WO2022125709A1 - Methods for extracting lignin - Google Patents

Methods for extracting lignin Download PDF

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Publication number
WO2022125709A1
WO2022125709A1 PCT/US2021/062482 US2021062482W WO2022125709A1 WO 2022125709 A1 WO2022125709 A1 WO 2022125709A1 US 2021062482 W US2021062482 W US 2021062482W WO 2022125709 A1 WO2022125709 A1 WO 2022125709A1
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WIPO (PCT)
Prior art keywords
lignin
solvent
limited
solubility
stream
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PCT/US2021/062482
Other languages
French (fr)
Inventor
Allison Jean Hulchanski
Philip TRAVISANO III
Shaun Knapp
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Virdia, Llc
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Publication of WO2022125709A1 publication Critical patent/WO2022125709A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
    • C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07G—COMPOUNDS OF UNKNOWN CONSTITUTION
    • C07G1/00—Lignin; Lignin derivatives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
    • C08B37/0003—General processes for their isolation or fractionation, e.g. purification or extraction from biomass
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
    • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
    • C08B37/0057—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Xylans, i.e. xylosaccharide, e.g. arabinoxylan, arabinofuronan, pentosans; (beta-1,3)(beta-1,4)-D-Xylans, e.g. rhodymenans; Hemicellulose; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
    • C08H8/00—Macromolecular compounds derived from lignocellulosic materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L5/00—Compositions of polysaccharides or of their derivatives not provided for in groups C08L1/00 or C08L3/00
    • C08L5/14—Hemicellulose; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L97/00—Compositions of lignin-containing materials
    • C08L97/005—Lignin

Definitions

  • Lignin a highly abundant natural polymer that can be extracted from biomass, is a polymer of preference for various applications and as a chemical feedstock that replaces petrochemicals.
  • Industrial utilization of lignin is difficult given its variable nature, functionality, reactivity, and heterogeneity. It is desirable to fractionate lignin into stable fractions that have reduced variability in size, composition and reactivity. Fractionation of lignin by membrane filtration using ultrafiltration and nanofiltration membranes can result in unstable fractions of lignin that change while being fractionated, and thus may be unsuitable for industrial and commercial purposes. It can also be a challenge to characterize the obtained fractions by a reliable method, as chromatography of lignin by size is notoriously dependent on experimental procedure, and a lack of good standards and suitable detectors render many measurements relative rather than absolute.
  • the present disclosure provides a method for producing a high purity lignin from a biomass, the method comprising: removing a hemicellulose sugar from the biomass to produce a lignin-containing remainder comprising lignin and cellulose; combining the lignin-containing remainder with a lignin extraction solution in a lignin extraction reactor to produce (i) a lignin extract comprising lignin dissolved in the limited-solubility solvent and (ii) a cellulosic remainder, wherein the lignin extraction solution comprises a limited-solubility solvent and water, and wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; separating the lignin extract from the cellulosic remainder, thereby producing the high purity lignin; and recycling a portion of the lignin extract to the lignin extraction reactor.
  • the limited-solubility solvent has a solubility in water of no more than 35 wt%. In some aspects, the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof.
  • the limited-solubility solvent comprises a solvent selected from the group consisting of 1 -chi oro-2 -butanone, 1- phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2- phenyl ethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5- dimethylpyridine, acetal, anisol, diacetyl, 2, 3 -pentanedi one, diethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tertbutyl ether,
  • the limited-solubility solvent comprises methyl ethyl ketone. In some aspects, the limited-solubility solvent consists of methyl ethyl ketone. In some aspects, the cellulosic remainder comprises less than 10 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 5 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 3 wt% residual lignin. In some aspects, the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.1.
  • the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.2. In some aspects, the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.3. In some aspects, a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent.
  • a system for producing high-purity lignin from biomass comprising: a lignin extraction unit configured to produce a stream comprising dissolved lignin and a cellulosic remainder; a cellulose recovery unit configured to produce a cellulosic remainder and a lignin extract; a lignin recovery unit configured to produce a lignin product; and a recycle stream connecting the lignin recovery unit to the lignin extraction reactor; wherein the recycle stream comprises a lignin extraction solvent with a dissolved solids content of at least 1%.
  • a system for producing high-purity lignin from biomass comprising: a lignin extraction unit; a cellulose separation unit; a lignin purification unit comprising a two-phase separation unit and a solvent purification unit; and a recycle stream that connects the lignin purification unit to the lignin extraction reactor.
  • the lignin extraction unit is configured to produce a lignin extract and a cellulosic remainder.
  • the lignin purification unit further comprises a strong acid cation exchanger.
  • the recycle stream is positioned upstream of the strong acid cation exchanger.
  • the recycle stream is positioned downstream of the strong acid cation exchanger. In some aspects, the system does not comprise a strong acid cation exchanger.
  • the lignin purification unit is configured to receive the lignin extract. In some aspects, the lignin purification unit is configured to produce a purified lignin product and a purified limited-solubility solvent stream. In some aspects, a portion of purified limitedsolubility solvent stream is returned to the lignin extraction reactor. In some aspects, the portion of the purified limited-solubility solvent stream and the portion of the lignin extract in the recycle stream are combined before entering the lignin extraction unit.
  • the limited-solubility solvent has a solubility in water of no more than about 35 wt%. In some aspects, the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof.
  • the limited-solubility solvent comprises a solvent selected from the group consisting of l-chloro-2-butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2-phenylethanol, 2-phenylethyl chloride, 2- methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3- pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tert-butyl
  • the limited-solubility solvent comprises methyl ethyl ketone. In some aspects, the limited-solubility solvent consists of methyl ethyl ketone. In some aspects, the cellulosic remainder comprises less than 10 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 5 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 3 wt% residual lignin. In some aspects, the recycle stream has a recycle ratio of at least about 0.1. In some aspects, the recycle stream has a recycle ratio of at least about 0.2. In some aspects, the recycle stream has a recycle ratio of at least about 0.3.
  • a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent. In some aspects, the cellulose recovery unit comprises a filtration unit or a centrifuge.
  • FIG. 1A is a schematic flowchart of an exemplary method of treating lignocellulosic biomass material according to some embodiments of the present disclosure.
  • FIG. IB is a schematic flowchart of an exemplary method of treating lignocellulosic biomass material utilizing a lignin extractant recycle loop, according to some embodiments of the present disclosure.
  • FIG. 2 depicts a schematic view of a lignin extraction system comprising a strong acid cation exchanger (SAC), in accordance with some embodiments of the present disclosure.
  • FIG. 3 depicts a schematic view of a lignin extraction system without an SAC, in accordance with some embodiments of the present disclosure
  • FIG. 4 depicts a schematic view of a lignin extraction system with a recycle loop before an SAC, in accordance with some embodiments of the present disclosure.
  • FIG. 5 depicts a schematic view of a lignin extraction system with a recycle loop after an SAC, in accordance with some embodiments of the present disclosure.
  • FIG. 6 depicts a schematic view of a lignin extraction system with a recycle loop in the absence of an SAC, in accordance with some embodiments of the present disclosure.
  • FIG. 7A shows an image of collected cellulose after a lignin extraction process conducted at 235 °C.
  • FIG. 7B shows an image of collected cellulose after a lignin extraction process conducted at 205 °C.
  • FIG. 1A An overview of the lignocellulosic biomass processing and refining according to embodiments disclosed herein is provided in FIG. 1A.
  • Many forms of lignocellulosic biomass processing and refining processes include: (1) pretreatment 1710; (2) hemicellulose sugar extraction 1720 and purification 1730; (3) direct lignin extraction 1740, and (4) lignin purification 1750.
  • a lignocellulosic biomass processing and refining process includes a recycling of an unpurified lignin extract 1740A to the lignin extraction step 1740.
  • the lignocellulosic biomass processing and refining can begin with pretreatment 1710, during which the lignocellulosic biomass can be, for example, debarked, chipped, shredded, dried, or grinded to particles.
  • the hemicellulose sugars can be extracted from the lignocellulosic biomass, forming an acidic hemicellulose sugar stream 1720A and a lignocellulosic remainder stream 1720B.
  • the lignocellulosic remainder stream 1720B may consist mostly of cellulose and lignin.
  • Hemicellulose the hemicellulose sugar stream can be effectively extracted and converted into monomeric sugars (e.g., >90% of the total sugar) by treating biomass under mild conditions such as low concentrations of an acid, heating, pressure, or a combination of conditions thereof. At least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of hemicellulose in the hemicellulose sugar stream can be converted into monomeric sugars.
  • the acidic hemicellulose sugar stream 1720A may be purified, wherein acids and impurities co-extracted with hemicellulose sugars can be removed from the hemicellulose sugar stream by solvent extraction. Once acids and impurities are removed from the hemicellulose sugar stream, the stream may be neutralized and optionally evaporated to a higher concentration, thus yielding a high purity hemicellulose sugar mixture, which can be further fractionated to obtain xylose and xylose-removed hemicellulose sugar mixture. Xylose may then be crystallized.
  • the lignocellulosic remainder 1720B can be processed to extract lignin.
  • This process can produce a high purity lignin 1750-P1 and a high purity cellulose 1750- P2.
  • the novel lignin purification process of the disclosure can utilize a limited-solubility solvent, and can produce a lignin having a purity greater than about 99%.
  • the limited-solubility solvent may have low solubility in water.
  • the solubility of the limited-solubility solvent in water at room temperature may be less than about 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or less than about 1 wt%.
  • the solubility of the limited-solubility solvent in water at room temperature may be at least about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 15 wt%, 20 wt %, 25 wt%, 30 wt%, 35 wt%, or greater than about 35 wt%.
  • the solvent may form two phases with water (e.g., upon mixing with water, the limited-solubility solvent may form a phase separate from the water), and the solubility of water in it should be at least about 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, or at least about 1 wt% at room temperature.
  • the solubility of water in the limitedsolubility solvent may be no more than about 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, or no more than about 1 wt% at room temperature.
  • the solvent may be stable at acidic conditions at temperatures of up to 100 °C.
  • the solvent may form a heterogeneous azeotrope with water, having a boiling point of less than about 100 °C where the azeotrope composition contains at least 50% of the solvent, at least 60% of the solvent out of total azeotrope.
  • the solvent may have a least one hydrophilic functional group selected from ketone, alcohol and ether, or another polar functional group.
  • the solvent may be commercially available at low cost.
  • Examples of limitedsolubility solvents suitable for the present disclosure can include l-chloro-2-butanone, 1- phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2- phenyl ethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5- dimethylpyridine, acetal, anisol, diacetyl, 2,3-pentanedione, diethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal
  • the limited-solubility solvent includes one or more of alcohols, esters, ethers and ketones with 4 to 8 carbon atoms.
  • the limited-solubility solvent can include or can consist of methyl ethyl ketone (MEK, also know as butanone).
  • the limited-solubility solvent consists essentially of, or consists of methyl ethyl ketone.
  • lignocellulosic biomass Prior to hemicellulose sugar extraction 1720, lignocellulosic biomass can be optionally pre-treated 1710.
  • pretreatment 1710 can refer to the reduction in biomass size (e.g., mechanical breakdown, milling (e.g., disc mill or hammer mill), cutting or shredding), which does not substantially affect the lignin, cellulose and hemicellulose compositions of the biomass.
  • Pretreatment can facilitate more efficient and economical processing of a downstream process (e.g., hemicellulose sugar extraction).
  • lignocellulosic biomass is debarked, chipped, shredded and/or dried to obtain pre-treated lignocellulosic biomass.
  • Pretreatment can also utilize, for example, ultrasonic energy or hydrothermal treatments including water, heat, steam or pressurized steam. Pretreatment can occur or be deployed in various types of containers, reactors, pipes, flow through cells and the like. In some methods, it is preferred to have the lignocellulosic biomass pre-treated before hemicellulose sugar extraction 1720. In some methods, no pre-treatment is required, e.g., lignocellulosic biomass can be used directly in the hemicellulose sugar extraction 1720.
  • lignocellulosic biomass can be milled or grinded to reduce particle size.
  • the lignocellulosic biomass is grinded such that the average size of the particles is in the range of about 100-10,000 micron, preferably about 400-5,000, e.g., about 100-400, 400-1,000, 1,000-3,000, 3,000-5,000, or about 5,000-10,000 microns.
  • the lignocellulosic biomass is grinded such that the average size of the particles is less than about 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,000, 3,000, 1,000, or 400 microns, or less than about 400 microns.
  • the present disclosure may include the partial or nearly total removal of hemicellulosic biomass from a lignocellulosic biomass before lignin extraction.
  • the present invention provides an advantageous method of extracting hemicellulose sugars from lignocellulosic biomass (e.g., hemicellulose sugar extraction 1720).
  • an aqueous acidic solution is used to extract lignocellulose biomass.
  • the aqueous acidic solution can contain any acids, inorganic or organic.
  • an inorganic acid is used.
  • the solution can be an acidic aqueous solution containing an inorganic acid such as H2SO4, H2SO3 (which can be introduced as dissolved acid or as SO2 gas), HC1, and/or an or organic acid such as acetic acid.
  • the solution may contain organic acids such as carboxylic acids and dicarboxylic acids.
  • the acidic aqueous solution can contain an acid in an amount of about 0 to 2% acid or more, e.g., 0.01-0.2%, 0.2- 0.4%, 0.4-0.6%, 0.6-0.8%, 0.8-1.0%, 1.0-1.2%, 1.2-1.4%, 1.4-1.6%, 1.6-1.8%, 1.8-2.0% or more than about 2% weight/weight.
  • the aqueous solution for the extraction includes about 0.2 - 0.7% or about 0.2-0.4% acid.
  • the acid is H2SO4 or HC1.
  • the aqueous solution may comprise about 10 - 3,000 ppm SO2.
  • the aqueous solution for the extraction includes about 0.2 - 0.7% H2SO4 or HC1.
  • the aqueous solution for the extraction includes about 0.2 - 0.4% H2SO4 or HC1.
  • the pH of the acidic aqueous solution is from about 1 to about 5.
  • the pH of the acidic aqueous solution is from about 1 to about 3.5.
  • the pH of the acidic aqueous solution is from about 2 to 3.
  • the hemicellulose sugar extraction comprises an elevated temperature or pressure.
  • a temperature in the range of about 100 - 200 °C, or more than about 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, or 200 °C, or more than about 200 °C can be used.
  • the temperature is in the range of about 110-160 °C, or about 120-150 °C.
  • the pressure can be in the range of from about 0.1 megapascal (MPa) to about 10 MPa, preferably, from about 0.1 MPa to about 1 MPa, from about 0.1 MPa to about 2 MPa, or from about 0.1 MPa to about 5 MPa.
  • the solution can be heated for about 0.5 - 5 hours, preferably about 0.5-3 hours, 0.5-1 hour, 1-2 hours, or 2-3 hours, optionally with a cooling down period of one hour.
  • Impurities such as ash, acid soluble lignin, fatty acids, organic acids such as acetic acid and formic acid, methanol, proteins and/or amino acids, glycerol, sterols, rosin acid and waxy materials can be extracted together with the hemicellulose sugars under the same conditions. These impurities can be separated from the aqueous phase by solvent extraction (e.g., using a solvent containing amine and alcohol).
  • the lignocellulosic remainder stream 1720B can be separated from the acidic hemicellulose sugar steam 1720A by any relevant means, including, filtration, centrifugation or sedimentation to form a liquid stream and a solid stream.
  • the acidic hemicellulose sugar steam 1720A can contain hemicellulose sugars and impurities.
  • the lignocellulosic remainder stream 1720B can contain predominantly cellulose and lignin.
  • the lignocellulosic remainder stream 1720B can be further washed to recover additional hemicellulose sugars and acidic catalyst trapped inside the biomass pores.
  • the recovered solution can be recycled back to the acidic hemicellulose sugar stream 1720A, or recycled back to the hemicellulose sugar extraction reactor 1720.
  • the remaining lignocellulosic remainder stream 1720B can be pressed mechanically to increase solid contents (e.g., dry solid contents about 40-60%). Filtrate from the pressing step can be recycled back to the acidic hemicellulose sugar stream 1720A, or recycled back to the hemicellulose sugar extraction reactor 1720.
  • the remaining lignocellulosic remainder 1720B is grinded to reduce particle sizes.
  • the pressed lignocellulosic remainder is then dried to lower the moisture content, e.g., less than about 15%.
  • the dried matter can be further processed to extract lignin and cellulose sugars.
  • the dried matter can be pelletized into pellets that can be burnt as energy source for heat and electricity production or can be used as feedstock for conversion to bio oil.
  • the lignocellulosic remainder stream 1720B can be further processed to extract lignin (e.g., process 1740 in Figs. 1A and IB). Prior to the lignin extraction, the lignocellulosic remainder stream 1720B can be separated, washed, and pressed as described above.
  • the present disclosure in one aspect provides a novel method of extracting lignin directly from lignocellulosic biomass following hemicellulose sugar extraction.
  • the method can utilize a limited-solubility solvent, and can be amenable to biomass particles of various sizes, for example lignocellulosic particles with sizes ranging from 100 to 5000 microns, 100 to 500 microns, 200 to 800 microns, 500 to 2000 microns, or 1000 to 5000 microns. Therefore, it may not be necessary to grind the particles prior to lignin extraction, as is required by some other lignin processing techniques.
  • the extraction of hemicellulose sugars from the biomass results in a lignin-containing remainder.
  • the extraction of hemicellulose sugars does not remove a substantial amount of the cellulosic sugars.
  • the extraction of hemicellulose sugars does not remove more than about 1, 2, 5, 10, 15, 20, 30, 40, 50, 60% weight/weight cellulose from the lignin-containing remainder.
  • the extraction of hemicellulose sugars removes at least about 1, 2, 5, 10, 15, 20, 30, 40, 50, 60% or more than 60% weight/weight cellulose from the lignin-containing remainder.
  • the lignin-containing remainder contains lignin and cellulose.
  • the lignin-containing remainder contains less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 2, 1%, or less than about 1% hemicellulose. In some methods, the lignin-containing remainder contains at least about 1%, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% or more than 50% weight/weight hemicellulose.
  • the lignin extraction solution may contain a limited-solubility solvent and water, and optionally an acid.
  • limited-solubility solvents suitable for the present disclosure include l-chloro-2-butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2- methylfuran, 2-ethylfuran, 2-phenylethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3 -pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone,
  • the limited-solubility solvent includes one or more of esters, ethers and ketones with 4 to 8 carbon atoms.
  • the limited-solubility solvent can include methyl ethyl ketone (MEK).
  • MEK methyl ethyl ketone
  • the limited-solubility solvent consists essentially of, or consists of, methyl ethyl ketone.
  • the ratio of the limited-solubility solvent to water suitable for carrying out the lignin extraction can vary depending on the biomass material and the particular limited-solubility solvent used.
  • the solvent to water ratio by mass (w/w) or volume (v/v) is in the range of about 100: 1 to 1 : 100, e.g., about 50: 1-1 :50, about 20: 1 to 1 :20, about 5:1 to 1 :5, about 3: l to 1 :3, about 3:2 to 3:2, and preferably about 1 : 1.
  • the limited-solubility solvent is fully or partially water saturated.
  • the solution can contain an inorganic or organic acid such as H2SO4, HC1, acetic acid and formic acid.
  • the acidic aqueous solution can contain about 0.1 to 10% acid or more, e.g., about 0.1- 0.4%, 0.4-0.6%, 0.6-1.0%, 1.0-2.0%, 2.0-3.0%, 3.0-4.0%, 4.0-5.0% or more acid.
  • the pH of the acidic aqueous solution can be in the range of about 0-6.5. In some cases, the pH is in the range of about 1 to 5. In some cases, the pH is in the range of about 1.5 to 3.5. In some cases, the pH is in the range of about 2 to 3.
  • Elevated temperatures and/or pressures are preferred in lignin extraction.
  • the temperature of lignin extraction can be in the range of about 50 - 300 °C, preferably 160 °C to 250 °C, e.g., 175 °C -185 °C, 190 °C - 210 °C, 200 °C - 220 °C, or 200 °C to 240 °C.
  • the lignin extraction temperature can be at least about 50 °C, 75 °C, 100 °C, 125 °C, 150 °C, 175 °C, 180 °C, 185 °C, 190 °C, 195 °C, 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C, 235 °C, 240 °C, 245 °C, 250 °C, 275 °C, 300 °C, or more than about 300 °C.
  • the lignin extraction temperature may be no more than about 300 °C, 275 °C, 250 °C, 245 °C, 240 °C, 235 °C, 230 °C, 225 °C, 220 °C, 215 °C, 210 °C, 205 °C, 200 °C, 195 °C, 190 °C, 185 °C, 180 °C, 175 °C, 150 °C, 125 °C, 100 °C, 75 °C, 50 °C, or less than about 50 °C.
  • the pressure can be in the range of about 1 megapascal (MPa) to about 10 MPa, preferably, from about 1 MPa to about 5 MPa.
  • the pressure of a lignin extraction process may be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 MPa. In some instances, the pressure of a lignin extraction process may be no more than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or less than 1 MPa.
  • the lignin extraction process may comprise a low oxygen atmosphere (e.g., less than 2% or less than 1% oxygen) or inert atmosphere (e.g., a nitrogen or argon atmosphere).
  • the solution can be heated for about 0.5 - 24 hours, preferably about 1-3 hours.
  • the necessary reaction time may be reduced with increasing reaction temperature. In some cases, the reaction may follow Arrhenius kinetics and thus a temperature increase of about 10 °C may reduce the reaction time by about 50%.
  • a solution comprising lignin has a starting pH from about 6 to about 7.
  • the pH of the solution is adjusted to about 3.0 to 4.5 (e.g., about 3.5-3.8).
  • the lignin may be protonated and thus may more readily be extracted into the organic phase.
  • the organic phase comprising solvent and lignin is contacted with a strong acid cation exchanger to remove residual metal cations.
  • the strong acid cation exchanger can be in a monovalent or multivalent metal cation form, e.g., in H+, Mg 2+ , Ca 2+ or Zn 2+ form.
  • the strong acid cation exchanger is in Na + form (e.g., the strong acid cation exchanger removes cations and releases Na + ).
  • the strong acid cation exchanger may comprise a resin with a styrene skeleton, which is preferably cross-linked with 3 to 8%, preferably 5 to 6.5% of divinylbenzene.
  • the limited-solubility solvent can be separated from lignin, e.g., evaporated.
  • the limited-solubility solvent can be separated from lignin by mixing the solvent solution containing acidic lignin with water at an elevated temperature (e.g., about 80 °C).
  • the precipitated lignin can then be recovered by, e.g., filtration or centrifugation.
  • the solid lignin can be dissolved in any suitable solvents (e.g., phenyl ethyl alcohol) to produce a lignin solution.
  • the limited-solubility solvent solution containing acidic lignin can be mixed with another solvent, e.g., a replacement solvent.
  • the limited-solubility solvent can be evaporated whereas the replacement solvent stays in the solution.
  • the replacement solvent is toluene.
  • a lignin solution can be prepared using any suitable solvent.
  • the present disclosure further describes methods of extracting lignin from a lignocellulosic biomass utilizing a lignin extractant recycling loop.
  • a recycling loop in the lignin extraction process may increase the single-pass lignin extraction efficiency from a lignin-containing remainder material compared to conventional methods.
  • the inclusion of a recycling loop in a lignin extraction process may also decrease the processing costs for obtaining high-purity lignin or high-purity cellulose by decreasing the overall process energy consumption, decreasing the processing temperature, decreasing the processing pressure, and/or decreasing the stream handling energy consumption (e.g., heating, pumping).
  • a lignin recovery system comprises a lignin extraction unit, a cellulose recovery unit, a lignin purification unit, and a recycle stream connecting the lignin purification unit to the lignin extraction reactor.
  • the lignin extraction unit may comprise one or more reactors that are configured to remove lignin from a hemicellulose- depleted biomass stream comprising lignin and cellulose.
  • the lignin extraction unit may produce a lignin extract stream comprising lignin in the form of a dissolved solid.
  • the lignin extraction unit may produce a stream comprising both extracted lignin and a cellulosic reaminder.
  • the lignin extraction unit may produce a first stream comprising a lignin extract and a second stream comprising a cellulosic remainder.
  • a stream comprising a cellulosic remainder may be fed to a cellulose recovery unit to produce a cellulose product and a lignin extract stream.
  • the cellulose recovery unit may produce a lignin extract stream that is combined with the lignin extract stream from the lignin extraction reactor before being fed to the lignin recovery unit.
  • the lignin recovery unit may comprise one or more separation units that recover a lignin product from the lignin extract.
  • the lignin recovery unit may include a strong cation exchanger and one or more solvent purification units.
  • a recycle stream may connect the lignin recovery unit to the lignin extraction reactor.
  • the recycle stream may carry a portion of the lignin extract from the lignin recovery unit to the lignin extraction reactor before the lignin recovery process has been completed.
  • FIG. 2 shows an exemplary lignin extraction process without a recycling loop.
  • a lignin containing remainder material 102 is fed to a lignin extraction reactor 110 with a solvent stream 104 of organic solvent, water, or a combination thereof.
  • the organic solvent may comprise a limited-solubility solvent.
  • a lignin extraction mixture 112 may be transferred from the lignin extraction reactor 110 to a cellulose separation unit 120.
  • the cellulose separation unit 120 may include a filtration system (e.g., belt filter) or a centrifuge.
  • the cellulose separation unit 120 may produce a stream of wet cellulose remainder 122, which may be transferred to a drying unit 130, resulting in a purified cellulose product stream 132.
  • the cellulose separation unit may also produce a two-phase lignin extractant 124, which may be transferred to a two-phase separation unit 140 (e.g., a decanter) to separate an organic phase from an aqueous phase.
  • the organic phase comprises a lignin extractant 142 that may be passed through an ion exchange resin 150 (e.g., strong acid cation (SAC) exchanger, weak acid cation (WAC) exchanger, strong base anion (SB A) exchanger, weak base anion (WB A) exchanger), producing a partially or fully desalted lignin extractant 152.
  • SAC strong acid cation
  • WAC weak acid cation
  • SB A strong base anion exchanger
  • WB A weak base anion exchanger
  • the desalted lignin extractant 152 may be transferred to a solvent purification unit 170 (e.g., using distillation), producing a purified lignin product 174 and a purified solvent stream 172.
  • the aqueous phase 144 from the second separator unit 140 may be transferred to a fourth separation unit 160 where additional organic solvent 162 may be recovered.
  • the recovered organic solvent 162 and purified solvent stream 172 may be combined and/or mixed with additional non-recycled solvents to form the initial solvent stream 104.
  • FIG. 3 shows an alternative lignin extraction process without an ion exchange resin 150.
  • the additional desalting and/or removal of metal ion species by the ion exchange resin may not be necessary to obtain a desired lignin purity.
  • the lignin extractant 142 is transferred directly to the solvent purification unit 170.
  • a lignin extraction process contains one or more recycling loops for returning a lignin extractant 142 to the lignin extraction reactor 110.
  • FIG. 4 shows a first exemplary case where a lignin extractant recycle stream 146 is drawn off of the lignin extractant 142 and returned to the lignin extraction reactor 110.
  • the recycle stream 146 may be mixed with the solvent stream 104 or the lignin-containing remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 146 may be fed separately to the lignin extraction reactor 110.
  • FIG. 5 shows a second exemplary case where a lignin extractant recycle stream 154 is drawn off of the desalted lignin extractant 152 and returned to the lignin extraction reactor 110.
  • the recycle stream 154 may be mixed with the solvent stream 104 or the lignincontaining remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 154 may be fed separately to the lignin extraction reactor 110.
  • FIG. 6 shows a third exemplary case where a lignin extractant recycle stream 146 is drawn off of the lignin extractant 142 and returned to the lignin extraction reactor 110 with no ion exchange resin 150 in the system.
  • the recycle stream 146 may be mixed with the solvent stream 104 or the lignin-containing remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 146 may be fed separately to the lignin extraction reactor 110.
  • FIGs. 2-6 exclude certain processing details such as fluid transfer and fluid heating processes.
  • the processes described herein may include any conceivable additional unit operation, such as pumps, compressors, fans, blowers, boilers, condensers, heat exchangers, flash tanks, distillations columns, strippers, absorbers, membrane separators, decanters, filters, presses, flares, etc., or a combination thereof.
  • the lignin extraction processes described herein may comprise more than one recycle stream.
  • the system may recycle some lignin extractant before the ion exchange resin 150 and after the ion exchange resin.
  • the system may have an optimal recycle ratio.
  • a lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or 0.99.
  • a lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of at least about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, or more than about 0.99.
  • a lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of no more than about 0.99, 0.95, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.01, or less than about 0.01.
  • the lignin extract stream recycled back to the lignin extraction process may contain a certain amount of lignin or other dissolved solids.
  • the total dissolved solids e.g., lignin or lignin with other dissolved solids
  • a lignin extract may be concentrated to increase the relative amount of dissolved solids in a lignin extract returned to the lignin extraction process.
  • a lignin extract may have lignin removed or may be diluted with additional solvent to decrease the relative amount of dissolved solids in the lignin extractant before recycling the extract back to a lignin extraction process.
  • the recycle stream may be combined with a solvent stream to form a solvent feed stream before being fed back to the lignin extraction process.
  • the quantity or size of the solvent stream may be adjusted to bring the total dissolved solids in the solvent feed stream to a targeted value.
  • the recycle stream or solvent feed stream may have a lignin content of about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%.
  • the recycle stream or solvent feed stream may have a lignin content of at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%.
  • the recycle stream or solvent feed stream may have a lignin content of no more than about 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or less than 0.1%.
  • the recycle stream may comprise between 0.5% and 20% lignin (e.g., in a limited solubility solvent).
  • the recycle stream may comprise between 1.5% and 12.7% lignin.
  • the recycle stream may comprise between 2.5% and 6.5% lignin
  • the recycle stream or solvent feed stream may have a total dissolved solids content of about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%.
  • the recycle stream or solvent feed stream may have a total dissolved solids content of at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%.
  • the recycle stream or solvent feed stream may have a total dissolved solids content of no more than about 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or less than 0.1%.
  • Lignin may comprise at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, or at least 99% of the total dissolved solids.
  • Adding a recycle loop of lignin extractant to a lignin extraction process may increase the recovery of lignin and/or the purity of cellulose remainder obtained from the process.
  • a process with a recycle loop of lignin extractant may have a lignin recovery of about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%.
  • a process with a recycle loop of lignin extractant may have a lignin recovery of at least about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%.
  • a process with a recycle loop of lignin extractant may have a lignin recovery of no more than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, or less than about 90%.
  • a process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%.
  • a process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of at least about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%.
  • a process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of no more than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, or less than about 90%.
  • a recycle loop of lignin extractant may increase the lignin removal or recovery relative to a nonrecycle process by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or about 99%.
  • a recycle loop of lignin extractant may increase the lignin removal or recovery relative to a non-recycle process by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or more than about 99%.
  • a recycle loop of lignin extractant may increase the lignin removal or recovery relative to a non-recycle process by no more than about 99%, 95%, 90%,
  • a cellulosic remainder may comprise a residual amount of lignin after lignin extraction. In some cases, the amount of lignin may be too small to be measured or detected using conventional analytical proceedures. In other cases, a cellulosic remainder may comprise a measureable amount of lignin.
  • a cellulosic remainder may comprise about 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, 4.1%, 4%, 3.9%, 3.8%, 3.7%, 3.6%, 3.5%, 3.4%, 3.3%, 3.2%, 3.1%, 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.3%, 2.2%, 2.1%, 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or less than 0.1% residual lignin.
  • a cellulosic remainder may comprise no more than about 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, 4.1%, 4%, 3.9%, 3.8%, 3.7%, 3.6%, 3.5%, 3.4%, 3.3%, 3.2%, 3.1%, 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.3%, 2.2%, 2.1%, 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or less than 0.1% residual lignin.
  • a cellulosic remainder may comprise at least about 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 10%, 15%, 20%, or more than 20% residual lignin.
  • a cellulosic remainder may comprise a residual amount of lignin relative to a lignin-containing remainder.
  • a cellulosic remainder may contain about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or more than 99% of the lignin relative to the amount of lignin in the lignin-containing remainder.
  • a cellulosic remainder may contain at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or more than 99% of the lignin relative to the amount of lignin in the lignin-containing remainder.
  • a cellulosic remainder may contain no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, or less than 1% of the lignin relative to the amount of lignin in the lignin-containing remainder.
  • a lignin recycling loop may decrease the overall energy consumption of a lignin extraction process, compared to a lignin extraction process that does not include a lignin extractant recycling loop.
  • a lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or about 99%.
  • a lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or more than about 99%.
  • a lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or about no more than about 5%.
  • a recycling loop in a lignin extraction process may alter the optimal reactor conditions in the lignin extraction reactor.
  • the presence of a recycle loop may increase or decrease the optimal lignin extraction temperature, reaction time and/or pressure.
  • the presence of a recycle loop may increase or decrease the optimal lignin extraction temperature by about 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, or about 50 °C.
  • the presence of a recycle loop may increase or decrease the optimal lignin extraction temperature by at least about 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, or more than about 50 °C.
  • the presence of a recycle loop may increase or decrease the optimal lignin extraction pressure by about 0.5 megapascal (MPa), 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa,
  • the presence of a recycle loop may increase or decrease the optimal lignin extraction pressure by at least about 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa,
  • the presence of a recycle loop may increase or decrease the lignin extraction time by about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99% or more than 99%.
  • the presence of a recycle loop may increase or decrease the lignin extraction time by at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99% or more than 99%.
  • the presence of a recycle loop may increase or decrease the lignin extraction time by no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or less than 1%.
  • the disclosure further provides a lignin composition produced by a process of producing high purity lignin from a biomass.
  • the process comprises (i) removing hemicellulose sugars from the biomass thereby obtaining a lignin-containing remainder; wherein the lignincontaining remainder comprises lignin and cellulose; (ii) contacting the lignin-containing remainder with a lignin extraction solution to produce a lignin extract and a cellulosic remainder; wherein the lignin extraction solution comprises one or more of a limited-solubility solvent, an organic acid, and water, wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; and (iii) separating the lignin extract from the cellulosic remainder; wherein the lignin extract comprises lignin dissolved in the limited-solubility solvent.
  • the lignin composition is produced by a process that further comprises one, two, three, four, or five additional step(s): (iv) contacting the lignin extract with a strong acid cation exchanger to remove residual cations thereby obtaining a purified lignin extract (v) distilling or flash evaporating the lignin extract thereby removing the bulk of the limited-solubility solvent from the lignin extract to obtain solid lignin; (vi) heating the solid lignin thereby removing trace limited-solubility solvent or water from the solid lignin; (vii) applying a vacuum to the solid lignin thereby removing trace limited-solubility solvent or water from the solid lignin; and (viii) dissolving the solid lignin with an organic solvent to form a resulting solution and separating the resulting solution from insoluble remainder.
  • the lignin composition is characterized by at least one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, or nineteen characteristics selected from the group consisting of: (i) lignin aliphatic hydroxyl group in an amount up to 2 mmole/g; (ii) at least 2.5 mmole/g lignin phenolic hydroxyl group; (iii) less than 0.40 mmole/g lignin carboxylic OH group; (iv) sulfur in an amount up to 1 % weight/weight; (v) nitrogen in an amount up to 0.5 % weight/weight; (vi) 5% degradation temperature higher than 220 °C; (vii) 10% degradation temperature higher than 260 °C; (viii) less than 1% ash weight/weight; (ix) a formula of C a HbO c ; wherein a is 9, b is less
  • the lignin composition is further characterized as having a glass transition as determined by Differential Scanning Calorimetry (DSC) according to DIN 53765 in the range of 80 °C to 160 °C; the DSC thermogram of the second heating cycle is substantially different from the first heating cycle, where the first heating cycle comprises a greater number of exothermic maxima, endothermic maxima or inflection points than the second cycle. In some embodiments, this greater number of points in the first cycle can be attributed to reactivity of the lignin sample taking place when heated, due to the lignin sample heterogeneity (e.g., a variety of functional groups, molecular structure and/or weight). In some embodiments, the reactivity results in further cross linking, resulting in elevation of the glass transition of the second cycle by greater than 5 °C, 10 °C, 15 °C, 20 °C or even 25 °C.
  • DSC Differential Scanning Calorimetry
  • Such thermal behavior is indicative of the instability of the lignin polymer under heat, and possibly under other conditions.
  • the disclosure further provides a lignin composition produced by a process of producing high purity lignin from a biomass.
  • the process can comprise (i) removing hemicellulose sugars from the biomass thereby obtaining a lignin-containing remainder; wherein the lignin-containing remainder comprises lignin and cellulose; (ii) contacting the lignin-containing remainder with a lignin extraction solution to produce a lignin extract solution and a cellulosic remainder; wherein the lignin extraction solution comprises one or more of a limited-solubility solvent, an organic acid, and water, wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; and (iii) separating the lignin extract from the cellulosic remainder; wherein the lignin extract comprises lignin dissolved in the limited-solubility solvent.
  • the process further comprises (iv) contacting the lignin extract with a cation exchanger (e.g., a strong acid cation exchanger) to remove residual cations thereby obtaining a purified lignin extract.
  • a cation exchanger e.g., a strong acid cation exchanger
  • the process further comprises (v) distilling or flash evaporating the lignin extract thereby removing the bulk of the limited-solubility solvent from the lignin extract to obtain solid lignin.
  • the process further comprises (vi) heating the solid lignin to thereby remove trace limited-solubility solvent or water from the solid lignin.
  • the process further comprises (vii) applying a vacuum to the solid lignin to thereby remove trace limited-solubility solvent or water from the solid lignin. In some cases, the process further comprises (viii) contacting the solid lignin with an organic solvent to form a resulting solution comprising a fraction of the lignin, designated as solvent soluble (SS) and a remainder solid designated as solvent insoluble (SI); and separating the resulting solution from insoluble remainder.
  • solvent soluble solvent soluble
  • SI solvent insoluble
  • Solvent fractionation can separate a sample of lignin into a solvent soluble (SS) fraction and solvent insoluble (SI) fraction.
  • said contacting is conducted at a ratio of 1 :3 to 1 : 10 solid to liquid ratio (wt/wt), in a stirred container at 20 °C - 50 °C for 1 - 1 Oh.
  • the solvent is at least one polar organic solvent with a molecular weight less than 200 Da.
  • the solvent is at least one organic solvent comprising 1-5 carbon atoms, 0-3 oxygen atoms, and 0-6 halogen atoms.
  • the solvent is a mixture of organic solvents.
  • the solvent is selected as an organic molecule wherein lignin has limited solubility in the solvent.
  • the solvent is selected so that a mixture of the solvent to lignin 5: 1 w/w results in solubilization of at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% of lignin is disolved in the solvent. In some embodiments, between 10 and 40% of lignin is dissolved in the solvent.
  • lignin has a solubility in the solvent of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60 ,70, 80, 85, 80, 95, 97, 98, 99 gram (g) lignin/500 g solvent under the described conditions.
  • the solvent is an organic solvent wherein a sample consisting essentially of lignin has a solubility in the solvent of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60 ,70, 80, 85, 80, 95, 97, 98, 99 g lignin/500 g solvent under the described conditions.
  • a mixture of solvents is applied. In some embodiments, at least 30%, 40%, 50%, 60% wt/wt of the lignin solid is soluble in such solvent under the described conditions, but not more than 70%, 60%, 50%, 40% is soluble. In some embodiments, the solvent is selected to form a soluble lignin fraction is at least 2, 4, 6, 8, 10, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 50, 52 wt/wt% of the total lignin in the sample under the solvent fractionation conditions described herein.
  • the solvent is selected from a group consisting of methanol, ethanol, isopropanol, ethyl acetate, ethyl formate and dichloromethane. In some embodiments, the solvent is selected from a group consisting of methanol, ethyl acetate and dichloromethane. In some embodiments, the solvent is methanol. In some embodiments, the solvent is dichloromethane. In some embodiments, the solvent is ethyl acetate.
  • the non-dissolved (SI) fraction is collected by filtration, washed and air dried at 100-110 °C or under vacuum (for example at 45-55 °C and less than 1 kiloPascal pressure).
  • the dissolved fraction is dried by evaporating the solvent or the solvent mixture in a rotavap or any other method to evaporate a solvent.
  • the remaining lignin is collected and air dried at 100-110 °C or under vacuum (for example at 45-55 °C).
  • the solvent insoluble fraction is collected by decantation of the solvent from the reactor.
  • the solvent soluble fraction is collected by decantation of the solvent away from the solvent insoluble fraction.
  • the method of solvent fractionation of a lignin sample can be selected such that the amount of lignin in the solvent soluble fraction is low relative to the amount of lignin in the solvent insoluble fraction.
  • the solvent soluble fraction comprises less than 65, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5% of the total lignin of the sample (w/w).
  • the SS fraction comprises between about 25% and 45% of the total lignin.
  • the method of solvent fractionation of a lignin sample can be selected such that the amount of lignin in the solvent insoluble (SI) fraction is low relative to the amount of lignin in the solvent soluble (SS) fraction.
  • the solvent insoluble fraction comprises less than 65, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5% of the total lignin of the sample (w/w).
  • the SI fraction comprises between about 25% and 45% of the total lignin.
  • a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the second amount to the third amount of lignin is greater than 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 3, 4, 5, 6, 7, 8, 9, 10, or 20 to 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
  • the lignin is substantially soluble when a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the second amount to the third amount of lignin is greater than 3 : 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5:1 (wt/wt).
  • a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein greater than 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50% of the first amount of lignin is dissolved in the organic solvent, and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
  • a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the third amount to the second amount of lignin is greater than 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 3, 4, 5, 6, 7, 8, 9, 10, or 20 to 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5:1 (wt/wt).
  • a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the third amount to the second amount of lignin is greater than 3:1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
  • a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein greater than 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50% of the first amount of lignin is not dissolved in the organic solvent, and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
  • Solvent fractionation can produce two or more fractions of lignin with different chemical compositions than non-fractionated lignin.
  • the chemcial composition of each fraction of solvent fractionated lignin can be distinct from non-fractionated lignin and distinct from each other fraction.
  • the solvent soluble and/or solvent insoluble lignin fractions can each independently have a ratio of oxygen to carbon atoms (O/C) larger than the O/C ratio of nonfractionated lignin.
  • the solvent soluble and/or solvent insoluble lignin fractions can each independently have a ratio of hydrogen to carbon atoms (H/C) smaller than the H/C ratio of nonfractionated lignin.
  • the O/C and H/C ratios of fractionated lignin are within 20, 18, 15, 12, 10, 5% of non-fractionated lignin.
  • the chemcial composition of each fraction of solvent fractionated lignin can be distinct from non-fractionated lignin.
  • the number of OH groups (mmol/g lignin) can be higher in fractionated lignin than in non-fractionated lignin.
  • the number of aliphatic, phenolic, and caroxylic OH groups (mmol/g lignin) can be higher in fractionated lignin than in non-fractionated lignin.
  • the SS fraction comprises more phenolic OH and carboxylic OH groups than the SI fraction (w/w).
  • the solvent-soluble (SS) and solvent insoluble (SI) fractions obtained by this process share the high purity of the lignin solid from which they were made.
  • the two samples are distinctively different in molecular weight, as demonstrated by characterizing them side by side by the same gel permeation method.
  • the solvent soluble (SS) lignin fraction obtained by the process described herein has a low glass transition temperature (Tg) as determined using differential scanning calorimetry (DSC) according to DIN 53765-1994.
  • Tg glass transition temperature
  • the SS fraction can have a measured Tg below the Tg of non-fractionated lignin.
  • the SS fraction can have a Tg less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, or 45 °C.
  • the Tg of non-fractionated lignin can be in the range of 80 to 160 °C.
  • the SS fraction can have a Tg less than, 90, 85, 80, 75, 70, 65, or 60 °C.
  • the SS fraction has a Tg between about 75 and about 110 °C. In some embodiments, the SS fraction has a Tg between about 75 and about 95 °C.
  • the SS fraction can have a measured Tg below the Tg of solvent insoluble (SI) lignin fraction.
  • the SS fraction can have a Tg less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, or 45% of the Tg of solvent insoluble (SI) lignin fraction. In some embodiments, the Tg of the SS lignin fraction is stable.
  • the Tg of the SS lignin fraction varies between the 1 st cycle and the 2 nd cycle by less than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 °C. In some embodiments, the Tg of the 2 nd cycle increases by less than 5 °C relative to the 1 st cycle wherein the the 1 st and 2 nd DIN cycle are measured within 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 days of each other. In some embodiments, the SS fraction does not have Tg at a temperature above room temperature. In some embodiments, the SS fraction is not a polymer.
  • the number average molar mass (Mn) of the SS lignin fraction is less than the Mn of non-fractionated lignin.
  • the Mn of the SS lignin fraction is less than 2000, 1500, 1000, 900, 800, 700, 600, 500, 400, 300, or 200 Da. Molar mass values disclosed in this disclosure are determined according to Asikkala et. al., Journal of agricultural and food chemistry, 2012, 60(36), 8968-73.
  • the polydispersity (PD) of the SS lignin fraction is higher than the poly dispersity of non-fractionated lignin.
  • the PD of the SS fraction is over 3.0, 3.5, 4.0, 4.5, or 5.0.
  • the weight average molar mass or mass average molar mass (Mw) of the solvent soluble (SS) lignin fraction is lower than the Mw of non-fractionated lignin.
  • the Mw of SS lignin fraction can be less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5% of Mw of non-fractionated lignin.
  • the Mw of SS lignin fraction is less than 3000, 2900, 2800, 2700, 2600, 2500, 2400, 2300, 2200, 2100, 2000, 1800, 1600, 1500, 1400, 1300, 1200, 1100, 1000, 900, 970, or 800 Da. In some embodiments, the Mw is of the SS fraction is less than 2000 Da.
  • the solvent insoluble (SI) lignin fraction obtained by the process described herein has a low glass transition temperature (Tg) as determined using differential scanning calorimetry (DSC) according to DIN 53765-1994.
  • Tg glass transition temperature
  • DSC differential scanning calorimetry
  • the SI fraction can have a Tg at more than 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 175, 180, 200, 220, 240, 250 °C.
  • the Tg of non-fractionated lignin is 80-160 °C.
  • the SI fraction can have a Tg higher than 120, 130, 140, 150, 160, 170, 180, 190, 195, or 200 °C.
  • the SI fraction has a Tg between about 145 and about 210 °C.
  • the SI fraction has a Tg between about 155 and about 200 °C.
  • the SI fraction can have a measured Tg above the Tg of solvent soluble (SS) lignin fraction.
  • the SI fraction can have a Tg greater 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 175, 180, 200, 220, 240, 260, 280, or 300% of the Tg of solvent soluble (SS) lignin fraction.
  • the Tg of the SI lignin fraction is stable between thermal cycles. In some embodiments, the Tg of the SI lignin fraction varies between the 1 st cycle and the 2 nd cycle by less than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 °C. In some embodiments, the Tg of the 2 nd cycle increases by less than 5 °C relative to the 1 st cycle wherein the the 1 st and 2 nd DIN cycle are measured within 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 days of each other. In some embodiments, the Tg of the 2 nd cycle increases by less than 5 °C relative to the 1 st cycle wherein the the 1 st and 2 nd DIN cycle are measured consecutively.
  • the size of individual polymeric molecules, and the size distribution of molecules in a sample of polymers such as lignin can be measured and understood in terms of the number average molar mass (Mn), the mass average molar mass (Mw), and polydispersity.
  • Mn number average molar mass
  • Mw mass average molar mass
  • polydispersity measured values of Mn and Mw (and thus poly dispersity) can be dependent on the experimental conditions.
  • the values disclosed herein for Mn and Mw of lignin samples are based on gel permiation chromatography (GPC), using acetobromination of the lignin, with a solution of LiBr in THF as an eluent and UV detection.
  • GPC gel permiation chromatography
  • the use of DMSO as eluent without derivatization can lead to unusable measured values of Mn and Mw for a lignin sample.
  • the number average molar mass (Mn) of the SI lignin fraction is greater than the Mn of non-fractionated lignin.
  • the Mn of the SI lignin fraction is more than 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, or 9000 Da.
  • the poly dispersity (PD) of the SI lignin fraction is lower than the poly dispersity of non-fractionated lignin.
  • the PD of the SI fraction is less than 2.0, 1.9, 1.8. 1.7, 1.6, 1.5, or 1.4.
  • the mass average molar mass or weight average molar mass (Mw) of the solvent insoluble (SI) lignin fraction is greater than the Mw of non-fractionated lignin.
  • the Mw of SI lignin fraction can be greater than 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.3, 2.5, 3.0, or 3.5 of Mw of nonfractionated lignin.
  • the Mw of SI lignin fraction is greater than 5000, 6000, 7000, 8000, 10000, 12000, 14000, 16000, 18000, or 20000 Da. In some embodiments, the Mw is of the SI fraction is greater than 6000 Da.
  • the SS fraction and the SI fraction have a distinctively different glass transition temperatures.
  • the difference between the glass transition temperatures of the SS and SI fractions is greater than 30 °C, 40 °C, 50 °C, 60°C.
  • the glass transition temperature can be stable between the first thermal cycle and the second thermal cycle, having a difference of less than 5 °C, 4 °C, 3 °C, 2 °C for each fraction.
  • the SI fraction does not show additional exotherms or endotherms in the DSC scan, indicating that the polymer is stable and does not react at the temperature range up to 250 °C.
  • the fractionated high purity lignin composition according to embodiments disclosed herein has a more defined character than other lignins.
  • the SI fraction is a preferred fraction for compounding purposes, due to higher molecular weight, the polymer is not changed by temperature up to 250 °C as seen in the DSC scan.
  • the SS fraction is lower molecular weight and solvent soluble is anticipated to be more suitable for using it as feedstock for cracking lignin to small aromatic molecules of high values.
  • both the SI fraction and the SS fraction have low oxygen content compared to other lignins, e.g. kraft lignin.
  • both fractions have low ash content, a low sulfur and/or phosphorous concentration.
  • Such a high purity lignin composition is particularly suitable for use in catalytic reactions by contributing to a reduction in catalyst fouling and/or poisoning.
  • a lignin composition having a low sulfur content is especially desired for use as fuel additives, for example in gasoline or diesel fuel.
  • Some other potential applications for high purity lignin include carbon-fiber production, asphalt production, and as a component in biopolymers. These uses include, for example, oil well drilling additives, concrete additives, dyestuffs dispersants, agriculture chemicals, animal feeds, industrial binders, specialty polymers for paper industry, precious metal recovery aids, wood preservation, sulfur-free lignin products, automotive brakes, wood panel products, biodispersants, polyurethane foams, epoxy resins, printed circuit boards, emulsifiers, sequestrants, water treatment formulations, strength additive for wallboard, adhesives, raw materials for vanillin and as a source for paracoumaryl, coniferyl, sinapyl alcohol.
  • composition comprising a portion of lignin as disclosed herein and another ingredient.
  • the composition can comprise up to 98, 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1% wt/wt the lignin.
  • the composition comprises up to 50% lignin wt/wt.
  • the composition comprises between 5% and 75% lignin, or between 10 and 60% lignin wt/wt.
  • the lignin is SI lignin.
  • the lignin is SS lignin.
  • the composition is a polymer, precursor to one or more commodity chemicals, a commodity chemical, or consumer good.
  • the composition can be selected from the group consisting of fuel additives in gasoline or diesel fuel, carbon-fiber, materials for carbon-fiber production, asphalt, a component of a biopolymer, oil well drilling additives, concrete additives, dyestuffs dispersants, agriculture chemicals, animal feeds, industrial binders, specialty polymers for paper industry, precious metal recovery aids, materials for wood preservation, sulfur-free lignin products, automotive brakes, wood panel products, bio-dispersants, polyurethane foams, epoxy resins, printed circuit boards, emulsifiers, sequestrants, water treatment formulations, strength additive for wallboard, adhesives, and a material for the production of vanillin, paracoumaryl, coniferyl, sinapyl alcohol, benzene, xylenes, or toluene.
  • method comprising: (i) providing a lignin composition as described herein, and (ii) converting at least a portion of lignin in the composition to a conversion product.
  • the converting comprises treating with hydrogen or a hydrogen donor.
  • the conversion product comprises a commodity chemical comprising at least one item selected from the group consisting of bio-oil, carboxylic and fatty acids, dicarboxylic acids, hydroxyl-carboxylic, hydroxyl di -carboxylic acids and hydroxyl-fatty acids, methylglyoxal, mono-, di- or poly-alcohols, alkanes, alkenes, aromatics, aldehydes, ketones, esters, phenols, benzene, toluenes, and xylenes.
  • the conversion product is selected from the group consisting of dispersants, emulsifiers, complexants, flocculants, agglomerants, pelletizing additives, resins, carbon fibers, active carbon, antioxidants, liquid fuel, aromatic chemicals, vanillin, adhesives, binders, absorbents, toxin binders, foams, coatings, films, rubbers and elastomers, sequestrants, fuels, and expanders.
  • the conversion product comprises a fuel or a fuel ingredient.
  • Table 1 provides a summary of chemical analysis of the liquor resulting from hemicellulose sugar extraction of various biomass types. The % monomeric sugar is expressed as %-weight out of total sugars weight. All other results are expressed as %-weight relative to dry biomass.
  • the % Degradation product is the sum of %Furfurals (GC or HPLC analysis), %Formic acid (HPLC) and % Levullinic acid (HPLC). Acid Soluble Lignin was analyzed according to NREL TP-510-42627 method.
  • Table 2 provides a summary of chemical analysis of various types of biomass after hemicellulose sugar extraction.
  • Pine (ref A1202102-5): Fresh Loblloly pine chips (145.9 Lb dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio. An acid aqueous solution (500 Lb) was prepared by adding 0.3% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 135 °C and then added to the digester to cover the wood. The solution was circulated through the wood for 40 minutes while maintaining the temperature.
  • the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (128.3 Lb dry wood) and vent the vapor.
  • the extracted wood was analyzed for sugar content, carbohydrate composition, ash, elements (by ICP), and DCM extractives.
  • the analyses of the hemi depleted lignocellulose material show extraction of 42.4% Arabinan, 10.5% Galactan, 9.6% Xylan, 14.3% Manan, and 11.8% Glucan, indicating that mostly hemicellulose is extracted. Analyses also show 11.6% of “others”, including ASL, extractives and ash.
  • the overall fraction of carbohydrates in the remaining solid is not different within the error of the measurement to that of the starting biomass due to this removal of “others”. It is however easily notices that the extracted woodchips are darker in color and are more brittle than the fresh biomass.
  • Pine (ref A12O4131-14(K1)): Fresh Loblloly pine chips (145.9 Lb dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio. An acid aqueous solution (500 Lb) was prepared by adding 0.3% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 135 °C and then added to digester to cover the wood. The solution was circulated through the wood for 180 minutes while maintaining the temperature. After 180 minutes, the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (121.6 Lb dry wood) and vent the vapor. The material was analyzed as described above.
  • Eucalyptus (ref A120702K6-9): Fresh Eucalyptus Globulus chips (79.1 Kg dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio). An acid aqueous solution was prepared by adding 0.5% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 145 °C and then added to digester to cover the wood. The solution was circulated through the wood for 60 minutes while maintaining the temperature, then heating was stopped while circulation continued for another 60 minute, allowing the solution to cool.
  • RDC Rapid Cycle Digester
  • the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (58.8 Kg dry wood) and vent the vapor.
  • the material was analyzed as described above. Analyses showed that 20.1% of the carbohydrates were extracted from the wood (dry wood base) xylose containing 70% of these sugars, 91% of the sugars in the liquor present as monomers. Under these conditions acetic acid concentration in the liquor was 3.6% (dry wood base) showing maximal removal of acetate groups from hemicellulose sugars; 4.2% (dry wood base) of acid soluble lignin.
  • Hemicellulose sugar extraction 135 °C for 180 minutes, 0.3% H 2 S0 4 , 0.2% S0 2 .
  • Eucalyptus wood chips (20.0 g) were mixed with a solution of 50/50 w/w of methyl ethyl ketone (MEK) and water that contains 1.2% acetic acid w/w of solution at a ratio of 1 : 10 (100 mL water, 100 mL MEK, and 2.2 g acetic acid). The mixture was treated at 175 °C for 4 hours in an agitated reactor. Then the system was allowed to cool to 30 °C before the reactor is opened. The slurry was decanted and the solid is collected for further analysis.
  • MEK methyl ethyl ketone
  • lignin from bagasse was extracted by reacting sulfuric acid pretreated bagasse (D.S -60%) in a mixture of acetic acid (0.3% w/w of o.d. bagasse), methyl ethyl ketone, and water at 200 °C for 160 min. Bagasse-to-liquid ratio was 1 : 10 and the liquid phase was 50% w/w MEK-to-water.
  • the reaction was carried out in a Parr reactor. After reaction time, the mixture was filtered and the liquid organic phase separated using a separatory funnel. The pH of the organic phase was adjusted to -3.8 with sodium hydroxide. Afterwards, the organic phase was passed through SAC resin and added dropwise to an 80 °C MEK bath. The lignin precipitated and collected by filtration. The lignin was dried in the oven at 105 °C.
  • Lignin samples were characterized by elemental analysis (e.g., determining the relative occurrence of C, H, O, N, and S).
  • NMR experiments were performed using Bruker Avance-400 spectrometer. Quantitative 13 C NMR spectrum was acquired using DMSO-d6 (500 pL) as solvent for lignin (80 mg), with an inverse gated decoupling sequence, 90° pulse angle, 12-s pulse delay, and 12000 scans. Hydroxyl content analyses were determined using a quantitative 31 P NMR procedure. An accurate weight (about 40 mg) of a dried lignin sample was dissolved in 500 pL of an anhydrous pyridine/CDCh mixture (1.6: 1, v/v).
  • Lignin was also thermally characterized by differential scanning calorimetry (DSC) using the DIN standard method number 53765.
  • GPC Gel-permeation chromatography
  • lignin samples non-fractionated, and fractionated with methanol (SS and SI) were characterized by the methods of example 5.
  • the original lignin sample was prepared from bagasse according to examples 1 through 3, it was used to prepare lignin fractions SS and SI according to example 4.
  • the results are presented in the following Table 4.
  • Table 4 Elemental Analysis and Chemical Composition of non-fractionated and methanol fractionated bagasse lignin including solvent soluble (SS) fraction and solvent insoluble (SI) fraction
  • GPC Gel-permeation chromatography
  • Table 7 GPC analysis of non-fractionated and fractionated bagasse lignin
  • DSC was performed according to DIN 53765: the sample is first dried by a pre-heat cycle. Then, two consecutive heat cycles were measured, typically in the first cycle annealing processes took place that affected the polymer structure, while in the second cycle the major transition Tg is ascribed to the glass transition of the polymer.
  • Table 8 Thermal characterization of non-fractionated and methanol fractionated bagasse lignin using DSC
  • thermogram of the non-fractionated lignin indicated multiple changes in the lignin polymer at temperatures above 150 °C and a large change of 23 °C in the glass transition between the first and the second cycle.
  • thermogram of the methanol soluble fraction showed a glass transition at lower temperatures, approximately 117 °C, consistent with it being the lower molecular weight fraction.
  • the change from cycle 1 to cycle 2 was only 3 °C and while the thermogram still showed some annealing processes occurring above the glass transition, the extent of these changes is lower than in the non-fractionated lignin.
  • the methanol insoluble fraction showed a glass transition at higher temperature, ca.
  • thermograms are essentially the same for 1 st and 2 nd cycle (decrease of 2 °C between the cycles), and no endotherms or exotherms observed at temperatures above the glass transition. These thermograms indicate that distinctively two different lignin fractions were prepared by methanol fractionation treatment. The thermograms also indicate that each fraction is stable under heating, and does not manifest thermal annealing processes that were observed in the untreated sample as is commonly found in the literature.
  • Lignocellulose ( ⁇ 6% dry solids loading on a 200-gram scale) was weighed into a 450- mL Hastelloy reaction vessel.
  • MEK methyl ethyl ketone
  • a nitrogen blanket (at about 150 psi) was added, and the reaction was stirred at 50% of the maximum stirring rate.
  • the reactor was heated to 232°C in approximately 30 minutes. The temperature was maintained at 232 to 235°C for 22 minutes. The reaction was then cooled back to room temperature in 30 minutes.
  • Solids were filtered out and washed 5 times with approximately 100 mL-portions of MEK saturated with water, then washed 2 times with approximately 100 mL-portions of dry MEK. Solids were dried in a 105 °C oven overnight in pre-weighed Petri dishes then, after coming to room temperature, reweighted in order to calculate cellulose recovery.
  • Organic phase with 1.5% dissolved solids was obtained from the Danville PDU (DAN191116) was concentrated to 12.7% dissolved solids. After concentration, liquids were placed into a separatory funnel to remove any aqueous layer that may have formed. The organic was then diluted with MEK saturated with water to the desired DS. Organic phases were analyzed for DS by mass by drying samples for 2 hours in a 105 °C oven and by density and sound velocity meter.
  • Lignocellulose ( ⁇ 6% dry solids loading on a 200-gram scale) was weighed into 450- mL Hastelloy reaction vessel. Water and methyl ethyl ketone (MEK) with various amounts of DS (1 : 1 water: MEK by mass) were added. A nitrogen blanket (at about 150 psi) was added, and the reaction was stirred at 50% of the maximum stirring rate. The reactor was heated to 205 °C in approximately 30 minutes. The temperature was maintained at 205 °C for 3 hours. The reaction was then cooled back to room temperature in 30 minutes. The organic phase was decanted off first to collect a sample for DS. This prevented the organic phase from being artificially concentrated during filtration of the full reaction mixture.
  • MEK methyl ethyl ketone
  • Table 9 Residual Lignin on Cellulose and Cellulose Recovery at 235°C, 20 minutes, with DS from 0 to 12.7%
  • Table 10 Residual Lignin on Cellulose and Cellulose Recovery at 205°C, 180 minutes, with DS from 0 to 12.7%

Abstract

The present disclosure relates to fractions of high purity lignin which are thermally stable, and to methods of producing such fractions from lignocellulosic materials. Methods for producing such high purity lignins are described, as well as methods for increasing the overall efficiency of the lignin extraction process.

Description

METHODS FOR EXTRACTING LIGNIN
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional Application No. 63/123,289, filed December 9, 2020, which is hereby incorporated by reference in its entirety.
INCORPORATION BY REFERENCE
[0002] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
BACKGROUND OF THE INVENTION
[0003] Lignin, a highly abundant natural polymer that can be extracted from biomass, is a polymer of preference for various applications and as a chemical feedstock that replaces petrochemicals. Industrial utilization of lignin is difficult given its variable nature, functionality, reactivity, and heterogeneity. It is desirable to fractionate lignin into stable fractions that have reduced variability in size, composition and reactivity. Fractionation of lignin by membrane filtration using ultrafiltration and nanofiltration membranes can result in unstable fractions of lignin that change while being fractionated, and thus may be unsuitable for industrial and commercial purposes. It can also be a challenge to characterize the obtained fractions by a reliable method, as chromatography of lignin by size is notoriously dependent on experimental procedure, and a lack of good standards and suitable detectors render many measurements relative rather than absolute.
[0004] It is the purpose of this disclosure to prepare thermally stable fractions of high purity lignin by methods that can be applied by industrial means and on industrial scales.
SUMMARY OF THE INVENTION
[0005] In various aspects, the present disclosure provides a method for producing a high purity lignin from a biomass, the method comprising: removing a hemicellulose sugar from the biomass to produce a lignin-containing remainder comprising lignin and cellulose; combining the lignin-containing remainder with a lignin extraction solution in a lignin extraction reactor to produce (i) a lignin extract comprising lignin dissolved in the limited-solubility solvent and (ii) a cellulosic remainder, wherein the lignin extraction solution comprises a limited-solubility solvent and water, and wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; separating the lignin extract from the cellulosic remainder, thereby producing the high purity lignin; and recycling a portion of the lignin extract to the lignin extraction reactor. In some aspects, the limited-solubility solvent has a solubility in water of no more than 35 wt%. In some aspects, the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof. In some aspects, the limited-solubility solvent comprises a solvent selected from the group consisting of 1 -chi oro-2 -butanone, 1- phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2- phenyl ethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5- dimethylpyridine, acetal, anisol, diacetyl, 2, 3 -pentanedi one, diethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tertbutyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and y-butyrolactone, or a combination thereof. In some aspects, the limited-solubility solvent comprises methyl ethyl ketone. In some aspects, the limited-solubility solvent consists of methyl ethyl ketone. In some aspects, the cellulosic remainder comprises less than 10 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 5 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 3 wt% residual lignin. In some aspects, the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.1. In some aspects, the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.2. In some aspects, the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.3. In some aspects, a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent.
[0006] In various aspects, further provided herein is a system for producing high-purity lignin from biomass, the system comprising: a lignin extraction unit configured to produce a stream comprising dissolved lignin and a cellulosic remainder; a cellulose recovery unit configured to produce a cellulosic remainder and a lignin extract; a lignin recovery unit configured to produce a lignin product; and a recycle stream connecting the lignin recovery unit to the lignin extraction reactor; wherein the recycle stream comprises a lignin extraction solvent with a dissolved solids content of at least 1%. [0007] In various aspects, further provided herein is a system for producing high-purity lignin from biomass, the system comprising: a lignin extraction unit; a cellulose separation unit; a lignin purification unit comprising a two-phase separation unit and a solvent purification unit; and a recycle stream that connects the lignin purification unit to the lignin extraction reactor. In some aspects, the lignin extraction unit is configured to produce a lignin extract and a cellulosic remainder. In some aspects, the lignin purification unit further comprises a strong acid cation exchanger. In some aspects, the recycle stream is positioned upstream of the strong acid cation exchanger. In some aspects, the recycle stream is positioned downstream of the strong acid cation exchanger. In some aspects, the system does not comprise a strong acid cation exchanger. In some aspects, the lignin purification unit is configured to receive the lignin extract. In some aspects, the lignin purification unit is configured to produce a purified lignin product and a purified limited-solubility solvent stream. In some aspects, a portion of purified limitedsolubility solvent stream is returned to the lignin extraction reactor. In some aspects, the portion of the purified limited-solubility solvent stream and the portion of the lignin extract in the recycle stream are combined before entering the lignin extraction unit. In some aspects, the limited-solubility solvent has a solubility in water of no more than about 35 wt%. In some aspects, the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof. In some aspects, the limited-solubility solvent comprises a solvent selected from the group consisting of l-chloro-2-butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2-phenylethanol, 2-phenylethyl chloride, 2- methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3- pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tert-butyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and - butyrolactone, or a combination thereof. In some aspects, the limited-solubility solvent comprises methyl ethyl ketone. In some aspects, the limited-solubility solvent consists of methyl ethyl ketone. In some aspects, the cellulosic remainder comprises less than 10 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 5 wt% residual lignin. In some aspects, the cellulosic remainder comprises less than 3 wt% residual lignin. In some aspects, the recycle stream has a recycle ratio of at least about 0.1. In some aspects, the recycle stream has a recycle ratio of at least about 0.2. In some aspects, the recycle stream has a recycle ratio of at least about 0.3. In some aspects, a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. In some aspects, the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent. In some aspects, the cellulose recovery unit comprises a filtration unit or a centrifuge.
DESCRIPTION OF THE FIGURES
[0008] Fig. 1A is a schematic flowchart of an exemplary method of treating lignocellulosic biomass material according to some embodiments of the present disclosure.
[0009] Fig. IB is a schematic flowchart of an exemplary method of treating lignocellulosic biomass material utilizing a lignin extractant recycle loop, according to some embodiments of the present disclosure.
[0010] FIG. 2 depicts a schematic view of a lignin extraction system comprising a strong acid cation exchanger (SAC), in accordance with some embodiments of the present disclosure. [0011] FIG. 3 depicts a schematic view of a lignin extraction system without an SAC, in accordance with some embodiments of the present disclosure
[0012] FIG. 4 depicts a schematic view of a lignin extraction system with a recycle loop before an SAC, in accordance with some embodiments of the present disclosure.
[0013] FIG. 5 depicts a schematic view of a lignin extraction system with a recycle loop after an SAC, in accordance with some embodiments of the present disclosure.
[0014] FIG. 6 depicts a schematic view of a lignin extraction system with a recycle loop in the absence of an SAC, in accordance with some embodiments of the present disclosure.
[0015] FIG. 7A shows an image of collected cellulose after a lignin extraction process conducted at 235 °C.
[0016] FIG. 7B shows an image of collected cellulose after a lignin extraction process conducted at 205 °C.
DETAILED DESCRIPTION
Introduction
[0017] Technology, methods, and processes to efficiently extract lignin from lignocellulose feedstocks are disclosed by Jansen et. al. in PCT/US2013/039585 and PCT/US2013/068824, and are hereby incorporated by reference in their entirety. An overview of the lignocellulosic biomass processing and refining according to embodiments disclosed herein is provided in FIG. 1A. Many forms of lignocellulosic biomass processing and refining processes include: (1) pretreatment 1710; (2) hemicellulose sugar extraction 1720 and purification 1730; (3) direct lignin extraction 1740, and (4) lignin purification 1750. As shown in FIG. IB, in some cases, a lignocellulosic biomass processing and refining process includes a recycling of an unpurified lignin extract 1740A to the lignin extraction step 1740.
[0018] The lignocellulosic biomass processing and refining can begin with pretreatment 1710, during which the lignocellulosic biomass can be, for example, debarked, chipped, shredded, dried, or grinded to particles.
[0019] During hemicellulose sugar extraction 1720, the hemicellulose sugars can be extracted from the lignocellulosic biomass, forming an acidic hemicellulose sugar stream 1720A and a lignocellulosic remainder stream 1720B. The lignocellulosic remainder stream 1720B may consist mostly of cellulose and lignin. Hemicellulose the hemicellulose sugar stream can be effectively extracted and converted into monomeric sugars (e.g., >90% of the total sugar) by treating biomass under mild conditions such as low concentrations of an acid, heating, pressure, or a combination of conditions thereof. At least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% of hemicellulose in the hemicellulose sugar stream can be converted into monomeric sugars.
[0020] The acidic hemicellulose sugar stream 1720A may be purified, wherein acids and impurities co-extracted with hemicellulose sugars can be removed from the hemicellulose sugar stream by solvent extraction. Once acids and impurities are removed from the hemicellulose sugar stream, the stream may be neutralized and optionally evaporated to a higher concentration, thus yielding a high purity hemicellulose sugar mixture, which can be further fractionated to obtain xylose and xylose-removed hemicellulose sugar mixture. Xylose may then be crystallized.
[0021] In some methods herein, the lignocellulosic remainder 1720B can be processed to extract lignin. This process can produce a high purity lignin 1750-P1 and a high purity cellulose 1750- P2. The novel lignin purification process of the disclosure can utilize a limited-solubility solvent, and can produce a lignin having a purity greater than about 99%.
[0022] The limited-solubility solvent may have low solubility in water. The solubility of the limited-solubility solvent in water at room temperature may be less than about 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or less than about 1 wt%. The solubility of the limited-solubility solvent in water at room temperature may be at least about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 15 wt%, 20 wt %, 25 wt%, 30 wt%, 35 wt%, or greater than about 35 wt%. The solvent may form two phases with water (e.g., upon mixing with water, the limited-solubility solvent may form a phase separate from the water), and the solubility of water in it should be at least about 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, or at least about 1 wt% at room temperature. The solubility of water in the limitedsolubility solvent may be no more than about 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, or no more than about 1 wt% at room temperature. Preferably, the solvent may be stable at acidic conditions at temperatures of up to 100 °C. Preferably, the solvent may form a heterogeneous azeotrope with water, having a boiling point of less than about 100 °C where the azeotrope composition contains at least 50% of the solvent, at least 60% of the solvent out of total azeotrope. The solvent may have a least one hydrophilic functional group selected from ketone, alcohol and ether, or another polar functional group. Preferably, the solvent may be commercially available at low cost. Examples of limitedsolubility solvents suitable for the present disclosure can include l-chloro-2-butanone, 1- phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2- phenyl ethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5- dimethylpyridine, acetal, anisol, diacetyl, 2,3-pentanedione, diethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tertbutyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and y-butyrolactone.
[0023] In some embodiments, the limited-solubility solvent includes one or more of alcohols, esters, ethers and ketones with 4 to 8 carbon atoms. For example, the limited-solubility solvent can include or can consist of methyl ethyl ketone (MEK, also know as butanone). In some embodiments, the limited-solubility solvent consists essentially of, or consists of methyl ethyl ketone.
[0024] The term “about,” as used herein, generally refers to a range that is 15% plus or minus from a stated numerical value within the context of the particular usage. For example, about 10 may include a range from 8.5 to 11.5.
I. Pretreatment
[0025] Prior to hemicellulose sugar extraction 1720, lignocellulosic biomass can be optionally pre-treated 1710. In some instance, pretreatment 1710 can refer to the reduction in biomass size (e.g., mechanical breakdown, milling (e.g., disc mill or hammer mill), cutting or shredding), which does not substantially affect the lignin, cellulose and hemicellulose compositions of the biomass. Pretreatment can facilitate more efficient and economical processing of a downstream process (e.g., hemicellulose sugar extraction). Preferably, lignocellulosic biomass is debarked, chipped, shredded and/or dried to obtain pre-treated lignocellulosic biomass. Pretreatment can also utilize, for example, ultrasonic energy or hydrothermal treatments including water, heat, steam or pressurized steam. Pretreatment can occur or be deployed in various types of containers, reactors, pipes, flow through cells and the like. In some methods, it is preferred to have the lignocellulosic biomass pre-treated before hemicellulose sugar extraction 1720. In some methods, no pre-treatment is required, e.g., lignocellulosic biomass can be used directly in the hemicellulose sugar extraction 1720.
[0026] Optionally, lignocellulosic biomass can be milled or grinded to reduce particle size. In some embodiments, the lignocellulosic biomass is grinded such that the average size of the particles is in the range of about 100-10,000 micron, preferably about 400-5,000, e.g., about 100-400, 400-1,000, 1,000-3,000, 3,000-5,000, or about 5,000-10,000 microns. In some embodiments, the lignocellulosic biomass is grinded such that the average size of the particles is less than about 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,000, 3,000, 1,000, or 400 microns, or less than about 400 microns.
II. Hemicellulose sugar extraction
[0027] The present disclosure may include the partial or nearly total removal of hemicellulosic biomass from a lignocellulosic biomass before lignin extraction. The present invention provides an advantageous method of extracting hemicellulose sugars from lignocellulosic biomass (e.g., hemicellulose sugar extraction 1720). Preferably, an aqueous acidic solution is used to extract lignocellulose biomass. The aqueous acidic solution can contain any acids, inorganic or organic. Preferably, an inorganic acid is used. For example, the solution can be an acidic aqueous solution containing an inorganic acid such as H2SO4, H2SO3 (which can be introduced as dissolved acid or as SO2 gas), HC1, and/or an or organic acid such as acetic acid. The solution may contain organic acids such as carboxylic acids and dicarboxylic acids. The acidic aqueous solution can contain an acid in an amount of about 0 to 2% acid or more, e.g., 0.01-0.2%, 0.2- 0.4%, 0.4-0.6%, 0.6-0.8%, 0.8-1.0%, 1.0-1.2%, 1.2-1.4%, 1.4-1.6%, 1.6-1.8%, 1.8-2.0% or more than about 2% weight/weight. Preferably, the aqueous solution for the extraction includes about 0.2 - 0.7% or about 0.2-0.4% acid. In some instances, the acid is H2SO4 or HC1. The aqueous solution may comprise about 10 - 3,000 ppm SO2. In various instances, the aqueous solution for the extraction includes about 0.2 - 0.7% H2SO4 or HC1. In some instances, the aqueous solution for the extraction includes about 0.2 - 0.4% H2SO4 or HC1. In various instances, the pH of the acidic aqueous solution is from about 1 to about 5. In some instances, the pH of the acidic aqueous solution is from about 1 to about 3.5. In some instances, the pH of the acidic aqueous solution is from about 2 to 3.
[0028] In some embodiments, the hemicellulose sugar extraction comprises an elevated temperature or pressure. For example, a temperature in the range of about 100 - 200 °C, or more than about 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, or 200 °C, or more than about 200 °C can be used. Preferably, the temperature is in the range of about 110-160 °C, or about 120-150 °C. The pressure can be in the range of from about 0.1 megapascal (MPa) to about 10 MPa, preferably, from about 0.1 MPa to about 1 MPa, from about 0.1 MPa to about 2 MPa, or from about 0.1 MPa to about 5 MPa. The solution can be heated for about 0.5 - 5 hours, preferably about 0.5-3 hours, 0.5-1 hour, 1-2 hours, or 2-3 hours, optionally with a cooling down period of one hour.
[0029] Impurities such as ash, acid soluble lignin, fatty acids, organic acids such as acetic acid and formic acid, methanol, proteins and/or amino acids, glycerol, sterols, rosin acid and waxy materials can be extracted together with the hemicellulose sugars under the same conditions. These impurities can be separated from the aqueous phase by solvent extraction (e.g., using a solvent containing amine and alcohol).
[0030] After the hemicellulose sugar extraction 1720, the lignocellulosic remainder stream 1720B can be separated from the acidic hemicellulose sugar steam 1720A by any relevant means, including, filtration, centrifugation or sedimentation to form a liquid stream and a solid stream. The acidic hemicellulose sugar steam 1720A can contain hemicellulose sugars and impurities. The lignocellulosic remainder stream 1720B can contain predominantly cellulose and lignin.
[0031] The lignocellulosic remainder stream 1720B can be further washed to recover additional hemicellulose sugars and acidic catalyst trapped inside the biomass pores. The recovered solution can be recycled back to the acidic hemicellulose sugar stream 1720A, or recycled back to the hemicellulose sugar extraction reactor 1720. The remaining lignocellulosic remainder stream 1720B can be pressed mechanically to increase solid contents (e.g., dry solid contents about 40-60%). Filtrate from the pressing step can be recycled back to the acidic hemicellulose sugar stream 1720A, or recycled back to the hemicellulose sugar extraction reactor 1720. Optionally, the remaining lignocellulosic remainder 1720B is grinded to reduce particle sizes. Optionally, the pressed lignocellulosic remainder is then dried to lower the moisture content, e.g., less than about 15%. The dried matter can be further processed to extract lignin and cellulose sugars. Alternatively, the dried matter can be pelletized into pellets that can be burnt as energy source for heat and electricity production or can be used as feedstock for conversion to bio oil.
[0032] The lignocellulosic remainder stream 1720B can be further processed to extract lignin (e.g., process 1740 in Figs. 1A and IB). Prior to the lignin extraction, the lignocellulosic remainder stream 1720B can be separated, washed, and pressed as described above.
III. Lignin extraction from lignocellulosic biomass
[0033] As discussed above in connection with hemicellulose sugars extraction, the present disclosure in one aspect provides a novel method of extracting lignin directly from lignocellulosic biomass following hemicellulose sugar extraction. The method can utilize a limited-solubility solvent, and can be amenable to biomass particles of various sizes, for example lignocellulosic particles with sizes ranging from 100 to 5000 microns, 100 to 500 microns, 200 to 800 microns, 500 to 2000 microns, or 1000 to 5000 microns. Therefore, it may not be necessary to grind the particles prior to lignin extraction, as is required by some other lignin processing techniques.
[0034] The extraction of hemicellulose sugars from the biomass results in a lignin-containing remainder. In some methods, the extraction of hemicellulose sugars does not remove a substantial amount of the cellulosic sugars. For example, the extraction of hemicellulose sugars does not remove more than about 1, 2, 5, 10, 15, 20, 30, 40, 50, 60% weight/weight cellulose from the lignin-containing remainder. In some examples, the extraction of hemicellulose sugars removes at least about 1, 2, 5, 10, 15, 20, 30, 40, 50, 60% or more than 60% weight/weight cellulose from the lignin-containing remainder. In some methods, the lignin-containing remainder contains lignin and cellulose. In some methods, the lignin-containing remainder contains less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 2, 1%, or less than about 1% hemicellulose. In some methods, the lignin-containing remainder contains at least about 1%, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% or more than 50% weight/weight hemicellulose.
[0035] The lignin extraction solution may contain a limited-solubility solvent and water, and optionally an acid. Examples of limited-solubility solvents suitable for the present disclosure include l-chloro-2-butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2- methylfuran, 2-ethylfuran, 2-phenylethanol, 2-phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3 -pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tert-butyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and y-butyrolactone. In some embodiments, the limited-solubility solvent includes one or more of esters, ethers and ketones with 4 to 8 carbon atoms. For example, the limited-solubility solvent can include methyl ethyl ketone (MEK). In some embodiments, the limited-solubility solvent consists essentially of, or consists of, methyl ethyl ketone.
[0036] The ratio of the limited-solubility solvent to water suitable for carrying out the lignin extraction can vary depending on the biomass material and the particular limited-solubility solvent used. In general, the solvent to water ratio by mass (w/w) or volume (v/v) is in the range of about 100: 1 to 1 : 100, e.g., about 50: 1-1 :50, about 20: 1 to 1 :20, about 5:1 to 1 :5, about 3: l to 1 :3, about 3:2 to 3:2, and preferably about 1 : 1. In some cases, the limited-solubility solvent is fully or partially water saturated.
[0037] Various inorganic and organic acids can be used for lignin extraction. For example, the solution can contain an inorganic or organic acid such as H2SO4, HC1, acetic acid and formic acid. The acidic aqueous solution can contain about 0.1 to 10% acid or more, e.g., about 0.1- 0.4%, 0.4-0.6%, 0.6-1.0%, 1.0-2.0%, 2.0-3.0%, 3.0-4.0%, 4.0-5.0% or more acid. The pH of the acidic aqueous solution can be in the range of about 0-6.5. In some cases, the pH is in the range of about 1 to 5. In some cases, the pH is in the range of about 1.5 to 3.5. In some cases, the pH is in the range of about 2 to 3.
[0038] Elevated temperatures and/or pressures are preferred in lignin extraction. For example, the temperature of lignin extraction can be in the range of about 50 - 300 °C, preferably 160 °C to 250 °C, e.g., 175 °C -185 °C, 190 °C - 210 °C, 200 °C - 220 °C, or 200 °C to 240 °C. The lignin extraction temperature can be at least about 50 °C, 75 °C, 100 °C, 125 °C, 150 °C, 175 °C, 180 °C, 185 °C, 190 °C, 195 °C, 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C, 235 °C, 240 °C, 245 °C, 250 °C, 275 °C, 300 °C, or more than about 300 °C. The lignin extraction temperature may be no more than about 300 °C, 275 °C, 250 °C, 245 °C, 240 °C, 235 °C, 230 °C, 225 °C, 220 °C, 215 °C, 210 °C, 205 °C, 200 °C, 195 °C, 190 °C, 185 °C, 180 °C, 175 °C, 150 °C, 125 °C, 100 °C, 75 °C, 50 °C, or less than about 50 °C. The pressure can be in the range of about 1 megapascal (MPa) to about 10 MPa, preferably, from about 1 MPa to about 5 MPa. The pressure of a lignin extraction process may be at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 MPa. In some instances, the pressure of a lignin extraction process may be no more than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or less than 1 MPa. The lignin extraction process may comprise a low oxygen atmosphere (e.g., less than 2% or less than 1% oxygen) or inert atmosphere (e.g., a nitrogen or argon atmosphere). The solution can be heated for about 0.5 - 24 hours, preferably about 1-3 hours. The necessary reaction time may be reduced with increasing reaction temperature. In some cases, the reaction may follow Arrhenius kinetics and thus a temperature increase of about 10 °C may reduce the reaction time by about 50%.
[0039] In some cases, a solution comprising lignin has a starting pH from about 6 to about 7. In some embodiments, the pH of the solution is adjusted to about 3.0 to 4.5 (e.g., about 3.5-3.8). At this pH range, the lignin may be protonated and thus may more readily be extracted into the organic phase. In some cases, the organic phase comprising solvent and lignin is contacted with a strong acid cation exchanger to remove residual metal cations. The strong acid cation exchanger can be in a monovalent or multivalent metal cation form, e.g., in H+, Mg2+, Ca2+ or Zn2+ form. In some cases, the strong acid cation exchanger is in Na+ form (e.g., the strong acid cation exchanger removes cations and releases Na+). The strong acid cation exchanger may comprise a resin with a styrene skeleton, which is preferably cross-linked with 3 to 8%, preferably 5 to 6.5% of divinylbenzene. To obtain high purity solid lignin, the limited-solubility solvent can be separated from lignin, e.g., evaporated. Preferably, the limited-solubility solvent can be separated from lignin by mixing the solvent solution containing acidic lignin with water at an elevated temperature (e.g., about 80 °C). The precipitated lignin can then be recovered by, e.g., filtration or centrifugation. The solid lignin can be dissolved in any suitable solvents (e.g., phenyl ethyl alcohol) to produce a lignin solution.
[0040] Alternatively, the limited-solubility solvent solution containing acidic lignin can be mixed with another solvent, e.g., a replacement solvent. The limited-solubility solvent can be evaporated whereas the replacement solvent stays in the solution. In some instances, the replacement solvent is toluene. However, a lignin solution can be prepared using any suitable solvent.
[0041] The present disclosure further describes methods of extracting lignin from a lignocellulosic biomass utilizing a lignin extractant recycling loop. Surprisingly, it was found that the use of a recycling loop in the lignin extraction process may increase the single-pass lignin extraction efficiency from a lignin-containing remainder material compared to conventional methods. The inclusion of a recycling loop in a lignin extraction process may also decrease the processing costs for obtaining high-purity lignin or high-purity cellulose by decreasing the overall process energy consumption, decreasing the processing temperature, decreasing the processing pressure, and/or decreasing the stream handling energy consumption (e.g., heating, pumping).
[0042] In some embodiments of the present disclosure, a lignin recovery system comprises a lignin extraction unit, a cellulose recovery unit, a lignin purification unit, and a recycle stream connecting the lignin purification unit to the lignin extraction reactor. The lignin extraction unit may comprise one or more reactors that are configured to remove lignin from a hemicellulose- depleted biomass stream comprising lignin and cellulose. The lignin extraction unit may produce a lignin extract stream comprising lignin in the form of a dissolved solid. In some cases, the lignin extraction unit may produce a stream comprising both extracted lignin and a cellulosic reaminder. In other cases, the lignin extraction unit may produce a first stream comprising a lignin extract and a second stream comprising a cellulosic remainder. A stream comprising a cellulosic remainder may be fed to a cellulose recovery unit to produce a cellulose product and a lignin extract stream. In the case where a lignin extraction unit produces a lignin extract stream and a cellulosic remainder stream, the cellulose recovery unit may produce a lignin extract stream that is combined with the lignin extract stream from the lignin extraction reactor before being fed to the lignin recovery unit. The lignin recovery unit may comprise one or more separation units that recover a lignin product from the lignin extract. The lignin recovery unit may include a strong cation exchanger and one or more solvent purification units. A recycle stream may connect the lignin recovery unit to the lignin extraction reactor. The recycle stream may carry a portion of the lignin extract from the lignin recovery unit to the lignin extraction reactor before the lignin recovery process has been completed.
[0043] FIG. 2 shows an exemplary lignin extraction process without a recycling loop. In this case, a lignin containing remainder material 102 is fed to a lignin extraction reactor 110 with a solvent stream 104 of organic solvent, water, or a combination thereof. The organic solvent may comprise a limited-solubility solvent. A lignin extraction mixture 112 may be transferred from the lignin extraction reactor 110 to a cellulose separation unit 120. The cellulose separation unit 120 may include a filtration system (e.g., belt filter) or a centrifuge. The cellulose separation unit 120 may produce a stream of wet cellulose remainder 122, which may be transferred to a drying unit 130, resulting in a purified cellulose product stream 132. The cellulose separation unit may also produce a two-phase lignin extractant 124, which may be transferred to a two-phase separation unit 140 (e.g., a decanter) to separate an organic phase from an aqueous phase. The organic phase comprises a lignin extractant 142 that may be passed through an ion exchange resin 150 (e.g., strong acid cation (SAC) exchanger, weak acid cation (WAC) exchanger, strong base anion (SB A) exchanger, weak base anion (WB A) exchanger), producing a partially or fully desalted lignin extractant 152. The desalted lignin extractant 152 may be transferred to a solvent purification unit 170 (e.g., using distillation), producing a purified lignin product 174 and a purified solvent stream 172. The aqueous phase 144 from the second separator unit 140 may be transferred to a fourth separation unit 160 where additional organic solvent 162 may be recovered. The recovered organic solvent 162 and purified solvent stream 172 may be combined and/or mixed with additional non-recycled solvents to form the initial solvent stream 104. [0044] FIG. 3 shows an alternative lignin extraction process without an ion exchange resin 150. In some cases, the additional desalting and/or removal of metal ion species by the ion exchange resin may not be necessary to obtain a desired lignin purity. In this case, the lignin extractant 142 is transferred directly to the solvent purification unit 170.
[0045] In some cases, a lignin extraction process contains one or more recycling loops for returning a lignin extractant 142 to the lignin extraction reactor 110. FIG. 4 shows a first exemplary case where a lignin extractant recycle stream 146 is drawn off of the lignin extractant 142 and returned to the lignin extraction reactor 110. In some cases, the recycle stream 146 may be mixed with the solvent stream 104 or the lignin-containing remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 146 may be fed separately to the lignin extraction reactor 110.
[0046] FIG. 5 shows a second exemplary case where a lignin extractant recycle stream 154 is drawn off of the desalted lignin extractant 152 and returned to the lignin extraction reactor 110. In some cases, the recycle stream 154 may be mixed with the solvent stream 104 or the lignincontaining remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 154 may be fed separately to the lignin extraction reactor 110.
[0047] FIG. 6 shows a third exemplary case where a lignin extractant recycle stream 146 is drawn off of the lignin extractant 142 and returned to the lignin extraction reactor 110 with no ion exchange resin 150 in the system. In some cases, the recycle stream 146 may be mixed with the solvent stream 104 or the lignin-containing remainder 102 before being fed to the lignin extraction reactor 110. In other cases, the recycle stream 146 may be fed separately to the lignin extraction reactor 110.
[0048] It shall be understood that the exemplary processes shown in FIGs. 2-6 exclude certain processing details such as fluid transfer and fluid heating processes. Thus, the processes described herein may include any conceivable additional unit operation, such as pumps, compressors, fans, blowers, boilers, condensers, heat exchangers, flash tanks, distillations columns, strippers, absorbers, membrane separators, decanters, filters, presses, flares, etc., or a combination thereof.
[0049] The lignin extraction processes described herein may comprise more than one recycle stream. For example, in a system with an ion exchange resin 150, the system may recycle some lignin extractant before the ion exchange resin 150 and after the ion exchange resin. The system may have an optimal recycle ratio. A lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or 0.99. A lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of at least about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, or more than about 0.99. A lignin extraction process may have a recycle ratio of recycled lignin extractant to total lignin extractant of no more than about 0.99, 0.95, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.01, or less than about 0.01.
[0050] The lignin extract stream recycled back to the lignin extraction process may contain a certain amount of lignin or other dissolved solids. The total dissolved solids (e.g., lignin or lignin with other dissolved solids) may be returned to the lignin extraction process in an optimal amount. A lignin extract may be concentrated to increase the relative amount of dissolved solids in a lignin extract returned to the lignin extraction process. A lignin extract may have lignin removed or may be diluted with additional solvent to decrease the relative amount of dissolved solids in the lignin extractant before recycling the extract back to a lignin extraction process. In some cases, the recycle stream may be combined with a solvent stream to form a solvent feed stream before being fed back to the lignin extraction process. The quantity or size of the solvent stream may be adjusted to bring the total dissolved solids in the solvent feed stream to a targeted value. The recycle stream or solvent feed stream may have a lignin content of about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%. The recycle stream or solvent feed stream may have a lignin content of at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%. The recycle stream or solvent feed stream may have a lignin content of no more than about 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or less than 0.1%. The recycle stream may comprise between 0.5% and 20% lignin (e.g., in a limited solubility solvent). The recycle stream may comprise between 1.5% and 12.7% lignin. The recycle stream may comprise between 2.5% and 6.5% lignin The recycle stream or solvent feed stream may have a total dissolved solids content of about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%. The recycle stream or solvent feed stream may have a total dissolved solids content of at least about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or more than 30%. The recycle stream or solvent feed stream may have a total dissolved solids content of no more than about 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, or less than 0.1%. Lignin may comprise at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 98%, or at least 99% of the total dissolved solids.
[0051] Adding a recycle loop of lignin extractant to a lignin extraction process may increase the recovery of lignin and/or the purity of cellulose remainder obtained from the process. A process with a recycle loop of lignin extractant may have a lignin recovery of about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%. A process with a recycle loop of lignin extractant may have a lignin recovery of at least about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%. A process with a recycle loop of lignin extractant may have a lignin recovery of no more than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, or less than about 90%. A process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%. A process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of at least about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more than about 99%. A process with a recycle loop of lignin extractant may have a final cellulose purity on a dry weight basis of no more than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, or less than about 90%. A recycle loop of lignin extractant may increase the lignin removal or recovery relative to a nonrecycle process by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or about 99%. A recycle loop of lignin extractant may increase the lignin removal or recovery relative to a non-recycle process by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or more than about 99%. A recycle loop of lignin extractant may increase the lignin removal or recovery relative to a non-recycle process by no more than about 99%, 95%, 90%,
85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or about no more than about 5%.
[0052] A cellulosic remainder may comprise a residual amount of lignin after lignin extraction. In some cases, the amount of lignin may be too small to be measured or detected using conventional analytical proceedures. In other cases, a cellulosic remainder may comprise a measureable amount of lignin. A cellulosic remainder may comprise about 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, 4.1%, 4%, 3.9%, 3.8%, 3.7%, 3.6%, 3.5%, 3.4%, 3.3%, 3.2%, 3.1%, 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.3%, 2.2%, 2.1%, 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or less than 0.1% residual lignin. A cellulosic remainder may comprise no more than about 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, 4.1%, 4%, 3.9%, 3.8%, 3.7%, 3.6%, 3.5%, 3.4%, 3.3%, 3.2%, 3.1%, 3%, 2.9%, 2.8%, 2.7%, 2.6%, 2.5%, 2.4%, 2.3%, 2.2%, 2.1%, 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, or less than 0.1% residual lignin. A cellulosic remainder may comprise at least about 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 10%, 15%, 20%, or more than 20% residual lignin. A cellulosic remainder may comprise a residual amount of lignin relative to a lignin-containing remainder. A cellulosic remainder may contain about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or more than 99% of the lignin relative to the amount of lignin in the lignin-containing remainder. A cellulosic remainder may contain at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or more than 99% of the lignin relative to the amount of lignin in the lignin-containing remainder. A cellulosic remainder may contain no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, or less than 1% of the lignin relative to the amount of lignin in the lignin-containing remainder.
[0053] The addition of a lignin recycling loop may decrease the overall energy consumption of a lignin extraction process, compared to a lignin extraction process that does not include a lignin extractant recycling loop. In such cases, a lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or about 99%. A lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or more than about 99%. A lignin extractant recycling loop in a lignin extraction process may decrease the overall energy consumption of a lignin extraction process by no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or about no more than about 5%.
[0054] A recycling loop in a lignin extraction process may alter the optimal reactor conditions in the lignin extraction reactor. In some cases, the presence of a recycle loop may increase or decrease the optimal lignin extraction temperature, reaction time and/or pressure. The presence of a recycle loop may increase or decrease the optimal lignin extraction temperature by about 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, or about 50 °C. The presence of a recycle loop may increase or decrease the optimal lignin extraction temperature by at least about 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, or more than about 50 °C. The presence of a recycle loop may increase or decrease the optimal lignin extraction pressure by about 0.5 megapascal (MPa), 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa,
3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, or about 10 MPa. The presence of a recycle loop may increase or decrease the optimal lignin extraction pressure by at least about 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa,
3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa,
8.5 MPa, 9 MPa, 9.5 MPa, 10 MPa, or more than 10 MPa. The presence of a recycle loop may increase or decrease the lignin extraction time by about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99% or more than 99%. The presence of a recycle loop may increase or decrease the lignin extraction time by at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99% or more than 99%. The presence of a recycle loop may increase or decrease the lignin extraction time by no more than about 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1% or less than 1%. [0055] The disclosure further provides a lignin composition produced by a process of producing high purity lignin from a biomass. The process comprises (i) removing hemicellulose sugars from the biomass thereby obtaining a lignin-containing remainder; wherein the lignincontaining remainder comprises lignin and cellulose; (ii) contacting the lignin-containing remainder with a lignin extraction solution to produce a lignin extract and a cellulosic remainder; wherein the lignin extraction solution comprises one or more of a limited-solubility solvent, an organic acid, and water, wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; and (iii) separating the lignin extract from the cellulosic remainder; wherein the lignin extract comprises lignin dissolved in the limited-solubility solvent. In some embodiments, the lignin composition is produced by a process that further comprises one, two, three, four, or five additional step(s): (iv) contacting the lignin extract with a strong acid cation exchanger to remove residual cations thereby obtaining a purified lignin extract (v) distilling or flash evaporating the lignin extract thereby removing the bulk of the limited-solubility solvent from the lignin extract to obtain solid lignin; (vi) heating the solid lignin thereby removing trace limited-solubility solvent or water from the solid lignin; (vii) applying a vacuum to the solid lignin thereby removing trace limited-solubility solvent or water from the solid lignin; and (viii) dissolving the solid lignin with an organic solvent to form a resulting solution and separating the resulting solution from insoluble remainder.
[0056] In some embodiments, the lignin composition is characterized by at least one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, or nineteen characteristics selected from the group consisting of: (i) lignin aliphatic hydroxyl group in an amount up to 2 mmole/g; (ii) at least 2.5 mmole/g lignin phenolic hydroxyl group; (iii) less than 0.40 mmole/g lignin carboxylic OH group; (iv) sulfur in an amount up to 1 % weight/weight; (v) nitrogen in an amount up to 0.5 % weight/weight; (vi) 5% degradation temperature higher than 220 °C; (vii) 10% degradation temperature higher than 260 °C; (viii) less than 1% ash weight/weight; (ix) a formula of CaHbOc; wherein a is 9, b is less than 12 and c is less than 3.5; (x) a degree of condensation of less than 0.9 (e.g., as determined by carbon 13 nuclear magnetic resonance (13C NMR)); (xi) a methoxyl content of at least 0.8; (xii) an O/C weight ratio of less than 0.4; (xiii) a glass transition elevation between first and second heat cycle according to DIN 53765 in the range of 10 to 30 °C; (xiv) less than 1% carbohydrate weight/weight; (xv) solubility in DMSO is >100 g/L; (xvi) solubility in THF is >35 g/L; (xvii) solubility in 0.1 M NaOH aqueous solution is >8 g/L; (xviii) less than 1% water by weight; and (xix) less than 1% volatile components at 200 °C by weight. [0057] In some embodiments, the lignin composition is further characterized as having a glass transition as determined by Differential Scanning Calorimetry (DSC) according to DIN 53765 in the range of 80 °C to 160 °C; the DSC thermogram of the second heating cycle is substantially different from the first heating cycle, where the first heating cycle comprises a greater number of exothermic maxima, endothermic maxima or inflection points than the second cycle. In some embodiments, this greater number of points in the first cycle can be attributed to reactivity of the lignin sample taking place when heated, due to the lignin sample heterogeneity (e.g., a variety of functional groups, molecular structure and/or weight). In some embodiments, the reactivity results in further cross linking, resulting in elevation of the glass transition of the second cycle by greater than 5 °C, 10 °C, 15 °C, 20 °C or even 25 °C.
[0058] Such thermal behavior is indicative of the instability of the lignin polymer under heat, and possibly under other conditions. For industrial application purposes of lignin, it may be advantageous not only to have the high purity demonstrated for lignin of this disclosure but also to have better defined lignin. This can be achieved by fractionating the lignin into stable fractions in terms of their thermal behavior, size, structure and other attributes. Stable fractions of lignin will allow development of lignin as feedstock for chemical conversion processes that break the molecule to obtain chemicals of value and/or utilization of the lignin as a polymer by compounding it with additional components.
IV. Lignin Fractionation
[0059] Surprisingly it was found that said lignin can be fractionated by a robust method to produce two distinct lignin fractions that are thermally stable and are distinctively different. Thus, the disclosure further provides a lignin composition produced by a process of producing high purity lignin from a biomass. The process can comprise (i) removing hemicellulose sugars from the biomass thereby obtaining a lignin-containing remainder; wherein the lignin-containing remainder comprises lignin and cellulose; (ii) contacting the lignin-containing remainder with a lignin extraction solution to produce a lignin extract solution and a cellulosic remainder; wherein the lignin extraction solution comprises one or more of a limited-solubility solvent, an organic acid, and water, wherein the limited-solubility solvent and water form an organic phase and an aqueous phase; and (iii) separating the lignin extract from the cellulosic remainder; wherein the lignin extract comprises lignin dissolved in the limited-solubility solvent. In some cases, the process further comprises (iv) contacting the lignin extract with a cation exchanger (e.g., a strong acid cation exchanger) to remove residual cations thereby obtaining a purified lignin extract. In some cases, the process further comprises (v) distilling or flash evaporating the lignin extract thereby removing the bulk of the limited-solubility solvent from the lignin extract to obtain solid lignin. In some cases, the process further comprises (vi) heating the solid lignin to thereby remove trace limited-solubility solvent or water from the solid lignin. In some cases, the process further comprises (vii) applying a vacuum to the solid lignin to thereby remove trace limited-solubility solvent or water from the solid lignin. In some cases, the process further comprises (viii) contacting the solid lignin with an organic solvent to form a resulting solution comprising a fraction of the lignin, designated as solvent soluble (SS) and a remainder solid designated as solvent insoluble (SI); and separating the resulting solution from insoluble remainder.
[0060] Solvent fractionation can separate a sample of lignin into a solvent soluble (SS) fraction and solvent insoluble (SI) fraction. In some embodiments, said contacting is conducted at a ratio of 1 :3 to 1 : 10 solid to liquid ratio (wt/wt), in a stirred container at 20 °C - 50 °C for 1 - 1 Oh. [0061] In some embodiments, the solvent is at least one polar organic solvent with a molecular weight less than 200 Da. In some embodiments, the solvent is at least one organic solvent comprising 1-5 carbon atoms, 0-3 oxygen atoms, and 0-6 halogen atoms. In some embodiments, the solvent is a mixture of organic solvents. In some embodiments, the solvent is selected as an organic molecule wherein lignin has limited solubility in the solvent. For example, in some embodiments, the solvent is selected so that a mixture of the solvent to lignin 5: 1 w/w results in solubilization of at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% of lignin is disolved in the solvent. In some embodiments, between 10 and 40% of lignin is dissolved in the solvent. In some embodiments, lignin has a solubility in the solvent of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60 ,70, 80, 85, 80, 95, 97, 98, 99 gram (g) lignin/500 g solvent under the described conditions. In some embodiments, the solvent is an organic solvent wherein a sample consisting essentially of lignin has a solubility in the solvent of at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60 ,70, 80, 85, 80, 95, 97, 98, 99 g lignin/500 g solvent under the described conditions. In some embodiments, a mixture of solvents is applied. In some embodiments, at least 30%, 40%, 50%, 60% wt/wt of the lignin solid is soluble in such solvent under the described conditions, but not more than 70%, 60%, 50%, 40% is soluble. In some embodiments, the solvent is selected to form a soluble lignin fraction is at least 2, 4, 6, 8, 10, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 50, 52 wt/wt% of the total lignin in the sample under the solvent fractionation conditions described herein. [0062] In some embodiments, the solvent is selected from a group consisting of methanol, ethanol, isopropanol, ethyl acetate, ethyl formate and dichloromethane. In some embodiments, the solvent is selected from a group consisting of methanol, ethyl acetate and dichloromethane. In some embodiments, the solvent is methanol. In some embodiments, the solvent is dichloromethane. In some embodiments, the solvent is ethyl acetate.
[0063] In some embodiments, the non-dissolved (SI) fraction is collected by filtration, washed and air dried at 100-110 °C or under vacuum (for example at 45-55 °C and less than 1 kiloPascal pressure). The dissolved fraction is dried by evaporating the solvent or the solvent mixture in a rotavap or any other method to evaporate a solvent. The remaining lignin is collected and air dried at 100-110 °C or under vacuum (for example at 45-55 °C). In some embodiments, the solvent insoluble fraction is collected by decantation of the solvent from the reactor. In some embodiments, the solvent soluble fraction is collected by decantation of the solvent away from the solvent insoluble fraction.
[0064] The method of solvent fractionation of a lignin sample can be selected such that the amount of lignin in the solvent soluble fraction is low relative to the amount of lignin in the solvent insoluble fraction. For example, in some embodiments of the methods described herein, the solvent soluble fraction comprises less than 65, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5% of the total lignin of the sample (w/w). In some embodiments, the SS fraction comprises between about 25% and 45% of the total lignin. The method of solvent fractionation of a lignin sample can be selected such that the amount of lignin in the solvent insoluble (SI) fraction is low relative to the amount of lignin in the solvent soluble (SS) fraction. For example, in some embodiments of the methods described herein, the solvent insoluble fraction comprises less than 65, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5% of the total lignin of the sample (w/w). In some embodiments, the SI fraction comprises between about 25% and 45% of the total lignin.
[0065] In some embodiments of the lignin compositions described herein, a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the second amount to the third amount of lignin is greater than 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 3, 4, 5, 6, 7, 8, 9, 10, or 20 to 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt). In some embodiments of the lignin compositions described herein, the lignin is substantially soluble when a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the second amount to the third amount of lignin is greater than 3 : 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5:1 (wt/wt).
[0066] In some embodiments of the lignin compositions described herein, a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein greater than 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50% of the first amount of lignin is dissolved in the organic solvent, and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
[0067] In some embodiments of the lignin compositions described herein, a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the third amount to the second amount of lignin is greater than 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 3, 4, 5, 6, 7, 8, 9, 10, or 20 to 1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5:1 (wt/wt). [0068] In some embodiments of the lignin compositions described herein, a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein the ratio of the third amount to the second amount of lignin is greater than 3:1 (wt/wt), and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
[0069] In some embodiments of the lignin compositions described herein, a first amount of lignin is agitated for 2 hours at room temperature in the presence of an amount of organic solvent to form a second amount of solubilized lignin and third amount of insoluble lignin, wherein greater than 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50% of the first amount of lignin is not dissolved in the organic solvent, and wherein the ratio of the amount of organic solvent to the first amount of lignin is 5: 1 (wt/wt).
[0070] Solvent fractionation can produce two or more fractions of lignin with different chemical compositions than non-fractionated lignin. The chemcial composition of each fraction of solvent fractionated lignin can be distinct from non-fractionated lignin and distinct from each other fraction. For example, the solvent soluble and/or solvent insoluble lignin fractions can each independently have a ratio of oxygen to carbon atoms (O/C) larger than the O/C ratio of nonfractionated lignin. The solvent soluble and/or solvent insoluble lignin fractions can each independently have a ratio of hydrogen to carbon atoms (H/C) smaller than the H/C ratio of nonfractionated lignin. In some embodiments, the O/C and H/C ratios of fractionated lignin are within 20, 18, 15, 12, 10, 5% of non-fractionated lignin.
[0071] The chemcial composition of each fraction of solvent fractionated lignin can be distinct from non-fractionated lignin. For example, the number of OH groups (mmol/g lignin) can be higher in fractionated lignin than in non-fractionated lignin. In some embodiments, the number of aliphatic, phenolic, and caroxylic OH groups (mmol/g lignin) can be higher in fractionated lignin than in non-fractionated lignin. In some embodiments, the SS fraction comprises more phenolic OH and carboxylic OH groups than the SI fraction (w/w).
[0072] The solvent-soluble (SS) and solvent insoluble (SI) fractions obtained by this process share the high purity of the lignin solid from which they were made. The two samples are distinctively different in molecular weight, as demonstrated by characterizing them side by side by the same gel permeation method.
[0073] In some embodiments, the solvent soluble (SS) lignin fraction obtained by the process described herein has a low glass transition temperature (Tg) as determined using differential scanning calorimetry (DSC) according to DIN 53765-1994. For example, the SS fraction can have a measured Tg below the Tg of non-fractionated lignin. The SS fraction can have a Tg less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, or 45 °C. The Tg of non-fractionated lignin can be in the range of 80 to 160 °C. The SS fraction can have a Tg less than, 90, 85, 80, 75, 70, 65, or 60 °C. In some embodiments, the SS fraction has a Tg between about 75 and about 110 °C. In some embodiments, the SS fraction has a Tg between about 75 and about 95 °C. For example, the SS fraction can have a measured Tg below the Tg of solvent insoluble (SI) lignin fraction. The SS fraction can have a Tg less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, or 45% of the Tg of solvent insoluble (SI) lignin fraction. In some embodiments, the Tg of the SS lignin fraction is stable. In some embodiments, the Tg of the SS lignin fraction varies between the 1st cycle and the 2nd cycle by less than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 °C. In some embodiments, the Tg of the 2nd cycle increases by less than 5 °C relative to the 1st cycle wherein the the 1st and 2nd DIN cycle are measured within 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 days of each other. In some embodiments, the SS fraction does not have Tg at a temperature above room temperature. In some embodiments, the SS fraction is not a polymer.
[0074] In some embodiments, the number average molar mass (Mn) of the SS lignin fraction is less than the Mn of non-fractionated lignin. In some embodiments, the Mn of the SS lignin fraction is less than 2000, 1500, 1000, 900, 800, 700, 600, 500, 400, 300, or 200 Da. Molar mass values disclosed in this disclosure are determined according to Asikkala et. al., Journal of agricultural and food chemistry, 2012, 60(36), 8968-73. In some embodiments, the polydispersity (PD) of the SS lignin fraction is higher than the poly dispersity of non-fractionated lignin. In some embodiments, the PD of the SS fraction is over 3.0, 3.5, 4.0, 4.5, or 5.0. In some embodiments, the weight average molar mass or mass average molar mass (Mw) of the solvent soluble (SS) lignin fraction is lower than the Mw of non-fractionated lignin. For example, the Mw of SS lignin fraction can be less than 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5% of Mw of non-fractionated lignin. In some embodiments, the Mw of SS lignin fraction is less than 3000, 2900, 2800, 2700, 2600, 2500, 2400, 2300, 2200, 2100, 2000, 1800, 1600, 1500, 1400, 1300, 1200, 1100, 1000, 900, 970, or 800 Da. In some embodiments, the Mw is of the SS fraction is less than 2000 Da. In some embodiments, the solvent insoluble (SI) lignin fraction obtained by the process described herein has a low glass transition temperature (Tg) as determined using differential scanning calorimetry (DSC) according to DIN 53765-1994. For example, the SI fraction can have a measured Tg above the Tg of nonfractionated lignin. The SI fraction can have a Tg at more than 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 175, 180, 200, 220, 240, 250 °C. In some embodiments, the Tg of non-fractionated lignin is 80-160 °C. The SI fraction can have a Tg higher than 120, 130, 140, 150, 160, 170, 180, 190, 195, or 200 °C. In some embodiments, the SI fraction has a Tg between about 145 and about 210 °C. In some embodiments, the SI fraction has a Tg between about 155 and about 200 °C. For example, the SI fraction can have a measured Tg above the Tg of solvent soluble (SS) lignin fraction. The SI fraction can have a Tg greater 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 175, 180, 200, 220, 240, 260, 280, or 300% of the Tg of solvent soluble (SS) lignin fraction.
[0075] In some embodiments, the Tg of the SI lignin fraction is stable between thermal cycles. In some embodiments, the Tg of the SI lignin fraction varies between the 1st cycle and the 2nd cycle by less than 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 °C. In some embodiments, the Tg of the 2nd cycle increases by less than 5 °C relative to the 1st cycle wherein the the 1st and 2nd DIN cycle are measured within 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 days of each other. In some embodiments, the Tg of the 2nd cycle increases by less than 5 °C relative to the 1st cycle wherein the the 1st and 2nd DIN cycle are measured consecutively.
[0076] The size of individual polymeric molecules, and the size distribution of molecules in a sample of polymers such as lignin can be measured and understood in terms of the number average molar mass (Mn), the mass average molar mass (Mw), and polydispersity. For lignin samples, measured values of Mn and Mw (and thus poly dispersity) can be dependent on the experimental conditions. The values disclosed herein for Mn and Mw of lignin samples are based on gel permiation chromatography (GPC), using acetobromination of the lignin, with a solution of LiBr in THF as an eluent and UV detection. In some embodiments, the method of experimental measuring Mn and Mw are disclosed in example 6. In some embodiments, the use of DMSO as eluent without derivatization can lead to unusable measured values of Mn and Mw for a lignin sample. In some embodiments, the number average molar mass (Mn) of the SI lignin fraction is greater than the Mn of non-fractionated lignin. In some embodiments, the Mn of the SI lignin fraction is more than 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, or 9000 Da. In some embodiments, the poly dispersity (PD) of the SI lignin fraction is lower than the poly dispersity of non-fractionated lignin. In some embodiments, the PD of the SI fraction is less than 2.0, 1.9, 1.8. 1.7, 1.6, 1.5, or 1.4. In some embodiments, the mass average molar mass or weight average molar mass (Mw) of the solvent insoluble (SI) lignin fraction is greater than the Mw of non-fractionated lignin. For example, the Mw of SI lignin fraction can be greater than 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.3, 2.5, 3.0, or 3.5 of Mw of nonfractionated lignin. In some embodiments, the Mw of SI lignin fraction is greater than 5000, 6000, 7000, 8000, 10000, 12000, 14000, 16000, 18000, or 20000 Da. In some embodiments, the Mw is of the SI fraction is greater than 6000 Da.
[0077] Furthermore, the SS fraction and the SI fraction have a distinctively different glass transition temperatures. Optionally, the difference between the glass transition temperatures of the SS and SI fractions is greater than 30 °C, 40 °C, 50 °C, 60°C. Further yet, the glass transition temperature can be stable between the first thermal cycle and the second thermal cycle, having a difference of less than 5 °C, 4 °C, 3 °C, 2 °C for each fraction. In some embodiments, the SI fraction does not show additional exotherms or endotherms in the DSC scan, indicating that the polymer is stable and does not react at the temperature range up to 250 °C.
V. Lignin Applications
[0078] The use of lignin as a precursor for many high value materials was previously disclosed and is reviewed in numerous articles, for example: R. J. Gosselink Ph. D Thesis, Wageningen University (2011) “Lignin as a renewable aromatic resource for the chemical industry”; R. J. Gosselink et al, “Valorization of lignin resulting from biorefineries” (2008), RRB4 Rotterdam; D. A. Bulushev and J. R. H. Ross “Catalysis for conversion of biomass to fuels via pyrolysis and gasification: A review” Catalysis Today 171 (2011), p 1-13; A. L. Compere et. al. “Low Cost Carbon Fiber from Renewable Resources” Oak Ridge Labs Report; J. E. Holladay et. al. “Top Value-Added Chemicals from Biomass” Volume II - Results of Screening for Potential Candidates from Biorefinery Lignin, report from Pacific Northwest National Laborator, Oct. 2007.
[0079] The fractionated high purity lignin composition according to embodiments disclosed herein has a more defined character than other lignins. In some embodiments, the SI fraction is a preferred fraction for compounding purposes, due to higher molecular weight, the polymer is not changed by temperature up to 250 °C as seen in the DSC scan. The SS fraction is lower molecular weight and solvent soluble is anticipated to be more suitable for using it as feedstock for cracking lignin to small aromatic molecules of high values. In some embodiments, both the SI fraction and the SS fraction have low oxygen content compared to other lignins, e.g. kraft lignin. In some embodiments, both fractions have low ash content, a low sulfur and/or phosphorous concentration. Such a high purity lignin composition is particularly suitable for use in catalytic reactions by contributing to a reduction in catalyst fouling and/or poisoning. A lignin composition having a low sulfur content is especially desired for use as fuel additives, for example in gasoline or diesel fuel.
[0080] Some other potential applications for high purity lignin include carbon-fiber production, asphalt production, and as a component in biopolymers. These uses include, for example, oil well drilling additives, concrete additives, dyestuffs dispersants, agriculture chemicals, animal feeds, industrial binders, specialty polymers for paper industry, precious metal recovery aids, wood preservation, sulfur-free lignin products, automotive brakes, wood panel products, biodispersants, polyurethane foams, epoxy resins, printed circuit boards, emulsifiers, sequestrants, water treatment formulations, strength additive for wallboard, adhesives, raw materials for vanillin and as a source for paracoumaryl, coniferyl, sinapyl alcohol.
[0081] Further provided is a composition comprising a portion of lignin as disclosed herein and another ingredient. For example, the composition can comprise up to 98, 95, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1% wt/wt the lignin. In some embodiments, the composition comprises up to 50% lignin wt/wt. In some embodiments, the composition comprises between 5% and 75% lignin, or between 10 and 60% lignin wt/wt. In some embodiments, the lignin is SI lignin. In some embodiments, the lignin is SS lignin. In some embodiments, the composition is a polymer, precursor to one or more commodity chemicals, a commodity chemical, or consumer good. For example, the composition can be selected from the group consisting of fuel additives in gasoline or diesel fuel, carbon-fiber, materials for carbon-fiber production, asphalt, a component of a biopolymer, oil well drilling additives, concrete additives, dyestuffs dispersants, agriculture chemicals, animal feeds, industrial binders, specialty polymers for paper industry, precious metal recovery aids, materials for wood preservation, sulfur-free lignin products, automotive brakes, wood panel products, bio-dispersants, polyurethane foams, epoxy resins, printed circuit boards, emulsifiers, sequestrants, water treatment formulations, strength additive for wallboard, adhesives, and a material for the production of vanillin, paracoumaryl, coniferyl, sinapyl alcohol, benzene, xylenes, or toluene.
[0082] In some embodiments, method is provided comprising: (i) providing a lignin composition as described herein, and (ii) converting at least a portion of lignin in the composition to a conversion product. In some embodiments, the converting comprises treating with hydrogen or a hydrogen donor. In some embodiments, the conversion product comprises a commodity chemical comprising at least one item selected from the group consisting of bio-oil, carboxylic and fatty acids, dicarboxylic acids, hydroxyl-carboxylic, hydroxyl di -carboxylic acids and hydroxyl-fatty acids, methylglyoxal, mono-, di- or poly-alcohols, alkanes, alkenes, aromatics, aldehydes, ketones, esters, phenols, benzene, toluenes, and xylenes. In some embodiments, the conversion product is selected from the group consisting of dispersants, emulsifiers, complexants, flocculants, agglomerants, pelletizing additives, resins, carbon fibers, active carbon, antioxidants, liquid fuel, aromatic chemicals, vanillin, adhesives, binders, absorbents, toxin binders, foams, coatings, films, rubbers and elastomers, sequestrants, fuels, and expanders. In some embodiments, the conversion product comprises a fuel or a fuel ingredient.
EXAMPLES
[0083] It is understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the claimed invention. It is also understood that various modifications or changes in light the examples and embodiments described herein will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
EXAMPLE 1
Small scale hemicellulose sugar extraction
[0084] Table 1 provides a summary of chemical analysis of the liquor resulting from hemicellulose sugar extraction of various biomass types. The % monomeric sugar is expressed as %-weight out of total sugars weight. All other results are expressed as %-weight relative to dry biomass.
[0085] All treatments were carried out in a 0.5 L pressure reactor equipped with a stirrer and heating-cooling system. The reactor was charged with the biomass and the liquid at amounts given in the table. The reactor was heated to the temperature indicated in the table, time count was started once the reactor reached 5 °C below the designated temperature. Once the time elapsed, the reactor was cooled down. Solid and liquid were separated, and the content of the obtained liquor was analyzed, all data was back calculated relative to dry biomass weight. HPLC methods were applied to evaluate %-Total Sugars in the liquor, % monomeric sugars and % Acetic Acid. The % Degradation product is the sum of %Furfurals (GC or HPLC analysis), %Formic acid (HPLC) and % Levullinic acid (HPLC). Acid Soluble Lignin was analyzed according to NREL TP-510-42627 method.
Table 1: Treatment conditions and chemical analysis of the resulting liquor
Figure imgf000030_0001
1 %Total Sugars (%TS) measured by HPLC in the liquor
2 DB - Dry Biomass
3 %Monomers out of total dissolved sugars measured by HPLC in the liquor
4 %Acetic Acid measured by HPLC in the liquor
5 “/(Degradation Products = %Furfurals +%Formic Acid +%Levullinic Acid. %Furfurals measured by GC or HPLC, %Formic acid and % Levullinic acid measured by HPLC
60.5% H2SO4 + 0.2% SO2
7 0.7% H2SO4 + 0.03% Acetic acid
EXAMPLE 2
Large scale Chemical analysis of lignocellulose matter after hemicellulose sugar extraction
[0086] Table 2 provides a summary of chemical analysis of various types of biomass after hemicellulose sugar extraction. [0087] Pine (ref A1202102-5): Fresh Loblloly pine chips (145.9 Lb dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio. An acid aqueous solution (500 Lb) was prepared by adding 0.3% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 135 °C and then added to the digester to cover the wood. The solution was circulated through the wood for 40 minutes while maintaining the temperature. After 60 minutes, the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (128.3 Lb dry wood) and vent the vapor. The extracted wood was analyzed for sugar content, carbohydrate composition, ash, elements (by ICP), and DCM extractives. The analyses of the hemi depleted lignocellulose material show extraction of 42.4% Arabinan, 10.5% Galactan, 9.6% Xylan, 14.3% Manan, and 11.8% Glucan, indicating that mostly hemicellulose is extracted. Analyses also show 11.6% of “others”, including ASL, extractives and ash. The overall fraction of carbohydrates in the remaining solid is not different within the error of the measurement to that of the starting biomass due to this removal of “others”. It is however easily notices that the extracted woodchips are darker in color and are more brittle than the fresh biomass.
[0088] Pine (ref A12O4131-14(K1)): Fresh Loblloly pine chips (145.9 Lb dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio. An acid aqueous solution (500 Lb) was prepared by adding 0.3% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 135 °C and then added to digester to cover the wood. The solution was circulated through the wood for 180 minutes while maintaining the temperature. After 180 minutes, the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (121.6 Lb dry wood) and vent the vapor. The material was analyzed as described above. The analyses of the hemi depleted lignocellulose material show extraction of 83.9% Arabinan, 84.3% Galactan, 50.1% Xylan, 59.8% Manan and no extraction of glucan, indicating effective extraction of hemicellulose. Analyses also show extraction of 21.8% of “others” including lignin, extractives and ash.
[0089] Eucalyptus (ref A120702K6-9): Fresh Eucalyptus Globulus chips (79.1 Kg dry wood) were fed into a Rapid Cycle Digester (RDC, Andritz, Springfield, Ohio). An acid aqueous solution was prepared by adding 0.5% H2SO4 and 0.2% SO2 to water in a separate tank. The solution was heated to 145 °C and then added to digester to cover the wood. The solution was circulated through the wood for 60 minutes while maintaining the temperature, then heating was stopped while circulation continued for another 60 minute, allowing the solution to cool. After 120 minutes, the resulting liquor was drained to a liquor tank and using steam the wood was blown to a cyclone to collect the wood (58.8 Kg dry wood) and vent the vapor. The material was analyzed as described above. Analyses showed that 20.1% of the carbohydrates were extracted from the wood (dry wood base) xylose containing 70% of these sugars, 91% of the sugars in the liquor present as monomers. Under these conditions acetic acid concentration in the liquor was 3.6% (dry wood base) showing maximal removal of acetate groups from hemicellulose sugars; 4.2% (dry wood base) of acid soluble lignin. These results indicate effective extraction of hemicellulose and in particularly xylose, along with hydrolysis of the acetate groups from substituted xylosans. At the same time a significant amount of acid soluble lignin, extractives and ash are also extracted into the liquor.
Table 2: Chemical analysis of lignocellulose matter after hemicellulose sugar extraction
Figure imgf000032_0001
1 Hemicellulose sugar extraction: 135 °C for 60 minutes, 0.3% H2S04, 0.2% S02.
2 Hemicellulose sugar extraction: 135 °C for 180 minutes, 0.3% H2S04, 0.2% S02.
3 Hemicellulose sugar extraction: 145 °C for 60 minutes + cool down 60 minutes, 0.3% H2S04, 0.2% S02.
EXAMPLE 3
Direct lignin extraction
[0090] After hemicellulose sugars were extracted from eucalyptus chips, the remainder was mainly cellulose and lignin. The remainder was delignified using an aqueous organic solution containing acetic acid according to the process described below.
[0091] Eucalyptus wood chips (20.0 g) were mixed with a solution of 50/50 w/w of methyl ethyl ketone (MEK) and water that contains 1.2% acetic acid w/w of solution at a ratio of 1 : 10 (100 mL water, 100 mL MEK, and 2.2 g acetic acid). The mixture was treated at 175 °C for 4 hours in an agitated reactor. Then the system was allowed to cool to 30 °C before the reactor is opened. The slurry was decanted and the solid is collected for further analysis.
[0092] After the reaction, there was 127 g free liquid, of which 47.2 g organic and 79.8 g aqueous. The organic phase contained 1.1 g acetic acid, 10.4 g water, and 5.5 g dissolved solids (0.1 g sugars and 5.4 g others, which is mainly lignin). The aqueous phase contained 1.4 g acetic acid, 2.1 g dissolved solids (1.5 g sugars and 0.6 g other).
[0093] After decanting of the liquid, black slurry and white precipitate were at the bottom of the bottle. This material was vacuum-filtered and washed thoroughly with 50/50 w/w MEK/water (119.3 g MEK 148.4 g water) at room temperature until the color of the liquid became very pale yellow. Three phases were collected; organic 19.7 g, aqueous 215 g, and white solid 7 g dry. The organic phase contained 0.08 g acetic acid and 0.37 g dissolved solids. The aqueous phase contained 0.56 g acetic acid and 0.6 g dissolved solids.
[0094] All organic phases were consolidated. The pH of the solution is adjusted to pH 3.8. The solution was then allowed to separate into an aqueous phase (containing salts) and an organic phase (containing lignin). The lignin-containing organic phase was recovered and purified using a strong acid cation column. The organic solution was then added drop-wise into an 80°C water bath to precipitate the lignin.
[0095] Simlarly, lignin from bagasse was extracted by reacting sulfuric acid pretreated bagasse (D.S -60%) in a mixture of acetic acid (0.3% w/w of o.d. bagasse), methyl ethyl ketone, and water at 200 °C for 160 min. Bagasse-to-liquid ratio was 1 : 10 and the liquid phase was 50% w/w MEK-to-water. The reaction was carried out in a Parr reactor. After reaction time, the mixture was filtered and the liquid organic phase separated using a separatory funnel. The pH of the organic phase was adjusted to -3.8 with sodium hydroxide. Afterwards, the organic phase was passed through SAC resin and added dropwise to an 80 °C MEK bath. The lignin precipitated and collected by filtration. The lignin was dried in the oven at 105 °C.
EXAMPLE 4
Fractionation of Lignin
[0096] Lignin from bagasse and eucalyptus feedstock was prepared according to examples 1 through 3. The dry lignin was mixed with a solvent at a ratio of 1 :5 wt/wt and stirred for two hours at room temperature. The mixture was filtered and the solvent phase was evaporated under reduced pressure. The two solids (from filtration and evaporation) were dried in the oven at 105 °C to obtain the solvent soluble (SS) fraction and the solvent insoluble (SI) fraction. Solvents tested included methanol, ethanol, isopropanol, ethyl acetate, ethyl formate and dichloromethane. It is anticipated that other solvents may be useful to achieve similar fractionation. [0097] The solvent soluble (SS) and solvent insoluble (SI) fractions were weighed after fractionation with each of three solvents (methanol, dichloromethane, and ethyl acetate), and the results are shown in Table 3.
Table 3: Weight percentage of bagasse lignin fractionation in several solvents
Figure imgf000034_0001
EXAMPLE 5 Lignin characterization methods
[0098] Lignin samples were characterized by elemental analysis (e.g., determining the relative occurrence of C, H, O, N, and S).
[0099] NMR experiments were performed using Bruker Avance-400 spectrometer. Quantitative 13C NMR spectrum was acquired using DMSO-d6 (500 pL) as solvent for lignin (80 mg), with an inverse gated decoupling sequence, 90° pulse angle, 12-s pulse delay, and 12000 scans. Hydroxyl content analyses were determined using a quantitative 31P NMR procedure. An accurate weight (about 40 mg) of a dried lignin sample was dissolved in 500 pL of an anhydrous pyridine/CDCh mixture (1.6: 1, v/v). Then, 200 pL of an endo-N-hydroxy-5-norbornene-2, 3- dicarboximide (e-NHI) solution (50 mmol/L serving as internal standard) and 50 pL of chromium (III) acetylacetonate solution (11.4 mg/mL serving as a relaxation reagent) were added. The solutions of the internal standard and relaxation reagent were both prepared using an anhydrous pyridine/CDCh mixture (1.6:1, v/v). Finally, 100 pL of the phosphitylating reagent 2- chloro-4,4,5,5-tetramethyl-l,2,3-dioxaphospholane) was added, and the mixture was vigorously shaken, transferred into an NMR tube, and subjected to immediate 31P NMR analysis. The spectrum was acquired using an inverse gated decoupling pulse sequence, 75° pulse angle, 10-s pulse delay, and 200 scans.
[00100] Lignin was also thermally characterized by differential scanning calorimetry (DSC) using the DIN standard method number 53765.
[00101] Gel-permeation chromatography (GPC) analysis was carried as followed. Approximately 5mg of lignin was dissolved in 92:8 (v/v) glacial acetic acid and acetyl bromide mixture (2 ml) and stirred for two hours at room temperature. Acetic acid and excess of acetyl bromide were evaporated with a rotary evaporator connected to a high vacuum pump and a cold trap. The acetylated lignin was immediately dissolved in THF (1 mg/ml), filtered and injected to GPC.
EXAMPLE 6
Lignin structure characterization
[00102] Three lignin samples: non-fractionated, and fractionated with methanol (SS and SI) were characterized by the methods of example 5. The original lignin sample was prepared from bagasse according to examples 1 through 3, it was used to prepare lignin fractions SS and SI according to example 4. The results are presented in the following Table 4.
Elemental analysis
Table 4: Elemental Analysis and Chemical Composition of non-fractionated and methanol fractionated bagasse lignin including solvent soluble (SS) fraction and solvent insoluble (SI) fraction
Figure imgf000035_0001
[00103] Further characterization of the fractionated lignin was performed. The results from the elemental analysis of the fractionated lignin of Table 4 showed no significant differences between non-fractionated and fractionated lignin. The O/C is slightly larger in the insoluble and soluble fractions than the non-fractionated one, while the H/C is smaller. Hydroxyl content by 31P NMR
Table 5: Hydroxyl Content of non-fractionated and methanol fractionated bagasse lignin as Determined by Quantitative 31P NMR
Figure imgf000036_0001
[00104] As seen from the 31P NMR data (Table 5), after lignin fractionation the two fractions are structurally different than the non-fractionated lignin. Methanol fractionation resulted in lignin fractions with more aliphatic, phenolic, and carboxylic OH groups. The solvent soluble SS fraction contains similar amounts of aliphatic OH to that of the insoluble fraction. However, the soluble fraction has more phenolic OH and carboxylic OH than the insoluble fraction. This is rational given the fact that more phenolic OH would be required for dissolution. The increase in guaiacyl OH in 31P data is also supported by the decrease in aliphatic linkages as shown in Table 6. The lignin macromolecule opened when mixed with methanol.
Structure analysis by 13C NMR
Table 6: Quantitative Comparison between non-fractionated and methanol fractionated bagasse lignin based on the 13C NMR Spectra
Figure imgf000036_0002
[00105] The 13C NMR spectra of the fractionated lignin vs. the material before fractionation are consistent with the observation made by 31P NMR that the methanol treatment opens some internal linkages in the lignin molecule, as seen in the decrease in methoxyl content, P-O-4 content, aromatic C-0 content, but not in the aromatic C-C content.
Molecular weight determination by GPC
[00106] Gel-permeation chromatography (GPC) analysis was carried according to Asikkala et. al., Journal of agricultural and food chemistry, 2012, 60(36), 8968-73. Approximately 5 mg of lignin was dissolved in 92:8 (v/v) glacial acetic acid and acetyl bromide mixture (2 mL) and stirred for two hours at room temperature. Acetic acid and excess of acetyl bromide were evaporated with a rotary evaporator connected to a high vacuum pump and a cold trap. The acetylated lignin was immediately dissolved in THF (1 mg/ml), filtered and injected to GPC. [00107] The molecular weight of lignin fractions as well as the non-fractionated sample was analyzed by GPC. Fig. 3 presents fractionation by methanol. NF denotes the non-fractioned lignin, SS the solvent soluble fraction and SI the solvent insoluble fraction; Fig. 4 presents fractionation by dichloromethane; Fig. 5 presents fractionation by ethyl acetate. It is observed that in all cases the solvent soluble fraction has lower MW compared to the insoluble fraction. The results are summarized in Table 7.
Table 7: GPC analysis of non-fractionated and fractionated bagasse lignin
Figure imgf000037_0001
Thermal analysis by DSC
[00108] DSC was performed according to DIN 53765: the sample is first dried by a pre-heat cycle. Then, two consecutive heat cycles were measured, typically in the first cycle annealing processes took place that affected the polymer structure, while in the second cycle the major transition Tg is ascribed to the glass transition of the polymer. The results of the thermal characterization of the non-fractionated lignin, the SS fraction and the SI fractions are summarized in Table 8. Table 8: Thermal characterization of non-fractionated and methanol fractionated bagasse lignin using DSC
Figure imgf000038_0001
*No Tg point was observed. This could mean that the DCM soluble fraction is not a polymer.
[00109] The thermogram of the non-fractionated lignin (data not shown) indicated multiple changes in the lignin polymer at temperatures above 150 °C and a large change of 23 °C in the glass transition between the first and the second cycle. In marked contrast to this, the thermogram of the methanol soluble fraction (data not shown) showed a glass transition at lower temperatures, approximately 117 °C, consistent with it being the lower molecular weight fraction. The change from cycle 1 to cycle 2 was only 3 °C and while the thermogram still showed some annealing processes occurring above the glass transition, the extent of these changes is lower than in the non-fractionated lignin. The methanol insoluble fraction showed a glass transition at higher temperature, ca. 157 °C, consistent with this fraction having larger molecular weight. The thermograms are essentially the same for 1st and 2nd cycle (decrease of 2 °C between the cycles), and no endotherms or exotherms observed at temperatures above the glass transition. These thermograms indicate that distinctively two different lignin fractions were prepared by methanol fractionation treatment. The thermograms also indicate that each fraction is stable under heating, and does not manifest thermal annealing processes that were observed in the untreated sample as is commonly found in the literature.
[00110] The differential scanning calorimeter (DSC) thermograms of dichloromethane solvent soluble (SS) bagasse lignin fraction and DSC thermogram of dichloromethane solvent insoluble (SI) bagasse lignin fraction were determined. Lignin fractionated by dichloromethane (DCM) furnished a dichloromethane soluble fraction that did not have a Tg point. Without being bound by a particular theory, this could support the assertion that the DCM soluble lignin fraction is not a polymer. However, the DCM insoluble fraction had a Tg 167 °C in the 1st cycle and 166 °C in the second cycle. This lignin has a Tg higher temperature than that of non-fracitonated lignin, and a change in temperature between cycles of only 1 °C.
[00111] The differential scanning calorimeter (DSC) thermograms of ethyl acetate solvent soluble (SS) bagasse lignin fraction and DSC thermogram of ethyl acetate solvent insoluble (SI) bagasse lignin fraction were determined. Lignin fractionated by ethyl acetate furnished a soluble fraction with low Tg points (80 and 87 °C). The ethyl acetate insoluble fraction had high and stable Tg points of 196 °C in the 1st cycle and 192 °C in the second cycle. This lignin has a Tg higher temperature than that of non-fracitonated lignin, and a change in temperature between cycles of only 4 °C.
EXAMPLE 7 Lignin Extractant Recycling
Reactions conducted at approximately 235°C
[00112] Organic phase with 1.5% dissolved solids (DS) was obtained from the Danville PDU (DAN191116) and was concentrated to 3.4%, 6.5% and 12.7% dissolved solids. After concentration, liquids were placed into a separatory funnel to remove any aqueous layer that may have formed. Organic phases were analyzed for DS by mass by drying samples for 2 hours in a 105 °C oven and by using a density and sound velocity meter.
[00113] Lignocellulose (~6% dry solids loading on a 200-gram scale) was weighed into a 450- mL Hastelloy reaction vessel. Water and methyl ethyl ketone (MEK) with various amounts of DS (using 1 : 1 waterMEK by mass) were added. A nitrogen blanket (at about 150 psi) was added, and the reaction was stirred at 50% of the maximum stirring rate. The reactor was heated to 232°C in approximately 30 minutes. The temperature was maintained at 232 to 235°C for 22 minutes. The reaction was then cooled back to room temperature in 30 minutes. The solids were filtered out and washed 5 times with approximately 100 mL-portions of MEK saturated with water, then washed 2 times with approximately 100 mL-portions of dry MEK. Solids were dried in a 105 °C oven overnight in pre-weighed Petri dishes then, after coming to room temperature, reweighted in order to calculate cellulose recovery.
Reactions conducted at 205 °C
[00114] Organic phase with 1.5% dissolved solids (DS) was obtained from the Danville PDU (DAN191116) was concentrated to 12.7% dissolved solids. After concentration, liquids were placed into a separatory funnel to remove any aqueous layer that may have formed. The organic was then diluted with MEK saturated with water to the desired DS. Organic phases were analyzed for DS by mass by drying samples for 2 hours in a 105 °C oven and by density and sound velocity meter.
[00115] Lignocellulose (~6% dry solids loading on a 200-gram scale) was weighed into 450- mL Hastelloy reaction vessel. Water and methyl ethyl ketone (MEK) with various amounts of DS (1 : 1 water: MEK by mass) were added. A nitrogen blanket (at about 150 psi) was added, and the reaction was stirred at 50% of the maximum stirring rate. The reactor was heated to 205 °C in approximately 30 minutes. The temperature was maintained at 205 °C for 3 hours. The reaction was then cooled back to room temperature in 30 minutes. The organic phase was decanted off first to collect a sample for DS. This prevented the organic phase from being artificially concentrated during filtration of the full reaction mixture. After, solids were filtered out and washed 5 times with approximately 100 mL-portions of MEK saturated with water, then 2 times with approximately 100 mL-portions of dry MEK. Solids were dried in a 105°C oven overnight in pre-weighed Petri dishes then, after coming to room temperature, reweighted in order to calculate cellulose recovery.
RESULTS AND DISCUSSION
[00116] The results for recycling of varying dissolved lignin in organic phase at both 235 °C and 205 °C show a synergistic effect between the DS in the organic phase and the extraction efficiency. Surprisingly, as the DS in the recycled organic increases, the lignin extracted increases resulting in lower residual lignin on cellulose (Table 9 and Table 10). As the DS in the organic increases, the viscosity of the cook liquors increases. A centrifuge may be a useful alternative to filtration for separating solids from viscous cook liquors and washing.
[00117] Also, surprisingly it was found that a lower lignin extraction temperature increases the extraction of lignin from cellulose. For example, at 235 °C, 4.1% w/w of lignin remained in the cellulose remainder when extracted at 12.7% DS in the reactor feed stream, but residual lignin dropped to 2.9% at 205 °C at 12.7% DS.
Table 9: Residual Lignin on Cellulose and Cellulose Recovery at 235°C, 20 minutes, with DS from 0 to 12.7%
Figure imgf000040_0001
Table 10: Residual Lignin on Cellulose and Cellulose Recovery at 205°C, 180 minutes, with DS from 0 to 12.7%
Figure imgf000041_0001
[00118] It was also observed that as the DS in the recycled organic increased there was some burned material observed after filtering and washing the recovered cellulose (FIG. 7 A and FIG. 7B). This may slightly affect the estimation of final residual lignin from samples collected at 235 °C, causing overestimation of the remaining residual lignin in the biomass samples.

Claims

CLAIMS WHAT IS CLAIMED IS:
1. A method for producing a high purity lignin from a biomass, the method comprising: removing a hemicellulose sugar from the biomass to produce a lignin-containing remainder comprising lignin and cellulose; combining the lignin-containing remainder with a lignin extraction solution in a lignin extraction reactor to produce (i) a lignin extract comprising lignin dissolved in the limited-solubility solvent and (ii) a cellulosic remainder, wherein the lignin extraction solution comprises a limited-solubility solvent and water, and wherein the limitedsolubility solvent and water form an organic phase and an aqueous phase; separating the lignin extract from the cellulosic remainder, thereby producing the high purity lignin; and recycling a portion of the lignin extract to the lignin extraction reactor.
2. The method of claim 1, wherein the portion of the lignin extract recycled to the lignin extraction reactor comprises a ratio of lignin to limited-solubility solvent of between about 1 :200 and 1 :5.
3. The method of either claim 1 or 2, wherein the portion of the lignin extract recycled to the lignin extraction reactor comprises a ratio of lignin to limited-solubility solvent of between about 1 :40 and 13:200.
4. The method of any one of claims 1-3, wherein the lignin extraction solution comprises a ratio of about 20: 1 to 1 :20 of the limited-solubility solvent to the water.
5. The method of any one of claims 1-4, wherein the lignin extraction solution comprises a ratio of about 3:2 to 2:3 of the limited-solubility solvent to the water.
6. The method of any one of claims 1-5, wherein the combining is performed under an inert atmosphere.
7. The method of any one of claims 1-6, wherein the combining comprises heating the lignin-containing remainder and the lignin extraction solution to at least 200 °C.
8. The method of any one of claims 1-7, further comprising filtering the cellulosic remainder from the lignin extract.
9. The method of any one of claims 1-8, further comprising drying the cellulosic remainder. The method of any one of claims 1-9, wherein the limited-solubility solvent is water saturated. The method of any one of claims 1-10, wherein the limited-solubility solvent has a solubility in water of no more than 35 weight % (wt%). The method of any one of claims 1-11, wherein the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof. The method of any one of claims 1-12, wherein the limited-solubility solvent comprises a solvent selected from the group consisting of 1 -chi oro-2 -butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2-phenylethanol, 2- phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3 -pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tert-butyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and y-butyrolactone, or a combination thereof. The method of any one of claims 1-13, wherein the limited-solubility solvent comprises methyl ethyl ketone. The method of any one of claims 1-9 or 11-14, wherein the limited-solubility solvent consists of methyl ethyl ketone. The method of any one of claims 1-15, wherein the cellulosic remainder comprises less than 10 wt% residual lignin. The method of any one of claims 1-16, wherein the cellulosic remainder comprises less than 5 wt% residual lignin. The method of any one of claims 1-17, wherein the cellulosic remainder comprises less than 3 wt% residual lignin. The method of any one of claims 1-18, wherein the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.1. The method of any one of claims 1-19, wherein the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.2. The method of any one of claims 1-20, wherein the portion of the lignin extract recycled to the lignin extraction reactor has a recycle ratio of at least about 0.3. The method of any one of claims 1-21, wherein a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. The method of any one of claims 1 -22, wherein the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. The method of any one of claims 1 -23, wherein the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent. The method of any one of claims 1-24, further comprising (iv) removing residual cations from the lignin extract with a cation exchanger. The method of any one of claims 1-25, further comprising (v) removing at least a portion of the limited-solubility solvent from the lignin extract to obtain solid lignin. The method of claim 26, wherein the removing of (v) comprises distilling or flash evaporating. The method of either claim 26 or 27, further comprising heating (vi) the solid lignin to remove at least a portion of the limited-solubility solvent remaining in the solid lignin following the removing of (v). The method of any one of claims 26-28, further comprising (vii) applying a vacuum to the solid lignin to remove at least a portion of the limited-solubility solvent following the removing of (v). The method of any one of claims 26-29, further comprising (viii) fractionating the solid lignin with an organic solvent, thereby forming a solvent soluble fraction of the solid lignin and a solvent insoluble fraction of the solid lignin. The method of claim 30, wherein the fractionating of (viii) comprises between a 1 :3 and 1 : 10 ratio of the solid lignin and the organic solvent. The method of either claim 30 or 31, wherein the fractionating of (viii) comprises agitating the lignin in the presence of the organic solvent for at least 2 hours. The method of any one of claims 30-32, wherein the solvent soluble fraction of the solid lignin comprises a solubility of at least 10 grams (g) per 500 g of the organic solvent. The method of any one of claims 30-33, wherein the solvent soluble fraction of the solid lignin comprises at least 30% of the mass of the solid lignin. The method of any one of claims 30-34, wherein the solvent soluble fraction of the solid lignin comprises at least 70% of the mass of the solid lignin. The method of any one of claims 30-35, further comprising collecting the solvent insoluble fraction of the solid lignin by filtration. The method of any one of claims 30-36, further comprising evaporating at least a portion of the organic solvent from the solid soluble fraction of the solid lignin. The method of any one of claims 30-37, wherein the solid soluble fraction of the solid lignin comprises a number average molar mass that is at most 80% a number average molar mass of the solid lignin prior to the fractionation of (viii). A system for producing high-purity lignin from biomass, the system comprising: a lignin extraction unit configured to produce a stream comprising dissolved lignin and a cellulosic remainder; a cellulose recovery unit configured to produce a cellulosic remainder and a lignin extract; a lignin recovery unit configured to produce a lignin product; and a recycle stream connecting the lignin recovery unit to the lignin extraction reactor; wherein the recycle stream comprises a lignin extraction solvent with a dissolved solids content of at least 1%. A system for producing high-purity lignin from biomass, the system comprising: a lignin extraction unit; a cellulose separation unit; a lignin purification unit comprising a two-phase separation unit and a solvent purification unit; and a recycle stream that connects the lignin purification unit to the lignin extraction unit. The system of claim 40, wherein the lignin extraction unit is configured to produce a lignin extract and a cellulosic remainder. The system of any one of claims 40 or 41, wherein the lignin purification unit further comprises a strong acid cation exchanger. The system of claim 42, wherein the strong acid cation exchanging is in Na+ form. The system of any one of claims 40-42, wherein the recycle stream is positioned upstream of the strong acid cation exchanger. The system of any one of claims 40-42, wherein the recycle stream is positioned downstream of the strong acid cation exchanger. The system of any one of claims 40 or 44-45, wherein the system does not comprise a strong acid cation exchanger. The system of any one of claims 40-46, wherein the lignin purification unit is configured to receive the lignin extract. The system of any one of claims 40-47, wherein the lignin purification unit is configured to produce a purified lignin product and a purified limited-solubility solvent stream. The system of claim 48, wherein a portion of purified limited-solubility solvent stream is returned to the lignin extraction unit. The system of either claim 48 or 49, wherein the portion of the purified limited-solubility solvent stream returned to the lignin extraction unit comprises between 0.5% and 20% lignin. The system of any one of claims 48-50, wherein the the purified limited-solubility solvent stream returned to the lignin extraction unit comprises between 1.5% and 12.7% lignin. The system of any one of claims 48-51, wherein the the purified limited-solubility solvent stream returned to the lignin extraction unit comprises between 2.5% and 6.5% lignin. The system of any one of claims 48-52, wherein the portion of the purified limitedsolubility solvent stream and the portion of the lignin extract in the recycle stream are combined before entering the lignin extraction unit. The system of any one of claims 48-53, wherein the limited-solubility solvent has a solubility in water of no more than about 35 wt%. The system of any one of claims 48-54, wherein the limited-solubility solvent comprises a 4- to 8-carbon alcohol, ester, ether, or ketone, or a combination thereof. The system of any one of claims 48-55, wherein the limited-solubility solvent comprises a solvent selected from the group consisting of 1 -chi oro-2 -butanone, 1 -phenyl ethanol, 2,4-pentanedione, 2, 5 -dimethylfuran, 2-methylfuran, 2-ethylfuran, 2-phenylethanol, 2- phenylethyl chloride, 2-methyl-2H-furan-3-one, 2-picoline, 2,5-dimethylpyridine, acetal, anisol, diacetyl, 2,3 -pentanedi one, di ethylketone, diisopropyl ether, dimethyl acetal, ethyl acetate, ethyl formate, isopropyl acetate, isopropyl formate, m-cresol, methyl ethyl acetal, methyl isopropyl ketone, methyl propyl ketone, mesityl oxide, methyl tert-butyl ether, methyl ethyl ketone, methyl acetate, morpholine, phenol, propyl acetate, propyl formate, pyrrol, toluene, and y-butyrolactone, or a combination thereof. The system of any one of claims 48-56, wherein the limited-solubility solvent comprises methyl ethyl ketone. The system of any one of claims 48-57, wherein the limited-solubility solvent consists of methyl ethyl ketone. The system of any one of claims 41-58, wherein the cellulosic remainder comprises less than 10 wt% residual lignin. The system of any one of claims 41-59, wherein the cellulosic remainder comprises less than 5 wt% residual lignin. The system of any one of claims 41-60, wherein the cellulosic remainder comprises less than 3 wt% residual lignin. The system of any one of claims 40-61, wherein the recycle stream has a recycle ratio of at least about 0.1. The system of any one of claims 40-62, wherein the recycle stream has a recycle ratio of at least about 0.2. The system of any one of claims 40-63, wherein the recycle stream has a recycle ratio of at least about 0.3. The system of any one of claims 40-64, wherein a solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 1 weight percent. The system of claim 65, wherein the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 3 weight percent. The system of claim 66, wherein the solvent feed stream to the lignin extraction unit has a dissolved solids content of at least 5 weight percent. The system of any one of claims 40-67, wherein the cellulose recovery unit comprises a filtration unit or a centrifuge. The system of any one of claims 40-68, wherein system is configured to maintain the lignin purification unit under inert atmosphere.
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