A method for deconstructing lignocellulose to separate non-condensed lignin and saccharide compounds

Abstract

The application discloses a method for separating non-condensed lignin and saccharide compounds from deconstructed lignocellulose. The lignocellulose is used as raw material, and a high-boiling alcohol aqueous solution such as dihydric alcohol or trihydric alcohol is added into an acid molten salt hydrate as a deconstruction reaction system. The acid molten salt hydrate hydrolyzes hemicellulose and cellulose in the lignocellulose into saccharide compounds, and the high-boiling alcohol in the system acts as a lignin dissolving agent and a structure protecting agent, so that the lignin is dissolved in the high-boiling alcohol. Then, water is added to precipitate the lignin, so that the non-condensed lignin and the saccharide compounds are separated. The biomass deconstruction method can effectively promote the full-component utilization of three components of lignocellulose, and has great industrial application potential.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lignocellulose deconstruction, and particularly relates to a method for deconstructing lignocellulose to separate non-condensed lignin and saccharide compounds. BACKGROUND

[0002] Lignocellulose is mainly composed of lignin, cellulose and hemicellulose. Due to the complex chemical connection and physical coating among the three components, the three components of lignocellulose are intertwined to form a dense structure. Among them, lignin is a heterogeneous, amorphous and complex phenolic polymer with complex structure, which is formed by connecting three phenylpropane units (guaiacyl, syringyl and p-hydroxyphenyl) through C-O bonds and C-C bonds, and widely exists in the roots and stems of trees, grasses and other plants, together with cellulose and hemicellulose to form the skeletal structure of plants. Lignin is the second largest renewable resource in nature after cellulose, and is the most abundant natural polymer containing aromatic structure. The structural characteristics of lignin make it have great application potential in the fields of building, medicine, cosmetics and wastewater treatment. At the same time, lignin can also be degraded into small molecular aromatic and naphthenic compounds by breaking the linkage between the structural units, and can be used to prepare liquid fuel or high-value chemicals instead of fossil resources.

[0003] Although lignin has a wide range of applications, the separation of lignin usually needs to be carried out under harsh conditions due to the dense structure between the three components. Current lignin separation methods can be divided into three categories: one is the "alkaline treatment" strategy, that is, lignin is dissolved in water by high-temperature cooking under alkaline conditions, while hemicellulose and cellulose are separated out in solid form. For example, the papermaking pulping process is based on this separation principle. Due to the high-temperature and high-pressure cooking, the β-O-4 bond in the structure of lignin inevitably breaks and forms a firm C-C bond, resulting in lignin being difficult to degrade due to condensation, which restricts its high-value utilization. The second is the "hydrolysis" strategy, which hydrolyzes hemicellulose and cellulose into monosaccharides at a higher temperature or for a long time by acid or enzyme catalysis, and lignin is separated out as insoluble residue. For example, by acid pretreatment of wood, hemicellulose and cellulose are hydrolyzed into sugars, and lignin is separated out in solid form. Due to the high temperature or long time of the separation process, the lignin obtained also produces more serious condensation. The third is the "organic solvent dissolution" strategy, which dissolves lignin in organic solvents, ionic liquids or deep eutectic solvents (DESs) at a lower temperature for a short time, in which lignin is the soluble component and other components are insoluble substances. The separated lignin is not prone to condensation, but the extraction rate of lignin is low, in addition, the high cost of organic solvents and their negative impact on the environment make this method not suitable for industrialization, but it is often used to study the structure of lignin itself. Therefore, it is of great significance to develop a mild, clean and efficient non-condensation lignin separation technology to deconstruct the complex entanglement of the three components while maximizing the retention of their functional structures, which is of great significance for the high-value utilization of lignocellulose.

[0004] Inorganic molten salt hydrates are concentrated inorganic salt solutions in which water molecules are close to the coordination number of cations, and the concentration of the salt is between that of a concentrated salt solution and a molten salt. Inorganic molten salt hydrates have similar effects to ionic liquids in dissolving cellulose, breaking hydrogen bonds, and increasing solubility, while also having the advantages of low viscosity, low cost, and non-toxicity that ionic liquids do not have. Li et al. (Green Chem., 2016, 18, 5367-5376) reported that using acidic molten salt hydrates, cellulose and hemicellulose can be hydrolyzed into glucose and xylose in one step, and high-purity lignin can be obtained, which has the advantage of simple process. However, Li et al. (Green Chem., 2020, 22, 7989) found that acidic molten salt hydrates easily cleave the β-O-4, β-5, and β-β bonds in the lignin structure in addition to the 4-O-5 bond, and the destruction of the β-O-4 bond leads to the condensation of the lignin structure, affecting the further high-value utilization of lignin. Although Liu et al. (Green Chem., 2022, 24, 8812) and Sadula et al. (Green Chem., 2021, 23, 1200) used inorganic molten salt hydrates without acid to directly hydrolyze lignocellulose to obtain oligosaccharides and lignin residues, their processes require long reaction times at high temperatures, which also leads to the condensation of the easily broken β-O-4 bond in lignin into the difficult-to-break C-C bond, making it impossible to obtain non-condensed lignin.

[0005] High-boiling alcohol solvents, such as ethylene glycol, glycerol, and butanediol, are popular solvents for acid-catalyzed lignin extraction because they are not easily volatile, have low operating pressure, and can capture the reactive benzyl cation formed under acidic conditions by alkoxylation of the C α -OH in the lignin phenylpropane structural unit, thereby preventing the condensation of lignin. A large number of documents have reported that high-boiling alcohols such as diols or triols can effectively protect the benzyl group of lignin during acid-catalyzed treatment of hardwood and herbaceous lignocellulose, thereby effectively isolating lignin with low condensation degree. For example, Dong et al. (Green Chem., 2019, 21:2788) used a variety of high-boiling alcohols in combination with dilute sulfuric acid to extract low-condensation lignin from eucalyptus wood at 170°C. Jia et al. (Applied Mechanics and Materials, 2013, 320:429-434) used a high-boiling solvent method to isolate high-boiling alcohol lignin from pine nut shells using a 90% 1,4-butanediol solution as the solvent, and the lignin yield was up to 70%.

[0006] However, the existing technologies are difficult to achieve the deconstruction of lignocellulose while separating non-condensed lignin and sugar compounds, and therefore, how to achieve the deconstruction of lignocellulose while separating non-condensed lignin and sugar compounds through a simple and mild process is a technical problem that needs to be solved at present. SUMMARY

[0007] To solve the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds.

[0008] The method described in the present application is to hydrolyze lignocellulose in an acidic molten salt hydrate combined with a high-boiling alcohol aqueous solvent system. Using lignocellulose as raw material, add a high-boiling alcohol aqueous solution such as dihydric alcohol or trihydric alcohol as the deconstruction reaction system in the acidic molten salt hydrate. The acidic molten salt hydrate first hydrolyzes hemicellulose and cellulose in lignocellulose into sugar compounds, and the high-boiling alcohol in the system acts as a lignin dissolving agent and a structure protecting agent, allowing lignin to dissolve in the high-boiling alcohol. Then add water to precipitate lignin, thereby separating non-condensed lignin and sugar compounds. The acidic molten salt hydrate used in the hydrolysis process can break the cellulose crystal at a lower temperature, catalyze the breaking of the β-1,4 glycosidic bond, and hydrolyze the lignocellulose to generate sugar compounds. The high-boiling alcohol can capture the reactive benzyl cation formed under acidic conditions and bind to the C α -OH in the lignin phenylpropane structural unit to prevent the condensation reaction of lignin. The depolymerization effect of lignin is directly related to its structure. Essentially, the depolymerization of lignin is to break the connecting bonds between the phenylpropane structural units. The main connecting bonds in lignin are ether bonds (C-O) and carbon-carbon bonds (C-C), and the dissociation energy of C-C bonds is higher than that of C-O bonds, while the bond energies of specific C-O and C-C bonds are different. The three main C-O bonds are located in the α-O-4 connecting bond, the β-O-4 connecting bond, and the 4-O-5 connecting bond. The dissociation energy of the β-O-4 bond is smaller. It is generally believed that the more connecting bonds in lignin, especially the β-O-4 bond which has lower bond energy and is more abundant, the higher the monophenol product obtained by depolymerization.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] A method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds, comprising the following steps:

[0011] (1) Mix inorganic molten salt, high-boiling alcohol, and a dilute solution of inorganic acid with a concentration of 0.4-1.2wt% to form an acidic molten salt high-boiling alcohol aqueous system;

[0012] (2) Add lignocellulose raw material to the acidic molten salt high-boiling alcohol aqueous system obtained in step (1) and mix uniformly. After hydrolysis by heating, add water for precipitation, filter, and the filtrate is a sugar compound solution, and the filter residue is non-condensed lignin.

[0013] Preferably, the inorganic molten salt in step (1) is at least one of LiCl, LiBr, and ZnBr2.

[0014] Preferably, the mass ratio of the inorganic fused salt to the inorganic acid dilute solution with a concentration of 0.4-1.2wt% in step (1) is (1-2.5):1; more preferably (1-2.3):1.

[0015] Preferably, the high-boiling alcohol in step (1) is at least one of 1,4-butanediol, glycerol and ethylene glycol.

[0016] Preferably, the mass ratio of the high-boiling alcohol to the inorganic acid dilute solution with a concentration of 0.4-1.2wt% in step (1) is 1:(1-1.5); more preferably 1:1.

[0017] Preferably, the inorganic acid in the inorganic acid dilute solution with a concentration of 0.4-1.2wt% in step (1) is at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

[0018] Preferably, the lignocellulose raw material in step (2) is at least one of birch, straw and pine.

[0019] More preferably, the lignocellulose raw material is crushed and sieved by a 60-mesh sieve before use.

[0020] Preferably, the temperature of the heating hydrolysis in step (2) is 110-130℃, and the time is 30-90min.

[0021] More preferably, the time of the heating hydrolysis in step (2) is 45-60min.

[0022] Most preferably, the temperature of the heating hydrolysis in step (2) is 110℃, and the time is 45min.

[0023] Preferably, the mass ratio of the lignocellulose raw material to the acid fused salt high-boiling alcohol water system in step (2) is (1-10):100.

[0024] Preferably, in the adding water for precipitation in step (2), the volume ratio of the hydrolysis mixture to the added water is 1:(3-8), more preferably 1:4.

[0025] The method adopted in the present application can convert hemicellulose and cellulose into sugar compounds with high utilization value and separate non-condensed lignin under relatively mild conditions. In the method, the coordination water of the cation of the fused salt hydrate replaces the hydroxyl in cellulose, the anion forms a hydrogen bond with the hydrogen in the hydroxyl of cellulose to destroy the hydrogen bonds between and within the cellulose molecules, and further destroy the crystal structure of cellulose, so that the cellulose swells and dissolves. Under the action of acid, the glycosidic bonds between cellulose chains are destroyed, so that the cellulose is hydrolyzed into sugar compounds. The high-boiling alcohol in the system not only can capture the reactive benzyl cation formed under acidic conditions, but also can capture the free radicals generated in the process of the reaction of the lignin phenylpropane structure unit and the acid, so as to prevent the degradation of the lignin phenylpropane structure unit and the formation of free radicals. αThe alkoxylation of -OH prevents the polycondensation reaction, and can promote the dissolution of lignin in the lignocellulosic raw material, which is beneficial to the further processing and utilization of lignin, and further realizes the comprehensive utilization of the three components of lignocellulose. Compared with the traditional molten salt treatment process, while obtaining a high yield of sugar compound solution, the beta-O-4 bond of lignin and the extraction rate of lignin can be greatly retained, and the consumption of inorganic acid in the process can be reduced. Compared with the traditional high-boiling alcohol treatment process, while retaining the beta-O-4 bond of lignin and the extraction rate of lignin, a high yield of sugar compound solution can be obtained, and the consumption of high-boiling alcohol in the process can be reduced. Using the biomass deconstruction method to extract non-condensed lignin and sugar compounds can effectively promote the full-component utilization of the three components of lignocellulose, and has great industrial application potential.

[0026] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0027] 1. The method of the present application uses an acidic molten salt high-boiling alcohol water system to deconstruct biomass materials under mild conditions, wherein the coordinated water of the cation of the molten salt hydrate replaces the hydroxyl group in the cellulose, and the anion forms a hydrogen bond with the hydrogen in the hydroxyl group of the cellulose to destroy the intermolecular and intramolecular hydrogen bonds of the cellulose, and further destroy the crystal structure of the cellulose, so that the cellulose swells and dissolves. Under the action of acid, the glycosidic bond between the cellulose chains is destroyed, so that it is hydrolyzed into sugar compounds. The high-boiling alcohol in the system can capture the reactive benzyl cation formed under acidic conditions, and the C α The alkoxylation of -OH prevents the polycondensation reaction.

[0028] 2. In the hydrolysis of lignocellulose, the high-boiling alcohol, molten salt and inorganic acid used in the present application are cheap and easy to obtain, easy to recover and easy to realize large-scale preparation, and the high-value utilization of lignocellulose can be realized.

[0029] 3. The method of the present application can achieve a xylose yield of 96.4%, a glucose yield of 93.5%, a non-condensed lignin extraction rate of 90.7%, and a monophenol yield of 24.9% after hydrogenolysis of lignin, realizing efficient deconstruction of the three components, while significantly reducing the consumption of high-boiling alcohol and inorganic acid.

[0030] 4. Compared with other inorganic molten salt hydrate hydrolysis processes, the present application can greatly retain the beta-O-4 bond of lignin, and does not use dangerous chemicals or flammable and explosive products, and the process is simple, safe, green and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The physical map of the lignin obtained in Example 1.

[0032] Figure 2 The physical map of the lignin obtained in Comparative Example 1.

[0033] Figure 3 2D-HSQC NMR spectra of the lignin obtained in Example 1 and Comparative Example 1.

[0034] Figure 4 GCMS spectra of the products after hydrogenolysis of the lignin obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0035] The present application will be described in further detail below with reference to Examples and the accompanying drawings, but the embodiments of the present application are not limited to them.

[0036] In the embodiments of the present application, unless specific conditions are specified, the routine conditions or the conditions recommended by the manufacturers are used. The raw materials, reagents, etc. used, for which the manufacturers are not specified, are all routine products that can be purchased on the market.

[0037] The calculation formulas of the yields of xylose, glucose, and the lignin extraction rate and the monophenol yield after hydrogenolysis of the lignin are shown below.

[0038]

[0039]

[0040]

[0041]

[0042] The structure of the milled wood lignin is considered to be the closest to the real lignin. The lignin obtained in the present application is subjected to hydrogenolysis, and the content of β-O-4 bonds in the lignin is indirectly determined by comparing the monophenol yield of the milled wood lignin, thereby determining the condensation degree of the lignin.

[0043] The preparation method of the milled wood lignin used in the present application for comparing and determining whether the lignin in the examples and comparative examples has undergone condensation is as follows:

[0044] About 30 g of birch wood flour after dewaxing was put into a planetary ball mill, zirconium oxide balls (20 x 20 mm) were used, and the ball milling was carried out in a zirconium oxide bottle at a speed of 400 rpm. The total ball milling time was 5 h, and each ball milling was paused for 5 min after 5 min. Then the ball-milled wood flour was extracted with a dioxane / water solution = 9:1 (v / v), the solid-liquid ratio was 1 g of sample per 20 mL of solvent, and the reaction mixture was filtered after being heated in a 100 ℃ oil bath for 12 h. The filtrate was evaporated and dried in a rotary evaporator at 40 ℃, and the crude lignin was obtained. Then the crude lignin was dissolved again in an acetic acid / water = 9:1 (v / v) solution, the solid-liquid ratio was 1 g of crude lignin sample per 25 mL of solvent. Then the mixture was precipitated into cold water, separated by centrifugation, ground in a agate mortar, and then dissolved in a 1,2-dichloroethane / ethanol = 1:2 (v / v) solution. The mixture was centrifuged to remove insoluble substances. The lignin in the supernatant was precipitated with diethyl ether and recovered by centrifugation. After centrifugation, the lignin was washed with petroleum ether and freeze-dried to obtain purified milled wood lignin.

[0045] The lignin hydrogenolysis method in the examples and comparative examples of the present application is as follows:

[0046] 0.2 g of lignin, 40 mg of Ru / C (Ru content 5%, water content about 50%), and 20 mL of ethanol were added to a 100 mL autoclave. The depolymerization reaction of the lignin was carried out at 225 ℃ under 2 MPa of H2 for 240 min. After the reaction, the autoclave was cooled to room temperature with cooling water. The depolymerization product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry.

[0047] Example 1

[0048] (1) 5 g of LiCl, 5 g of a 1.2 wt% concentration hydrochloric acid solution, and 5 g of 1,4-butanediol were uniformly mixed to form an acidic eutectic high-boiling alcohol water system;

[0049] (2) 0.3 g of birch wood flour raw material was added to 10 g of the acidic eutectic high-boiling alcohol water system prepared in step (1) and uniformly mixed, and hydrolysis was carried out at 110 ℃ for 45 min;

[0050] (3) 15 mL of the hydrolysis mixture of step (2) was added to 60 mL of water to precipitate the lignin, which was filtered, and the filtrate was a sugar solution. The precipitate was washed and dried to obtain non-condensed lignin, which was subjected to hydrogenolysis;

[0051] (4) The filtrate of step (3) was mixed with an equal volume of an 8 wt% sulfuric acid solution, and hydrolysis was carried out at 130 ℃ for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, thereby obtaining a completely hydrolyzed sugar solution. The yield of xylose and glucose was determined by high performance liquid chromatography.

[0052] Example 2 (Changing the type of acid)

[0053] (1) 5 g of LiCl, 5 g of 0.6 wt% sulfuric acid solution, and 5 g of 1,4-butanediol were mixed to form an acidic molten salt high-boiling alcohol-water system;

[0054] (2) adding 0.3 g of birch wood powder raw material to 10 g of the acidic molten salt high-boiling alcohol water system prepared in step (1), mixing them evenly, and hydrolyzing them at 110° C. for 45 min;

[0055] (3) 15 mL of the hydrolysis mixture from step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was filtered to obtain a sugar solution. The precipitate was washed and dried to obtain non-condensed lignin, and the lignin was hydrogenolyzed;

[0056] (4) The filtrate from step (3) was mixed with an equal volume of 8 wt % sulfuric acid solution and hydrolyzed at 130° C. for 60 min to hydrolyze part of the oligosaccharides into monosaccharides to obtain a completely hydrolyzed sugar solution, and the yields of xylose and glucose were determined by high performance liquid chromatography.

[0057] Example 3 (Changing the type of acid)

[0058] (1) 5 g of LiCl, 5 g of 0.4 wt% phosphoric acid solution, and 5 g of 1,4-butanediol were mixed to form an acidic molten salt high-boiling alcohol-water system;

[0059] (2) adding 0.3 g of birch wood powder raw material to 10 g of the acidic molten salt high-boiling alcohol water system prepared in step (1), mixing evenly, and hydrolyzing at 110° C. for 45 min;

[0060] (3) 15 mL of the hydrolysis mixture from step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was filtered to obtain a sugar solution. The precipitate was washed and dried to obtain non-condensed lignin, and the lignin was hydrogenolyzed;

[0061] (4) The filtrate from step (3) was mixed with an equal volume of 8 wt % sulfuric acid solution and hydrolyzed at 130° C. for 60 min to hydrolyze part of the oligosaccharides into monosaccharides to obtain a completely hydrolyzed sugar solution, and the yields of xylose and glucose were determined by high performance liquid chromatography.

[0062] Example 4 (Changing the Type of High-Boiling Alcohol)

[0063] (1) 5 g of LiCl, 5 g of 1.2 wt% hydrochloric acid solution, and 5 g of glycerol were mixed to form an acidic molten salt high-boiling alcohol-water system;

[0064] (2) 0.3 g birch wood powder raw material was added into 10 g of the acidic fused salt high boiling alcohol water system prepared in step (1) and mixed uniformly, and hydrolysis was carried out at 110°C for 45 min;

[0065] (3) 15 mL of the hydrolysis mixture in step (2) was measured and added into 60 mL of water to precipitate the lignin, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0066] (4) The filtrate in step (3) was mixed with an equal volume of 8 wt% sulfuric acid solution, and hydrolysis was carried out at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, thereby obtaining a completely hydrolyzed sugar solution, and the yield of xylose and glucose was determined by high performance liquid chromatography test.

[0067] Example 5 (changing the type of high boiling alcohol)

[0068] (1) 5 g LiCl, 5 g of 1.2 wt% hydrochloric acid solution and 5 g of ethylene glycol were uniformly mixed to form an acidic fused salt high boiling alcohol water system;

[0069] (2) 0.3 g birch wood powder raw material was added into 10 g of the acidic fused salt high boiling alcohol water system prepared in step (1) and mixed uniformly, and hydrolysis was carried out at 110°C for 45 min;

[0070] (3) 15 mL of the hydrolysis mixture in step (2) was measured and added into 60 mL of water to precipitate the lignin, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0071] (4) The filtrate in step (3) was mixed with an equal volume of 8 wt% sulfuric acid solution, and hydrolysis was carried out at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, thereby obtaining a completely hydrolyzed sugar solution, and the yield of xylose and glucose was determined by high performance liquid chromatography test.

[0072] Example 6 (changing the concentration of LiCl)

[0073] (1) 7.5 g LiCl, 5 g of 1.2 wt% hydrochloric acid solution and 5 g of 1,4-butanediol were uniformly mixed to form an acidic fused salt high boiling alcohol water system;

[0074] (2) 0.3 g birch wood powder raw material was added into 10 g of the acidic fused salt high boiling alcohol water system prepared in step (1) and mixed uniformly, and hydrolysis was carried out at 110°C for 45 min;

[0075] (3) 15 mL of the hydrolysis mixture in step (2) was measured and added into 60 mL of water to precipitate the lignin, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0076] (4) The filtrate from step (3) was mixed with an equal volume of 8 wt % sulfuric acid solution and hydrolyzed at 130° C. for 60 min to hydrolyze part of the oligosaccharides into monosaccharides to obtain a completely hydrolyzed sugar solution, and the yields of xylose and glucose were determined by high performance liquid chromatography.

[0077] Example 7 (Changing the Type, Concentration and Hydrochloric Acid Concentration of Molten Salt)

[0078] (1) 7.5 g of LiBr, 5 g of a 0.7 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol were mixed to form an acidic molten salt high-boiling alcohol-water system;

[0079] (2) adding 0.3 g of birch wood powder raw material to 10 g of the acidic molten salt high-boiling alcohol water system prepared in step (1), mixing them evenly, and hydrolyzing them at 110° C. for 45 min;

[0080] (3) 15 mL of the hydrolysis mixture from step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was filtered to obtain a sugar solution. The precipitate was washed and dried to obtain non-condensed lignin, and the lignin was hydrogenolyzed;

[0081] (4) The filtrate from step (3) was mixed with an equal volume of 8 wt % sulfuric acid solution and hydrolyzed at 130° C. for 60 min to hydrolyze part of the oligosaccharides into monosaccharides to obtain a completely hydrolyzed sugar solution, and the yields of xylose and glucose were determined by high performance liquid chromatography.

[0082] Example 8 (Changing the Type, Concentration and Hydrochloric Acid Concentration of Molten Salt)

[0083] (1) 11.6 g ZnBr2, 5 g 0.8 wt% hydrochloric acid solution and 5 g 1,4-butanediol were mixed to form an acidic molten salt high-boiling alcohol-water system;

[0084] (2) adding 0.3 g of birch wood powder raw material to 10 g of the acidic molten salt high-boiling alcohol water system prepared in step (1), mixing them evenly, and hydrolyzing them at 110° C. for 45 min;

[0085] (3) 15 mL of the hydrolysis mixture from step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was filtered to obtain a sugar solution. The precipitate was washed and dried to obtain non-condensed lignin, and the lignin was hydrogenolyzed;

[0086] (4) The filtrate from step (3) was mixed with an equal volume of 8 wt % sulfuric acid solution and hydrolyzed at 130° C. for 60 min to hydrolyze part of the oligosaccharides into monosaccharides to obtain a completely hydrolyzed sugar solution, and the yields of xylose and glucose were determined by high performance liquid chromatography.

[0087] Example 9 (changing hydrolysis temperature)

[0088] (1) 5 g of LiCl, 5 g of a 1.2 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol were mixed uniformly to form an acidic fused-salt high-boiling alcohol water system;

[0089] (2) 0.3 g of birch wood powder raw material was added to 10 g of the acidic fused-salt high-boiling alcohol water system prepared in step (1) and mixed uniformly, and hydrolysis was performed at 130°C for 45 min;

[0090] (3) 15 mL of the hydrolysis mixture of step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0091] (4) The filtrate of step (3) was mixed with an equal volume of an 8 wt% sulfuric acid solution, and hydrolysis was performed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, and a completely hydrolyzed sugar solution was obtained; the yield of xylose and glucose was determined by high-performance liquid chromatography test.

[0092] Example 10 (changing raw material)

[0093] (1) 5 g of LiCl, 5 g of a 1.2 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol were mixed uniformly to form an acidic fused-salt high-boiling alcohol water system;

[0094] (2) 0.3 g of corn straw raw material was added to 10 g of the acidic fused-salt high-boiling alcohol water system prepared in step (1) and mixed uniformly, and hydrolysis was performed at 110°C for 45 min;

[0095] (3) 15 mL of the hydrolysis mixture of step (2) was added to 60 mL of water to precipitate lignin, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0096] (4) The filtrate of step (3) was mixed with an equal volume of an 8 wt% sulfuric acid solution, and hydrolysis was performed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, and a completely hydrolyzed sugar solution was obtained; the yield of xylose and glucose was determined by high-performance liquid chromatography test.

[0097] Example 11 (changing raw material)

[0098] (1) 5 g of LiCl, 5 g of a 1.2 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol were mixed uniformly to form an acidic fused-salt high-boiling alcohol water system;

[0099] (2) 0.3 g pine wood powder was added into 10 g of the acidic fused salt high boiling alcohol water system prepared in step (1) and mixed uniformly, and then hydrolyzed at 110°C for 45 min;

[0100] (3) 15 mL of the hydrolysis mixture in step (2) was added into 60 mL of water to precipitate lignin, and then filtered, and the filtrate was a sugar solution; the obtained precipitate was washed and dried to obtain non-condensed lignin, and the lignin was subjected to hydrogenolysis;

[0101] (4) The filtrate in step (3) was mixed with an equal volume of 8 wt% sulfuric acid solution, and then hydrolyzed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, and a completely hydrolyzed sugar solution was obtained, and the yield of xylose and glucose was determined by high performance liquid chromatography test.

[0102] Comparative Example 1 (compared with Example 1, without high boiling alcohol)

[0103] (1) 3.33 g of LiCl and 6.67 g of 0.6 wt% hydrochloric acid solution were mixed uniformly to form an acidic fused salt hydrate system;

[0104] (2) 0.3 g of birch wood powder was added into 10 g of the acidic fused salt hydrate system prepared in step (1) and mixed uniformly, and then hydrolyzed at 110°C for 45 min;

[0105] (3) The hydrolysis mixture in step (2) was filtered, and the filtrate was a sugar solution; the obtained filter residue was washed and dried to obtain lignin, and the lignin was subjected to hydrogenolysis;

[0106] (4) The filtrate in step (3) was mixed with an equal volume of 8 wt% sulfuric acid solution, and then hydrolyzed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, and a completely hydrolyzed sugar solution was obtained, and the yield of xylose and glucose was determined by high performance liquid chromatography test.

[0107] Comparative Example 2 (compared with Example 1, without fused salt)

[0108] (1) 6.67 g of 0.6 wt% hydrochloric acid solution and 3.33 g of 1,4-butanediol were mixed uniformly to form a high boiling alcohol water system;

[0109] (2) 0.3 g of birch wood powder was added into 10 g of the high boiling alcohol water system prepared in step (1) and mixed uniformly, and then hydrolyzed at 110°C for 45 min;

[0110] (3) The hydrolysis mixture (lignin and residue mixture) obtained in step (2) is filtered to obtain a filtrate containing lignin and a filter residue of unhydrolyzed hemicellulose and cellulose. 5 mL of the filtrate is added to 20 mL of water to precipitate the lignin, which is filtered. The filtrate is a sugar solution. The precipitated lignin is washed and dried to obtain lignin, which is subjected to hydrogenolysis.

[0111] (4) The sugar solution obtained in step (3) is mixed with an equal volume of an 8 wt% sulfuric acid solution, and hydrolysis is performed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, thereby obtaining a completely hydrolyzed sugar solution. The yield of xylose and glucose is determined by high-performance liquid chromatography.

[0112] Comparative Example 3 (compared with Example 1, the concentration of hydrochloric acid is increased)

[0113] (1) 5 g of LiCl, 5 g of a hydrochloric acid solution with a concentration of 6.0 wt%, and 5 g of 1,4-butanediol are uniformly mixed to form an acidic fused salt high-boiling alcohol water system;

[0114] (2) 0.3 g of birch wood powder raw material is uniformly mixed in 10 g of the acidic fused salt high-boiling alcohol water system prepared in step (1) and hydrolysis is performed at 110°C for 45 min;

[0115] (3) 15 mL of the hydrolysis mixture obtained in step (2) is added to 60 mL of water to precipitate the lignin, which is filtered. The filtrate is a sugar solution. The precipitated lignin is washed and dried to obtain lignin, which is subjected to hydrogenolysis;

[0116] (4) The filtrate obtained in step (3) is mixed with an equal volume of an 8 wt% sulfuric acid solution, and hydrolysis is performed at 130°C for 60 min to hydrolyze part of the oligosaccharides into monosaccharides, thereby obtaining a completely hydrolyzed sugar solution. The yield of xylose and glucose is determined by high-performance liquid chromatography.

[0117] Comparative Example 4 (compared with Example 1, the concentration of 1,4-butanediol is increased)

[0118] (1) 3.33 g of LiCl, 0.67 g of a hydrochloric acid solution with a concentration of 5.97 wt%, and 6.0 g of 1,4-butanediol are uniformly mixed to form an acidic fused salt high-boiling alcohol water system;

[0119] (2) 0.3 g of birch wood powder raw material is uniformly mixed in 10 g of the acidic fused salt high-boiling alcohol water system prepared in step (1) and hydrolysis is performed at 110°C for 45 min;

[0120] (3) 15 mL of the hydrolysis mixture obtained in step (2) is added to 60 mL of water to precipitate the lignin, which is filtered. The filtrate is a sugar solution. The precipitated lignin is washed and dried to obtain lignin, which is subjected to hydrogenolysis;

[0121] (4) The filtrate of step (3) is mixed with an equal volume of 8 wt% sulfuric acid solution, hydrolyzed at 130°C for 60 min, and part of the oligosaccharides are hydrolyzed into monosaccharides to obtain a completely hydrolyzed sugar solution. The yield of xylose and glucose is determined by high performance liquid chromatography test.

[0122] Comparative Example 5 (compared with Example 1, reducing the hydrolysis temperature)

[0123] (1) 5 g of LiCl, 5 g of 1.2 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol are uniformly mixed to form an acidic fused salt high-boiling alcohol water system;

[0124] (2) 0.3 g of birch wood powder raw material is added to 10 g of the acidic fused salt high-boiling alcohol water system prepared in step (1) and uniformly mixed, and hydrolyzed at 80°C for 45 min;

[0125] (3) 15 mL of the hydrolysis mixture of step (2) is added to 60 mL of water to precipitate lignin, filtered, and the filtrate is a sugar solution. The obtained precipitate is washed and dried to obtain lignin, and the lignin is subjected to hydrogenolysis;

[0126] (4) The filtrate of step (3) is mixed with an equal volume of 8 wt% sulfuric acid solution, hydrolyzed at 130°C for 60 min, and part of the oligosaccharides are hydrolyzed into monosaccharides to obtain a completely hydrolyzed sugar solution. The yield of xylose and glucose is determined by high performance liquid chromatography test.

[0127] Comparative Example 6 (compared with Example 1, increasing the hydrolysis temperature)

[0128] (1) 5 g of LiCl, 5 g of 1.2 wt% hydrochloric acid solution, and 5 g of 1,4-butanediol are uniformly mixed to form an acidic fused salt high-boiling alcohol water system;

[0129] (2) 0.3 g of birch wood powder raw material is added to 10 g of the acidic fused salt high-boiling alcohol water system prepared in step (1) and uniformly mixed, and hydrolyzed at 220°C for 45 min;

[0130] (3) 15 mL of the hydrolysis mixture of step (2) is added to 60 mL of water to precipitate lignin, filtered, and the filtrate is a sugar solution. The obtained precipitate is washed and dried to obtain lignin, and the lignin is subjected to hydrogenolysis;

[0131] (4) The filtrate of step (3) is mixed with an equal volume of 8 wt% sulfuric acid solution, hydrolyzed at 130°C for 60 min, and part of the oligosaccharides are hydrolyzed into monosaccharides to obtain a completely hydrolyzed sugar solution. The yield of xylose and glucose is determined by high performance liquid chromatography test.

[0132] The biomass deconstruction effect and product yield of the examples and comparative examples are shown in Table 1.

[0133] Table 1 Biomass conversion and product yield

[0134]

[0135] Effect of the embodiment: Table 1 is the test data of biomass deconstruction effect and product yield obtained by the embodiment and the comparative example of the present application. From Table 1, it can be seen that the effects of different concentrations and types of dilute acid solution, different concentrations and types of fused salt, different concentrations and types of high boiling alcohol system and treatment process on the yield of xylose, glucose, lignin extraction rate and monophenol yield are different. The treatment method in Example 1 can obtain high yield of xylose and glucose, and at the same time, the β-O-4 structure of lignin is maximally retained, and the monophenol yield of groundwood lignin is equivalent. Preferably, by adding acid fused salt high boiling alcohol water system to birch wood powder, reacting at 110℃ for 45min, hydrolyzing hemicellulose and cellulose to obtain sugar compounds, adding water to separate and filter to obtain non-condensed lignin, the yield of xylose can reach 96.4%, the yield of glucose is 93.5%, the extraction rate of lignin is 90.7%, and the yield of monophenol after hydrogenolysis of lignin is 24.9%, realizing the efficient development and utilization of three components of biomass.

[0136] The above embodiment is the preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, substitution, combination, simplification made without departing from the spirit and principles of the present application shall be equivalent replacement method, which is included in the protection scope of the present application.

Claims

1. A method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds, characterized in that: The following steps are involved: (1) uniformly mixing an inorganic molten salt, a high-boiling alcohol, and a dilute inorganic acid solution having a concentration of 0.4 to 1.2 wt% to form an acidic molten salt high-boiling alcohol water system; (2) adding the lignocellulose raw material to the acidic molten salt high-boiling alcohol water system obtained in step (1) and mixing them uniformly, heating and hydrolyzing them, then adding water for precipitation, filtering, the filtrate is a carbohydrate compound solution, and the filter residue is non-condensed lignin; The mass ratio of the inorganic molten salt to the inorganic acid dilute solution with a concentration of 0.4-1.2 wt% in step (1) is (1-2.5):1; The mass ratio of the high boiling alcohol in step (1) to the inorganic acid dilute solution with a concentration of 0.4-1.2 wt% is 1:(1-1.5); The temperature of the heating hydrolysis in step (2) is 110-130° C. and the time is 30-90 min; The inorganic molten salt in step (1) is at least one of LiCl, LiBr and ZnBr2; The high boiling alcohol in step (1) is at least one of 1,4-butanediol, propylene glycol and ethylene glycol.

2. A method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 1, characterized in that: The mass ratio of the inorganic molten salt to the inorganic acid dilute solution with a concentration of 0.4-1.2 wt% in step (1) is (1-2.3):1; The mass ratio of the high-boiling alcohol in step (1) to the inorganic acid dilute solution with a concentration of 0.4-1.2 wt% is 1:(1-1.5).

3. A method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 2, characterized in that: The mass ratio of the inorganic molten salt to the inorganic acid dilute solution with a concentration of 0.4-1.2 wt% in step (1) is (1-2.3):1; The mass ratio of the high-boiling alcohol in step (1) to the inorganic acid dilute solution with a concentration of 0.4-1.2wt% is 1:

1.

4. The method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 1, characterized in that: The temperature of the heating hydrolysis in step (2) is 110-130° C., and the time is 45-60 min.

5. A method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 4, characterized in that: The temperature of the heating hydrolysis in step (2) is 110° C. and the time is 45 minutes.

6. The method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 1, characterized in that: The inorganic acid in the inorganic acid dilute solution with a concentration of 0.4 to 1.2 wt% in step (1) is at least one of hydrochloric acid, sulfuric acid and phosphoric acid; The lignocellulose raw material in step (2) is at least one of birch, straw and pine.

7. The method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 1, characterized in that: The mass ratio of the lignocellulose raw material and the acidic molten salt high-boiling alcohol water system in step (2) is (1-10):

100.

8. The method for deconstructing lignocellulose to separate non-condensed lignin and sugar compounds according to claim 1, characterized in that: In the step (2) of adding water for precipitation, the volume ratio of the hydrolysis mixture to the added water is 1:(3-8).

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