Hardwood-derived carbohydrate compositions

Abstract

A hardwood-derived carbohydrate composition comprising from 75 to 97% by weight of monomeric sugars is disclosed. The monomeric sugar comprises 55-75% by weight of monomeric xylose. The carbonyl content of the carbohydrate composition is 4000-9000 [mu] g / g based on the total dry matter content of the carbohydrate composition. A method for producing a hardwood-derived carbohydrate composition and uses thereof are also disclosed.

Description

Technical Field

[0001] The present disclosure relates to hardwood-derived carbohydrate compositions comprising monomeric sugars. In addition, the present disclosure relates to a method for producing a hardwood-derived carbohydrate composition. In addition, the present disclosure relates to uses of a hardwood-derived carbohydrate composition. Background of the Invention

[0003] Different processes are known for converting bio-based feedstocks, such as lignocellulosic biomass, into liquid streams of various sugars. Being able to provide sufficiently pure carbohydrate compositions with properties suitable for further applications, such as the production of ethylene glycol, ethanol or xylitol, remains a task for researchers. Summary of the invention

[0004] A carbohydrate composition derived from hardwood is disclosed. The carbohydrate composition derived from hardwood comprises 75-97 wt % of monomeric sugars based on the total dry matter content of the carbohydrate composition, wherein the monomeric sugars include monomeric xylose. The amount of monomeric xylose in the carbohydrate composition is 55-75 wt % based on the total dry matter content of the carbohydrate composition. The carbonyl content of the carbohydrate composition is 4000-9000 μg / g based on the total dry matter content of the carbohydrate composition.

[0005] Also disclosed is a method for producing a hardwood-derived carbohydrate composition as defined in the present application, wherein the method comprises:

[0006] i) providing a carbohydrate feedstock derived from hardwood in the form of a liquid fraction having a total dry matter content of 7-13 wt.%;

[0007] ii) adjusting the pH of the hardwood derived carbohydrate feedstock to 2.2-3.0;

[0008] iii) evaporating the feed having a pH of 2.2-3.0 until the total dry matter content of the feed is 45-55 wt. %;

[0009] iv) adjusting the pH of the evaporated feed to 5.5-7.5;

[0010] v) chromatographing the feed at a pH of 5.5-7.5 using a strong acid cation exchange resin; and

[0011] vi) evaporating the chromatographically treated feedstock until the total dry matter content of the feedstock is 60-70 wt. %;

[0012] Thereby producing a hardwood derived carbohydrate composition.

[0013] Also disclosed is the use of a hardwood derived carbohydrate composition as disclosed in this specification for producing a sweetener or biogas. DETAILED DESCRIPTION

[0014] A carbohydrate composition derived from hardwood is disclosed. The carbohydrate composition derived from hardwood comprises 75-97 wt % monomeric sugars based on the total dry matter content of the carbohydrate composition, wherein the monomeric sugars include monomeric xylose. The amount of monomeric xylose in the carbohydrate composition is 55–75 wt % based on the total dry matter content of the carbohydrate composition. The carbonyl content of the carbohydrate composition is 4000-9000 μg / g based on the total dry matter content of the carbohydrate composition.

[0015] The hardwood derived carbohydrate composition may be liquid or in liquid form. The methods disclosed in this specification may produce a hardwood derived carbohydrate composition in liquid form.

[0016] Also disclosed is a method for producing a hardwood-derived carbohydrate composition as defined in the present application, wherein the method comprises:

[0017] i) providing a carbohydrate feedstock derived from hardwood in the form of a liquid fraction having a total dry matter content of 7-13 wt.%;

[0018] ii) adjusting the pH of the hardwood derived carbohydrate feedstock to 2.2-3.0;

[0019] iii) evaporating the feed having a pH of 2.2-3.0 until the total dry matter content of the feed is 45-55 wt. %;

[0020] iv) adjusting the pH of the evaporated feed to 5.5-7.5;

[0021] v) chromatographing the feed at a pH of 5.5-7.5 using a strong acid cation exchange resin; and

[0022] vi) evaporating the chromatographically treated feedstock until the total dry matter content of the feedstock is 60-70 wt. %;

[0023] Thereby producing a hardwood derived carbohydrate composition.

[0024] In one embodiment, steps i), ii), iii), iv), v) and vi) are performed sequentially in this order. In one embodiment, steps i), ii), iii), iv), v) and vi) are performed sequentially in this order without other steps being performed in between.

[0025] Also disclosed is the use of a carbohydrate composition derived from hardwood as disclosed in this specification for producing a sweetener or biogas. The sweetener can be, for example, xylitol or xylose. In one embodiment, the production of the sweetener comprises crystallizing xylose from the carbohydrate composition derived from hardwood. In one embodiment, the sweetener is xylose in the form of crystals or syrup.

[0026] In one embodiment, the hardwood derived carbohydrate composition is a sweetener composition. In one embodiment, the method of producing a hardwood derived carbohydrate composition is a method of producing a sweetener composition.

[0027] Also disclosed is a carbohydrate composition derived from hardwood that can be obtained by the method disclosed in this specification. In one embodiment, the carbohydrate composition derived from hardwood that can be obtained by the method disclosed in this specification is a carbohydrate composition derived from hardwood disclosed in this specification. That is, the carbohydrate composition derived from hardwood disclosed in this specification can be produced by the method disclosed in this specification.

[0028] The carbohydrate composition derived from hardwood can be a carbohydrate composition derived from beech, a carbohydrate composition derived from birch, a carbohydrate composition derived from eucalyptus, a carbohydrate composition derived from poplar, or the carbohydrate composition derived from hardwood can be a combination of these compositions, or a combination of these compositions with other hardwood species. In one embodiment, the carbohydrate composition derived from hardwood is a carbohydrate composition derived from beech, a carbohydrate composition derived from birch, a carbohydrate composition derived from eucalyptus, or a carbohydrate composition derived from poplar. In one embodiment, the carbohydrate composition derived from hardwood is a carbohydrate composition derived from beech.

[0029] The hardwood-derived carbohydrate compositions disclosed in this specification refer to compositions comprising carbohydrates, but the compositions may also further comprise additional components and / or elements, such as those disclosed in this specification. Thus, a "hardwood-derived carbohydrate composition" may be considered a "hardwood-derived carbohydrate-containing composition" or a "hardwood-derived composition comprising carbohydrates".

[0030] Monomeric sugars, i.e. the amount of monomeric C5 sugars and monomeric C6 sugars, and oligosaccharides, i.e. the amount of oligomeric C5 sugars and oligomeric C6 sugars, can be qualitatively and quantitatively determined by high performance liquid chromatography (HPLC) by comparison with standard samples. Examples of analytical methods can be found in, for example, Sluiter, A. et al., "Determination of sugars, byproducts, and degradation products in liquid fraction process samples," Technical Report, National Renewable Energy Laboratory, 2008, and Sluiter, A. et al., "Determination of Structural Carbohydrates and Lignin in Biomass," Technical Report, National Renewable Energy Laboratory, revised in 2012.

[0031] As used herein, any weight percentage is given as a percentage of the total dry matter content of the carbohydrate composition, unless otherwise specified. Similarly, other weight fractions (ppm, etc.) may also refer to fractions of the total dry matter content of the carbohydrate composition, unless otherwise specified.

[0032] Unless otherwise stated, the expression "C5 sugar" is understood in this specification to mean xylose, arabinose or any mixture or combination thereof. Unless otherwise stated, the expression "C6 sugar" is understood in this specification to mean glucose, galactose, mannose, fructose or any mixture or combination thereof. Unless otherwise stated, the expression that a sugar is a "monomer" is understood in this specification to mean a sugar molecule present as a monomer, i.e. not coupled or linked to any other sugar molecule.

[0033] In the present specification, the amounts of the different components / elements in the carbohydrate composition derived from hardwood are expressed in weight % based on the total dry matter content of the carbohydrate composition.

[0034] The expression "total dry matter content" may refer to the total amount of solids, including soluble or dissolved solids. The hardwood derived carbohydrate composition may contain no suspended solids, only soluble solids.

[0035] In this specification, the term "total dry matter content of a carbohydrate composition" may refer to the weight of the carbohydrate composition determined after any solid particles or materials have been removed from the carbohydrate composition (e.g., by filtration) and the filtrate has been dried at a temperature of 45°C for 24 hours. The effectiveness of drying may be ensured by weighing the sample, drying for an additional two hours at a specified temperature, and re-weighing the sample. If the measured weights are the same, drying is complete and the total weight may be recorded.

[0036] It is clear to the skilled person that the total amount of the different components / elements in the hardwood derived carbohydrate composition must not exceed 100 wt%. The amounts in wt% of the different components / elements in the hardwood derived carbohydrate composition may vary within the given ranges.

[0037] In one embodiment, the amount of monomeric xylose in the carbohydrate composition is 57-72 wt %, based on the total dry matter content of the carbohydrate composition.

[0038] In one embodiment, the carbonyl content of the carbohydrate composition is 4250-8500 μg / g, or 4500-8000 μg / g, based on the total dry matter content of the carbohydrate composition. The expression "carbonyl content" can be understood as the content of carbonyl compounds, which contain a functional group consisting of a carbon atom double bonded to an oxygen atom, i.e., C=O. Carbonyl groups are common in several classes of organic compounds and are part of many larger functional groups. Compounds containing carbonyl groups are generally referred to as carbonyl compounds. For example, aldehydes, ketones, and carboxylic acids all contain carbonyl groups in their structures. The carbonyl content in the carbohydrate composition can be determined according to standard ASTME411-05 (2009).

[0039] The hardwood derived carbohydrate composition has the added benefit of containing only a small amount of carbonyl groups. Thus, for example, fermentation of the carbohydrate composition may proceed more smoothly when there are fewer carbonyl groups in the carbohydrate composition that could lead to unwanted side reactions.

[0040] In one embodiment, the ICUMSA color value of the carbohydrate composition is 17500-45000 IU, or 20000-40000 IU, or 22500-37500 IU. The ICUMSA color value can be measured using a modified ICUMSA GS1 method without adjusting the pH value of the sample to be analyzed or filtering the sample with a 0.45 μm filter before analysis. The measurement is performed at room temperature and the pH value of the carbohydrate composition is 2.2-3.

[0041] In one embodiment, the carbohydrate composition comprises 1.5-4.5 wt%, or 1.75-4.0 wt%, or 2.0-3.5 wt% soluble lignin based on the total dry matter content of the carbohydrate composition. The presence of soluble lignin in the carbohydrate composition can prove that the carbohydrate composition is derived from wood.

[0042] The amount of soluble lignin can be determined by UV-VIS absorption spectroscopy in the following manner: The amount of soluble lignin present in the carbohydrate composition is determined by diluting the carbohydrate composition sample so that its absorbance at 205 nm is 0.2-0.7 absorbance units (AU) when compared to a pure water reference sample using a cuvette with a light path of 1 cm. The soluble lignin content of the sample (in mg / l) can then be calculated using the following equation:

[0043]

[0044] Where A is the absorbance of the sample, a is the absorption coefficient 0.110 l / mgcm, and D is the dilution factor.

[0045] The total dry matter content of the hardwood derived carbohydrate composition may be 8-80 wt%, or 15-75 wt%, or 20-70 wt% when measured after drying at a temperature of 45°C for 24 hours.

[0046] In one embodiment, the conductivity of a 65% aqueous solution of the carbohydrate composition is 0.1 - 1.5 mS / cm, or 0.15 - 1.0 mS / cm, or 0.2 - 0.75 mS / cm when measured according to SFS-EN 27888 (1994).

[0047] In one embodiment, the carbohydrate composition comprises 0.5-5 wt%, or 0.75-4.5 wt%, or 1.0-4.0 wt% rhamnose based on the total dry matter content of the carbohydrate composition. The amount of rhamnose can be determined by high performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD).

[0048] In one embodiment, the carbohydrate composition comprises a total amount of 0.4-4 wt%, or 0.5-3.5 wt%, or 0.6-3.0 wt% carboxylic acid based on the total dry matter content of the carbohydrate composition.

[0049] In one embodiment, the carbohydrate composition comprises a total amount of 80-95 wt. % or 85-90 wt. % monomeric sugars, based on the total dry matter content of the carbohydrate composition.

[0050] In one embodiment, the carbohydrate composition comprises a total of 86-99 wt % or 88-98 wt % or 90-97 wt % monomeric sugars and oligosaccharides based on the total dry matter content of the carbohydrate composition. In one embodiment, the carbohydrate composition comprises 0.1-9 wt % or 0.2-7 wt % or 0.3-5 wt % oligosaccharides based on the total dry matter content of the carbohydrate composition. The chromatographic treatment also has the additional effect of reducing the amount of oligosaccharides in the carbohydrate composition derived from hardwood.

[0051] Unless otherwise stated, in this specification the expression that a sugar is "oligomeric" is understood to mean a sugar molecule consisting of two or more monomers coupled or linked to each other.

[0052] The C5 oligosaccharide may be xylose and / or arabinose. The C6 oligosaccharide may be glucose, galactose, mannose, fructose and / or rhamnose.

[0053] In one embodiment, the carbohydrate composition comprises 12-24 wt. % or 15-22 wt. % monomeric C6 sugars, based on the total dry matter content of the carbohydrate composition.

[0054] In one embodiment, the monomeric sugars include monomeric glucose and monomeric xylose, and the weight ratio of monomeric glucose to monomeric xylose is 0.067-0.2, or 0.08-0.17, or 0.1-0.14. The inventors surprisingly found that by the method disclosed in this specification, a carbohydrate composition derived from hardwood can be produced, which contains a high content of monomeric C5 sugars, especially a high ratio of monomeric xylose to monomeric glucose. By the method disclosed in this specification, C5 sugars can be effectively recovered as a carbohydrate composition derived from hardwood.

[0055] The carbohydrate composition may comprise 3-12 wt%, or 4-11 wt%, or 5-10 wt% of organic impurities (including soluble lignin), based on the total dry matter content of the carbohydrate composition.

[0056] Organic acids can be mentioned as examples of organic impurities. Non-limiting examples of organic impurities are oxalic acid, citric acid, succinic acid, formic acid, acetic acid, levulinic acid, 2-furoic acid, 5-hydroxymethylfurfural (5-HMF), furfural, glycolaldehyde, glyceraldehyde, and various acetates, formates and other salts or esters. The quality and quantity of organic impurities in the carbohydrate composition can be determined using, for example, HPLC plus, for example, a suitable detector, infrared (IR) spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy or nuclear magnetic resonance (NMR) spectroscopy.

[0057] The carbohydrate composition may contain inorganic impurities. Based on the total dry matter content of the carbohydrate composition, the carbohydrate composition may contain 0-2% by weight, or 0.05-1.5% by weight, or 0.075-1.0% by weight, or 0.1-0.75% by weight of inorganic impurities. The inorganic impurities may be soluble inorganic compounds, for example, in the form of various salts. The inorganic impurities may be salts of elements selected from the group consisting of Al, As, B, Ca, Cd, Cl, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si and Zn. The amount of inorganic impurities in the carbohydrate composition may be analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES) according to standard SFS-EN ISO 11885:2009. Alternatively, ion chromatography (IC) may also be used.

[0058] The method for producing a hardwood-derived carbohydrate composition comprises providing a hardwood-derived carbohydrate feedstock in the form of a liquid fraction having a total dry matter content of 7-13 wt%. Such a hardwood-derived carbohydrate feedstock can be provided, for example, by:

[0059] First, a wood-based feedstock derived from a wood-based raw material and comprising hardwood chips can be provided. The wood-based feedstock can then be subjected to a pretreatment to form a pulp, wherein the pretreatment comprises:

[0060] Impregnating the wood-based feedstock with an impregnation solution comprising sulfuric acid, wherein the impregnation is performed at a temperature of 40-100° C. for 1-30 minutes;

[0061] subjecting the impregnated wood-based feedstock to a steam explosion treatment to form a steam-treated wood-based feedstock, wherein the amount of sulfuric acid in the steam explosion treatment is 0.10-0.75 wt % based on the total dry matter content of the wood-based feedstock;

[0062] mixing the steam treated wood-based feedstock with a liquid to form a slurry; and

[0063] The slurry is separated into a liquid portion and a portion containing solid cellulose particles by a solid-liquid separation process to recover the liquid portion as a hardwood-derived carbohydrate feedstock.

[0064] Unless otherwise indicated, the expression "pretreatment" or "pretreatment" in this specification should be understood as a process by which (a) a wood-based feedstock is converted into a slurry that can be separated into a liquid portion and a portion containing solid cellulose particles. That is, the liquid portion can be separated from the portion containing solid cellulose particles. The portion containing solid cellulose particles can further include a certain amount of lignocellulose particles and lignin particles in free form. Lignocellulose contains lignin chemically bonded to the cellulose particles.

[0065] The wood-based raw material can be derived from beech, birch, eucalyptus, ash, oak, maple, chestnut, willow, aspen or poplar, for example. The wood-based raw material can also be any combination or mixture of these materials.

[0066] In general, wood and wood-based raw materials are mainly composed of cellulose, hemicellulose, lignin and extractives. Cellulose is a polysaccharide composed of chains of glucose units. Hemicellulose includes polysaccharides such as xylan, mannan and glucan.

[0067] Providing wood-based feedstock may include subjecting the wood-based raw material to a mechanical treatment selected from the group consisting of peeling, chipping, splitting, cutting, pulping, grinding, crushing, splitting, screening and / or washing the wood-based raw material to form the wood-based feedstock. During the mechanical treatment, for example, logs may be debarked and / or formed into chips of a specific size and structure. The formed chips may also be cleaned, for example with water, to remove materials such as sand, gravel and stone therein. In addition, the structure of the chips may be loosened prior to the pretreatment step. The wood-based feedstock may contain a certain amount of bark from the logs.

[0068] Providing the wood-based feedstock may include purchasing the wood-based feedstock. The purchased wood-based feedstock may include purchased wood chips or wood shavings derived from wood-based raw materials.

[0069] The pretreatment of wood-based feedstock may include one or more different pretreatment steps. In the different pretreatment steps, the wood-based feedstock itself may change. The purpose of the pretreatment steps is to form a pulp for further processing.

[0070] Pretreatment may include pre-steaming the wood-based feedstock. Pretreatment may include pre-steaming the wood-based feedstock received from mechanical treatment. Pretreatment may include, prior to impregnation treatment, pre-steaming the wood-based feedstock to form pre-steamed wood-based feedstock. Pretreatment may include an impregnation treatment and a steam explosion treatment, and may include pre-steaming the wood-based feedstock prior to impregnation treatment and then steam explosion treatment.

[0071] Pre-steaming of the wood-based feedstock may be performed at atmospheric pressure using steam at a temperature of 100-130°C. During pre-steaming, the wood feedstock is treated with low pressure steam. Pre-steaming may also be performed using steam at a temperature below 100°C, or below 98°C, or below 95°C. Pre-steaming has the added benefit of reducing or removing air from the wood-based feedstock. Pre-steaming may be performed in at least one pre-steaming reactor.

[0072] The pretreatment may include impregnating the wood-based feedstock with an impregnation liquid comprising sulfuric acid. The impregnation liquid may consist of sulfuric acid and water. The impregnation liquid may contain up to 20% by weight of sulfuric acid based on the total weight of the impregnation liquid. Subjecting the wood-based feedstock to the impregnation treatment may form an impregnated wood-based feedstock comprising at least 0.5% by weight of sulfuric acid based on the total dry matter content of the wood-based feedstock.

[0073] The impregnation process can be performed on wood-based feedstock received from mechanical treatment and / or from pre-steaming. A feeder can be used to transfer the wood-based feedstock from the mechanical treatment and / or from pre-steaming to the impregnation process. The feeder can be a screw feeder, such as a plug screw feeder. The feeder can compress the wood-based feedstock during the transfer process. When the wood-based feedstock subsequently enters the impregnation process, it may swell and absorb the impregnation liquid.

[0074] The sulfuric acid may be dilute sulfuric acid. The total amount of acid added to the wood-based feedstock may be 0.3–5.0% w / w, 0.5–3.0% w / w, 0.6–2.5% w / w, 0.7–1.9% w / w, or 1.0–1.6% w / w based on the total dry matter content of the wood-based feedstock. The impregnation liquid may act as a catalyst to affect the hydrolysis of hemicellulose in the wood-based feedstock. In one embodiment, the sulfuric acid catalyzes the hydrolysis of hemicellulose in the wood-based feedstock into monomeric sugars.

[0075] The impregnation process can be carried out in at least one impregnation reactor or vessel. In one embodiment, two or more impregnation reactors are used. The transfer from one impregnation reactor to another impregnation reactor can be carried out with a screw feeder.

[0076] The impregnation process can be performed by conveying the wood-based feedstock through at least one impregnation reactor at least partially filled with an impregnation liquid, i.e., the wood-based feedstock can be transferred into the impregnation reactor, where it is immersed in the impregnation liquid, and then transferred out of the impregnation reactor, so that the wood-based feedstock is uniformly impregnated with the impregnation liquid. As a result of the impregnation process, an impregnated wood-based feedstock is formed. The impregnation process can be performed in a batch process or in a continuous manner.

[0077] The residence time of the wood-based feedstock in the impregnation reactor, i.e. the time the wood-based feedstock is in contact with the impregnation liquid, may be 1-30 minutes. The temperature of the impregnation liquid may be, for example, 20-99°C, or 40-95°C, or 60-93°C. Maintaining the temperature of the impregnation liquid below 100°C has the additional effect of preventing or reducing the dissolution of hemicellulose. In one embodiment, the impregnation treatment is carried out at a temperature of 80-100°C or 90-99°C for 1-30 minutes.

[0078] After the impregnation treatment, the impregnated wood-based feedstock may be allowed to remain in, for example, a storage tank or silo for a predetermined period of time to allow the impregnation liquid absorbed into the wood-based feedstock to stabilize. This predetermined period of time may be 15-60 minutes, or for example about 30 minutes.

[0079] In one embodiment, the wood-based feedstock is subjected to an impregnation treatment with dilute sulfuric acid at a concentration of 1.32% w / w and a temperature of 92°C.

[0080] Pre-treatment may include subjecting the wood-based feedstock to a steam explosion process. The wood-based feedstock from an impregnation process may be subjected to a steam explosion process. That is, pre-treatment may include subjecting the impregnated wood-based feedstock to a steam explosion process to form a steam-treated wood-based feedstock.

[0081] Therefore, the pretreatment may include mechanically treating the wood-based material to form a wood-based feedstock, pre-steaming the wood-based feedstock to form a pre-steamed feedstock, impregnating the pre-steamed wood-based feedstock to form an impregnated wood-based feedstock, and steam explosion treating the impregnated wood-based feedstock. In one embodiment, the pretreatment in ii) includes pre-steaming the wood-based feedstock, impregnating the pre-steamed wood-based feedstock, and steam explosion treating the impregnated wood-based feedstock. In one embodiment, the pretreatment in ii) includes impregnating the wood-based feedstock, and steam explosion treating the impregnated wood-based feedstock. That is, the wood-based feedstock that has been impregnated can subsequently be steam exploded. In addition, the pre-steamed wood-based feedstock can subsequently be impregnated, and then the impregnated wood-based feedstock that has been impregnated can be steam exploded.

[0082] Between different treatments, the wood-based feedstock may be stored in, for example, wood chip boxes or silos. Alternatively, the wood-based feedstock may be transferred from one treatment process to another in a continuous manner.

[0083] The pretreatment may include subjecting the impregnated wood-based feedstock to a steam explosion treatment to form a steam-treated wood-based feedstock. The amount of sulfuric acid in the steam explosion treatment may be 0.10-0.75 wt % based on the total dry matter content of the wood-based feedstock. The steam explosion treatment may be performed by treating the impregnated wood-based feedstock with steam at a temperature of 130-240°C, or 180-200°C, or 185-195°C at a pressure of 0.17-3.25 MPaG, followed by a sudden, explosive decompression of the feedstock. The feedstock may be treated with steam for 1-20 minutes, or 1-18 minutes, or 2-15 minutes, or 4-13 minutes, or 3-10 minutes, or 3-8 minutes, followed by a sudden, explosive decompression of the steam-treated wood-based feedstock.

[0084] In this specification, the term "steam explosion treatment" may refer to a semi-hydrolysis process in which a feedstock is treated with steam at a temperature of 130-240°C, or 180-200°C, or 185-195°C at a pressure of 0.17-3.25 MPaG in a reactor (steam explosion reactor), and then the feedstock is suddenly and explosively depressurized, resulting in the rupture of the fiber structure of the feedstock.

[0085] In one embodiment, the amount of sulfuric acid in the steam explosion process may be 0.10-0.75 wt. % based on the total dry matter content of the wood-based feedstock. The amount of acid present in the steam explosion process may be determined by measuring the sulfur content of the liquid of the steam-treated wood-based feedstock or the liquid portion of the steam-treated wood-based feedstock after the steam explosion process. The amount of sulfuric acid in the steam explosion reactor may be determined by subtracting the amount of sulfur in the wood-based feedstock from the total amount of sulfur measured in the steam-treated wood-based feedstock.

[0086] The steam explosion treatment may be carried out in a pressurized reactor. The steam explosion treatment may be carried out in a pressurized reactor by treating the impregnated wood-based feedstock with steam at a temperature of 130-240°C, or 180-200°C, or 185-195°C at a pressure of 0.17–3.25 MPaG, followed by a sudden, explosive decompression of the feedstock. The impregnated wood-based feedstock may be introduced into the pressurized reactor using a compression conveyor, such as a screw feeder. If a screw feeder is used, the acid in liquid form is removed during the conveying process using the screw feeder, a portion of the impregnation liquid absorbed by the feedstock is removed as a pressate, and a large portion remains in the feedstock. The impregnated wood-based feedstock may be introduced into the pressurized reactor together with steam and / or gas. The pressure of the pressurized reactor may be controlled by adding steam. The pressurized reactor may be operated in a continuous manner or as a batch process. The impregnated wood-based feedstock, for example, a wood-based feedstock that has been subjected to an impregnation treatment, can be introduced into the pressure reactor at a temperature of 25-140° C. The residence time of the feedstock in the pressure reactor can be 0.5-120 minutes. Unless otherwise specified, the term “residence time” in this specification is to be understood as the time between the introduction or entry of the feedstock into, for example, a pressure reactor and the exit or discharge of the feedstock therefrom.

[0087] Due to the semi-hydrolysis of the wood-based feedstock affected by the steam explosion treatment in the reactor, the hemicellulose present in the wood-based feedstock may be hydrolyzed or degraded into, for example, xylose oligomers and / or monomers. Hemicellulose includes polysaccharides, such as xylans, mannans and glucans. Xylans are therefore hydrolyzed into xylose, i.e., monosaccharides. In one embodiment, 87-95%, or 89-93%, or 90-92% of the xylans present in the impregnated wood-based feedstock are converted into xylose.

[0088] Thus, steam explosion of feedstock can result in the formation of an output stream. The output stream from steam explosion can be subjected to steam separation. The output stream from steam explosion can be mixed or merged with a liquid (e.g., water). The output stream from steam explosion can be mixed with a liquid to form a slurry. The liquid can be pure water or water containing C5 sugars. The water containing C5 sugars can be recycled water from an operation of separating and / or washing the portion containing solid cellulose particles before enzymatic hydrolysis. The output stream can be mixed with a liquid, and the resulting material can be mechanically homogenized to break up agglomerates. Pretreatment can include mixing the steam-treated wood-based feedstock with a liquid to form a slurry.

[0089] Thus, as a result of the pretreatment, a slurry may thus be formed. The slurry may comprise a liquid phase and a solid phase. The slurry may comprise solid cellulose particles. The slurry may be separated into a liquid portion and a portion comprising solid cellulose particles.

[0090] The method may include: separating a liquid portion and a portion containing solid cellulose particles by a solid-liquid separation process to recover the liquid portion as a carbohydrate feedstock derived from hardwood. The solid-liquid separation process may include washing. Washing is continued until the amount of soluble organic components in the portion containing solid cellulose particles is 0.5-5% by weight, or 1-4% by weight, or 1.5-3% by weight based on the total dry matter content.

[0091] The separation of the liquid portion and the portion comprising solid cellulose particles can be performed by displacement washing or countercurrent washing. Thus, the solid-liquid separation process can be selected from displacement washing and countercurrent washing.

[0092] Displacement washing, or also known as replacement washing, is a method of separating solids and liquids from each other by using a relatively small amount of washing liquid. Therefore, displacement washing can be considered as an operation that can wash solid particles with a minimum amount of washing liquid, such as water.

[0093] In countercurrent washing, the fraction containing the solid cellulose particles usually moves in the forward direction, while the washing liquid, such as water, flows in the reverse direction. Like displacement washing, countercurrent washing can also reduce the consumption of washing liquid to a great extent.

[0094] The countercurrent washing may comprise at least two solid-liquid separation steps and a dilution step with a washing solution between the steps. The washing solution may be clean water. The amount of water required may vary, depending on how many solid-liquid separation steps are performed in total, the total dry matter content in the feed to the solid-liquid separation steps and the total dry matter content in the fraction containing solid cellulose particles after each solid-liquid separation step.

[0095] The washing liquid may be fresh washing water or recycled washing water. The washing water may be fresh water, drinking water or a sugary liquid with a low sugar content. The conductivity of the washing liquid may be about 0.1 mS / cm.

[0096] In the case of displacement washing, the ratio of washing liquid to solid used may be 0.5:1-8:1 (w / w), or 0.5:1-5:1 (w / w), or 0.5:1-3:1 (w / w), or 0.5:1–2:1 (w / w). In the case of countercurrent washing, the ratio of washing liquid to solid used may be 0.5:1-8:1 (w / w), or 0.5:1-5:1 (w / w).

[0097] The progress of displacement washing and countercurrent washing can be monitored by measuring the conductivity of the liquid fraction recovered from the process. Once the conductivity of the liquid fraction is below or equal to a predetermined threshold value of 0.35 mS / cm, it can be concluded that the desired amount of C5 sugars and other soluble impurities have been removed from the fraction containing solid cellulose particles, and washing can be terminated. In one embodiment, washing is continued until the conductivity of the liquid fraction is 0.1-1.0 mS / cm or 0.2-0.5 mS / cm.

[0098] Alternatively, separation can be performed by filtration, decantation and / or by centrifugation. Filtration can be vacuum filtration, filtration based on the use of reduced pressure, filtration based on the use of excess pressure or filter press. Decantation can be repeated to improve separation.

[0099] The above separation and / or washing may include, for example, recycling of the washing liquid to concentrate the liquid fraction, ie the hardwood derived carbohydrate feedstock, if desired to provide the hardwood derived carbohydrate feedstock in the form of a liquid fraction having a total dry matter content of 7-13 wt%.

[0100] Thus, a method for producing a hardwood derived carbohydrate composition comprises the step of providing a hardwood derived carbohydrate feedstock in the form of a liquid fraction having a total dry matter content of 7-13 wt%.

[0101] Based on the total dry matter content of the carbohydrate feedstock derived from hardwood, the feedstock may contain 50-80% by weight of monomeric sugars. The amount of monomeric xylose in the feedstock may be 40-60% by weight. In the carbohydrate feedstock derived from hardwood, the weight ratio of monomeric glucose to monomeric xylose may be 0.067-0.2. Based on the total dry matter content of the carbohydrate feedstock derived from hardwood, the feedstock may contain 5-15% by weight of soluble lignin. Based on the total dry matter content of the carbohydrate feedstock derived from hardwood, the feedstock may contain 6-30% by weight of organic impurities. Based on the total dry matter content of the carbohydrate feedstock derived from hardwood, the feedstock may contain 5-20% by weight of carboxylic acids. Based on the total dry matter content of the carbohydrate feedstock derived from hardwood, the feedstock may contain 0-6% by weight, or 0.1-3% by weight, or 0.2-2% by weight, or 0.3-1% by weight of inorganic impurities.

[0102] The pH of the hardwood derived carbohydrate feedstock is then adjusted to 2.2-3.0. The pH can be adjusted using, for example, sodium hydroxide, potassium hydroxide, etc. Adjusting the pH prior to evaporation also has the added benefit of reducing or preventing precipitation of lignin that may be present in the feedstock during the evaporation process. In addition, adjusting the pH also ensures that organic acids that may be present in the feedstock are removed with the condensate.

[0103] The feedstock having a pH of 2.2-3.0 may then be evaporated. The evaporation may be performed in a vacuum using steam at a temperature of 75-85°C, or 77-83°C, or about 79°C. During the evaporation, the temperature of the feedstock may be 65-70°C, or 67-69°C.

[0104] After evaporation, the pH of the evaporated feed is adjusted to 5.5-7.5. This pH adjustment also helps in efficient chromatography.

[0105] The resin used in the chromatography process is a strong acid cation exchange resin. The strong acid cation exchange resin is a beaded product that has sulfonic acid groups in a cross-linked styrene framework. The strong acid cation exchange resin can be Na + Form or H + In one embodiment, the strong acid cation exchange resin is Na + Form. + The strong acid cation exchange resin in the form of may have a polystyrene structure with divinylbenzene groups cross-linked thereto. The average particle size may be 350 μm. Sulfonic acid may be used as a functional group.

[0106] In one embodiment, the chromatography is performed using simulated moving bed (SMB) chromatography or any variant of simulated moving bed chromatography. Intermittent simulated moving bed chromatography (ISMB) and smart simulated moving bed chromatography (SSMB) can be used as examples of such variants.

[0107] In one embodiment, the chromatography is performed as a single stage process. That is, the hardwood derived carbohydrate feedstock is chromatographed once before proceeding to the next step. The single stage chromatography can be performed using one or more continuous chromatography columns. The flow rate through the one or more chromatography columns can be 1-3 bed volumes per hour. Water can be used as the eluent.

[0108] Chromatographic treatment can also, for example, reduce the color caused by the presence of lignin, reduce the amount of organic salts, inorganic salts and metals in the carbohydrate composition derived from hardwood.The purpose of chromatography is not to fractionate or separate the sugars in the feed, but to remove unwanted components.

[0109] The methods disclosed in this specification have the additional utility of providing a carbohydrate composition derived from hardwood having a high content of monomeric sugars, particularly monomeric xylose. The carbohydrate composition derived from hardwood has the additional utility of meeting the purity requirements required for further use in sweetener production processes such as xylitol. The carbohydrate composition derived from hardwood also has the additional utility of being useful for the production of biogas.

[0110] Example

[0111] Embodiments of the present disclosure will now be described in detail.

[0112] The following description discloses some embodiments in such detail that those skilled in the art can utilize methods based on the present disclosure. Not all steps of the embodiments are discussed in detail, because many steps will be obvious to those skilled in the art based on the present disclosure.

[0113] Example 1 - Production of Hardwood-Derived Carbohydrate Compositions

[0114] In this example, a hardwood derived carbohydrate composition was prepared.

[0115] First, a wood-based feedstock comprising beech wood chips is provided. The wood-based feedstock is then pretreated in the following manner:

[0116] The wood-based feedstock was pre-steamed. The pre-steaming of the wood-based feedstock was carried out at atmospheric pressure using steam at a temperature of 100°C for 180 minutes. The pre-steamed feedstock was then impregnated with dilute sulfuric acid having a concentration of 1.32% w / w (weight %) and a temperature of 92°C. The pre-steamed wood-based feedstock was subjected to the impregnation solution for 30 minutes. The acid-impregnated wood-based feedstock was then subjected to steam explosion. The steam explosion was carried out by treating the impregnated wood-based feedstock with steam at a temperature of 191°C at atmospheric pressure and then subjecting the wood-based feedstock to a sudden, explosive decompression. The amount of sulfuric acid in the steam explosion reactor was 0.33% by weight, based on the total dry matter content of the wood-based feedstock. When determining the amount of sulfuric acid, the sulfur content of the wood was 0.02% by weight, based on the total dry matter content of the wood used.

[0117] In the pretreatment, the conversion of xylan to xylose in the wood-based feedstock was 91% and the ratio of dissolved glucose to dissolved xylose was 0.14 as determined by HPLC-RI, as described in detail below. The steam-treated wood-based feedstock was then mixed with water in a mixing vessel.

[0118] As a result of the above-mentioned pretreatment step, a slurry is formed. The slurry comprises a liquid portion and a portion comprising solid cellulose particles. The slurry is then separated into a liquid portion and a portion comprising solid cellulose particles by a solid-liquid separation process, which is a countercurrent washing in this embodiment. Countercurrent washing is continued until the amount of soluble components in the portion comprising solid cellulose particles is 2.0 weight % based on the total dry matter content. The dry solid content of the portion comprising solid cellulose particles after washing is 32 weight %. The total dry matter content of the liquid portion is 9 weight %.

[0119] The recovered liquid portion is used as the hardwood-derived carbohydrate feedstock. The pH of the hardwood-derived carbohydrate feedstock is then adjusted to 2.9 using sodium hydroxide (NaOH). The feedstock is then evaporated until the total dry matter content of the feedstock is about 50% by weight. The temperature of the steam used for evaporation is 79° C. under vacuum. The temperature of the feedstock during evaporation is 68° C.

[0120] The pH of the evaporated feed was then adjusted to 6.0 using sodium hydroxide (NaOH).

[0121] The pH adjusted feed was then chromatographed on a simulated moving bed (SMB) chromatograph using Na + The chromatographic treatment was performed by using a chromatographic column system at a flow rate of two bed volumes per hour through the chromatographic column.

[0122] The regeneration solution was run after every 30 bed volumes. The cation exchange resin was regenerated using a 5% sulfuric acid solution. After regeneration, the resin was rinsed with water.

[0123] The simulated moving bed chromatography treated feedstock was then evaporated until the total dry matter content of the feedstock was 65 wt%. The temperature of the steam used for evaporation was 79° C. under vacuum. As a result, a carbohydrate composition derived from hardwood was formed.

[0124] The recovered carbohydrate composition from hardwood was analyzed by HPLC-RI using a Waters e2695 Alliance separation module, a Waters 2998 photodiode array, and a Waters 2414 refractive index detector. Separation was achieved using a Bio-Rad Aminex HPX-87 column with dimensions of 300 mm × 7.8 mm, equipped with a Micro-Guard Deashing and a Carbo-P guard column in series. Ultrapure water was used as the eluent.

[0125] The amount of oligosaccharides in the sample is determined by hydrolyzing the oligosaccharides into monomeric sugars using acid hydrolysis, analyzing the acid hydrolyzed sample using HPLC-RI and comparing the results with the results of the sample that was not subjected to hydrolysis. The amount of oligosaccharides is calculated by subtracting the amount of monomeric sugars in the untreated sample.

[0126] The results are shown in the following table:

[0127]

[0128]

[0129] Weight % = weight % based on total dry matter content

[0130] *This is the total amount of lignin (UV-205) and organic impurities (organic acids + furans + aldehydes) measured by HPLC-PDA, and the total amount of formate, acetate and lactate measured by IC.

[0131] **Metal ions are measured by ICP-OES, chloride, sulfate and phosphate are measured by IC.

[0132] It is obvious to a person skilled in the art that, as technology develops, the basic idea can be implemented in various ways. Therefore, the implementations are not limited to the above-described embodiments; instead, they may vary within the scope of the claims.

[0133] The embodiments described above can be used in any combination with each other. Several embodiments can be combined together to form further embodiments. The hardwood-derived carbohydrate composition, method or use disclosed herein may include at least one embodiment described above. It will be understood that the above benefits and advantages may relate to one embodiment, or may relate to several embodiments. The embodiments of the present invention are not limited to embodiments that can solve any or all of the problems described, nor are they limited to embodiments that have any or all of the benefits and advantages described. It should be further understood that the "one" item mentioned refers to one or more items therein. The term "comprising" used in this specification includes the features or behaviors thereafter, without excluding the presence of one or more other features or behaviors.

Claims

1. A carbohydrate composition derived from hardwood, wherein: The hardwood derived carbohydrate composition comprises 75-97 wt. % monomeric sugars based on the total dry matter content of the carbohydrate composition, wherein the monomeric sugars include monomeric xylose, the amount of monomeric xylose in the carbohydrate composition is 55-75 wt. % based on the total dry matter content of the carbohydrate composition, wherein the carbonyl content of the carbohydrate composition is 4000–9000 μg / g based on the total dry matter content of the carbohydrate composition.

2. The hardwood-derived carbohydrate composition of claim 1, wherein: The amount of monomeric xylose in the carbohydrate composition is 57-72 wt. %, based on the total dry matter content of the carbohydrate composition.

3. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The carbonyl content of the carbohydrate composition is 4250-8500 μg / g, or 4500-8000 μg / g, based on the total dry matter content of the carbohydrate composition.

4. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The ICUMSA color value of the carbohydrate composition is 17500-45000 IU, or 20000-40000 IU, or 22500-37500 IU.

5. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The carbohydrate composition comprises 1.5-4.5 wt%, or 1.75-4.0 wt%, or 2.0-3.5 wt% soluble lignin, based on the total dry matter content of the carbohydrate composition.

6. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The conductivity of a 65% aqueous solution of the carbohydrate composition when measured according to SFS-EN 27888 is 0.1-1.5 mS / cm, or 0.15-1.0 mS / cm, or 0.2-0.75 mS / cm.

7. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The carbohydrate composition comprises 0.5-5 wt. %, or 0.75-4.5 wt. %, or 1.0-4.0 wt. % rhamnose, based on the total dry matter content of the carbohydrate composition.

8. A hardwood derived carbohydrate composition as claimed in any one of the preceding claims, wherein The carbohydrate composition comprises 0.4-4 wt. %, or 0.5-3.5 wt. %, or 0.6-3.0 wt. % of carboxylic acid, based on the total dry matter content of the carbohydrate composition.

9. A method for producing a hardwood derived carbohydrate composition according to any one of claims 1 to 8, wherein: The method comprises: i) providing a carbohydrate feedstock derived from hardwood in the form of a liquid fraction having a total dry matter content of 7-13 wt.%; ii) adjusting the pH of the hardwood derived carbohydrate feedstock to 2.2-3.0; iii) evaporating the feed having a pH of 2.2-3.0 until the total dry matter content of the feed is 45-55 wt. %; iv) adjusting the pH of the evaporated feed to 5.5-7.5; v) chromatographing the feed at a pH of 5.5-7.5 using a strong acid cation exchange resin; and vi) evaporating the chromatographically treated feedstock until the total dry matter content of the feedstock is 60-70 wt. %; Thereby producing a hardwood derived carbohydrate composition.

10. Use of a hardwood derived carbohydrate composition according to any one of claims 1 to 8 for producing a sweetener or biogas.

11. The use according to claim 9, wherein The production of the sweetener involves crystallizing xylose from a carbohydrate composition derived from hardwood.

Images