EP4549649A1 - Organosolv-fraktionierungsverfahren zur fraktionierung von lignocellulosebiomasse - Google Patents

Organosolv-fraktionierungsverfahren zur fraktionierung von lignocellulosebiomasse Download PDF

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EP4549649A1
EP4549649A1 EP23206718.1A EP23206718A EP4549649A1 EP 4549649 A1 EP4549649 A1 EP 4549649A1 EP 23206718 A EP23206718 A EP 23206718A EP 4549649 A1 EP4549649 A1 EP 4549649A1
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Prior art keywords
organosolv
biomass
originating
liquor
fractionation
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French (fr)
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Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
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Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
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Priority to EP23206718.1A priority Critical patent/EP4549649A1/de
Priority to PCT/EP2024/080619 priority patent/WO2025093570A1/en
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/20—Pulping cellulose-containing materials with organic solvents or in solvent environment
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0007—Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides

Definitions

  • the present invention is in the field of an organosolv fractionation process for fractionating lignocellulosic biomass.
  • Lignocellulosic biomass is the most abundant renewable material on the Earth and it comprises cellulose and hemicelluloses (polysaccharides) and lignin (aromatic polymer). Lignocellulosic biomass is a valuable resource for the production of (bio)fuels, chemicals, performance products and energy.
  • Lignocellulosic biomass suitable for biorefining can preferably come from 2 nd generation feedstocks (non-edible), e.g. agricultural residues, forestry residues, food-processing residues, dedicated energy crops, or biomass from other origins such as cattle manure and biomass from roadside verges.
  • Organosolv fractionation of lignocellulosic biomass is used for the production of lignocellulosic components; cellulose (a glucan), hemicellulose and lignin.
  • cellulose a glucan
  • hemicellulose hemicellulose
  • the two major types of hemicellulose are xylans and (gluco)mannans.
  • Xylans have xylose (C5 sugar) backbones, sometimes substituted with arabinose or glucuronic acid side groups, and are predominant in hardwood and grasses
  • (gluco)mannans have backbones with a glucose:mannose (both C6 sugars) ratio of about 1:3, sometimes substituted with galactose side groups, and are predominant in softwood.
  • Minor hemicellulose types include xyloglucans and arabino- galactans.
  • Hemicelluloses may be chemically linked to lignin.
  • the lignocellulose biomass is fractionated into a cellulose-enriched solid product stream (pulp) and a liquid product stream (liquor) comprising lignin and hemicellulose derivatives.
  • Hemicellulose is first hydrolysed into sugar oligomers, then to sugar monomers (C 5 and/or C 6 sugars), which may subsequently dehydrate to furans such as furfural, and react further to other compounds (including condensation products with lignin (“pseudo-lignin”)).
  • Degradation products may be part of the aqueous hemicellulose stream (obtained after solvent recovery and lignin precipitation) and/or the lignin stream, which are produced by the organosolv process, thereby reducing their purity and the efficiency of further treatment of these streams to produce valuable end- products.
  • Lignin solubilization from the feedstocks occurs via (acid-catalysed) cleavage of lignin ⁇ -O-4 linkages which starts with elimination of a hydroxyl group on the ⁇ -position of the linkage. This leads to formation of a carbenium ion, followed by linkage cleavage and Hibbert ketone end group formation. Both the carbenium ion as well as Hibbert ketone end groups are involved in undesired lignin repolymerization or condensation reactions and formation of stabile C-C bonds.
  • Organosolv fractionation process focusses on an efficient way to obtain high yields and quality of all lignocellulosic components.
  • WO2015009145 discloses a batch-wise process for fractionating lignocellulosic biomass into a cellulose-enriched product stream, a hemicellulose-enriched product stream and a lignin-enriched product stream, comprising subjecting optionally pre-extracted biomass to a batch-wise organosolv step using a non-hydroxylic solvent.
  • WO2007120210 discloses a biomass fractionation process wherein biomass is digested at 120-220 °C in an aqueous extraction mixture containing a solvent for lignin such as ethanol.
  • the invention relates to an organosolv fractionation process for fractionating lignocellulosic biomass into a cellulose-enriched product stream (pulp) and a hemicellulose sugar/lignin-enriched product stream (liquor) thereby reducing the degradation of hemicellulose sugars and lignin. Further, the process according to the invention reduces the costs and energy usage thus, improves process economics and sustainability impact.
  • the process according to the invention includes a mild treatment step (a) and a severe treatment step (b).
  • the mild treatment step the majority of the lignin is extracted from the biomass at relatively mild conditions, such that the lignin degradation reactions are diminished.
  • this mild treatment step (a) the extent of delignification is quite significant, such that significant amounts of lignin are extracted and in view of its native state can be used beneficially.
  • step (b) In order to obtain pulp that is sufficiently delignified for further use, it is crucial that the mild treatment step (a) is followed by a severe treatment step (b). During step (b), the conditions are more severe and most of the remaining lignin and hemicellulose can be extracted from the biomass. The occurrence of lignin degradation reactions may be bigger during step (b), but since the majority of the lignin is removed after step (a), these degradation reactions only affect a small portion of the lignin.
  • the invention relates to an organosolv fractionation process for fractionating lignocellulosic biomass into a biomass pulp and an organosolv liquor comprising:
  • the present invention relates to an organosolv fractionation process for fractionating lignocellulosic biomass and reducing the degradation of hemicellulose sugars and lignin during that process.
  • the inventors have found that it is possible to extract sugar and lignin before substantial degradation took place, by conducting fractionation in two sub-steps (a) and (b).
  • the organosolv fractionation process according to the invention allows to increase the yield of lignin and hemicellulose sugars and reduce the residual lignin in the pulp.
  • Pre-extraction wherein the biomass is contacted with a solvent in order to remove soluble components such as minerals and organics. During pre-extraction, the conditions are such that no hydrolysis of the structural components of the biomass takes place.
  • Fractionation wherein the biomass is contacted with a liquid under conditions that enable the hydrolysis of the structural components of the biomass, in particular of the chemical bonds that exists between lignin and (hemi)cellulose. Fractionation of the biomass is also referred to organosolv and affords a liquor wherein the solubilized components of the biomass are dissolved and a cellulose pulp containing the solid cellulose residues of the pulp.
  • Washing wherein the biomass (pulp) is contacted with a solvent to remove remaining solubilized components from the biomass (pulp). During washing, the conditions are such that hardly any hydrolysis takes place.
  • the organosolv fractionation process according to the invention is typically conducted as a semi-continuous process (SCP). Different than the batch-wise processing, in this process the reactors are coupled allowing for liquor (containing solubilised sugars/lignin) exchange between percolation reactors. In a preferred configuration, the solids remain in their respective reactors and only liquids are transferred, wherein this transfer of liquids is typically directly between the reactors without the use of storage tanks. This way, a stepwise counter-current flow can be achieved while maintaining the robustness of batch-wise processing.
  • the organosolv fractionation process according to the invention is not only different in terms of process design but also in terms of fractionation process severity. The severity of fractionation depends on the liquor acidity. In the process of the invention, fractionation is divided to two steps: mild and severe fractionation.
  • the process of the present invention helps to minimise hemicellulose sugar and lignin degradation and improve hemicellulose and lignin solubilisation thereby producing a cellulose enriched pulp with improved quality. Further, this process helps to reduce the pulp washing requirements, consumption of acids and energy and reduce overall process costs.
  • any lignocellulosic biomass is suitable for the process according to the invention.
  • the biomass is selected from herbaceous biomass, softwood, hardwood and combinations thereof, preferably the lignocellulosic biomass comprises herbaceous biomass.
  • herbaceous biomass in the form of agricultural residues and/or biodegradable municipal waste is used in the process according to the invention, more preferably, the herbaceous biomass is selected from straw, leaves, (fresh or dried) grasses and combinations thereof, most preferably straw (e.g. rice straw, barley straw, wheat straw).
  • Such biomass comprises in general 20 to 80 wt.% carbohydrates (based on dry matter), which are valuable starting materials for production of fuels and chemicals.
  • the biomass has a lignin content of at least 5 wt%, more preferably at least 10 wt%, such as 20-35 wt%, based on total dry weight.
  • the biomass subjected to the process according to the invention may be fresh or dried biomass, optionally after removal of large impurities such as stones and pieces of metal, and optionally chopped or milled to pieces for ease of handling (e.g. pieces of 0.01 to 50 cm, in particular 0.1-10 cm in length or diameter, depending on the type of biomass).
  • the biomass may be subjected to a pre-treatment prior to being subjected to step (a).
  • the biomass is subjected to a pre-extraction step to remove non-lignocellulose compounds (extractives) prior to fractionation.
  • a pre-extraction steps enables valorisation of biomass extractives (e.g., bioactive compounds, nutrients), improved fractionation performance (i.e., increased sugar yield and lignin purity) at reduced acid doses and provides potential for reduced equipment corrosion (by chloride removal).
  • the pre-extraction may be an aqueous extraction or an organic extraction. Since both extractions remove different components from the biomass, it is especially preferred that an aqueous and an organic extraction is performed as pre-extraction.
  • the biomass is extracted with an extracting liquid before conducting the organosolv treatment step in step (a), preferably wherein the extracting liquid comprises at least 50 wt% of an organic solvent selected from lower alcohols and ketones at a temperature below 100 °C.
  • extracting liquid comprises at least 50 wt% of an organic solvent selected from lower alcohols and ketones at a temperature below 100 °C.
  • lower means containing 1-6 carbon atoms (C 1 -C 6 ), especially C 1 -C 4 .
  • organic solvent examples include methanol, ethanol, propanol, isopropanol, butanol and its isomers, ethylene glycol, propylene glycol, methoxy- ethanol, dimethoxyethane, diethylene glycol, dioxane, acetone, methyl ethyl ketone, tetrahydrofuran, dimethyl formamide, dimethyl acetamide, N-methylpyrrolidone, and mixtures thereof.
  • the organic solvent used during pre-extraction is the same as the organic solvent used during the organosolv treatment.
  • the extracting liquid may comprise between 0 and 50 vol. % of water.
  • the extraction step can be performed with an organic solvent and/or water, wherein the extracting liquid has a temperature between its melting temperature and its boiling temperature (or higher if pressurised).
  • Preferred extracting temperatures are from 10 to 100 °C and have a duration in the range of 30 s - 15 min. The skilled person will appreciate how to control the temperatures for optimal results when using a mixture of water and organic solvent.
  • the extraction step may be performed using any extraction technique known in the art.
  • the organosolv fractionation process separates the lignocellulose biomass into a cellulose-enriched product stream (the pulp) and a hemicellulose/lignin-enriched product stream (the liquor).
  • Organosolv processes to delignify biomass are known in the art, and can be performed as deemed appropriate by the skilled person.
  • organosolv fractionation process at reduced temperatures is desirable in order to reduce the costs and to already reduce degradation of valuable hemicellulose derivatives and lignin, when compared with conventional organosolv typically at temperatures around 200 °C.
  • the organosolv fractionation process according to the invention is performed at a temperature between 100 °C - 170 °C, preferably between 110 °C - 160 °C, more preferably between 120 °C - 150 °C.
  • Steps (a) and (b) may be performed at the same temperature or at different temperature.
  • the temperature of step (b) is the same as or higher than the temperature in step (a). Most preferably, the temperature in both steps is the same.
  • the organosolv fractionation step can be performed at any suitable pressure as known in the art, which typically is about 0.5 to 50 bar (absolute), preferably between 1 and 25 bar (absolute). Typically, the process is performed at atmospheric pressure wherein the only pressure increase is the result of the heating within a pressurized reactor.
  • the total fractionation time of the organosolv fractionation process is at least 30 minutes.
  • the total fractionation time refers to the duration of steps (a) and (b), as during these steps the biomass is fractioned into a liquor and a pulp. Even if some minor additional fractionation would take place before (e.g. during a pre-extraction) or after (e.g. during washing) steps (a) and (b), this is not included in the total fractionation time.
  • steps (a) and (b) together make up the organosolv process.
  • the total fractionation time is in the range of 60 - 180 minutes.
  • each individual step has a duration that deviates at most 50 %, preferably at most 25 %, from the average fractionation time defined as the total fractionation time divided by the total number of steps.
  • the individual steps may refer to the two steps (a) and (b).
  • step (a) and step (b) both have a duration in the range of 15 to 45 min, and together have a duration of 60 min.
  • the individual steps may refer to each individual substep within steps (a) and (b).
  • the process may contain one step (a) and two sub-steps (b1) and (b2) for step (b).
  • steps (a), (b1) and (b2) all have a duration in the range of 10 to 30 min, and together have a duration of 60 min.
  • the total fractionation time is in the range of 60 - 180 minutes, preferably 60 -120 minutes, and the duration of each individual step is in the range of 5 - 45 minutes, more preferable 10 - 30 min.
  • the suspension of biomass and treatment liquid is obtained by mixing at most 50 L and at least 0.1 L of treatment liquid per kg dry weight of the biomass, preferably between 1.0 L and 20 L, most preferably between 3 L and 15 L.
  • organosolv treatment of biomass uses 1 L of treatment liquid per between 20 g and 10 kg of biomass, preferably per between 50 and 1000 g, most preferably per between 67 and 333 g of biomass (dry weight).
  • the optimum ratio of treatment liquid to biomass depends on the type of biomass.
  • the liquid to solid weight ratio (L/S in liter/kg) of the organosolv fractionation step is preferably as low as possible, preferably lower than 20/1, more preferably lower than 12/1, most preferably lower than 8/1.
  • the L/S ratio is at least 0.5/1, preferably at least 1/1, even more preferably at least 1.5/1, most preferably at least 2/1.
  • the organosolv process involves contacting the biomass with an organosolv treatment liquid.
  • an organosolv treatment liquid may be used during the process according to the invention.
  • an organosolv treatment liquid comprises water, an organic solvent and optionally an acid catalyst.
  • the acid is preferably present to enable working at reduced pH as defined for steps (a) and (b).
  • a compound is considered to be a solvent in the context of the present invention, when it is liquid under ambient conditions. The presence of water in the treatment liquid allows hydrolysis reactions to take place during organosolv, in order to break up the network of structural components.
  • the organosolv treatment liquid comprises at least 5 wt% water, more preferably at least 10 wt%, even more preferably between 20 wt% and 80 wt%, even more preferably between 30 wt% and 75 wt% water, most preferably between 40 wt% and 70 wt% water.
  • the weight ratio of organic solvent to water is preferably between 20/80 and 80/20, more preferably between 30/70 and 75/25, even more preferably between 40/60 and 70/30, even more preferably between 40/60 and 65/35, more preferably between 40/60 and 60/40.
  • Any organic solvent suitable for organosolv may be used in the treatment liquid, including mixtures of organic solvents.
  • Suitable solvents include alcohols, esters, ethers and/or ketones, more preferably the organic solvent is an alcohol or a ketone, most preferably a ketone solvent.
  • Preferred alcohols include methanol, ethanol, (iso)propanol, butanol, ethylene glycol, methoxyethanol and mixtures thereof, most preferred the alcohol is ethanol.
  • Preferred ethers include dimethoxyethane, tetrahydrofuran (THF), 1,4-dioxane and 1,3-dioxolane.
  • ketones include acetone, butanone (methyl-ethyl-ketone or MEK), methyl isobutyl ketone (MIBK), cyclohexanone, acetoacetic (3-oxo-butanoic) acid esters and levulinic (4-oxopentanoic) esters, such as methyl levulinate and ethyl levulinate, most preferred the ketone is acetone.
  • solvents having both a ketone and an ester functionality are listed as ketones.
  • Preferred esters i.e. solvents not having a separate ketone functionality, include C 3 -C 5 esters such as ethyl acetate.
  • the organic solvent is methanol, ethanol or acetone.
  • the organosolv treatment liquid comprises acetone as organic solvent.
  • the inventors have obtained excellent results using acetone as organic solvent.
  • Organosolv fractionation occurs at acidic pH, to enable optimum fractionation into cellulose pulp and lignin-containing liquor.
  • the amount of acid used for optimum performance of the organosolv reaction may vary depending on the strength of the acid (pKa) and the acid neutralisation capacity (ANC) of the biomass, as well as on the process conditions. The skilled person will appreciate how to adjust the amount of acid in order to obtain optimal results.
  • Working at decreased L/S ratios favours an increase in acid concentration in the treatment liquid, but at the same a reduction in acid load per kg biomass.
  • the pH of the liquid is continuously monitored and if needed adjusted to the target pH for fractionation, using a sensor or probe and acid and/or alkaline dosing system.
  • Suitable acids include sulfuric acid, sulfurous acid, hydrochloric acid, phosphoric acid, perchloric acid, sulfonic acids such as methanesulfonic acid and para -toluenesulfonic acid, formic acid, oxalic acid, benzoic acid, lactic acid, malonic acid, maleic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, and combinations thereof.
  • the acid is selected from sulfuric acid, sulfurous acid, hydrochloric acid, phosphoric acid, para- toluenesulfonic acid, and combinations thereof. Most preferably, sulfuric acid is used.
  • the acid may refer to a single compound, or to a mixture of different acids. Preferably, a single acid is used.
  • biomass is contacted with a treatment liquid and fractioned into a pulp and a liquor.
  • biomass which may optionally be pre-treated as defined below
  • treatment liquid which has optionally been used as washing liquid in step (c) as defined below
  • a key aspect of the present invention is that the optionally pre-treated biomass is fed into the mild fractionation of step (a), whereas the treatment liquid is fed into the severe fractionation of step (b).
  • the "liquor” or “organosolv liquor” is obtained from step (a), whereas the "pulp” or “biomass pulp” is obtained from step (b), optionally after it has been subjected to a washing step (c).
  • the liquid fraction that is obtained from step (b) is herein referred to as "intermediate organosolv liquor” and the solid fraction that is obtained from step (a) is herein referred to as "mildly treated biomass".
  • the process according to the invention operates in counter-current mode, whereby the liquid stream starts at step (b) - or even step (c) if present - and ends at step (a), while the solid stream starts at step (a) and ends at step (b) - or even (c) if present.
  • the process typically runs semi-continuously, where organosolv treatment liquid is fed into step (b) (semi-)continuously and biomass is fed into step (a) (semi-)continuously, while during the process the liquids move from the severe treatment of step (b) to the mild treatment of step (a), while the solids remain in the same reactor.
  • reactors containing solids shift from step (a) to step (b), while liquids flow from reactor to reactor.
  • the duration that the liquid is outside of the reactors during the transfer of the liquid from steps (b) to (a) and from steps (c) to (b) is preferably kept as low as possible, preferably below 1 min, more preferably below 10 s per transfer.
  • the aim of step (a) is to conduct a mild fractionation of the biomass thereby solubilizing the most labile part of the hemicellulose and lignin.
  • the aim of step (b) is to increase the liquor acidity to promote fractionation and separate as much lignin as possible from the cellulose.
  • Most hemicellulose and lignin solubilization occurs during the mild fractionation step (a) followed by consecutively lower solubilization during the severe fractionation step (b).
  • the biomass feedstock is either pre-extracted or pre-wetted with 50% organic solvent, preferably with acetone prior to fractionation steps. Pre-wetting can be done to ensure the sufficient liquid transfer.
  • the mild fractionation step is applied to remove hemicellulose and lignin at a temperature in the range of 100 °C - 170 °C and a pH between 1.5 and 3.0.
  • the organosolv fractionation process according to the invention comprises step (a), which involves contacting fresh or pre-extracted lignocellulosic biomass to the intermediate organosolv liquor originating from step (b). The contacting of step (a) occurs at a temperature in the range of 100 °C - 170 °C and at a pH between 1.5 and 3.0.
  • step (a) a mildly treated biomass and the organosolv liquor are obtained.
  • the organosolv liquor obtained in step (a) is one of the key end-products of the process according to the present invention.
  • step (a) is a mild fractionation with respect to the severe fractionation of step (b)
  • at least one of the following should apply:
  • the pH during step (a) is higher than the pH during step (b); the temperature during step (a) is lower than the temperature during step (b); the duration of step (a) is shorter than the duration of step (b).
  • at least the pH is higher and/or the temperature is lower.
  • step (a) operates at a higher pH than step (b). The inventors found that a small pH difference already provides a significantly reduced sugar and lignin degradation.
  • the pH during step (a) is at least 0.1 pH-point higher than the pH during step (b), preferably 0.1 - 1.0 pH-point higher, more preferably 0.2 - 0.5 pH-point higher.
  • Optimal results have been obtained with step (a) at a pH of about 2.1 and step (b) at a pH of about 1.8.
  • the incoming intermediate organosolv liquor may be more acidic then desired for step (a), depending on the conditions at which step (b) is conducted.
  • a significant part of the liquor acidity can be removed when contacted with the biomass in step (a), depending on the acid neutralising capacity of biomass.
  • step (a) will typically be conducted at a higher pH then step (b).
  • step (a) the liquor acidity of step (b) is partly removed to create mild fractionation conditions for first lignin and hemicellulose hydrolysis and solubilisation.
  • step (a) is performed at a pH preferably between 1.6 and 2.8, more preferably between 1.8 and 2.6.
  • Liquor acidity is one of the most important parameter for this step in order to ensure sufficient fractionation with reduced product degradation.
  • the severe fractionation step is applied to obtain pulp at a temperature in the range of 100 °C -170 °C and a pH below 2.0.
  • the organosolv fractionation process according to the invention comprises step (b) wherein the mildly treated biomass originating from step (a) is contacted with an organosolv treatment liquid at a temperature in the range of 100 °C - 170 °C and a pH below 2.0, to obtain the intermediate organosolv liquor and a biomass pulp. This step is performed at a pH preferably between 1.5 and 2.0, more preferably between 1.6 and 1.8.
  • the biomass pulp obtained in step (b), which is optionally washed in step (c), is one of the key end-products of the process according to the present invention.
  • the organosolv treatment liquid that is used in step (b) may be a fresh organosolv treatment liquid, i.e. a liquid which has not yet been subjected to a process step, in particular no fractionation step or washing step.
  • the organosolv treatment liquid that is used in step (b) may be a spent washing liquid that originates from a washing step, typically a washing step (c) as defined below.
  • step (b) is a severe fractionation with respect to the mild fractionation of step (a)
  • the pH during step (b) is lower than the pH during step (a); the temperature during step (b) is higher than the temperature during step (a); the duration of step (b) is longer than the duration of step (a).
  • at least the pH is lower and/or the temperature is higher.
  • step (b) operates at a lower pH than step (a).
  • the pH during step (b) is at least 0.1 pH-point lower than the pH during step (a), preferably 0.1 - 1.0 pH-point lower, more preferably 0.2 - 0.5 pH-point lower.
  • step (b1) Preferably, higher acid concentrations are applied in step (b1) in order to increase hydrolysis power and thus hemicellulose/lignin solubilisation in this step.
  • Acid concentrations in step (b2) and step (b3) are preferably kept constant to solubilise the remaining hemicellulose and lignin to obtain a cellulose-enriched pulp.
  • the present invention relates to an organosolv fractionation process comprising:
  • step (b3) is performed, if step (b3) is not performed, the second treated biomass from step (b2) is the biomass pulp obtained from step (b). If step (b3) is performed, the third treated biomass from step (b3) is the biomass pulp obtained from step (b). Likewise, if step (b3) is not performed, the first intermediate organosolv liquor fed to step (b2) is the intermediate organosolv liquor fed to step (b). Preferably, step (b3) is performed.
  • the organosolv treatment liquid comprises 40 - 70 vol% organic solvent and 30 - 60 vol% water, preferably wherein the organic solvent comprises acetone, most preferably wherein the organic solvent is acetone.
  • the organosolv fractionation process according to the present invention may comprise a pulp washing step (c).
  • the washing step the biomass pulp obtained in step (b) is contacted with a washing liquid to obtain washed biomass pulp and spent washing liquid.
  • the spent washing liquid is used as the organosolv treatment liquid in step (b), preferably as the first intermediate organosolv liquor in step (b2), when step (b3) is not performed, or as the organosolv treatment liquid in step (b3), when step (b3) is performed.
  • the composition of the spent washing liquid may need to be changed in order to make it suitable as the treatment liquid in step (b). For example, some organic solvent and/or acid may need to be added.
  • washing step (c) removes organic solvent from the pulp
  • the spent washing liquid will at all times contain some organic solvent, but this may be insufficient for the treatment of step (b).
  • the benefits of the present invention are obtained.
  • the spent washing liquid may be partially or fully used for the organosolv treatment liquid. In case not all of the spent washing liquid is used, the remainder may be used for recovery of the organic solvent or can be used in a pre-extraction step.
  • the purpose of the washing step is to remove any remaining solvents from the treatment liquid as well as the solutes contained therein from the pulp. As such, the pulp will contain less residual lignin and hemicellulose, which will be contained in the liquor. So the washing step also increases the yield of lignin and hemicellulose in the final organosolv liquor that is obtained in step (a).
  • organic solvent is beneficially removed from the pulp before it is further used or processed. Typically, the pulp may be subjected to enzymatic hydrolysis into glucose, for which the presence of organic solvent is detrimental.
  • the washing step (c) may include at least two distinct steps (c1) and (c2) as follows:
  • washing step (c1) typically occurs at elevated temperature, which is close to the temperature at which the severe treatment step (b) is performed. As such, the heat of the biomass pulp can effectively be used for washing step (c1) and the effectiveness of the washing is increased. At such elevated temperatures, the solubility of the solutes (mainly lignin and hemicellulose residues) is higher than at ambient temperature, and therefore these are more effectively removed.
  • the washing liquid used in step (c1) also referred to as the "intermediate washing liquid"
  • the spent washing liquid may immediately be suitable as treatment liquid in step (b), without the need for addition of organic solvent, optionally with the addition of acid.
  • Washing step (c2) typically occurs at lower temperatures than washing step (c2).
  • the passive cooling of the biomass pulp after the treatment of step (b) can be used as the temperature at which the washing steps are performed.
  • the washing of step (c2) occurs at ambient temperature.
  • water is used as washing liquid in step (c2).
  • the intermediate washing liquid obtained in step (c2) may contain 10-25 vol% organic solvent. It may be beneficial to supplement the intermediate washing liquid with organic solvent before it is used in step (c1). As such, the spent washing liquid may contain about 50 vol% organic solvent.
  • organic solvent can be added to the intermediate washing liquid or the spent washing liquid to make sure the content of organic solvent is suitable for step (b).
  • the present invention relates to an organosolv fractionation process comprising:
  • step (b2) is performed, more preferably steps (b2) and (b3) are both performed.
  • the present invention relates to an organosolv fractionation process comprising:
  • step (b2) is performed, more preferably steps (b2) and (b3) are both performed.
  • a pre-extraction step is part of the step sequence of the process according to the invention.
  • the present invention relates to an organosolv fractionation process comprising:
  • the present invention relates to an organosolv fractionation process comprising:
  • Pre-extraction step (x), or steps (x1) and (2), as defined above, are compatible with all the above embodiments.
  • the liquor obtained in step (a) typically contains lignin, carbohydrates (notably hemicellulose and its degradation products), organic acids, salts and possibly other compounds originating from the biomass. It may be used as deemed fit by the skilled person. For example, it may be further treated or separated for the purpose of isolating valuable products.
  • the liquor may be depleted in lignin by precipitation of lignin through decreasing the organic solvent content of the liquor, e.g. by dilution with water and/or by evaporation of organic solvent, e.g. followed by centrifugation.
  • the ratio within a mixture of organic solvents may be altered, which may lead to phase separation between the aqueous and organic phases, facilitating the separation which may e.g. be performed by decantation. For example, reducing the acetone content (e.g. by evaporation) or increasing the butanone content (e.g. by addition thereof) leads to such phase separation.
  • the biomass pulp obtained in step (b), or in step (c) if performed contains cellulose and typically some hemicellulose residues. Although minor amounts of lignin may be present in the pulp, the delignification rate of the process according to the invention is high such that content of residual lignin is low.
  • the biomass pulp may be used as deemed fit by the skilled person. For example, it may be further treated by enzymatic hydrolysis of the cellulose polymers into glucose monomers, which in turn is a suitable intermediate for the manufacture of biofuels.
  • the ambient dry beech wood (BW), wheat straw (WS), roadside grass (RS) and almond shells (AS) were selected as feedstocks considering composition, physical characteristics and fractionation performance.
  • WS, RS and AS were pre-extracted.
  • WS and RS were extracted by premixing 2.5 kg feedstock (dry weight) with 7.5 L demineralised water before loading into a pre-extraction unit.
  • the wetted feedstocks were transferred to the pre-extraction unit and preheated at 50 °C for 2 h.
  • Demineralised water of 48 °C was sprayed onto the top of the biomass bed with a flow rate of 200 mL/min. After water addition, the liquid was allowed to percolate down the biomass bed for 30 min and collected in a vessel.
  • AS was extracted by stepwise soaking 3 kg of the shells in extraction liquid followed by draining rather than using percolation to maintain a comparable contact time for all feedstock extractions.
  • a series of integrated 2 L autoclave experiments were conducted to simulate semi-continuous processing (SCP) according to the invention.
  • the semi-continuous processing experiments were conducted as shown in Figure 2 : Fresh or pre-extracted dry feedstock was pre-wetted with 50% acetone and fractionated through three fractionation stages (steps (a), (b1) and (b2)) and the pulp washed (step (c)) and dried.
  • the SCP experiments for each feedstock consisted of two startup cycles (each cycle comprising of steps (a), (b1) and (b2)), followed by two or three cycles from which the average values are presented in the results.
  • the mixtures were heated to 140 °C and kept isothermal for the specified reaction time (Table 2) while stirring.
  • step (b2) 1200 mL of 50% acetone/water mixture containing 20 mM sulfuric acid was used as treatment liquid.
  • the organosolv liquor was acidified (Table 2) and transferred to step (b1).
  • the organosolv liquor was transferred to step (a).
  • the step (a) fractionation step the final organosolv liquor was obtained for further processing.
  • the wet pulp was then washed with 600 ml 50% acetone in step (c1) followed by a wash with 1200 ml water to remove the acetone in step (c2).
  • the pH of the liquid streams was determined with a pH meter.
  • Table 2 Experimental conditions Experiment Time (min) L/S (L per kg feed) Acid added (mM H 2 SO 4 ) BR SCP (b1) SCP (b2) BW-BR 3 ⁇ 30 6 40 BW-SCP 3 ⁇ 30 6 20 20 WS-BR 3 ⁇ 20 10 60 WS-SCP 3 ⁇ 20 10 30 20 RG-BR 3 ⁇ 20 10 50 RG-SCP 3 ⁇ 20 10 30 20 AS-BR 3 ⁇ 20 10 30 AS-SCP 3 ⁇ 20 10 10 20
  • a wet pulp sample was dried for determining pulp yield and duplicate biochemical composition analysis. The remainder of the wet pulp was stored frozen for subsequent pulp enzymatic saccharification.
  • the obtained liquors were processed using the lab-scale LigniSep lignin precipitation method as described in Smit, A. T.; Verges, M.; Schulze, P.; van Zomeren, A.; Lorenz, H., Laboratory-to Pilot-Scale Fractionation of Lignocellulosic Biomass Using an Acetone Organosolv Process. ACS sustainable chemistry & engineering 2022 .
  • the precipitated lignin was washed, dried and their biochemical composition was analysed. Lignin was also precipitated from the washing liquids obtained from the step (c1) at 60 °C.
  • Figure 4 A shows the fractionation performance of wheat straw (WS) and pre-extracted wheat straw (WA-WS) as a function of liquor acidity
  • Figure 4 B shows the fractionation performance of wheat straw (WS) and pre-extracted wheat straw (WA-WS) as a function of acid dose.
  • Figure 4 A shows no difference between the fractionation of WS and WA-WS at similar liquor acidities but Figure 4 B shows a difference at similar acid dose.
  • the reason for this is the effect of pre-extraction step.
  • Pre-extraction removes organic extractives as well as minerals and reduces the acid neutralising capacity of the feedstock. As a result, acid dose requirements decreases for fractionation.
  • Figure 6 C shows an inverse relation to the sugar yield with furfural formation decreasing from batchwise processing to semi-continuous processing. It is concluded that the compositions of the cellulose pulp obtained from batchwise and semi-continuous processing are mostly affected by feedstock type and fractionation process severity (liquor acidity). Overall, the results in Figures 4 - 6 show that early removal of sugars during semi-continuous fractionation increases the sugar yield, mostly by reduced degradation to furanics.
  • lignin structural changes during fractionation are more complex.
  • Lignin solubilisation from the feedstocks occur via (acid-catalysed) cleavage of lignin ⁇ -O-4 linkages which starts with elimination of a hydroxyl group on the ⁇ -position of the linkage. This leads to formation of a carbenium ion, followed by linkage cleavage and Hibbert ketone end group formation. Both the carbenium ion as well as Hibbert ketone end groups are involved in lignin condensation reactions and formation of stabile C-C bonds. Overall, a more condensed and altered lignin hampers its application in biobased materials.
  • the ⁇ -O-4 content of all BR and SCP lignins are related to the feedstock delignification to include a measure for process severity.
  • the SCP lignins show both improved delignification and a higher ⁇ -O-4 content as compared to the BR lignins.
  • Reduced ⁇ -O-4 bond cleavage in the SCP lignin in turn results in less formation of condensed lignin structures as shown in Figure 7 B . This further supports the results from the C5 sugar mass balance, with again improved product yield and quality through the application of stepwise counter-current flow.

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WO2008017145A1 (en) * 2006-08-07 2008-02-14 Emicellex Energy Corporation Process for recovery of holocellulose and near-native lignin from biomass
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