Method for purifying hemicellulose sugars from a prehydrolysis liquor of a plant fiber feedstock

Abstract

The application discloses a method for purifying hemicellulose sugar in a plant fiber raw material pre-hydrolysate, and belongs to the field of biomass refining. The method comprises the following steps: S1, adding molybdate and hydrogen peroxide to the plant fiber pre-hydrolysate for oxidative degradation treatment; S2, adding cross-linked polyvinylpyrrolidone to the pre-hydrolysate after the oxidative degradation treatment, removing the cross-linked polyvinylpyrrolidone adsorbed with lignin after adsorption treatment, and obtaining a preliminarily purified pre-hydrolysate; and S3, adding activated carbon to the preliminarily purified pre-hydrolysate, removing the activated carbon adsorbed with lignin after adsorption treatment, and obtaining a purified hemicellulose sugar solution. Compared with the prior art, the method can realize efficient removal of lignin, and greatly reduce the sugar loss rate, and has good popularization and application value.

Description

Technical Field

[0001] This invention relates to the field of biomass refining, specifically providing a method for purifying hemicellulose sugars in pre-hydrolyzed plant fiber raw materials. Background Technology

[0002] Pre-hydrolysis-sulfate cooking is currently the main method for producing dissolving pulp worldwide. Pre-hydrolysis primarily employs autohydrolysis (including high-temperature pre-hydrolysis with water or steam) or dilute acid hydrolysis. The main function of pre-hydrolysis is to remove hemicellulose from the raw material. During pre-hydrolysis, most of the hemicellulose in the cellulose raw material dissolves into the pre-hydrolysate in the form of oligosaccharides and monosaccharides. A smaller portion of lignin and carbohydrate degradation products such as acetic acid and furfural also enter the pre-hydrolysate. Hemicellulose sugars are important biomass resources and crucial raw materials for producing platform chemicals, materials, and biomass energy. To better utilize the hemicellulose sugars in the pre-hydrolysate, it is necessary to effectively remove impurities, primarily lignin (including colloidal lignin and dissolved lignin). This is because lignin, besides affecting the purity of hemicellulose sugars, can cause membrane blockage during subsequent ultrafiltration or nanofiltration concentration and removal of small molecule impurities, reducing production efficiency and membrane lifespan. When using sugars from the pre-hydrolysate for fermentation to produce biomass fuels, lignin impurities can be toxic to the microorganisms, affecting sugar fermentation. While numerous studies have been conducted on the removal of lignin from pre-hydrolyzed solutions, including acidification treatment, flocculation with polymers such as polypropylene, polyethyleneimine, polyethylene oxide, chitosan, and polyaluminum chloride, adsorption treatment with activated carbon, ion exchange resins, and quicklime, organic solvent extraction, and laccase or horseradish peroxidase-catalyzed polymerization, a combination of several treatment methods is generally employed to improve lignin removal efficiency. Many patented technologies exist for the treatment and removal of lignin from pre-hydrolyzed solutions.

[0003] Invention patent 2022109527433 discloses a method for high-purity separation and purification of dissolved sugars in lignocellulose prehydrolysate. The method involves first adjusting the pH of the prehydrolysate to 4.5-5.5, then adding xylanase for enzymatic hydrolysis. After enzyme treatment, the enzyme is inactivated in a boiling water bath, followed by cooling and centrifugation. The resulting supernatant is then subjected to adsorption treatment with activated carbon, followed by centrifugation to obtain a sugar solution as the supernatant.

[0004] Invention patent 2022100883714 discloses a method for purifying sugars in pre-hydrolyzed hardwood pulp. First, the pre-hydrolyzed liquid is treated with manganese peroxidase. After enzyme treatment, it is then treated with adsorbent materials such as activated carbon. Finally, the activated carbon and other adsorbent materials are separated by filtration to obtain purified pre-hydrolyzed liquid.

[0005] Invention patent 2020106005254 discloses a method for purifying sugars in plant fiber pre-hydrolysate using metal-organic frameworks. This method involves preparing ZIF-8 nanoparticles, using these nanoparticles to adsorb the pre-hydrolysate, followed by centrifugation to remove dissolved lignin, organic acids, and furfural, thereby purifying the degraded sugars in the plant fiber pre-hydrolysate.

[0006] Invention patent 2019101615398 discloses a method for removing lignin from hot water pre-hydrolyzed solution. The method involves centrifuging the hot water pre-hydrolyzed solution, then treating it with ultrasound in conjunction with calcium hydroxide, followed by laccase treatment. The hydrolysate treated with laccase is then treated with an ion exchange column to obtain a purified sugar solution.

[0007] Invention patent 2018111608127 discloses a method for separating and purifying hemicellulose in the pre-hydrolysate of the dissolving pulp pretreatment section. The method first adjusts the pH of the pre-hydrolysate to 1.5-2.5 with acid, centrifuges it, treats it with non-ionic polymer, centrifuges it again, alkalizes the supernatant to pH 6-10, centrifuges it again, mixes the supernatant with ethanol, lets it stand, collects the precipitate, and dries it to obtain hemicellulose.

[0008] Although many methods exist for removing lignin from pre-hydrolysate and purifying hemicellulose sugars, these methods suffer from low efficiency, significant hemicellulose loss, complex processes, or poor economic feasibility due to lignin's complex chemical structure, uneven molecular weight distribution, and numerous functional groups. This hinders the effective utilization of hemicellulose sugars, an important biomass resource, in the pre-hydrolysate. Therefore, to purify hemicellulose sugars from pre-hydrolysate, it is necessary to develop a pre-hydrolysate treatment method that is simple in process, achieves high lignin removal rates, and minimizes sugar loss. Summary of the Invention

[0009] This invention addresses the shortcomings of the prior art by providing a method for purifying hemicellulose sugars in pre-hydrolyzed plant fiber raw materials, which can significantly reduce sugar loss during the process while improving the removal rate of lignin.

[0010] The technical solution adopted by this invention to solve its technical problem is: a method for purifying hemicellulose sugars in pre-hydrolyzed plant fiber raw materials, comprising: S1. adding molybdate and hydrogen peroxide to the pre-hydrolyzed plant fiber for oxidative degradation treatment; S2. adding cross-linked polyvinylpyrrolidone to the pre-hydrolyzed solution after oxidative degradation treatment, and removing the cross-linked polyvinylpyrrolidone adsorbed with lignin after adsorption treatment to obtain a pre-purified pre-hydrolyzed solution; S3. adding activated carbon to the pre-purified pre-hydrolyzed solution, and removing the activated carbon adsorbed with lignin after adsorption treatment to obtain a purified hemicellulose sugar solution.

[0011] In a further technical solution, the amount of molybdate used in step S1 is 0.05~1.0 g / L of prehydrolysate, and the amount of hydrogen peroxide used is 1.0~10 g / L of prehydrolysate.

[0012] In a further technical solution, the oxidation degradation treatment temperature in step S1 is 60~95℃, the treatment time is 0.5~10 h, and the pH is 2.0~6.0.

[0013] In a further technical solution, the amount of cross-linked polyvinylpyrrolidone used in step S2 is 2.0~20 g / L of prehydrolysate.

[0014] In a further technical solution, the temperature of the cross-linked polyvinylpyrrolidone adsorption treatment in step S2 is 20~90℃ and the time is 30~90 min.

[0015] In a further technical solution, the amount of activated carbon added in step S3 is 10~100 g / L of pre-hydrolyzed solution.

[0016] In a further technical solution, the temperature for activated carbon adsorption treatment is 20~70℃, and the time is 30~180 min.

[0017] In a further technical solution, the plant fiber raw material pre-hydrolyzed solution is a pre-hydrolyzed solution obtained by pre-hydrolyzing the plant fiber raw material with water, water vapor or dilute acid.

[0018] Compared with existing technologies, the purification method of hemicellulose sugar in the pre-hydrolyzed solution of plant fiber raw materials of the present invention achieves efficient removal of lignin by modifying lignin and treating it with different adsorbents to gradually remove lignin with different structures, and minimizes the sugar loss rate. Detailed Implementation

[0019] This invention relates to a method for purifying hemicellulose sugars in a pre-hydrolyzed solution of plant fiber raw materials, comprising: S1. adding molybdate and hydrogen peroxide to the pre-hydrolyzed solution of plant fiber for oxidative degradation treatment; S2. adding cross-linked polyvinylpyrrolidone to the pre-hydrolyzed solution after oxidative degradation treatment, and removing the cross-linked polyvinylpyrrolidone adsorbed with larger molecular weight lignin after adsorption treatment to obtain a pre-purified pre-hydrolyzed solution; S3. adding activated carbon to the pre-purified pre-hydrolyzed solution, and removing the activated carbon adsorbed with small molecular weight lignin after adsorption treatment to obtain a purified hemicellulose sugar solution.

[0020] As described above, this invention first employs molybdate and hydrogen peroxide to selectively oxidize and degrade lignin, simultaneously inducing a ring-opening reaction in lignin to generate a large number of lignin molecules with carboxyl and phenolic hydroxyl groups. Then, cross-linked polyvinylpyrrolidone (XLPE) is used for adsorption treatment. The higher molecular weight lignin with carboxyl and phenolic hydroxyl groups more easily complexes with the XLPE surface and is thus removed. The applicant has found that XLPE exhibits high selectivity for lignin adsorption but low adsorption for sugars. Furthermore, XLPE is insoluble in water and common solvents, allowing for easy separation from solutions and recycling after solvent elution. Activated carbon primarily removes impurities through pore adsorption, and it is more effective at adsorbing low molecular weight lignin. Therefore, the low molecular weight lignin remaining after XLPE adsorption can be effectively removed by activated carbon adsorption, resulting in a purified hemicellulose sugar solution. The entire process efficiently removes lignin while significantly reducing sugar loss during treatment.

[0021] Next, the various steps in the purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to the present invention will be described in more detail.

[0022] First, step S1. Add molybdate and hydrogen peroxide to the pre-hydrolyzed plant fiber solution for oxidative degradation treatment.

[0023] In one embodiment of the present invention, the plant fiber prehydrolysate can be a prehydrolysate obtained by prehydrolyzing plant fiber raw materials with water, water vapor or dilute acid, and the lignin content in the prehydrolysate is generally 3~10g / L.

[0024] The plant fiber raw materials are selected from coniferous wood, broadleaf wood, bamboo, wheat straw, rice straw, corn stalks, and / or reeds. The coniferous wood is selected from one or a mixture of two of Masson pine, larch, or spruce. The broadleaf wood is selected from one or a mixture of two of poplar, birch, and eucalyptus.

[0025] In one embodiment of the present invention, based on a lignin content of 3-10 g / L in the pre-hydrolyzed solution, the amount of molybdate used is 0.05-1.0 g / L of the pre-hydrolyzed solution, and the amount of hydrogen peroxide used is 1.0-10 g / L of the pre-hydrolyzed solution. Preferably, the amount of molybdate used is 0.1-0.5 g / L of the pre-hydrolyzed solution, and the amount of hydrogen peroxide used is 2.0-6.0 g / L of the pre-hydrolyzed solution. More preferably, the amount of molybdate used is 0.1-0.2 g / L of the pre-hydrolyzed solution, and the amount of hydrogen peroxide used is 2.0-5.0 g / L of the pre-hydrolyzed solution. Within the ranges described above, excellent oxidative degradation treatment effect can be ensured. The molybdate can be sodium molybdate or ammonium molybdate.

[0026] In one embodiment of the present invention, the oxidative degradation treatment temperature is 60~95℃, the treatment time is 0.5~10h, and the pH is 2.0~6.0; preferred treatment conditions are a treatment temperature of 70~90℃, a treatment time of 0.5~4h, and a pH of 2.5~4.5. Under the above treatment conditions, excellent oxidative degradation treatment efficiency and effect can be ensured.

[0027] As a specific example, when using dilute acid to pre-hydrolyze plant fiber raw materials to obtain pre-hydrolyzed solution, the pH is adjusted to 2.5~4.5 using an alkali (such as sodium hydroxide).

[0028] Next, step S2 can be performed, in which cross-linked polyvinylpyrrolidone is added to the pre-hydrolysate after oxidative degradation treatment. After adsorption treatment, the cross-linked polyvinylpyrrolidone adsorbed with large molecular weight lignin is removed, and a pre-purified pre-hydrolysate is obtained.

[0029] In one embodiment of the present invention, the amount of cross-linked polyvinylpyrrolidone added to the pre-hydrolysate after oxidative degradation treatment is 2.0~20 g / L of pre-hydrolysate, preferably 8.0~20 g / L. Within this range, a high lignin removal rate and low sugar loss can be ensured, i.e., high lignin removal selectivity.

[0030] In one embodiment of the present invention, the adsorption treatment conditions for cross-linked polyvinylpyrrolidone can be a temperature of 20~90°C and a time of 30~90 min; the preferred treatment conditions are a temperature of 20~60°C and a time of 30~60 min.

[0031] In one embodiment of the present invention, after treatment with cross-linked polyvinylpyrrolidone, the pre-hydrolyzed solution is allowed to stand or centrifuged to remove the precipitate, wherein the precipitate is cross-linked polyvinylpyrrolidone that has adsorbed a large molecular weight lignin.

[0032] The mixture after adsorption treatment can be allowed to stand for 6-20 hours to remove the precipitate at the bottom, and the supernatant can be used as a pre-hydrolyzed solution for preliminary purification; or the mixture after adsorption treatment can be centrifuged at 2000-4000 rpm to remove the precipitate and obtain a pre-hydrolyzed solution for preliminary purification.

[0033] Next, step S3 can be performed, where activated carbon is added to the pre-hydrolyzed solution that has been pre-purified. After adsorption treatment, the activated carbon that has adsorbed small molecule lignin is removed, and a purified hemicellulose sugar solution is obtained.

[0034] In one embodiment of the present invention, the amount of activated carbon added to the pre-hydrolyzed solution is 10-100 g / L, preferably 30-60 g / L. Within this range, a high lignin removal rate and low sugar loss can be ensured.

[0035] In one embodiment of the present invention, the treatment conditions for adsorption with activated carbon can be a temperature of 20-70°C and a time of 30-180 min, with preferred conditions being a temperature of 20-50°C and a time of 60-90 min. Within this range, a high lignin removal rate and low sugar loss can be ensured.

[0036] In one embodiment of the present invention, after activated carbon treatment, the pre-hydrolyzed solution is allowed to stand or centrifuged to remove the precipitate, wherein the precipitate is activated carbon that has adsorbed low molecular weight lignin.

[0037] The mixture after adsorption treatment can be allowed to stand for 6-20 hours to remove the precipitate at the bottom, and the supernatant can be the purified hemicellulose sugar solution; or the mixture after adsorption treatment can be centrifuged at 2000-4000 rpm to remove the precipitate and obtain the purified hemicellulose sugar solution.

[0038] Next, the purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials of the present invention will be described in more detail through examples. However, the following examples are only for reference in providing a detailed description of the present invention, and the present invention is not limited thereto, but can be implemented in various forms.

[0039] Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in describing this application is for the purpose of effectively illustrating specific embodiments only and is not intended to limit the scope of the invention.

[0040] Furthermore, the unit for additives not explicitly stated in this specification may be by weight.

[0041] Terminology Explanation: Sugar loss rate: The percentage of sugar reduction during pre-hydrolysate treatment relative to the original sugar content in the pre-hydrolysate, expressed as a percentage. Lignin removal rate: The percentage reduction of lignin in the pre-hydrolysate before and after treatment.

[0042] Example 1

[0043] The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials in this embodiment includes the following steps: S1. The pre-hydrolysate obtained after steam pre-hydrolysis of poplar wood had a sugar content of 17.2 g / L and a lignin content of 5.83 g / L. The pre-hydrolysate was treated with sodium molybdate and hydrogen peroxide under the following conditions: sodium molybdate dosage 0.1 g / L, hydrogen peroxide dosage 3.0 g / L, treatment temperature 70℃, treatment time 60 min, and pH not adjusted (3.6). S2. Add cross-linked polyvinylpyrrolidone to the pre-hydrolyzed solution after sodium molybdate / hydrogen peroxide treatment for adsorption treatment. The amount of cross-linked polyvinylpyrrolidone is 10 g / L, the treatment temperature is room temperature, the treatment time is 30 min, the pH is not adjusted (about 3.5), and after cross-linked polyvinylpyrrolidone treatment, centrifuge at 2000 rpm for 15 min and pour off the supernatant. S3. The supernatant obtained in step S2 is added to activated carbon for adsorption treatment. The activated carbon adsorption treatment is carried out in a shaking incubator. The activated carbon dosage is 30 g / L of pre-hydrolyzed solution, the pH is not adjusted, the treatment temperature is 40℃, and the treatment time is 60 min. After adsorption, the mixture is centrifuged at 2000 rpm for 15 min, and the supernatant is poured off as the purified hemicellulose sugar solution.

[0044] After the above steps, the lignin removal rate of the pre-hydrolyzed solution was 72.3%, and the sugar loss rate was 15.2%.

[0045] Comparative Example 1: The pre-hydrolysate obtained after pre-hydrolyzing poplar wood by steam was treated with activated carbon only, and the treatment conditions were the same as step S3 in Example 1.

[0046] After treatment with control example 1, the lignin removal rate was 27.9%, while the sugar loss rate in the hydrolysate was 31.2%.

[0047] Example 2

[0048] The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials in this embodiment includes the following steps: S1. The pre-hydrolysate obtained after steam pre-hydrolysis of eucalyptus wood had a sugar content of 21.9 g / L and a lignin content of 6.22 g / L. The pre-hydrolysate was treated with sodium molybdate and hydrogen peroxide under the following conditions: sodium molybdate dosage 0.2 g / L, hydrogen peroxide dosage 5.0 g / L, treatment temperature 90℃, treatment time 60 min, and pH not adjusted (3.4). S2. Add cross-linked polyvinylpyrrolidone to the pre-hydrolyzed solution after sodium molybdate / hydrogen peroxide treatment for adsorption treatment. The amount of cross-linked polyvinylpyrrolidone is 12 g / L, the treatment temperature is room temperature, the time is 30 min, and the pH is not adjusted (about 3.5). After cross-linked polyvinylpyrrolidone treatment, centrifuge at 2000 rpm for 15 min and pour off the supernatant. S3. The supernatant obtained in step S2 is added to activated carbon for adsorption treatment. The activated carbon adsorption treatment is carried out in a shaking incubator. The activated carbon dosage is 40 g / L of pre-hydrolyzed solution. The pH is not adjusted. The treatment temperature is room temperature, and the treatment time is 60 min. After adsorption, the supernatant is centrifuged at 2000 rpm for 15 min, and the supernatant is poured off as the purified hemicellulose sugar solution.

[0049] After the above steps, the lignin removal rate of the pre-hydrolyzed solution was 74.5%, and the sugar loss rate was 15.4%.

[0050] Comparative Example 21: The pre-hydrolysate obtained after steam pre-hydrolysis of eucalyptus was treated with activated carbon only, and the treatment conditions were the same as step S3 of Example 2.

[0051] After treatment with control example 21, the lignin removal rate was 31.6%, and the sugar loss rate in the hydrolysate was 29.8%.

[0052] Compare with Example 22: The pre-hydrolysate obtained after eucalyptus steam pre-hydrolysis was treated with activated carbon only. Except that the amount of activated carbon used was 60 g / L of pre-hydrolysate, the treatment conditions were the same as step S3 of Example 2.

[0053] After treatment with control example 22, the lignin removal rate was 40.0%, and the sugar loss rate in the hydrolysate was 44.2%.

[0054] Compare with Example 23 The pre-hydrolysate obtained after eucalyptus steam pre-hydrolysis was degraded by sodium molybdate and hydrogen peroxide, and then directly subjected to activated carbon adsorption treatment. The treatment conditions for oxidative degradation treatment and activated carbon adsorption treatment were the same as those in steps S1 and S3 of Example 2.

[0055] After treatment with control example 23, the lignin removal rate was 61.4% and the sugar loss rate was 25.5%.

[0056] Example 3

[0057] A method for purifying hemicellulose sugars in a pre-hydrolyzed solution of plant fiber raw materials, comprising the following steps: S1. The hydrolysate from wheat straw hydrolyzed with dilute sulfuric acid had a sugar content of 15.6 g / L and a lignin concentration of 4.35 g / L. The pre-hydrolysate was treated with sodium molybdate and hydrogen peroxide under the following conditions: sodium molybdate dosage 0.15 g / L, hydrogen peroxide dosage 2.0 g / L, treatment temperature 80℃, treatment time 30 min, and pH adjusted to 3.0 with sodium hydroxide. S2. Add cross-linked polyvinylpyrrolidone to the pre-hydrolyzed solution after sodium molybdate / hydrogen peroxide treatment for adsorption treatment. The amount of cross-linked polyvinylpyrrolidone is 8 g / L, the treatment temperature is 60℃, the time is 30 min, and the pH is not adjusted (about 2.8). After cross-linked polyvinylpyrrolidone treatment, let it stand for 12 h and pour off the supernatant. S3. The supernatant obtained in step S2 is added to activated carbon for adsorption treatment. The activated carbon adsorption treatment is carried out in a shaking incubator. The activated carbon dosage is 30 g / L of pre-hydrolyzed solution, the pH is not adjusted, the treatment temperature is 40℃, and the time is 90 min. After adsorption, the mixture is centrifuged at 2000 rpm for 15 min, and the supernatant is poured off as the purified hemicellulose sugar solution.

[0058] After the above steps, the lignin removal rate of the pre-hydrolyzed solution was 73.1%, and the sugar loss rate was 12.5%.

[0059] Compare with Example 31: The pre-hydrolysate after the dilute sulfuric acid hydrolysis of wheat straw was treated with activated carbon only. Except that the amount of activated carbon used was 50 g / L of the pre-hydrolysate, the treatment conditions were the same as step S3 of Example 3.

[0060] After treatment with control example 31, the lignin removal rate was 39.5%, and the sugar loss rate in the hydrolysate was 30.1%.

[0061] Compare with Example 32: The pre-hydrolyzed solution of wheat straw after dilute sulfuric acid hydrolysis is not treated with sodium molybdate / hydrogen peroxide in step S1, but is directly subjected to adsorption treatment with cross-linked polyvinylpyrrolidone and activated carbon in sequence, and the treatment conditions are the same as those in steps S2 and S3 of Example 3.

[0062] After treatment with control example 32, the lignin removal rate was 45.8%, while the sugar loss rate was 22.5%.

[0063] Example 4 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 1 is basically the same, except that: In step S1, the amount of sodium molybdate used is 0.2 g / L.

[0064] The lignin removal rate of the pre-hydrolysate treated in Example 4 was 74.5%, and the sugar loss rate was 15.0%.

[0065] Compare with Example 41: The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 4 is basically the same, except that: In step S1, sodium molybdate is not added; hydrogen peroxide is used to oxidize and degrade the prehydrolysate. The amount of hydrogen peroxide used is 3.0 g / L of the prehydrolysate.

[0066] After treatment with control example 41, the lignin removal rate was 47.2%, while the sugar loss rate was 24.5%.

[0067] Compare with column 42: The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 4 is basically the same, except that: In step S1, sodium molybdate is not added; hydrogen peroxide is used to oxidize and degrade the prehydrolysate. The amount of hydrogen peroxide used is 5.0 g / L of the prehydrolysate.

[0068] After treatment with control example 42, the lignin removal rate was 51.5%, while the sugar loss rate was 23.3%.

[0069] Compare with column 43: The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 4 is basically the same, except that: In step S1, no hydrogen peroxide is added; only sodium molybdate is used to oxidize and degrade the prehydrolysate. The amount of sodium molybdate used is 1.0 g / L of the prehydrolysate.

[0070] After treatment with control example 43, the lignin removal rate was 44.7%, while the sugar loss rate was 28.9%.

[0071] Compare with column 44: The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 4 is basically the same, except that: In step S1, no hydrogen peroxide is added; only sodium molybdate is used to oxidize and degrade the prehydrolysate. The amount of sodium molybdate used is 2.0 g / L of the prehydrolysate.

[0072] After treatment with control example 44, the lignin removal rate was 44.2%, while the sugar loss rate was 28.6%.

[0073] Compare with column 45: The pre-hydrolysate obtained after pre-hydrolyzing poplar wood by steam is not treated with sodium molybdate / hydrogen peroxide in step S1, but is directly subjected to adsorption treatment with cross-linked polyvinylpyrrolidone and activated carbon in sequence, and the treatment conditions are the same as those in steps S2 and S3 of Example 1.

[0074] After treatment with control example 45, the lignin removal rate was 45.0%, while the sugar loss rate was 24.2%.

[0075] Example 5 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 1 is basically the same, except that: In step S2, the amount of cross-linked polyvinylpyrrolidone added is 15 g / L.

[0076] The lignin removal rate of the pre-hydrolysate treated in Example 5 was 73.9%, and the sugar loss rate was 15.8%.

[0077] Example 6 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 1 is basically the same, except that: In step S2, the amount of cross-linked polyvinylpyrrolidone used is 20 g / L, and the treatment temperature is 60℃.

[0078] The lignin removal rate of the pre-hydrolysate treated in Example 6 was 74.7%, and the sugar loss rate was 16.1%.

[0079] Example 7 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 3 is basically the same, except that: In step S1, the pre-hydrolysate obtained after acid hydrolysis of pine wood (sugar content 18.4 g / L, lignin concentration 7.01 g / L) is used instead of the hydrolysate obtained after dilute sulfuric acid hydrolysis of wheat straw. In step S1, the amount of hydrogen peroxide used is 5 g / L.

[0080] The lignin removal rate of the pre-hydrolysate treated in Example 7 was 71.6%, and the sugar loss rate was 16.7%.

[0081] Example 8 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 1 is basically the same, except that: In step S1, the pre-hydrolysate of bamboo (sugar content of 16.5 g / L and lignin concentration of 6.06 g / L) is used instead of the pre-hydrolysate of poplar wood after steam pre-hydrolyzing.

[0082] The lignin removal rate of the pre-hydrolysate treated in Example 8 was 73.1%, and the sugar loss rate was 15.5%.

[0083] Example 9 The purification method for hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials described in Example 1 is basically the same, except that: In step S1, the pre-hydrolysate obtained from the steam pre-hydrolysis of reeds (sugar content of 14.9 g / L and lignin concentration of 5.05 g / L) is used instead of the pre-hydrolysate obtained from the steam pre-hydrolysis of poplar.

[0084] The lignin removal rate of the pre-hydrolyzed solution treated in Example 9 was 73.4%, and the sugar loss rate was 14.1%.

Claims

1. A method for purifying hemicellulose sugars from pre-hydrolyzed plant fiber raw materials, characterized in that, include: S1. Add molybdate and hydrogen peroxide to the pre-hydrolyzed plant fiber solution for oxidative degradation treatment; S2. Add cross-linked polyvinylpyrrolidone to the pre-hydrolysate after oxidative degradation treatment. After adsorption treatment, remove the cross-linked polyvinylpyrrolidone that has adsorbed lignin to obtain a pre-purified pre-hydrolysate. S3. Add activated carbon to the pre-hydrolyzed solution that has been pre-purified. After adsorption treatment, remove the activated carbon that has adsorbed lignin to obtain a purified hemicellulose sugar solution.

2. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1, characterized in that: In step S1, the amount of molybdate used is 0.05~1.0 g / L of prehydrolysate, and the amount of hydrogen peroxide used is 1.0~10 g / L of prehydrolysate.

3. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1 or 2, characterized in that: The oxidation degradation treatment in step S1 is carried out at a temperature of 60~95℃ for 0.5~10 h, with a pH of 2.0~6.

0.

4. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1, characterized in that: In step S2, the amount of cross-linked polyvinylpyrrolidone used is 2.0~20 g / L of prehydrolysate.

5. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1 or 4, characterized in that: In step S2, the temperature for cross-linked polyvinylpyrrolidone adsorption treatment is 20~90℃, and the time is 30~90 min.

6. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1, characterized in that: In step S3, the amount of activated carbon added is 10~100 g / L of pre-hydrolysate.

7. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1 or 6, characterized in that: The temperature for activated carbon adsorption treatment is 20~70℃, and the time is 30~180 min.

8. The method for purifying hemicellulose sugars in the pre-hydrolyzed solution of plant fiber raw materials according to claim 1, characterized in that: The plant fiber raw material pre-hydrolyzed solution is a pre-hydrolyzed solution obtained by pre-hydrolyzing plant fiber raw materials with water, water vapor or dilute acid.