate clean vial and measured approximately 2.1 mL in volume. The liquid is viscoelastic due to the presence of some dissolved polyelectrolyte. Some 100 μΐ, of the liquid is diluted 10-fold in deionized water and analyzed by HPLC. Results show that the top liquid layer retains approximately 109 mg of the ionic liquid and 1 14 mg of the glucose. Example 3 - Gel Extraction with Water and No Acid.

To the vial with gel, 4 mL of deionized water is added. The heterogenous mixture is heated to 50 °C for 3 minutes and then vortexed vigorously for 5 minutes. Then the mixture is centrifuged at 4000 g for 5 minutes. The result is a liquid layer on top of a smaller gel layer. The liquid layer is sampled as gel extract and diluted 10-fold and analyzed by HPLC. Results show that this procedure liberated 1 13 mg of the glucose.

Example 4 - Gel Extraction with Acid.

Gel is extracted with acid. The polyelectrolyte gives an alkaline pH when mixed with water and polymer swelling can be reversed by neutralizing with an acid. To the resulting two phases from Example 3, 1 mL of concentrated phosphoric acid is added. Again, the mixture is vortexed vigorously for 5 minutes and centrifuged at 4000 g for another 5 minutes. The result is a liquid layer on top of a much smaller gel layer. Again, the liquid is sampled an analyzed by HPLC. Results indicate that approximately 150 mg of glucose is recovered with acid extraction. In summary, of the initial sample, about 53% of glucose but only 1 1% of the ionic liquid were extracted.

Example 5 - Polymer Phase.

An initial sample of 2.4 mL of ionic liquid with 0.6 mL of water is pre- mixed to form a homogenous solution. This mixture is allowed to equilibrate to room temperature. A second mixture is prepared by mixing deionized water with about 3% (by weight) sodium polyacrylate (Mw ~ 5100). The mixture is vortexed vigorously for 3 minutes, during which time the polymer powder intermixes and swells. The pH is measured by be 8.1. Next, 2.0 mL of the sodium polyacrylate mixture is added to the ionic liquid and water solution. This mixture is again vortexed vigorously for at least 3 minutes, and then centrifuged on high for 1 minute. The result is an ionic liquid-rich layer on top of a polymer solution layer (FIG. 1). The top layer has a moderate viscosity and is pale yellow, indicating the presence of ionic liquid. The bottom layer is viscous and cloudy -white, indicating a polymer rich phase. The interface between the two phases is weak and difficult to see. Example 6 - Polymer Phase with Indigo Carmine.

An initial sample of 2.0 mL of ionic liquid with 2.0 mL of water is pre- mixed to form a homogenous solution. To this sample, about 2% (by weight) of sodium polyacrylate (Mw ~ 5100) is added. The mixture is vortexed vigorously for 3 minutes, during which time the polymer powder intermixes and swells. Then, about 30 μΐ, οΐ dilute indigo carmine is added and vortexed for 1 minute. This mixture is again vortexed vigorously for at least 3 minutes, and then centrifuged on high for 1 minute. The result is an ionic liquid-rich layer on top of a polymer solution layer. The top layer has a moderate viscosity and is blue due to the indigo carmine preferentially

partitioning into the ionic liquid-rich phase. The bottom layer is viscous and cloudy- white, indicating a polymer rich phase.

Example 7 - Polymer Phase with Biomass Hydrolysate.

Ionic liquid hydrolysate from Poplar whole trees is prepared. A 3.0 mL sample of hydrolysate without lignin solids is loaded into a centrifuge tube. Then, 2.5 mL of pre-mixed sodium polyacrylate to 3% is added. The result is vortexed for 5 minutes and then centrifuged for 3 minutes, until two phases are formed. The top layer has the brown color characteristic of the hydrolysate and is rich in ionic liquid. The bottom layer is clear. Chromatographic analysis shows that sugars and other hydrolysate solutes partition between the two phases and therefore this method can be used for extracting desired products.

Example 8 - Extraction with pH adjustment.

A 15-mL centrifuge vial is loaded with 6 mL of water, 2 mL of 0.86 M ionic liquid, and 2 mL of 3.1 M glucose solution, and vortexed to form a homogenous solution. About 910 mg of polyacrylic acid (Mw ~ 3,000,000, 0.1% cross-linking) is added to the sample and vortexed for 2 minutes, causing minimal swelling. The pH is measured to be 2.1. Then, 0.1 mL of 5 M NaOH is added to increase the pH to about 3.6. The mixture is vortexed, causing the polyelectrolyte to swell moderately and form a gel. Then the mixture is centrifuged, resulting in two layers. The top layer is sampled and analyzed by HPLC. To the bottom layer, 2.0 mL of deionized water and 3 mL of 8 M HC1 is added and vortexed vigorously for 5 minutes, breaking the gel. The result is centrifuged at 4000 g for 2 minutes. The result is a clear liquid with foaming at the top and a small gel layer at the bottom. The supernatant liquor contained the extract and is analyzed by HPLC. The results show that the ratio of glucose concentration over ionic liquid concentration in the extract increases by a factor of 5 compared to the initial sample.

Example 9 - Preparation of Poplar Hydrolysate By Single-Stage Hydrolysis

Poplar (whole tree) biomass was ground to millimeter-sized particles passing a 4-mm mesh. This feedstock contains all parts of the Poplar tree, including bark and limbs, but excluding leaves. To a 250-mL glass reactor in a glycerol bath, 100 g of l-butyl-3-methylimidazolium chloride was loaded. The reactor was brought to a temperature of 140°C while stirring, which resulted in the complete melting of the ionic liquid. Then, 5.04 g of milled biomass was loaded under stirring at 300 RPM. After 30 minutes, the biomass particle density was visibly reduced, after 100 minutes no particles could be distinguished visually. At this time, temperature was reduced to 105°C by injecting ambient temperature water to the glycerol bath.

Once the lower temperature stabilized, at 130 minutes, stirring was increased to 700 RPM and 3.4 mL of 4 M HC1 (catalyst) was injected, marking the start of hydrolysis. At 145 minutes, gradual water addition was started at a rate of 1 mL/min for the next 55 minutes. During that time, temperature was manually controlled to the 105°C set point to compensate for heat transfers from acid and water dilutions. Then, the mixture was stirred for another 100 minutes. At the 295 minute (almost 5 hours) the reactor was allowed to cool to ambient temperature.

All compositions were determined by HPLC. The resulting 131.9 g of hydrolysate contained 26.9 g of water (20%) and 1.34 g of insoluble lignin. Hydrolysate sugars were 3.5 g/L of glucose, 4.0 g/L of xylose, plus other C5 and C6 monomers totaling 8.0 g/L. The solution also contained 1.6 g/L of acetic acid, 0.4 g/L of hydroxymethylfurfural and 1.3 g/L of furfural. Example 10 - Lignin Filtration

By the end of the hydrolysis described in Example 9, the resulting hydrolysate slurry was cooled to about 50°C, still under stirring. An 84 mm diameter Buchner funnel with a filter paper was prepared and fitted to an Erlenmeyer flask coupled to a vacuum pump. The slurry was carefully poured onto the funnel and the pump was turned on, creating a suction of -75 kPa. Filtration took a few minutes and produced particle-free filtrate in the flask. The cake was washed with an amount of water approximately equal to the cake mass. This was repeated 6 times, giving a total wash ratio of 6 (or 8.0 g of water). The wash was collected separately from the filtrate and stored. The lignin cake was carefully scraped from the filter paper and stored. The filtrate was set aside for the sugar recovery process.

Example 11 - Liquid-Liquid Extraction of Hydrolysate

The filtered hydrolysate described in Example 10 underwent liquid- liquid separation with an extractant. The extractant solution was prepared by mixing an amount of K ₂ C0 ₃ in excess of its solubility in water. After stirring the salt and water for 2 hours, the resulting slurry was allowed to settle overnight forming a saturated solution over a solid deposit. In a conventional beaker, 130 mL of hydrolysate and 130 mL of clear extractant was stirred at ambient temperature for 10 minutes. Then, the mixture was quickly transferred to a glass (chromatographic) column, equipped with a glass frit and a stopcock at the bottom. The dispersed phase in the mixture quickly coalesced and auto-separated, forming an IL-rich layer over a salt-rich (extract) layer. After about 4 minutes the phases reached equilibrium and the stopcock was opened to drain the extract phase.

HPLC analysis revealed that 95-97% of the glucose and 89-94% of xylose from the hydrolysate were obtained in the extract phase in a single stage. In contrast, only 5-6%> of the ionic liquid was co-extracted. This represented a selectivity of 380 and 200 for glucose and xylose, respectively. No acetic acid,

hydroxymethylfurfural, furfural, or any other molecules were detected in the extract. We estimate the errors in this step to be as much as ±3%.

Example 12 - Salt Precipitation & Filtration

The extract described in Example 11 was loaded into a long cylindrical glass vessel equipped with a sparger. To this vessel, an equal volume of methanol was added, about 128 mL. The sparger was connected to a C0 ₂ cylinder equipped with a pressure regulator adjusted to produce moderate bubbling and agitation. After an interval of a several minutes the solution became cloudy and the bubbling was stopped. The slurry was poured into a Buchner with a glass frit and a gentle vacuum was pulled to filter the solids. The filtrate was transferred back to the glass cylinder and bubbling resumed. This was repeated until the pH was dropped to about 8.3 and bubbling ceased to produce additional precipitate. This final solution was filtered one last time and the totality of the produced cake was washed with solution containing 80% methanol and 20% water. Both filtrate and wash were mixed and analyzed by HPLC. The solution contained 70%> of the sugars initially present in the hydrolysate (both glucose and xylose), and a small amount of IL and salt. The relatively low sugar yield was due to liquid handling losses incurred by the many iterations (~20) between bicarbonate generation and filtration, and difficulties in washing a thick (~5 cm) and uneven cake layer manually. In other instances, when the formed cake was even and adequate washing could be applied, 99% of the sugar entrained in the cake liquor was recovered. Example 13 - Extractant Regeneration

The cake described in Example 12 was transferred from the Buchner funnel into a beaker and water was added to make the concentration of KHCO ₃ about 30%. Then, the contents were heated to 120°C and stirred until all the water was evaporated. The salt deposited on the bottom of the beaker was broken up and dissolved in a minimal amount of water. The pH of the resulting solution was measured at 12.5, suggesting a partial regeneration of K ₂ CO ₃ . This solution was then mixed with a hydrolysate solution, which resulted in two liquid phases.

Example 14 - Ion Exchange & Distillationa

The filtrate from the salt precipitation and filtration step described in Example 13 contained mostly water, methanol and sugars (both C5 and C6). However, even though the concentrations of the ionic liquid and salt extractant was greatly reduced, trace amounts persisted in the parts per thousand range (ppt).

For the next step, the filtrate solution was eluted through an Amberlyst Wet 15 cation exchange resin. This resin is a macroreticular strong polysulfonic acid. Before use, 184 mL of the resin was loaded into a chromatographic column, which was equipped with a glass frit to hold the resin and a stopcock to control flow. The resin was washed several times with deionized water to remove residues and until the eluate became clear. Then, the resin was regenerated for 20 min with 400 mL of 2 M HCl acid solution. Lastly, the resin was washed again with deionized water to remove any entrained acid.

The filtrate was eluted for 30 min by controlling the flowrate with the stopcock. During elution, a large amount of C0 ₂ gas was produced in the column due to the neutralization of HCO ₃ ^" (bicarbonate) by the resin. The eluate was collected in a flask and the pH was measured to be 1.56. The initial pH of the filtrate was 8.34. This large drop in pH suggests that most of the potassium and l-butyl-3-methylimidazolium cations were exchanged for protons.

Next, the eluate from cation exchange was eluted through a second, similar chromatographic column, this one loaded with a Dowex resin. Dowex is a weak base anion exchange resin composed of polyamines. Before use, the Dowex underwent a preparation procedure similar to Aminex. A 45 mL volume of the resin was loaded into the column and washed several times with deionized water to remove any residues. Then, it was regenerated with 160 mL of 1 M NaOH for 6 min. Lastly, it was washed with deionized water again to remove any entrained base. Elution of the result from cation exchange through the anion exchanger lasted 15 min. The result was collected and analyzed. Its pH was 6.64 and it contained the same amounts of sugars contained in the filtrate but no detectable ions. Methanol content here was approximately 26%.

The eluate from anion exchange was submitted to distillation in order to remove and recycle the methanol, producing aqueous sugar as the bottoms product. The full volume produced thus far was loaded into a spherical glass flask and attached to a rig comprised of a condensation column with flowing cold water and a distillate receiving flask. In addition, a side-port was connected to a vacuum pump to reduce the overall pressure of the apparatus. The spherical flask was heated gently while a vacuum of about 7 kPa (absolute) was applied. This caused the solution to boil at a low temperature, and methanol to be collected in the receiving flask. This was allowed to continue until the vapor temperature rose significantly, indicating that the vapor composition was then mostly water and distillation was complete.

Example 15 - Color Removal & Sugar Characterization

The result from the distillation step described in Example 14 was a light amber translucent liquid. This liquid was mixed with a small amount of activated charcoal and stirred for 10 minutes. The result was filtered to achieve a clear solution with no color. The composition of the final sugar solution was determined to contain about 70% of the sugars found in the hydrolysate - the same level found in the output from the salt Precipitation and filtration step (Example 12). The solution contained no detectable amounts of ions, either the ionic liquid or salt extractant. This indicates that the ion concentration was in the parts per million range (ppm). No methanol or any other compounds were detected in the final sugar solution.

Example 16 - Fermentations

Final sugars solutions obtained in Example 15 were tested for its effectiveness as carbon sources for Saccharomyces Cerevisiae and Escherichia Coli. In all experiments, control sugars were prepared by dissolving pure, research-grade components at similar concentrations to hydrolysate sugars in DI water.

First, as shown in FIG 31, fermentation was carried out by S. Cerevisiae, an ethanologenic organism, in a medium composed of 50% optimal yeast medium and 50% sugar (control or hydrolysate) solution (by volume). The pH of both media were similar. Fermentation was done at 30°C in ventilated glass test tubes. As before, compositions were determined by HPLC equipped with refractive index detection. Elution was driven through an ion-exchange Aminex HPX-87H column using a 5 mM H ₂ SO ₄ mobile phase at a flow rate of 0.6 mL/min at 65°C. The concentration trajectories for glucose and ethanol were very similar between the control and hydrolysate, indicating that the present method produces good quality sugars.

Next, as shown in FIG 32, fermentation was performed by Escherichia Coli strain JM101 (New England Bio labs) in M9 minimal salt media with yeast extract. Each of two test tubes contained 10 mL of medium with 1.2% of lab-grade glucose or hydrolysate sugars. Each tube was inoculated with 50 iL of an initial seed batch grown in Luria-Bertani medium and stored with 50% glycerol at -35°C. To maintain neutral pH during acid turnover, calcium carbonate was added and kept in suspension by moderate shaking. Test tubes were capped with a rubber septum and so growth conditions were anaerobic. Product species were succinic acid, lactic acid, acetic acid and ethanol. Calibration curves of all individual components were used to calculate their concentrations in g/L. Concentrations were normalized by their maximum values.

Results showed that sugar consumption and product formation were similar between hydrolysate and control sugars. Even though the initial concentrations of lab-grade and hydrolysate glucose were closely matched (1.2%), the xylose present in hydrolysate and absent in the control was partially consumed and contributed to a somewhat higher product turnover for hydrolysate sugars.

Example 17 - Biomass Preparation

Sugarcane bagasse samples were received fresh from a sugar mill. The samples were chips of about 0.5 to 4 cm in length and were stored in a refrigerator at 4°C until use. Chips were taken off from the fridge and about 50 g were weighed and transferred to a beaker. The chips were then ground in a small hammer mill for 1 min with a cool off period of 1 min. This was repeated 4 times for a total of 4 min of grinding. The result was a powder of varying size distribution. The power was allowed to air dry under a chemical hood for 6 hours. Then, the moisture content of the power was measured by a tabletop moisture analyzer to be 92.2% (or 7.8% water). This was set aside to be used in hydrolysis experiments. Example 18 - Biomass Reactor

The biomass reactor main body was a clear glass jacketed 2-L filter- reactor. The reactor was assembled and connected to a heating/cooling unit designed to circulate mineral oil to maintain the desired temperature and execute rapid cooling when necessary. The reactor head was clamped with an o-ring seal in place on the reactor top with all five ports, which comprised an agitation metal shaft with horizontal teflon paddles (center port), an overhead Ahlin condenser, a septum-covered addition port, a sampling port, and a temperature probe port. The heating/cooling unit also circulates mineral oil through a second loop attached to a jacketed 2-L addition funnel with a pressure equalization tube. The bottom of the 2-L reactor is shut by a teflon screw equipped with a fine (25 um) polyester filter screen over a coarse glass support. The other side of the teflon screw is equipped with a valve fitted to a teflon tube. The tube is connected to a spherical flask. The spherical flask is connected to a vacuum hose, pump and pressure gauge. With this setup, biomass dissolution, biomass hydrolysis, and hydro lysate filtration be done conveniently and in a single vessel while tracking the kinetics, compositions and other variables of the process.

Example 19 - Biomass Dissolution

About 200 mL of l-butyl-3-methylimidazolium chloride ionic liquid solid was added to the 2-L jacketed addition funnel described in Example 18. The heater was turned on and set to 105°C while circulating through both the filter-reactor and the addition funnel. The powdered biomass described in Example 17 (15 g) was transferred to the filter-reactor through a simple addition funnel fitted to a dip tube to prevent biomass from coating the reactor inner wall. After about 1 hour, the ionic liquid was completely melted. A vacuum pump was connected to the top of the Ahlin condenser and turned on. The 2-L addition funnel stopcock was opened and the IL flowed through a teflon tube and deposited inside the reactor. The agitator was turned on at 100 RPM. IL and biomass was mixed for 6 hours, when dissolution was complete. The solution appeared dark brown and non-homogenous.

Example 20 - First Stage Biomass Hydrolysis

The hydrolysis reaction was started by adding 10 mL of 8 M HC1 acid catalyst to the biomass solution of Example 19 using a 8-inch stainless steel needle and glass gas tight syringe through the septum-covered addition. After 10 minutes, the same addition method was used to deliver 20 mL of water. This was followed by water injections of 20 mL by minute 15, 10 mL by minute 20, 10 mL by minute 25, 30 mL by minute 30, and 40 mL by minute 60. Then, the solution was allowed to stir for another 1 hour. The result was filtered after 120 minutes as described in Example 21.

Example 21 - Hydrolysate Filtration

At the end of the reaction, the bottom valve was opened and heated with a heating tape to melt any IL that may have frozen inside the valve. After this, the vacuum pump attached to the spherical flask was turned on. This caused the hydrolysate to filter through the polyester screen, into the teflon tube, and deposit in the spherical flask. Hydrolysate solid residue formed a cake on the filter screen. About 10 mL of water was added to the reactor, which formed a layer on top of the cake. Again, the vacuum pump was turned on, causing the cake to wash with water. This was repeated 3 times until the filtrate appeared clear, indicating that most of the IL in the cake had been recovered. The cake was allowed to dry overnight inside the reactor at 40°C.

Example 22 - Second Stage Biomass Dissolution, Hydrolysis and Filtration

Another 200 mL of IL was transferred into the dry cake (as described in Example 21) from the addition funnel following the same procedure described in

Example 19. With the temperature at the reactor temperature probe set to 105°C, the agitator was turned on, causing the cake to re-suspend into the IL. Like the first stage dissolution described in Example 19, the first stage material was dissolved in IL for another 6 hours. Then, the hydrolysis reaction was started with the addition of 10 mL of 8 M HC1 acid catalyst to the biomass solution using a 8-inch stainless steel needle and glass gas tight syringe through the septum-covered addition. After 10 minutes, the same addition method was used to deliver 20 mL of water. This was followed by water injections of 20 mL by minute 15, 10 mL by minute 20, 10 mL by minute 25, 30 mL by minute 30, and 40 mL by minute 60. Then, the solution was allowed to stir for another 1 hour until by minute 120 the result was filtered and the cake was washed with water 3 times.

Example 23 - Gravimetric and Chromatographic Measurements

The reactor bottom was unscrewed and the filter screen was removed. The screen and cake from Example 22 were then dried on a hot plate set to 100°C for 45 mins. By the end of this time period, the cake weighed 3.32 g (or 24% of the biomass on a dry basis). The hydrolysate filtrates from both stages were combined, which yielded 0.71 L of hydrolysate. About 100 of this mixture was sampled and analyzed by HPLC. Yields of glucose and xylose were 77% and 92% of theoretical maximum, respectively.

Example 24 - Liquid-Liquid Extraction

About 0.12 L of saturated K ₂ C0 ₃ solution (with some suspended salt crystals) is added to the 0.71 L of hydrolysate that was pooled in Example 23. The mixture becomes alkaline and cloudy. Upon settling, the mixture auto-separates into an upper IL-rich layer and a lower K ₂ C0 ₃ rich layer within a few minutes. The upper layer, the raffinate (0.65 L), the lower layer, and the extract (0.24 L), are decanted and saved in separate containers. Example 25 - Salt Precipitation and Filtration

The 0.24 L of extract produced in Example 24 is loaded into a closed reactor equipped with a gas diffuser. About 0.24 L of methanol is loaded in addiiton and allowed to mix with the extract, causing some precipitate to form. The reactor bottom valve is opened, allowing the slurry to be pumped by a peristaltic pump into a chromatographic column of 1.5 aspect ratio equipped with a bottom glass frit. In the column, the slurry is filtered, and the filtrate is pumped back into the reactor by a second peristaltic pump. Then, C0 ₂ gas is metered through the diffuser, which causes acidification and additional precipitation. The recirculation between the acidification reactor and the column filter is continued. Excess C0 ₂ and methanol vapor is run through a condenser, which condenses and refluxes the methanol back into the reactor, but allows C0 ₂ to escape. The reaction is continued for about 55 min until C0 ₂ ceases to create additional precipitate. Then, the salt cake formed at the chromatographic column is rinsed with three bed volumes of 80% methanol and 20% water solution. The filtrate is mixed with the contents found inside the acidification reactor to give about 0.51 L of an amber solution. The cake is removed from the chromatographic column and saved.

Example 26 - Ion Exchange of Salt Precipitation Filtrate

The 0.51 L amber filtrate solution produced in Example 25 is run through two chromatographic columns in series. The solution is dispensed into the first, cation exchange column packed with Amberlyst Wet 15, a strong acid resin. Contact with the resin causes the solution to release C0 ₂ , and several minutes are allowed for this reaction. Then, a peristaltic pump is turned on, which meters the transfer of the liquid through the first column and into the second. The second column is packed with Dowex, a weak base anion exchanger. Another pump connected to the bottom of the second column meters the flow through the column and delivered deionized solution into a receiving flask. Finally, air is pushed through both columns to ensure the recovery of residual solution. The total volume of deionized solution is 0.51 L. The result is passed through a third, smaller column packed with activated charcoal. By the end, a vacuum pump is attached to a sealed spherical receiving flask, and is turned on to recover the entrained liquid. This procedure results in about 0.50 L of clear solution.

Example 27 - Vacuum Distillation

The pH of the clear solution produced in Example 26 is measured to be 6.7. The 0.5 L clear solution is loaded into a heavy- walled 2-L spherical flask on top of a temperature-controlled heating mantle. The spherical flask has three necks, which are equipped with a thermocouple with an adapter, a condenser with separate reflux, and a barbed connector to a vacuum hose and pump. The contents are heated to the boiling point of the methanol/water mixture under vacuum (-80 kPa). The temperature at boiling is monitored, as the rise in temperature indicates the depletion of methanol relative to water. As the level drops down to about 50 mL, the heating power is monitored closely to achieve a small volume without burning the sugars. The evaporation is stopped at about 15 mL. HPLC analysis shows the production of 19.3 mL of solution containing about 6.29 g of sugars (mostly glucose and xylose). This corresponds to an overall recovery of sugars from hydrolysate of about 97%.

The methods of the present disclosure can be used to extract solutes other than sugar from hydrophilic ionic liquids.

While embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention.