Processes and systems for producing sulfonated lignin from lignocellulosic biomass

Abstract

The disclosed technology provides processes to sulfonate lignin to enhance the processability, solubility, and reactivity of the lignin, which significantly improves the value of the lignin. The sulfonated lignin may be recovered as a lignosulfonate product. The sulfonated lignin may be catalytically converted to various chemicals. In some variations, a process for making sulfonated lignin from lignocellulosic biomass comprises: providing a feedstock comprising lignocellulosic biomass; in a digestor, fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and lignin; removing cellulose-rich solids from the liquor, thereby generating a lignin-containing stream; introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignin-containing stream, thereby generating sulfonated lignin; and recovering a sulfonated lignin product.

Description

PROCESSES AND SYSTEMS FOR PRODUCING SULFONATED LIGNINFROM LIGNOCELLULOSIC BIOMASSPRIORITY DATA

[0001] This international patent application claims priority to U.S. Provisional Patent App. No. 63 / 664,248, filed on June 26, 2024, which is hereby incorporated by reference herein.FIELD

[0002] The present invention generally relates to processes and systems for converting lignocellulosic biomass into sulfonated lignin.BACKGROUND

[0003] Biomass refining (or biorefining) is becoming more prevalent in industry. Cellulose fibers and sugars, hemicellulose sugars, lignin, syngas, and derivatives of these intermediates are being used by many companies for chemical and fuel production. Indeed, we are now observing the commercialization of integrated biorefineries that are capable of processing incoming biomass much the same as petroleum refineries now process crude oil. Underutilized lignocellulosic biomass feedstocks have the potential to be much cheaper than petroleum, on a carbon basis, as well as much better from an environmental life-cycle standpoint.

[0004] Lignocellulosic biomass is the most abundant renewable material on the planet and has long been recognized as a potential feedstock for producing chemicals, fuels, and materials. Lignocellulosic biomass normally comprises primarily cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are natural polymers of sugars, and lignin is an aromatic / aliphatic hydrocarbon polymerreinforcing the entire biomass network. Some forms of biomass (e.g., recycled materials) do not contain hemicellulose.

[0005] After being isolated from lignocellulosic biomass, lignin can in principle be converted to a wide variety of chemicals and fuels. However, historical efforts to economically convert lignin to useful chemicals and fuels have failed for various reasons, including severe fouling of catalysts and plugging of reactors, caused by lignin condensation and other reactions that precipitate lignin on surfaces.

[0006] One type of lignin that has achieved some commercial success (market size exceeding $1 billion annually) is lignosulfonate, a water-soluble anionic polymer derived from lignin. Lignosulfonates are used to stably disperse carbon black, pesticides, dyes, and other insoluble solids and liquids into water. Lignosulfonates are used in concrete additives, animal feed binders, and oil well additives.

[0007] Lignosulfonates may be used as a feedstock for producing a variety of products. Compared to unsulfonated lignin, lignosulfonates may avoid the above- mentioned fouling and plugging when being purified for a final product, or when used to produce other chemicals and fuels.

[0008] There is a desire for improved processes for producing lignosulfonates, lignosulfonic acid, or other forms of sulfonated lignin.SUMMARY

[0009] In some variations, the present invention provides a process for making sulfonated lignin from lignocellulosic biomass, the process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignincontaining stream, thereby generating sulfonated lignin; and(e) recovering the sulfonated lignin.

[0010] In some embodiments, the acid or acid precursor contains sulfur. For example, the acid or acid precursor may be selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof. In other embodiments, the acid or acid precursor does not contain sulfur.

[0011] In some embodiments, the starting lignin contains from 0 to about 3 wt% sulfur content.

[0012] In some embodiments, the starting lignin generated in step (b) includes colloidal lignin and soluble lignin. The soluble lignin may have a higher sulfur content compared to the colloidal lignin. Optionally, the colloidal lignin and the soluble lignin are separated from each other using a lignin-separation unit.

[0013] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains the colloidal lignin but not the soluble lignin. In these embodiments, the colloidal lignin, but not the soluble lignin, is conveyed to the sulfonation reactor.

[0014] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains the soluble lignin but not the colloidal lignin. In these embodiments, the soluble lignin, but not the colloidal lignin, is conveyed to the sulfonation reactor.

[0015] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains both of the soluble lignin and the colloidal lignin. In these embodiments, although the colloidal lignin and soluble lignin had been separated, they may be recombined and fed to the sulfonation reactor, or they may be separately fed to the sulfonation reactor. In certain embodiments, there are two sulfonation reactors — one for sulfonating the colloidal lignin, and one for sulfonating the soluble lignin.

[0016] In some embodiments, the lignin-containing stream comprises the solvent for lignin.

[0017] The solvent for lignin may be a Ci-Ce alcohol, for example. The Ci- Ce alcohol may be selected from the group consisting of methanol, ethanol, ethylene glycol, 1 -propanol, 2-propanol, propanediol, glycerol, 1 -butanol, 2-butanol, isobutanol, butanediol, 1 -pentanol, 1 -hexanol, cyclohexanol, and combinations thereof.

[0018] In other embodiments, the lignin-containing stream does not comprise the solvent for lignin. In these embodiments, the solvent is removed prior to lignin sulfonation in the sulfonation reactor.

[0019] In some embodiments, the lignin-containing stream comprises the hemicellulose sugars.

[0020] In other embodiments, the lignin-containing stream does not comprise the hemicellulose sugars.

[0021] In some embodiments, the sulfur-containing reactant is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfite ions, sulfite salts, bisulfite ions, bisulfite salts, sulfur trioxide, sulfuric acid, sulfate salts, bisulfate salts, sulfonic acid, sulfonate ions, sulfonate salts, lignosulfonic acid, lignosulfonate ions, lignosulfonate salts, elemental sulfur, hydrogen sulfide, dialkyl sulfides, dialkyl disulfides, polysulfides, and combinations thereof. In certain embodiments, the sulfur-containing reactant is SO2.

[0022] In some embodiments, the sulfonation reactor is operated in step (d) at a sulfonation temperature selected from about 120°C to about 180°C. In some embodiments, the sulfonation temperature is selected from about 130°C to about 170°C. In some embodiments, the sulfonation temperature is selected from about 140°C to about 160°C.

[0023] In some embodiments, the sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 2.0 to about 4.0. In some embodiments, the sulfonation pH is selected from about 2.0 to about 3.5. In some embodiments, the sulfonation pH is selected from about 2.0 to about 3.0. In some embodiments, the sulfonation pH is selected from about 2.5 to about 3.5.

[0024] In some embodiments, the sulfonation reactor is operated in step (d) at a reactor residence time selected from about 10 minutes to about 2 hours. In someembodiments, the reactor residence time is selected from about 20 minutes to about 1 hour.

[0025] In some embodiments, the sulfonation reactor is operated using a concentration of the sulfur-containing reactant selected from about 1 wt% to about 20 wt% sulfur, on a pure-sulfur basis. In some embodiments, the concentration of the sulfur-containing reactant is selected from about 3 wt% to about 15 wt% sulfur, on a pure-sulfur basis. In certain embodiments, the concentration of the sulfur-containing reactant is selected from about 6 wt% to about 12 wt% sulfur, on a pure-sulfur basis.

[0026] The sulfonation reactor is preferably operated such that the rate of lignin sulfonation is higher than the rate of lignin condensation. In some embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least twice the rate of lignin condensation. In certain embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least five times the rate of lignin condensation. In certain embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least ten times the rate of lignin condensation.

[0027] In some embodiments, the sulfonated lignin contains from about 1 wt% to about 10 wt% sulfur content. In certain embodiments, the sulfonated lignin contains from about 3 wt% to about 8 wt% sulfur content.

[0028] In some embodiments, the sulfonated lignin is lignosulfonic acid. In some embodiments, the sulfonated lignin is a lignosulfonate salt.

[0029] The process may further comprise recovering the hemicellulose sugars. In some embodiments, the process further comprises fermenting the hemicellulose sugars (e.g., xylose and / or mannose) into a hemicellulose fermentation product, such as ethanol.

[0030] The process may further comprise hydrolyzing the cellulose-rich solids to produce glucose. In some embodiments, the process further comprises fermenting the glucose sugars into a glucose fermentation product, such as ethanol.

[0031] Ethanol from hemicellulose fermentation and / or glucose fermentation may be converted into olefins (e.g., ethylene and propylene). In some embodiments, the process further comprises converting the olefins into ethanol-derivedhydrocarbons. At least a portion of the ethanol -derived hydrocarbons may be recovered as sustainable aviation fuel (SAF), or components of SAF.

[0032] In some embodiments, the sulfonated lignin is converted to one or more lignin-derived hydrocarbons. The lignin-derived hydrocarbons may also be recovered as SAF, or components of SAF. The lignin-derived hydrocarbons may be combined with ethanol-derived hydrocarbons for use as SAF or components of SAF.

[0033] Other variations provide a sulfonated lignin product produced by a process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignincontaining stream, thereby generating sulfonated lignin; and(e) recovering the sulfonated lignin.BRIEF DESCRIPTION OF THE FIGURES

[0034] FIG. 1 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass, in some variations in which the sulfonation reactor is positioned following pulp separation and prior to solvent separation.

[0035] FIG. 2 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass, in some variations in which the sulfonation reactor is positioned following pulp separation as well as following separation of solvent, acid, and hemicellulose.

[0036] FIG. 3 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass, in some variations in which the sulfonation reactor is positioned following pulp separation as well as following separation of hemicellulose.

[0037] FIG. 4 depicts exemplary sulfonation reactions of lignin, as well as exemplary condensation reactions of lignin.

[0038] FIG. 5 shows a summary table of experimental results, in the Example of the specification.DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0039] This description will enable one skilled in the art to make and use the invention, and it describes several embodiments, adaptations, variations, alternatives, and uses of the invention. These and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following detailed description of the invention in conjunction with any accompanying drawings.

[0040] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this invention belongs. All composition numbers and ranges based on percentages are weight percentages, unless indicated otherwise. All ranges of numbers or conditions are meant to encompass any specific value contained within the range, rounded to any suitable decimal point.

[0041] Unless otherwise indicated, all numbers expressing parameters, reaction conditions, concentrations of components, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending at least upon a specific analytical technique.

[0042] Unless otherwise stated, all elemental concentrations expressed in weight percent (wt%) use a pure-element basis, even if the element is contained in various compounds. For example, 5 wt% sulfur in a compound means that the compound contains 5 grams pure sulfur for every 100 grams of the compound, where the sulfur may be present in sulfite or sulfate groups, or other groups.

[0043] The term “comprising,” which is synonymous with “including,” “containing,” or “characterized by” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. “Comprising” is a term of art used in claim language which means that the named claim elements are essential, but other claim elements may be added and still form a construct within the scope of the claim.

[0044] As used herein, the phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of’ (or variations thereof) appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. As used herein, the phase “consisting essentially of’ limits the scope of a claim to the specified elements or method steps, plus those that do not materially affect the basis and novel characteristic(s) of the claimed subject matter.

[0045] With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of’ or, alternatively, by “consisting essentially of.”

[0046] Certain exemplary embodiments of the invention will now be described. These embodiments are not intended to limit the scope of the invention as claimed. The order of steps may be varied, some steps may be omitted, and / or other steps may be added. Reference herein to first step, second step, etc. is for illustration purposes only.

[0047] The present invention is premised on the sulfonation of lignin, obtained from lignocellulosic biomass, to produce sulfonated lignin that is useful for many applications. The initial production of lignin to be sulfonated, or furthersulfonated, is preferably integrated with a downstream lignin sulfonation reactor with optimized reaction conditions to produce tailored sulfonated lignin products.

[0048] Some variations of the invention utilize AVAP® technology to generate the lignin to be sulfonated. The AVAP process, developed over the past two decades, is commonly owned with the assignee (GranBio Intellectual Property Holdings, LLC) of the present patent application. AVAP technology fractionates a lignocellulosic biomass feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin. Some variations are premised on external sulfonation of colloidal AVAP lignin, which does not contain much sulfur, to generate a sulfonated lignin for various uses. In some embodiments of the AVAP process, both a low-sulfur colloidal lignin and a higher-sulfur soluble lignin are generated in the digestor. It can be beneficial for all the lignin from a starting biomass to end up in highly sulfonated form, to maximize production of lignosulfonates for sale or for conversion to other chemicals.Sulfonated lignin tends to remain soluble in aqueous solutions, avoiding undesirable precipitation in reactors, process pumps, and piping. While the AVAP digestor itself can be optimized to make more sulfonated lignin, such as via higher SO2 concentrations in the digestor, it has been discovered that ex situ sulfonation of the colloidal lignin, the soluble lignin, or both, is advantageous.

[0049] In this specification, “sulfonation” is synonymous with “sulfurization” and refers to any chemical reaction in which sulfur atoms, sulfur-containing groups (e.g., -SO3H), or a combination thereof, are reacted with a starting compound to form ionic or covalent chemical bonds with the compound. In typical embodiments, lignin sulfonation is specifically a chemical reaction with lignin that introduces a sulfonic acid group (-SO3H) or a sulfonate group (-SO3R, where R = organic group) into the lignin. The sulfonic acid group, or other sulfur-containing group which may be -S-, -S-S-, -S-O-, or -SH, may react with an aliphatic side chain attached to the aromatic ring of lignin, or may react directly with the aromatic ring.

[0050] In some variations, the present invention provides a process for making sulfonated lignin from lignocellulosic biomass, the process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignincontaining stream, thereby generating sulfonated lignin; and(e) recovering the sulfonated lignin.

[0051] In some embodiments, the acid or acid precursor contains sulfur. For example, the acid or acid precursor may be selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof. In other embodiments, the acid or acid precursor does not contain sulfur.

[0052] In some embodiments, the acid or acid precursor does not contain sulfur. For example, the acid or acid precursor may be carbonic acid, acetic acid, formic acid, lactic acid, nitric acid, hydrochloric acid, phosphoric acid, or a combination thereof.

[0053] In some embodiments, the starting lignin contains from 0 to about 3 wt% sulfur content. In various embodiments, the starting lignin contains about, at least about, or at most about 0, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, or 10 wt% sulfur, including any intervening range.

[0054] In some embodiments, the starting lignin generated in step (b) includes colloidal lignin and soluble lignin. The soluble lignin may have a higher sulfur content compared to the colloidal lignin. Optionally, the colloidal lignin and the soluble lignin are separated from each other using a lignin-separation unit, such as a filter or a centrifuge.

[0055] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains the colloidal lignin but not the soluble lignin. In these embodiments, the colloidal lignin, but not the soluble lignin, is conveyed to the sulfonation reactor.

[0056] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains the soluble lignin but not the colloidal lignin. In these embodiments, the soluble lignin, but not the colloidal lignin, is conveyed to the sulfonation reactor. Even though the soluble lignin may have higher starting sulfur content than the colloidal lignin, it may be desirable to further sulfonate the soluble lignin.

[0057] In some embodiments employing separation of colloidal lignin and soluble lignin, the lignin-containing stream contains both of the soluble lignin and the colloidal lignin. In these embodiments, although the colloidal lignin and soluble lignin had been separated, they may be recombined and fed to the sulfonation reactor, or they may be separately fed to the sulfonation reactor. In certain embodiments, there are two sulfonation reactors — one for sulfonating the colloidal lignin, and one for sulfonating the soluble lignin. In certain embodiments, a single sulfonation reactor is used in different sulfonation campaigns, which may separately process the colloidal lignin and the soluble lignin. When the soluble lignin and the colloidal lignin are processed in different reactors or campaigns, the sulfonation agent may be different. As just one example, sulfonation of colloidal lignin may employ SO2, while sulfonation of soluble lignin may employ calcium sulfite.

[0058] In typical embodiments, a single lignin-containing stream is fed to the sulfonation reactor. The lignin-containing stream contains at least lignin and may or may not contain solvent, acid catalyst (from the digestor), and hemicellulosic sugars. That is, the lignin-containing stream may be processed to remove some or all solvent prior to feeding the sulfonation reactor. Independently, the lignin-containing stream may be processed to remove or neutralize some or all acid catalyst prior to feeding the sulfonation reactor. Independently, the lignin-containing stream may be processed to remove some or all hemicellulose prior to feeding the sulfonation reactor. The lignincontaining stream may have solvent-soluble lignin plus solvent-insoluble lignin. The lignin-containing stream may contain various lignin molecules of different sulfur content, oxygen content, molecular weight, etc.

[0059] FIG. 1 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass (e.g., wood chips), in some variations. Biomass is fed to a digestor, along with water, an acid catalyst (e.g., SO2), and a solvent for lignin (e.g.,ethanol). Following fractionation in the digestor, cellulose separation removes a cellulose-rich solids stream from the liquor. The remaining liquor is fed to a sulfonation reactor, into which is also fed a sulfur-containing reactant, which may also be SO2. Following lignin sulfonation, solvent is removed and recycled to the digestor. Sulfonated lignin is recovered.

[0060] FIG. 2 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass (e.g., cane straw), in some variations. Biomass is fed to a digestor, along with water, an acid catalyst (e.g., H2SO4), and a solvent for lignin (e.g., methanol). Following fractionation in the digestor, cellulose separation removes a cellulose-rich solids stream from the liquor. The remaining liquor is fed to a ligninseparation unit, which removes lignin from the liquor. The solvent, acid, and hemicellulose may be separated individually or as a combined stream. The lignin from lignin separation is fed to a sulfonation reactor, into which is also fed a sulfur- containing reactant, which may be SO2. Following lignin sulfonation, sulfonated lignin is recovered.

[0061] FIG. 3 depicts an exemplary process for making sulfonated lignin from lignocellulosic biomass (e.g., com stover), in some variations. Biomass is fed to a digestor, along with water, an acid catalyst (e.g., lignosulfonic acid), and a solvent for lignin (e.g., isobutanol). Following fractionation in the digestor, cellulose separation removes a cellulose-rich solids stream from the liquor. The remaining liquor is fed to a hemicellulose-separation unit, which removes hemicellulose from the liquor. The lignin with solvent are fed to a sulfonation reactor, into which is also fed a sulfur- containing reactant, which may be SO2. Following lignin sulfonation, sulfonated lignin is recovered along with solvent, which may be removed downstream.

[0062] “Biomass” refers to any biologically produced organic matter and includes the mass of living or once-living organisms, including plants and microorganisms. Biomass includes both the above-ground and below-ground tissues of plants — for example, leaves, twigs, branches, boles, as well as roots of trees and rhizomes of grasses. The chemical energy contained in biomass is derived from solar energy using the natural process of photosynthesis. Biomass is effectively stored solar energy. Photosynthesis is the process by which plants take in carbon dioxideand water from their surroundings and, using energy from sunlight, convert them into sugars, starches, cellulose, hemicellulose, and lignin.

[0063] In various embodiments, the biomass is selected from softwood chips or sawdust, hardwood chips or sawdust, timber harvesting residues, milled tree branches, milled tree stumps, leaves, bark, cardboard, paper waste, off-spec paper pulp, bamboo, corn stover, wheat straw, rice straw, grass straw, cotton burr, switchgrass, miscanthus, sugarcane bagasse, sugarcane straw, energy cane bagasse, energy cane straw, fruit shells, fruit stalks, fruit peels, fruit pits, hemp, vegetable shells, vegetable stalks, vegetable peels, vegetable pits, grape pumice, almond shells, pecan shells, coconut shells, coffee grounds, grass pellets, hay pellets, wood pellets, or a combination thereof. The processes and systems of the invention can accommodate a wide range of feedstocks of various types, sizes, and moisture contents. A person of ordinary skill in the art will appreciate that the biomass feedstock options are virtually unlimited, as long as the biomass contains at least some lignin that can be used to generate sulfonated lignin.

[0064] Different biomass feedstocks have different sugar profiles in the cellulose and hemicellulose fractions. For example, in hardwoods and herbaceous feedstocks, the main hemicellulose sugar is the Cs sugar xylose, while in softwoods, both Cs and Ce sugars (particularly mannose) are prevalent in hemicellulose.

[0065] In some embodiments, the biomass is a herbaceous biomass feedstock. A herbaceous biomass feedstock has little or no woody tissue and typically persists for a single growing season. A herbaceous biomass feedstock may be selected from the group consisting of sugarcane bagasse, sugarcane straw, energy cane bagasse, energy cane straw, corn stover, wheat straw, rice straw, grass straw, switchgrass, cotton burr, miscanthus, empty fruit bunches, and combinations thereof, for example. In other embodiments, the biomass feedstock is a non-herbaceous biomass feedstock, such as sawdust or forest waste. A mixture of a herbaceous biomass feedstock and a non-herbaceous biomass feedstock may be used.

[0066] In some embodiments, a biomass feedstock contains cellulose, hemicellulose, lignin, and sucrose (a C12 sugar). Examples include whole sugarcane and whole energy cane. These materials may be processed to first mechanically remove sucrose juice, with the remaining material (bagasse) then fed to a processdescribed herein. Alternatively, whole sugarcane or whole energy cane may be processed, with the sucrose — or glucose plus fructose derived from sucrose hydrolysis — optionally being fermented to ethanol or another product, or recovered as a sugar product, for example. When sucrose is fermented, it may be fermented to something different than products made from the cellulose sugars or hemicellulose sugars.

[0067] The biomass feedstock can be provided or processed into a wide variety of particle sizes or shapes. For example, the feed material can be a fine powder, or a mixture of fine and coarse particles. The feed material can be in the form of relatively large pieces of material, such as milled wood chips. In some embodiments, the feed material comprises pellets or other agglomerated forms of particles that have been pressed together or otherwise bound, such as with a binder.

[0068] In some embodiments, the biomass has a maximum average particle dimension selected from about 0.1 millimeters to about 500 millimeters, such as from about 10 millimeters to about 100 millimeters. The maximum average particle dimension is the maximum of average particle length, average particle width, and average particle height. For typical herbaceous biomass feedstocks, the maximum particle dimension is the particle length. A starting herbaceous biomass feedstock is often a long piece of biomass (e.g., a corn stalk) that, when milled, can generate high- aspect-ratio particles of biomass. However, the invention is not limited to any specific particle shape. The invention may utilize a flour of lignocellulosic biomass feedstock (e.g., finely milled material) or fine material collected during preprocessing (e.g., com stover pith). In various embodiments, the lignocellulosic biomass feedstock has a maximum average particle dimension of about, at least about, or at most about 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 50, 75, 100, 150, 200, 250, 300, 400, or 500 millimeters, including any intervening range.

[0069] In some embodiments, the initial moisture content of the biomass is about 35 wt% or less H2O, such as about 20 wt% or less H2O. In various embodiments, the initial moisture content of the biomass is about, at least about, or at most about 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 wt% (water), including any intervening range. The initial moisture content of the lignocellulosic biomassfeedstock may be the natural moisture content of the biomass feedstock as harvested, or may be the result of transportation or storage, for example.

[0070] In some embodiments, the lignin-containing stream comprises the solvent for lignin. In these embodiments, some or all of the solvent for lignin is conveyed to the sulfonation reactor, rather than being removed from the liquor. It can be beneficial to include the solvent (e.g., ethanol) to avoid lignin precipitation during sulfonation, especially early in the reaction while the lignin is not yet water-soluble.

[0071] The solvent for lignin may be a Ci-Ce alcohol, for example. The Ci- Ce alcohol may be selected from the group consisting of methanol, ethanol, ethylene glycol, 1 -propanol, 2-propanol, propanediol, glycerol, 1 -butanol, 2-butanol, isobutanol, butanediol, 1 -pentanol, 1 -hexanol, cyclohexanol, and combinations thereof. In some embodiments, the solvent for lignin is selected from the group consisting of a linear alcohol, a branched alcohol, an aromatic alcohol, a ketone, an aldehyde, an ether, a non-oxygenated hydrocarbon, an ionic liquid, and combinations thereof.

[0072] In principle, a different solvent (besides the digestor solvent) could be added to the lignin-containing stream, or directly to the sulfonation reactor. For example, if the digestor solvent is methanol or ethanol, a higher alcohol such as cyclohexanol could be added to the lignin-containing stream being fed to the sulfonation reactor. In other embodiments, an additional quantity of the solvent for lignin (the same type of solvent as used in the digestor) is added to the lignincontaining stream being fed to the sulfonation reactor.

[0073] In other embodiments, the lignin-containing stream fed to the sulfonation reactor does not comprise the solvent for lignin. In these embodiments, the solvent is removed prior to lignin sulfonation in the sulfonation reactor. These embodiments may be used when the lignin-containing stream is sufficiently water- soluble so that lignin precipitation does not occur upon solvent removal, or when pH and / or temperature adjustment is used to avoid lignin precipitation. These embodiments may also be used when a dry form of the lignin-containing stream (e.g., lignin powder) is fed to the sulfonation reactor.

[0074] In some embodiments, the lignin-containing stream fed to the sulfonation reactor comprises hemicellulose sugars. In these embodiments, at leastsome hemicellulose sugars are conveyed to the sulfonation reactor. These embodiments may be used in various configurations, such as when hemicellulose content in the sulfonated lignin product is tolerable or even desirable (e.g., when the sulfonated lignin product will be catalytically converted to other chemicals), or when a downstream separation of hemicellulose from sulfonated lignin is utilized.

[0075] In other embodiments, the lignin-containing stream does not comprise hemicellulose sugars. See, for example, FIGS. 2 and 3, in which at least some of the hemicellulose is separated out prior to feeding the sulfonation reactor. Separating hemicellulose before the sulfonation reactor may be desirable to avoid the possible generation of sugar sulfonates, for example.

[0076] Typically, the cellulose-rich solids (which may be referred to as pulp) are essentially completely removed from the liquor prior to feeding the lignincontaining stream to the sulfonation reactor. Of course, small amounts of cellulose fines may still be present in the lignin-containing stream. In certain embodiments, a significant fraction of the pulp is allowed to be fed into the sulfonation reactor. These embodiments may be used in various configurations, such as when cellulose content in the sulfonated lignin product is tolerable or even desirable, or when a downstream separation of cellulose from sulfonated lignin is utilized.

[0077] The sulfonation reactor may vary widely in terms of the physical apparatus. The sulfonation reactor may be a continuously stirred reactor, a plug-flow reactor, a cross-flow reactor, a membrane-assisted reactor, an extruder, a fluidized- bed reactor, or another suitable apparatus. The sulfur-containing reactant may flow cocurrent or countercurrent with the lignin to be sulfonated. The sulfonation reactor may be a modified tank, equipped to safely carry out the sulfonation reaction.

[0078] In a continuous or semi-continuous process, the sulfonation reactor is distinct from the digestor, i.e., they are physically different apparatus. In a batch process, it is possible to reuse the digestor as the sulfonation reactor, at a different point in time after collecting the liquor from the vessel and separating out the pulp.

[0079] The sulfur-containing reactant for step (d) may vary widely. In some embodiments, the sulfur-containing reactant is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfite ions, sulfite salts (e.g., calcium sulfite), bisulfite ions, bisulfite salts (e.g., ammonium bisulfite), sulfur trioxide, sulfuric acid, sulfatesalts, bisulfate salts, sulfonic acid (e.g., a-hydroxyalkane sulfonic acid), sulfonate ions, sulfonate salts, lignosulfonic acid (e.g., 3-(2-hydroxy-3-methoxyphenyl)-2-[2- methoxy-4-(3-sulfopropyl)phenoxy]propane-l -sulfonic acid), lignosulfonate ions, lignosulfonate salts, elemental sulfur (e.g., Ss), hydrogen sulfide, dialkyl sulfides, dialkyl disulfides, polysulfides, and combinations thereof.

[0080] In certain embodiments, the sulfur-containing reactant is SO2. Although sulfur dioxide has no hydrogen atoms and thus is not a Bronsted acid, SO2 is a Lewis acid since it acts as an electron-pair acceptor due to the presence of a vacant d-orbital on the sulfur atom. The vacant d-orbital allows SO2 to accept an electron pair from a Lewis base.

[0081] At any pH below 7, there will be hydrogen ions (H+) present, and with water present, the hydrogen ions form hydronium ions (H3O ). There is a chemical equilibrium among dissolved SO2, sulfite, bisulfite, and sulfurous acid, as described by the following reaction network:HSO3 + H+H2SO3H2SO3^ SO2(aq) + H2OSO2(aq) SO2(g)

[0082] The sulfur-containing compound that actually reacts with lignin may be SO2, SO32, HSO3 , H2SO3, or a combination thereof. SO2 itself will typically need to dissolve into the liquid phase before it can react with lignin. At high concentrations of SO2, there may be solubility limitations such that some SO2 remains in the gas phase and cannot readily participate in the sulfonation chemistry. The pH is important in determining the distribution of sulfur-containing species. For example, at a pH of about 2, approximately 50% of the SO2 will be in the bisulfite form, HSO3 , while at a pH of about 3, approximately 90% of the SO2 will be in the bisulfite form. In some embodiments, the bisulfite form is what primarily reacts with lignin, as depicted in FIG. 4 (sulfonation pathway). For that reason, a pH closer to 3 may be preferred, compared to a pH of 2 or lower. However, in a closed sulfonation reactor,bisulfite ions may be continuously produced according to equilibrium with SO2 and water, such that even at pH = 2, bisulfite ions are generated about as fast as they are consumed in the reaction.

[0083] In some embodiments, the sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 2.0 to about 4.0. In some embodiments, the sulfonation pH is selected from about 2.5 to about 4.0. In some embodiments, the sulfonation pH is selected from about 2.0 to about 3.5. In some embodiments, the sulfonation pH is selected from about 2.5 to about 3.5. In various embodiments, the sulfonation pH is about, at least about, or at most about 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7,1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0, including any intervening range.

[0084] The pH of the liquor may be adjusted in various ways. The liquor received from the digestor may already have the desired pH, or the pH may be too low, or the pH may be too high. The digestor pH depends on the choice and concentration of the acid or acid precursor. In some AVAP processes which use ethanol as solvent and SO2 as acid catalyst, the liquor pH is about 1 or less than 1. If the desired pH in the sulfonation reactor is e.g. 2-3, then the pH needs to be raised. The pH can be increased by selectively removing acidic species, such as via membrane separation. The pH can be increased by adding a base, such as ammonia, methylamine, aluminum hydroxide, copper hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, or a combination thereof. Weak bases, such as ammonia, methylamine, aluminum hydroxide, copper hydroxide, may be preferred. Ammonia is advantageous because when ammonia reacts with sulfite or bisulfite ions, the ammonium sulfite or ammonium bisulfite remain in solution at low pH and the ammonia can be readily removed using evaporation at higher pH.

[0085] In some embodiments, the sulfonation reactor is operated in step (d) at a sulfonation temperature selected from about 120°C to about 180°C. In some embodiments, the sulfonation temperature is selected from about 130°C to about 170°C. In some embodiments, the sulfonation temperature is selected from about 140°C to about 160°C. In various embodiments, the sulfonation temperature is about, at least about, or at most about 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C,155°C, 160°C, 165°C, 170°C, 175°C, or 180°C, including any intervening range. Multiple sulfonation temperatures may be used, such as in a temperature ramp or program.

[0086] In some embodiments, the sulfonation reactor is operated in step (d) at a reactor residence time selected from about 10 minutes to about 2 hours. In a continuous sulfonation reactor, the residence time is the liquid-phase residence time, defined as the liquid (or slurry) volumetric flow rate divided by the reactor volume. In a batch sulfonation reactor, the residence time is the batch reaction time. In some embodiments, the reactor residence time is selected from about 20 minutes to about 1 hour, such as about 30 minutes. In various embodiments, the reactor residence time is about, at least about, or at most about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2,2.5, 3, 4, 5, 6, 7, or 8 hours, including any intervening range.

[0087] In some embodiments, the sulfonation reactor is operated using a concentration of the sulfur-containing reactant selected from about 1 wt% to about 20 wt% sulfur, on a pure-sulfur basis. For example, SO2 itself is 50 wt% S, so a reactor concentration of 10 wt% SO2 means 5 wt% S. In some embodiments, the concentration of the sulfur-containing reactant is selected from about 3 wt% to about 15 wt% sulfur, on a pure-sulfur basis. In certain embodiments, the concentration of the sulfur-containing reactant is selected from about 6 wt% to about 12 wt% sulfur, on a pure-sulfur basis. In various embodiments, the concentration of the sulfur- containing reactant is about, at least about, or at most about 0.1, 0.5, 1, 1.5, 2, 2.5, 3,3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 wt%, including any intervening range.

[0088] In some embodiments, the sulfonation reactor is operated in step (d) at a sulfonation pressure selected from about 1 bar to about 10 bar. The sulfonation pressure may be higher than atmospheric due to the sulfur-containing reactant (e.g., SO2) itself, or using an inert gas (e.g., CO2 or N2), for example. In certain embodiments, the sulfonation reactor is operated under vacuum, which may be done to continuously remove light sulfur-containing compounds, for example. In various embodiments, the sulfonation pressure is about, at least about, or at most about 0.1, 0.2, 0.5, 0.8, 0.9, 1, 1.1, 1.2, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, or 10 bar, including any intervening range.

[0089] The sulfonation reactor may be operated continuously or semi- continuously, or as a batch reactor. The sulfonation reactor may be a fed-batch reactor in which the sulfur-containing reactant is intermittently fed to the reactor, which can be beneficial to allow the sulfur-containing reactant to dissolve and react before adding additional amounts of the reactant. Preferably, the sulfonation reactor is a continuous reactor that is part of a continuous biorefinery process.

[0090] FIG. 4 depicts exemplary sulfonation reactions of lignin, as well as exemplary condensation reactions of lignin. In condensation, multiple lignin molecules react together, usually creating a new C-C bond, to create a larger molecule. Essentially, condensation is a type of polymerization that increases molecular weight, often reducing solubility to the point that lignin precipitates out of solution, which is usually problematic. There are many possible condensation reactions, not limited to what is shown in FIG. 4.

[0091] The sulfonation reactor is preferably operated such that the rate of lignin sulfonation is higher than the rate of lignin condensation. In some embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least twice the rate of lignin condensation. In certain embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least five times the rate of lignin condensation. In certain embodiments, the sulfonation reactor is operated such that the rate of lignin sulfonation is at least ten times the rate of lignin condensation. The rates of lignin sulfonation and lignin condensation may be measured dynamically in the sulfonation reactor, such as by analyzing samples during the reaction. Alternatively, or additionally, the average rates of lignin sulfonation and lignin condensation may be calculated after reaction based on analyzed samples obtained from the reactor. To ensure that the rate of lignin sulfonation is higher than the rate of lignin condensation, the sulfonation reactor may be controlled using one or more of concentration of sulfur-containing reactant, pH, additives, temperature, pressure, flow patterns within the reactor, recycle strategies, or any combination thereof.

[0092] Although lignin condensation is generally to be avoided, it is not irreversible. Lewis acids may be used to break lignin-condensation bonds, or reduce the rate of lignin condensation. Exemplary Lewis acids for this purpose include metalchlorides, such as FeCh, ZnCh, or AlCh. In some embodiments, a small concentration (e.g., 0.01-1 wt%) of a non-sulfur-containing Lewis acid is used as an additive in the sulfonation reactor.

[0093] When a mixture of lignins is sulfonated there may be various extents of reaction among the different lignins. For example, starting lignin that is already sulfonated might not be further sulfonated, or might be slightly further sulfonated. Other lignin starting with little or no sulfonation might undergo much more sulfur addition. Lignin that is more reactive for another reason, such as the presence of a high concentration of reactive groups in side chains, might undergo more sulfur addition.

[0094] For a given starting quantity of sulfur-containing reactant added to the sulfonation reactor, a conversion can be calculated following reaction. For example, in the case of SO2 used as the sulfur-containing reactant, a feed stream containing 1 kg / hour of SO2 and an exit stream containing 0.1 kg / hour of SO2 means that the SO2 conversion was 90%. In various embodiments, the conversion of the sulfur- containing reactant is about, or at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or 100%, including any intervening range. Excess, unreacted sulfur-containing reactant may be recycled and reused.

[0095] Some sulfur-containing reactant may react, but not to make sulfonated lignin. For example, a sulfur-containing reactant may react with a salt to make a sulfite salt, not having any lignin. Preferably, the reaction selectivity is high toward sulfonated lignin. For a given starting quantity of sulfur-containing reactant added to the sulfonation reactor, a selectivity can be calculated following reaction. For example, in the case of SO2 used as the sulfur-containing reactant, a conversion of 0.9 kg / hr of SO2 and a rate of SO2 incorporation into sulfonated lignin of 0.8 kg / hr means a selectivity of 0.8 / 0.9 = 89%. In various embodiments, the selectivity to sulfonated lignin is about, or at least about 50%, 60%, 70%, 80%, 90%, 95%, 99%, or 100%, including any intervening range. The product yield is a function of both selectivity and conversion.

[0096] Another measure of the extent of sulfonation reaction is the average increase in sulfur content of the lignin fed to the sulfonation reactor. As an example, when the feed lignin contains, on average, 3 wt% sulfur, and the product lignincontains, on average, 6 wt% sulfur, the sulfur content increase is 100% (a doubling of sulfur content). In various embodiments, the average sulfur increase is about, at least about, or at most about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 350%, 400%, or higher, including any intervening range.

[0097] Another measure of the extent of sulfonation reaction is the average increase in sulfur content of the lignin fed to the sulfonation reactor, calculated as a wt% difference. As an example, when the feed lignin contains, on average, 3 wt% sulfur, and the product lignin contains, on average, 6 wt% sulfur, the sulfur content increase calculated as a wt% difference is 6 - 3 = 3 wt%. In various embodiments, the average sulfur increase, calculated as a wt% difference, is about, at least about, or at most about 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, 4 wt%, 4.1 wt%, 4.2 wt%, 4.3 wt%, 4.4 wt%, 4.5 wt%, 4.6 wt%, 4.7 wt%, 4.8 wt%, 4.9 wt%, 5 wt%, or higher, including any intervening range.

[0098] In some embodiments, the sulfonated lignin contains from about 1 wt% to about 10 wt% sulfur content. In certain embodiments, the sulfonated lignin contains from about 3 wt% to about 8 wt% sulfur content. In various embodiments, the sulfonated lignin contains about, at least about, or at most about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 wt% sulfur content, including any intervening range.

[0099] In some embodiments, the sulfonated lignin is lignosulfonic acid (e.g., C20H26O10S2). In some embodiments, the sulfonated lignin is a lignosulfonate salt, such as calcium lignosulfonate, sodium lignosulfonate, magnesium lignosulfonate, potassium lignosulfonate, or a mixture of two or more of the foregoing.

[0100] Following sulfonation, the sulfonated lignin may be processed or purified in a variety of ways. For example, the sulfonated lignin may be treated using a cation-exchange resin, to remove calcium and / or other metals. This step can cause protonation, reducing the pH, which enables stripping of non-lignin-containingsulfites or bisulfites, for example. The sulfonated lignin may be treated in an evaporation unit to remove components other than the sulfonated lignin. The components removed may or may not contain sulfur. When evaporation is used, the evaporation temperature and pressure may vary. For example, vacuum evaporation may be used at a temperature from about 30°C to about 80°C, such as from about 40°C to about 70°C, for example. Atmospheric evaporation (about 1 bar) may be used at a temperature from about 50°C to about 150°C, such as from about 70°C to about 120°C, for example.

[0101] The process may further comprise recovering the hemicellulose sugars. In some embodiments, the process further comprises fermenting the hemicellulose sugars (e.g., xylose and / or mannose) into a hemicellulose fermentation product, such as ethanol.

[0102] The process may further comprise hydrolyzing the cellulose-rich solids to produce glucose. In some embodiments, the process further comprises fermenting the glucose sugars into a glucose fermentation product, such as ethanol.

[0103] Ethanol from hemicellulose fermentation and / or glucose fermentation may be converted into olefins (e.g., ethylene and propylene). In some embodiments, the process further comprises converting the olefins into ethanol-derived hydrocarbons. At least a portion of the ethanol -derived hydrocarbons may be recovered as aviation fuel, which preferably qualifies as sustainable aviation fuel (“SAF”) according to ASTM D7566, or components of SAF.

[0104] There is extraordinary commercial interest in SAF. SAF essentially recycles CO2 emissions that were emitted previously and subsequently absorbed from the atmosphere during biomass production. SAF must have the same characteristics as conventional jet fuel so that manufacturers do not need to redesign engines or aircraft, and so that fuel suppliers and airports do not need to build new fuel delivery systems. Taking into consideration that the same aircraft can be fueled in different countries, international specifications have been adopted for jet fuels.

[0105] A widely utilized standard to ensure jet fuel is fit for purpose is American Society for Testing Materials (ASTM) standard number D1655, which is incorporated by reference. ASTM DI 655 sets requirements for criteria such as composition, volatility, fluidity, combustion, corrosion, thermal stability,contaminants, and additives, to ensure that the fuel is compatible when blended. The drop-in condition is a major requirement for the aviation industry, to ensure safety and performance that is equivalent to conventional Jet A or Jet Al kerosene. The standard regulating the technical certification of SAF is ASTM D7566, which is incorporated by reference.

[0106] In some embodiments, the sulfonated lignin is converted to one or more lignin-derived hydrocarbons. The lignin-derived hydrocarbons may also be recovered as SAF, or components of SAF. The lignin-derived hydrocarbons may be combined with ethanol-derived hydrocarbons for use as SAF or components of SAF. By producing sulfonated lignin according to the present disclosure, the overall yield of SAF in a biorefinery can be increased for a given feed rate of starting biomass.

[0107] Other variations provide a sulfonated lignin product produced by a process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignincontaining stream, thereby generating sulfonated lignin; and(e) recovering the sulfonated lignin as a sulfonated lignin product.

[0108] The enhanced sulfur content of the sulfonated lignin product can offer a wide variety of advantages, as will now be described — without being limited by the stated attributes and without being limited by theory or speculation.

[0109] An increase in the sulfur content of lignosulfonates, such as in the form of sulfonate groups, can lead to several desirable property improvements, including enhanced dispersibility and water solubility of lignosulfonates. Lignosulfonates possess sulfonate groups that are negatively charged when dissolved in water. A higher sulfur content means a greater number of these charged groups, leading tostronger electrostatic repulsion between particles in a suspension. This repulsion helps to keep the particles separated and evenly distributed, resulting in improved dispersion. Also, a sulfonated lignin backbone can adsorb onto the surfaces of dispersed particles, creating a protective layer that further enhances stability and prevents aggregation. Polar sulfonate groups attached to the lignin structure make lignosulfonates significantly more hydrophilic, meaning they have a strong affinity for water. Increased sulfonation increases this affinity, leading to enhanced water solubility. The presence of ionizable sulfonate groups facilitates the dissolution of lignosulfonates in water by forming charged entities that interact strongly with water molecules. Lignosulfonates with higher sulfur content exhibit greater dispersibility for materials such as gypsum paste, likely due to enhanced electrostatic repulsion and interaction with the material’s surface.

[0110] Sulfonated lignin may be used in photocatalysis. Photocatalysts derived from lignosulfonates may have improved photocatalytic activity due to enhanced charge separation and charge transfer, for example.[OHl] The sulfonated lignin disclosed herein may be useful for chemical reactions to produce a wide variety of chemicals and fuels, for many reasons.

[0112] Sulfonation reduces lignin precipitation which can cause significant operational problems in a biorefinery. Sulfonation renders the lignin less susceptible to catalyst fouling and reactor plugging.

[0113] Lignin, whether or not sulfonated, is ordinarily a solid, unless it is present as a monomer. To catalyze the reaction of lignin to another product, the solid lignin usually needs to be dissolved or at least suspended in some type of solvent, unless a fluidized bed of solid lignin particles is used.

[0114] Lignosulfonic acid is highly water-soluble due to the presence of sulfonic acid groups. This allows lignin, which is naturally insoluble in water, to be processed in an aqueous phase, which is convenient since water is the primary solvent. Improved solubility ensures better contact with the solid-phase catalyst, enhancing reaction efficiency. Because sulfonation makes the lignin soluble in an aqueous solution, the desired functional groups (e.g., -SO3H) of sulfonated lignin may be better oriented with the reactive sites of the catalyst. This can be especially useful in heterogeneous catalysis.

[0115] Increased reactivity of sulfonated lignin, compared to unsulfonated (or less-sulfonated) lignin, is a significant benefit of the disclosed technology. The sulfonic acid groups render the sulfonated lignin more polar and chemically reactive compared to native lignin as present in the original biomass. The sulfonic acid groups can groups can weaken lignin's complex structure, such as by facilitating cleavage of P-O-4 linkages, making it more susceptible to catalytic depolymerization or transformation into smaller, more-valuable molecules. Because sulfonated lignin is more amenable to a range of catalytic processes (e.g., hydrogenation, hydrogenolysis, or acid-catalyzed reactions), there is greater flexibility in choosing catalysts and reaction conditions to optimize yields of desired products from a biorefinery making various chemicals and fuels.

[0116] Sulfonation can add specific functional groups to the lignin that are required for a specific step of the mechanism of the catalytic reaction. For example, in a catalytic reaction for which sulfonic acid groups (-SO3H) are a reactive intermediate, the presence of sulfonic acid groups can enable a higher reaction rate and / or a better reaction selectivity.

[0117] Sulfur-containing functional groups can draw electrons away from the rest of the lignin. Similar to the way that the carbonyl carbon-oxygen group draws electrons from the rest of a molecule, sulfonic groups are highly electronegative and can do the same thing. This chemical property can make other parts of the lignin molecule (including aromatic rings) more susceptible to the desired reaction.

[0118] Sulfonated lignin may be catalytically and / or thermally converted to a wide variety of chemicals, including (but not limited to) esters, alcohols, furans, ethers, ketones, aromatic hydrocarbons, aromatic ethers, aromatic esters, aromatic alcohols, phenolics, guaiacols, syringols, olefinic hydrocarbons, olefinic ethers, olefinic esters, olefinic alcohols, or combination thereof.

[0119] Sulfonated lignin may be thermally and / or catalytically converted to a sulfur-free chemical, a sulfur-containing chemical, or a combination thereof. In some embodiments, a sulfonated variant of one of the chemicals listed above is made, in which for example -OH is replaced with -SH (e.g., making thiophenol rather than phenol), or -O- is replaced with -S- (e.g., making a thioester rather than an ester).

[0120] In certain embodiments, a sulfonated variant of one of the chemicals listed above is made, and then some or all of the sulfur is removed, such as via catalytic hydrodesulfurization. For example, catalytic hydrodesulfurization of thioesters is a hydrodesulfurization process used to remove sulfur from thioesters, converting the thioester into the corresponding alcohol and thiol, releasing hydrogen sulfide as a byproduct. An exemplary hydrodesulfurization catalyst is alumina- supported molybdenum sulfide promoted by nickel or cobalt. During hydrodesulfurization or other types of sulfur removal, H2S or SO2 are typically released. These sulfur-containing gases (especially SO2) may be recycled and reused in the sulfonation reactor, or in the biomass digestor.

[0121] In some embodiments, non-catalyzed thermal conversion of sulfonated lignin is used to make one or more chemicals. Typically, without a catalyst, the selectivity to particular chemicals will be reduced. However, for some applications, a mixture of chemicals may be further separated, or may be used in a fuel product for which energy value is more important than chemical-species profile. Another example of a product made from thermal conversion of sulfonated lignin is a pyrolyzed sulfonated lignin that contains carbon and sulfur, which may be useful for electrode materials in sulfur-ion batteries.

[0122] Various catalysts may be used to catalytically convert sulfonated lignin to one or more chemicals. Catalysts include, but are not limited to, solid metals, solid metal oxides, metal salts, acid catalysts, base catalysts, or combinations thereof. Exemplary solid-metal catalysts include Pt, Rh, Pd, Ru, Ni, Fe, Co, or a combination thereof. Exemplary solid metal oxides include NiO, MgO, CoO, MgCoQ. (0 < x < 4), NiMgCoQv (0 < x < 4), SiCh, AI2O3, or a combination thereof. Exemplary metal salts include copper salts and cobalt salts. Exemplary acid catalysts include H2SO4 and HC1. Exemplary base catalysts include NaOH and NH3.

[0123] The reactor for catalytically converting sulfonated lignin to one or more chemicals may be a fixed-bed tubular reactor using a heterogenous catalyst such as a metal or metal oxide, a stirred-tank reactor using a homogenous (solution) catalyst such as a metal salt or an acid, or a fluidized-bed reactor that uses a metal or metal oxide fluidized in a reaction medium.

[0124] In some embodiments in which sulfur is added to lignin in the form of sulfonic acid groups (-SO3H), certain chemistry advantages may arise. Sulfur- containing sulfonic acid groups in lignosulfonic acid are highly electronegative and significantly influence the electronic properties of the lignin structure, making it more susceptible to certain reactions, as will now be further explained.

[0125] The sulfonic acid group contains a sulfur atom bonded to three oxygen atoms — two oxygens via double bonds (S=O) and one oxygen via a single bond to a hydroxyl group (S-OH). Sulfur and oxygen are both highly electronegative. The electron-withdrawing nature of the oxygen atoms in the -SO3H group makes it strongly electron-deficient. Indeed, -SO3H is one of the most electronegative functional groups in organic chemistry, comparable to or stronger than carboxylic acid groups (-COOH) or nitro groups (-NO2). The -SO3H group acts as a strong electron-withdrawing group through both inductive effects — due to the electronegative atoms pulling electron density through <5 bonds — and resonance effects when the -SO3H group is conjugated with lignin’s aromatic system. This electron withdrawal reduces electron density in the lignin structure, particularly in nearby aromatic rings or other conjugated systems.

[0126] Lignin is a complex polymer composed of aromatic (phenolic) units (e.g., guaiacyl, syringyl, and p-hydroxyphenyl units) linked by various bonds, such as P-O-4, a-O-4, and C-C linkages. The introduction of sulfonic acid groups from sulfonation modifies lignin’s electronic and chemical properties. When -SO3H groups are attached to the lignin structure (at the aliphatic side chains or directly at the aromatic rings), they withdraw electron density from the aromatic rings. If the sulfonic group is directly attached to or near an aromatic ring, resonance effects may further delocalize electron density. This reduction in electron density makes the aromatic rings less electron-rich, increasing their electrophilicity. As a result, the aromatic rings become more susceptible to nucleophilic attack (reactions involving electron-deficient intermediates), such as electrophilic aromatic substitution or oxidative cleavage.

[0127] Also, the electron-withdrawing effect of -SChH groups can destabilize certain lignin linkages, particularly ether bonds such as P-O-4, which are abundant in lignin. By reducing electron density in the vicinity of these bonds, the -SO3H groupsmay facilitate bond cleavage through acid-catalyzed and / or redox-mediated mechanisms. For example, electron withdrawal can polarize C-0 or C-C bonds, making them more prone to hydrolysis, hydrogenolysis, or other catalytic processes in used in heterogeneous or homogeneous catalysis.

[0128] Additionally, -SO3H groups increase the overall polarity of lignosulfonic acid, enhancing its solubility in aqueous media (as noted previously) and improving its interaction with polar catalysts or reagents. The electron-deficient regions created by -SO3H groups can serve as reactive sites for catalytic transformations, such as hydrogenation or hydrodeoxygenation, and optionally desulfurization, which is useful for producing sulfur-free fuels or chemicals.

[0129] The electron-deficient sulfonated lignin is more easily depolymerized and transformed into smaller molecules, improving the yield of liquid fuels or chemical feedstocks, compared to unsulfonated lignin. The electron-withdrawing nature of sulfonic acid groups makes sulfonated lignin more susceptible to many types of reactions in a heterogeneous or homogeneous catalytic process.

[0130] In catalytic depolymerization, the reduced electron density in aromatic rings and linkages lowers the activation energy for bond cleavage reactions, such as hydrogenolysis or acid-catalyzed hydrolysis, over solid catalysts (e.g., Ni, Pd, or zeolites). This facilitates the breakdown of lignin into smaller fragments, such as phenols or aromatic monomers, which can be further processed into fuels or feedstocks.

[0131] In hydrodeoxygenation and desulfurization, the electron-deficient aromatic rings are more amenable to hydrogenation reactions, where hydrogen is added to reduce unsaturation or remove oxygen (as H2O) or sulfur (usually as H2S). The -SO3H groups themselves can be removed during desulfurization, yielding sulfur-free products. The -SO3H groups are labile enough to be removed during desulfurization, for the production of sulfur-free products.

[0132] In hydrodeoxygenation, commonly used catalysts such as NiMo or C0M0 can exploit the increased electrophilicity of the lignin structure to enhance reaction rates.

[0133] In oxidative or reductive transformations, the electron withdrawal makes lignosulfonic acid more susceptible to oxidative cleavage (e.g., breaking C-Cor C-0 bonds) or reductive processes (e.g., reducing aromatic rings to cycloalkanes for fuel or chemical production). For example, in a packed-bed reactor with a metal- supported catalyst, the electron-deficient sulfonated lignin may interact more readily with active sites, promoting redox reactions.

[0134] In acid-catalyzed reactions, the -SO3H groups themselves are strongly acidic (pKa from about -2 to -3), contributing to the acidity of the reaction medium. This acidity can catalyze reactions such as dehydration or hydrolysis, further enhancing lignin breakdown in the presence of a solid acid catalyst (e.g., zeolites or sulfonated resins).

[0135] For a range of processes, sulfonated lignin may enhance catalyst compatibility, compared to unsulfonated lignin. The above-mentioned electronwithdrawing effect ensures better interaction with metal or acid sites on a solid catalyst, optimizing catalytic efficiency. The choice of catalyst and reaction conditions may further enhance these effects, optimizing the process efficiency.

[0136] In heterogeneous catalysis, the solubility of lignosulfonic acid in the aqueous phase reduces viscosity and improves mass transfer to the catalyst surface. This ensures efficient interaction between the lignin substrate and the active surface sites on the solid catalyst, minimizing diffusion limitations.

[0137] Other variations of the invention utilize a biomass digestor that does not use a solvent for lignin, and possibly not an acid catalyst either. In these variations, the lignin may be completely unsulfonated before entering the sulfonation reactor.

[0138] The Green Power+® process, developed over the past two decades, is commonly owned with the assignee (GranBio Intellectual Property Holdings, LLC) of the present patent application. Green Power+ technology treats a lignocellulosic biomass feedstock in the presence of steam and / or hot water, and optionally an acid catalyst, to produce a liquor containing cellulose-rich solids, lignin, and hemicellulose sugars.

[0139] In some variations, the present invention provides a process for making sulfonated lignin from lignocellulosic biomass, the process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating the feedstock in the presence of steam and / or hot water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and the lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignincontaining stream, thereby generating sulfonated lignin; and(e) recovering the sulfonated lignin.

[0140] Other variations of the invention utilize a generic source of starting lignin, which may be partially sulfonated or completely unsulfonated. In these embodiments, the starting lignin may be AVAP lignin, Green Power+ lignin, sulfite lignin, kraft lignin, soda lignin, organosolv lignin, or another type of lignin.

[0141] In some variations, the present invention provides a process for making sulfonated lignin from lignin, the process comprising:(a) providing a starting lignin;(b) introducing a sulfur-containing reactant and the starting lignin to a sulfonation reactor, to sulfonate at least a portion of starting lignin, thereby generating sulfonated lignin; and(c) recovering the sulfonated lignin.

[0142] The block-flow diagrams of FIGS. 1, 2, and 3 may also refer to systems configured for making sulfonated lignin from lignocellulosic biomass. It should be noted that in the FIGS. 1-3, specific unit operations may be omitted in some embodiments and in these or other embodiments, other unit operations not explicitly shown may be included. The invention is not limited to what is shown, or not shown, in the exemplary drawings.

[0143] The present invention also provides a system configured for making sulfonated lignin from lignocellulosic biomass, the system comprising:(a) a system input configured for feeding a feedstock comprising lignocellulosic biomass;(b) a digestor configured for fractionating the feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acidprecursor, and water, to produce a liquor containing hemicellulose sugars, cellulose- rich solids, and starting lignin;(c) means for removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) a sulfonation reactor;(e) means for introducing a sulfur-containing reactant and the lignincontaining stream to the sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignin-containing stream, thereby generating sulfonated lignin; and(e) a system output configured for recovering the sulfonated lignin.

[0144] The present invention also provides a system configured for making sulfonated lignin from lignocellulosic biomass, the system comprising:(a) a system input configured for feeding a feedstock comprising lignocellulosic biomass;(b) a digestor configured for fractionating the feedstock in the presence of steam and / or hot water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) means for removing at least some of the cellulose-rich solids from the liquor, thereby generating a lignin-containing stream;(d) a sulfonation reactor;(e) means for introducing a sulfur-containing reactant and the lignincontaining stream to the sulfonation reactor, to sulfonate at least a portion of lignin contained in the lignin-containing stream, thereby generating sulfonated lignin; and(e) a system output configured for recovering the sulfonated lignin.

[0145] Various valves, pumps, meters, sensors, sample ports, etc. are not shown in the simple block-flow diagrams of FIGS. 1-3. Additionally, multiple pieces of equipment (rather than single pieces of equipment), either in series or in parallel, may be utilized for any unit operations. Also, solid, liquid, and vapor streams produced or existing within the method and system may be independently recycled, passed to subsequent steps, or removed / purged at any point. In FIGS. 1-3, a portion or all of an intermediate stream may be recovered as a co-product, if desired. Or, a product may be passed to another unit for further processing, in which case the product becomes an intermediate rather than final product.

[0146] Material can generally be conveyed into and out of the sulfonation reactor by pumps, screws, and the like. Material can be conveyed mechanically by physical force, pressure-driven flow, pneumatically driven flow, centrifugal flow, gravitational flow, fluidized flow, or some other known means of moving material.

[0147] A system may include a subsystem for adjusting temperature, pH, pressure, and / or residence time within the sulfonation reactor. A subsystem may be configured to vary parameters, such as over a prescribed protocol, or in response to measured variables. For example, an unintended change in sulfonation reactor pH may be compensated by a change in temperature and / or residence time. As another example, temperature may be maintained constant (isothermal operation) or pressure may be maintained constant (isobaric operation). The subsystem may utilize well- known control logic principles, such as feedback control and feedforward control. Control logic may incorporate results from previous experiments or production campaigns.

[0148] In some embodiments, a reaction probe is disposed in operable communication with a reaction zone in the sulfonation reactor. Such a reaction probe can be useful to extract vapors, liquids, or solids and analyze them, in order to determine extent of sulfonation, pH, temperature, or other process monitoring. Then, based on the measurement, the process can be controlled or adjusted in any number of ways, such as by adjusting processing rate, pH, temperature, pressure, agitation, additives, and so on. Process adjustments based on the measurements, if deemed necessary or desirable, may be made using well-known principles of process control (feedback, feedforward, proportional-integral-derivative logic, etc.).

[0149] For example, SO2 concentration in a vapor phase within the sulfonation reactor may be measured using a gas probe to extract a sample, which is then analyzed using a suitable technique, such as gas chromatography, GC; mass spectroscopy, MS; GC-MS, or Fourier-Transform Infrared Spectroscopy, FTIR.

[0150] Safety considerations may be applied to the methods and systems. A unit may include protective devices (e.g., a safety release valve) that automatically activate when the temperature or pressure exceeds a maximum value, for example. Practical safety-related design may be built into the system as well. Those skilled in the art will understand how to design safe units.

[0151] In some embodiments, the system input is in flow communication with a storage tank or other storage unit that received a pretreated biomass stream, such as from another site, which may be a co-located adjacent site.

[0152] The system may be in flow communication with a biomass-processing unit that generates the pretreated biomass stream at the same site as the sulfonation reactor.

[0153] Some embodiments utilize a business system in which steps of a method are practiced at different sites and potentially by different corporate entities, acting in conjunction with each other in some manner, such as in a joint venture, an agency relationship, a toll producer, a customer with restricted use of product, etc. For example, biomass may be pretreated at a first site to generate a pretreated biomass stream that is then sent to a second site for processing in the sulfonation reactor.

[0154] The recited method and system options and embodiments may be utilized entirely or partially. Some embodiments may omit method steps or system components. Some embodiments include other method steps or system components that are not explicitly taught herein but are conventional in the chemical-engineering and biorefinery arts. Solid, liquid, and gas streams produced or existing within the biorefinery can be independently recycled, passed to subsequent steps, or removed / purged from the process at any point.

[0155] The throughput, or process capacity, can vary widely from small experimental units to full operations, including any pilot, demonstration, or semicommercial scale. In various embodiments, the process capacity (for feedstocks, products, or both) is at least about 0.1 tons / day (all tons are metric tons), 1 ton / day, 10 tons / day, 100 tons / day, 500 tons / day, 1000 tons / day, 2000 tons / day, 3000 tons / day, 4000 tons / day, 5000 tons / day, or higher.

[0156] The biorefinery may be a retrofit to an existing plant. In other embodiments, the biorefinery is a greenfield plant. As will be appreciated by a person skilled in the art, the principles of this disclosure may be applied to many biorefinery plant configurations beyond those explicitly disclosed or described in the drawings hereto. Various combinations are possible and selected embodiments from some variations may be utilized or adapted to arrive at additional variations that do not necessarily include all features disclosed herein.

[0157] In this detailed description, reference has been made to multiple embodiments of the invention and non-limiting examples relating to how the invention can be understood and practiced. Other embodiments that do not provide all of the features and advantages set forth herein may be utilized, without departing from the spirit and scope of the present invention. This invention incorporates routine experimentation and optimization of the methods and systems described herein. Such modifications and variations are considered to be within the scope of the invention defined by the claims.

[0158] All publications, patents, and patent applications cited in this specification are herein incorporated by reference in their entirety as if each publication, patent, or patent application were specifically and individually put forth herein.

[0159] This disclosure hereby incorporates by reference herein U.S. Patent App. Pub. No. 2021 / 013103 Al by Zebroski, published on May 6, 2021, for its teachings of various process and system options that are applicable to embodiments of this invention.

[0160] This disclosure also hereby incorporates by reference herein U.S. Patent App. Pub. No. 2023 / 0287468 Al by Zebroski, published on September 14, 2023, for its teachings of various process and system options that are applicable to embodiments of this invention.

[0161] This disclosure also hereby incorporates by reference herein U.S. Patent App. Pub. No. 2022 / 0304051 Al by Zebroski, published on September 28, 2023, for its teachings of various process and system options that are applicable to embodiments of this invention.

[0162] This disclosure also hereby incorporates by reference herein U.S. Patent App. Pub. No. 2023 / 0313251 Al by Zebroski, published on October 5, 2023, for its teachings of various process and system options that are applicable to embodiments of this invention.

[0163] This disclosure also hereby incorporates by reference herein U.S. Patent App. No. 18 / 597,459 by Zebroski, filed on March 6, 2024, for its teachings of various process and system options that are applicable to embodiments of this invention.

[0164] Where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art will recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially.

[0165] Therefore, to the extent there are variations of the invention, which are within the spirit of the disclosure or equivalent to the inventions found in the appended claims, it is the intent that this patent will cover those variations as well. The present invention shall only be limited by what is claimed.EXAMPLE

[0166] In this Example, experiments are carried out to increase the degree of sulfonation of lignin contained in AVAP cook liquor following cellulose separation and prior to an ethanol stripper column. This Example is based on FIG. 1.

[0167] The conditions of the AVAP cook (digestion) were as follows. The feedstock was hardwood residuals. The digestor temperature was about 150°C and the digestor residence time was about 1 hour. The digestor reaction solution was 12 wt% SO2, 44 wt% ethanol, and 44 wt% water. The liquid / wood ratio in the digestor was 4 / 1. Following the digestion, the total SO2 content, as free sulfur dioxide and bisulfite, was about 1.5 wt%, and the pH was measured as 0.9.

[0168] Cellulose-rich solids are removed from the digestor slurry using a filter press that separates and washes the cellulose-rich solids. This AVAP cook liquor is depleted in SO2 content, compared to the SO2 content (12 wt%) in the digestor.

[0169] The experiments were conducted using sulfur dioxide (SO2) as the sulfur-containing reactant for sulfonation. The AVAP cook liquor and SO2 were added to a laboratory-scale sulfonation reactor and then tested in multiple experiments for lignin sulfonation at 6 wt% and 12 wt% SO2 concentration, pH = 2 and pH = 3 (adjusting using ammonia), a sulfonation temperature of 150°C, and a sulfonation time of 30 minutes. No lignin condensation or sudden precipitation was observedduring handling after the sulfonation reaction, demonstrating that the sulfonation reactor was operated such that the rate of lignin sulfonation was higher than the rate of lignin condensation.

[0170] Following sulfonation, the cooked liquor was processed through a cation-exchange resin, followed by vacuum evaporation at 40°C or at 70°C, for about 30 minutes, to remove volatile sulfur groups. Some dilution occurred due to both the added ammonia and moisture contribution from the cation-exchange resin. Vacuum evaporation is performed at two different temperatures (40°C and 70°C) to study the impact of temperature and ethanol concentration on the removal of sulfites. At either temperature, it is expected that free SO2 is readily removed.

[0171] The processes samples were then analyzed using ion chromatography (IC) to measure sulfur content. FIG. 5 shows a summary table of experimental results. The first two rows correspond to control samples in which there was no SO2 addition or ammonia adjustment of pH, but which did undergo vacuum evaporation at 40°C and at 70°C. These control samples were measured as having about 3 wt% sulfur in the lignin, which is believed to correspond to lignin sulfonation from the original AVAP cook.

[0172] According to this data, all experiments with added SO2 (6 wt% or 12 wt%), either pH = 2 or 3, and evaporation at 40°C or 70°C resulted in lignin being sulfonated in the sulfonation reactor. At fixed pH and evaporation temperature, sulfonation was always more effective at 12 wt% SO2 compared to 6 wt% SO2. Generally, both pH values tested (2 and 3) were effective for sulfonation, under these conditions. The results at 12 wt% SO2, pH = 3, and 70°C evaporation give 6.3 wt% sulfur, which is over double the sulfur content of the feedstock that was not processed in the sulfonation reactor.

Claims

CLAIMSWhat is claimed is:

1. A process for making sulfonated lignin from lignocellulosic biomass, said process comprising:(a) providing a feedstock comprising lignocellulosic biomass;(b) in a digestor, fractionating said feedstock under effective fractionation conditions in the presence of a solvent for lignin, an acid or acid precursor, and water, to produce a liquor containing hemicellulose sugars, cellulose-rich solids, and starting lignin;(c) removing at least some of said cellulose-rich solids from said liquor, thereby generating a lignin-containing stream;(d) introducing a sulfur-containing reactant and said lignin-containing stream to a sulfonation reactor, to sulfonate at least a portion of lignin contained in said lignin-containing stream, thereby generating sulfonated lignin; and(e) recovering said sulfonated lignin.

2. The process of claim 1, wherein said acid or acid precursor contains sulfur.

3. The process of claim 2, wherein said acid or acid precursor is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof.

4. The process of claim 1, wherein said acid or acid precursor does not contain sulfur.

5. The process of claim 1, wherein said starting lignin contains from 0 to about 3 wt% sulfur content.

6. The process of claim 1, wherein said starting lignin generated in step (b) includes colloidal lignin and soluble lignin.

7. The process of claim 6, wherein said soluble lignin has a higher sulfur content compared to said colloidal lignin.

8. The process of claim 6, wherein said colloidal lignin and said soluble lignin are separated from each other using a lignin-separation unit.

9. The process of claim 8, wherein said lignin-containing stream contains said colloidal lignin but not said soluble lignin.

10. The process of claim 8, wherein said lignin-containing stream contains said soluble lignin but not said colloidal lignin.

11. The process of claim 8, wherein said lignin-containing stream contains both of said soluble lignin and said colloidal lignin.

12. The process of claim 1, wherein said lignin-containing stream comprises said solvent for lignin.

13. The process of claim 12, wherein said solvent for lignin is a Ci-Ce alcohol.

14. The process of claim 13, wherein said Ci-Ce alcohol is selected from the group consisting of methanol, ethanol, ethylene glycol, 1 -propanol, 2-propanol, propanediol, glycerol, 1 -butanol, 2-butanol, isobutanol, butanediol, 1 -pentanol, 1- hexanol, cyclohexanol, and combinations thereof.

15. The process of claim 12, wherein said solvent for lignin is methanol, ethanol, or a mixture of methanol and ethanol.

16. The process of claim 1, wherein said lignin-containing stream does not comprise said solvent for lignin.

17. The process of claim 1, wherein said lignin-containing stream comprises said hemicellulose sugars.

18. The process of claim 1, wherein said lignin-containing stream does not comprise said hemicellulose sugars.

19. The process of claim 1, wherein said sulfur-containing reactant is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfite ions, sulfite salts, bisulfite ions, bisulfite salts, sulfur trioxide, sulfuric acid, sulfate salts, bisulfate salts, sulfonic acid, sulfonate ions, sulfonate salts, lignosulfonic acid, lignosulfonate ions, lignosulfonate salts, elemental sulfur, hydrogen sulfide, dialkyl sulfides, dialkyl disulfides, polysulfides, and combinations thereof.

20. The process of claim 19, wherein said sulfur-containing reactant is SO2.

21. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation temperature selected from about 120°C to about 180°C.

22. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation temperature selected from about 130°C to about 170°C.

23. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation temperature selected from about 140°C to about 160°C.

24. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 1.5 to about 4.0.

25. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 2.0 to about 4.0.

26. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 2.0 to about 3.5.

27. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a sulfonation pH selected from about 2.5 to about 4.0.

28. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a reactor residence time selected from about 10 minutes to about 2 hours.

29. The process of claim 1, wherein said sulfonation reactor is operated in step (d) at a reactor residence time selected from about 20 minutes to about 1 hour.

30. The process of claim 1, wherein said sulfonation reactor is operated using a concentration of said sulfur-containing reactant selected from about 1 wt% to about 20 wt% sulfur, on a pure-sulfur basis.

31. The process of claim 1, wherein said sulfonation reactor is operated using a concentration of said sulfur-containing reactant selected from about 3 wt% to about 15 wt% sulfur, on a pure-sulfur basis.

32. The process of claim 1, wherein said sulfonation reactor is operated using a concentration of said sulfur-containing reactant selected from about 6 wt% to about 12 wt% sulfur, on a pure-sulfur basis.

33. The process of claim 1, wherein said sulfonation reactor is operated such that the rate of lignin sulfonation is higher than the rate of lignin condensation.

34. The process of claim 1, wherein said sulfonation reactor is operated such that the rate of lignin sulfonation is at least twice the rate of lignin condensation.

35. The process of claim 1, wherein said sulfonation reactor is operated such that the rate of lignin sulfonation is at least five times the rate of lignin condensation.

36. The process of claim 1, wherein said sulfonation reactor is operated such that the rate of lignin sulfonation is at least ten times the rate of lignin condensation.

37. The process of claim 1, wherein said sulfonated lignin contains from about 1 wt% to about 10 wt% sulfur content.

38. The process of claim 1, wherein said sulfonated lignin contains from about 3 wt% to about 8 wt% sulfur content.

39. The process of claim 1, wherein said sulfonated lignin is lignosulfonic acid.

40. The process of claim 1, wherein said sulfonated lignin is a lignosulfonate salt.

41. The process of claim 1, said process further comprising recovering said hemicellulose sugars.

42. The process of claim 41, said process further comprising fermenting said hemicellulose sugars into a hemicellulose fermentation product.

43. The process of claim 1, said process further comprising hydrolyzing said cellulose-rich solids to produce glucose.

44. The process of claim 43, said process further comprising fermenting said glucose sugars into a glucose fermentation product.

45. The process of either one of claims 42 or 44, wherein said hemicellulose fermentation product and / or said glucose fermentation product is ethanol.

46. The process of claim 45, said process further comprising converting said ethanol into olefins.

47. The process of claim 46, said process further comprising converting said olefins into ethanol -derived hydrocarbons.

48. The process of claim 47, wherein at least a portion of said ethanol-derived hydrocarbons are recovered as sustainable aviation fuel.

49. The process of claim 1, wherein said sulfonated lignin is converted to one or more lignin-derived hydrocarbons.

50. The process of claim 47, wherein said sulfonated lignin is converted to one or more lignin-derived hydrocarbons, and wherein said lignin-derived hydrocarbons and said ethanol-derived hydrocarbons are both recovered as sustainable aviation fuel.

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