Process for producing oligosaccharide from lignocellulose and recycling acid

Abstract

The invention discloses a process for producing oligosaccharide from lignocellulose and performing acid circulation, which comprises the following steps of: (1) performing swelling reaction on the lignocellulose by using more than 70wt% of inorganic acid solution to obtain high-acid biomass candy pomace; (2) extracting the high-acid biomass candy pomace with an organic solvent to obtain low-acid biomass candy pomace and an acid-containing organic phase; (3) removing insoluble substances of the low-acid biomass candy pomace to obtain an oligosaccharide solution; and (4) adding water into the acid-containing liquid obtained in the step (2) for reverse extraction, standing and layering to obtain an acid solution and an organic phase. According to the method, the acid in the high-acid and solid biomass candy pomace is effectively recycled, the process is efficient and mild, energy does not need to be additionally provided, and all used reagents can be recycled and reused.

Description

Technical Field

[0001] The present invention relates to the fields of biochemical engineering and bioenergy, and in particular to a process for producing oligosaccharides from straw-based lignocellulose and acid circulation. Background Art

[0002] Oligosaccharides have a wide range of applications in food, medicine, and health supplements. In the food industry, oligosaccharides serve as functional food additives, regulating intestinal flora, enhancing immunity, and maintaining freshness and preservation. In the pharmaceutical field, oligosaccharides are used as drug ingredients, demonstrating blood sugar and lipid-lowering properties.

[0003] Currently, the production of oligosaccharides mainly relies on the decomposition of polysaccharides (such as starch and cellulose) into oligosaccharides using specific enzymes. This process requires specific reaction conditions, substrate specificity limitations, and low reaction efficiency. In addition, the reuse and recovery of enzymes in large-scale industrial production are difficult. Therefore, the process of obtaining oligosaccharides by enzymatic methods usually requires the support of pretreatment technology to break down the recalcitrance of lignin in lignocellulose.

[0004] In order to overcome the key problems faced in the process of preparing monosaccharides from the above-mentioned lignocellulosic biomass, many researchers have proposed corresponding solutions. Chinese invention patent CN202410406654.8 discloses a method for co-producing high-purity arabinose and xylooligosaccharides using lignocellulose, but this method has the problem of complex separation process. Chinese invention patent CN202310555465.2 discloses a method for producing xylooligosaccharides by hydrothermal pretreatment of lignocellulose, but this method requires high temperature and high pressure and the product only contains xylan. Chinese invention patent CN202310735005.8 discloses a method for preparing cellulosic oligosaccharides, but this method uses a ball milling device, which is difficult to achieve scaled-up production in actual production.

[0005] The acid sugar production process faces certain challenges in acid recovery and reuse. Currently, the main acid recovery methods include ion exchange resin method, solvent extraction method, electrodialysis method and alkali salt neutralization method, each of which has its own advantages and disadvantages. The ion exchange resin method has the advantage of being recyclable and recyclable, but it is only applicable to conditions with lower acid concentrations and has a certain dilution effect on the recovered acid, which limits the increase in acid concentration. The electrodialysis method can effectively separate sugar and acid at low acid concentrations. However, when the acid concentration increases, its separation efficiency will be significantly reduced, affecting the efficiency and quality of acid recovery. The alkali salt neutralization method, such as using ammonia or sodium hydroxide to partially neutralize the acidic medium, is simple and convenient to operate, but often requires additional auxiliary treatment measures to prevent the generation and accumulation of harmful compounds in the system and ensure the environmental friendliness and safety of the process. The solvent extraction method can effectively solve the problem of acid recovery under high acid concentrations and better cope with the recovery challenges of high-concentration acids.

[0006] Therefore, it is urgent to develop an economical, efficient and green process to obtain oligosaccharide solutions to solve and develop the key issues in the preparation of functional sugars. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a process for producing oligosaccharides from lignocellulose and acid circulation in view of the shortcomings of the existing technology.

[0008] In order to solve the above technical problems, the present invention discloses the following technical solutions:

[0009] A process for producing oligosaccharides from lignocellulose and acid circulation, such as Figure 1 As shown, the following steps are included:

[0010] (1) subjecting lignocellulose to a swelling reaction with an inorganic acid solution of 70 wt % or more to obtain a high-acid biomass sugar residue;

[0011] (2) extracting the high-acid biomass sugar residue with an organic solvent to obtain a low-acid biomass sugar residue and an acid-containing organic phase;

[0012] (3) removing insoluble matter from the low-acid biomass sugar residue to obtain an oligosaccharide solution;

[0013] (4) adding water to the acid-containing liquid phase obtained in step (2) for back extraction, allowing it to stand and then separating the layers to obtain an acid solution and an organic phase.

[0014] In step (1), the lignocellulose is straw-based lignocellulose, including any one or a combination of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cobs, switchgrass, reeds, rapeseed, wood chips, fruit shells, furfural residue, xylose residue, cellulose powder and hemicellulose powder.

[0015] In step (1), the inorganic acid is any one or a combination of sulfuric acid, hydrochloric acid and phosphoric acid.

[0016] In step (1), the concentration of the acid in the inorganic acid solution is 70 wt%-90 wt%, such as 80 wt%.

[0017] In step (1), the mass ratio of the lignocellulose to the acid in the acid solution is 1:0.5-3, preferably 1:1-2.

[0018] In step (1), the temperature of the swelling reaction is 20-30° C., preferably room temperature; and the pressure of the swelling reaction is normal pressure.

[0019] In step (1), the swelling reaction is continued until the reaction system has a good mobile phase, and the reaction is completed. For example, taking 10 kg of straw as an example, the reaction takes about 1 hour to complete.

[0020] In step (2), the organic solvent is any one or a combination of an alcohol organic solvent, a ketone organic solvent and a tertiary amine organic solvent, preferably an alcohol organic solvent, preferably isobutanol and / or sec-octanol; the ketone organic solvent includes any one or a combination of acetone, cyclohexanone, triethylamine and tri(2-hexylhexyl)amine; the tertiary amine organic solvent includes tri(2-hexylhexyl)amine.

[0021] In step (2), the mass ratio of the high-acid biomass sugar residue to the organic solvent is 1:1-5, such as 1:3.

[0022] In step (2), the extraction is to mix the high-acid biomass sugar residues with an organic solvent and then separate the solid and liquid.

[0023] In step (2), the purpose of the extraction is to extract and recover the acid in the biomass sugar residue. The number of extractions is not limited and can be adjusted according to actual conditions, such as 1-7 extractions, such as 3 times or 4 times.

[0024] In step (4), the number of back extractions is not limited and can be adjusted according to actual conditions, such as 1-7 times, such as 3 times or 4 times.

[0025] In step (4), in the stripping, the total mass of water is 1-5 times the mass of the acid-containing organic phase.

[0026] In step (4), the organic phase obtained is purified and returned to step (2) for use as an organic solvent; the acid solution obtained in step (4) is concentrated or diluted and returned to step (1) for use as an inorganic acid solution.

[0027] The high-acid biomass sugar residue in the present invention is a biomass sugar residue with an acid content of more than 50 wt %; the low-acid biomass sugar residue is a biomass sugar residue with an acid content of less than 50 wt %.

[0028] The lignocellulose oligosaccharide production and acid recycling process provided by the present invention effectively addresses existing problems in oligosaccharide preparation, including the difficulty in recycling and reusing chemical reagents, low oligosaccharide yields, complex and harsh reaction conditions, and expensive enzyme costs. In particular, the present invention utilizes sec-octanol and / or isobutanol to achieve a high acid recovery rate, and the used isobutanol has a relatively low boiling point, enabling the purification and reuse of the isobutanol with low energy consumption.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0030] The present invention realizes the separation of chemical reagents at low cost under mild conditions in the hydrolysis reaction stage of lignocellulose biomass.

[0031] (1) The present invention effectively solves a series of problems in the traditional process of preparing oligosaccharides, such as long cycle, complex process and low yield.

[0032] (2) The present invention realizes the adjustability of oligosaccharide concentration (by adjusting the proportion of dissolved water solvent), and the storage and transportation of oligosaccharides in solid form (deacidified biomass sugar residue) under low-cost conditions, providing convenience for subsequent industrialization and commercialization.

[0033] (3) The present invention effectively solves the problem of acid recovery from high-acid, solid-state biomass sugar residues. The process is efficient and gentle, does not require additional energy, and the reagents used can be recycled and reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0035] Figure 1 This is a flow chart for preparing oligosaccharides from lignocellulosic biomass in an embodiment of the present invention.

[0036] Figure 2 This is the two-dimensional NMR spectrum of oligosaccharides prepared from lignocellulosic biomass in Example 9 of the present invention. DETAILED DESCRIPTION

[0037] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0038] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0039] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0040] The wheat straw (40-60 mesh) used in the following examples has a cellulose content of 34.92% by mass, a hemicellulose content of 22.58% by mass, and a lignin content of 23.03% by mass.

[0041] In the following examples, the acid content can be determined by acid-base titration.

[0042] In the following examples, the percentage of input acid extracted from the biomass sugar residue = (mass of input acid - mass of acid in the third low-acid biomass sugar residue) / mass of input acid × 100%.

[0043] In the following examples, the acid recovery rate = mass of acid in the acid solution / mass of input acid × 100%.

[0044] In the following examples, the obtained biomass sugar residue was dissolved in an aqueous solution, and the polysaccharide content in the biomass sugar residue was detected by the National Renewable Energy Laboratory (NREL) method. The polysaccharide was calculated as follows:

[0045] Glucan yield % = m 葡聚糖 / (C 原料-纤 *m 原料 )*100%

[0046] Xylan yield % = m 木聚糖 / (C 原料-纤 *m 原料 )*100%

[0047] Total polysaccharide yield = (m 葡聚糖 +m 木聚糖 ) / m 原料

[0048] Total polysaccharide concentration = (m 葡聚糖 +m 木聚糖 ) / volume of supernatant containing soluble total polysaccharides

[0049] Where C represents the percentage content of the corresponding component in the biomass, and M represents the mass of the corresponding substance. Specifically, C 原料-纤 Expressed as the cellulose content in the raw material, C 残渣-纤 Expressed as the cellulose content in the residue; m 原料 Expressed as the mass of raw material, m 葡聚糖 Expressed as the mass of glucan in biomass sugar residue, m 木聚糖 Expressed as the mass of xylan in biomass sugar residue.

[0050] In the following examples, the uniform mixing refers to uniform stirring at room temperature and a rotation speed of 100 rpm.

[0051] Example 1

[0052] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0053] ① Wheat straw is swelled with 70 wt% sulfuric acid solution at room temperature and pressure until it has good fluidity to obtain a high-acid biomass sugar residue. The wheat straw biomass can be added in batches or all at once, with the mass ratio of wheat straw to sulfuric acid being 1:1.

[0054] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with sec-octanol and subjected to solid-liquid separation. The mass ratio of the high-acid biomass sugar residue to the sec-octanol is 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with sec-octanol. The mass ratio of the low-acid biomass sugar residue to the sec-octanol is 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0055] The third low-acid biomass sugar residue obtained after three extractions was fully dissolved in water, and the acid content in the low-acid biomass sugar residue was measured. The results showed that 87.18% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0056] ③ The third low-acid biomass sugar residue obtained after three extractions in step ② was added with water, and the insoluble lignin component was removed by centrifugation. The supernatant containing soluble total polysaccharides was collected. The glucan and xylan contents in the supernatant containing soluble total polysaccharides were assayed using the NREL method (4% sulfuric acid at 121° C. for 60 min). The glucan yield was 73.97%, the xylan yield was 64.66%, and the total polysaccharide yield was 0.453 kg / kg biomass. The resulting total polysaccharide solution had a volume of 51.28 L at a pH of 1.5 and a total polysaccharide concentration of 8.832 g / L.

[0057] ④ Combine the acid-containing organic phases after the 3 extractions in step ② (i.e., the first acid-containing organic phase, the second acid-containing organic phase, and the third acid-containing organic phase), add water for back extraction, let stand and then separate to obtain a first acid solution and a first organic phase. The obtained first organic phase has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted in step ② 3 times after the combination. After 3 back extractions, a first acid solution, a second acid solution, a third acid solution, and a third organic phase are obtained.

[0058] The acid solutions obtained from the three stripping operations (i.e., the first acid solution, the second acid solution, and the third acid solution) were combined and the acid content was determined. The results showed that after three stripping operations, a recovery rate of 78.46% of the input acid mass could be achieved.

[0059] The obtained third organic phase is purified by rotary evaporation and then returned to step ② for use as an organic solvent; the obtained acid solution is concentrated or diluted to the acid concentration of step ① and then returned to step ① for use as an acid solution.

[0060] Example 2

[0061] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0062] ① Wheat straw is swelled with 70 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:1.

[0063] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with the organic solvent isobutanol, followed by solid-liquid separation. The mass ratio of biomass sugar residue to isobutanol is 1:3, resulting in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is then extracted twice with the organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0064] The acid content in the third low-acid biomass sugar residue was measured, and the results showed that 89.35% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0065] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 78.18%, the xylan yield was 69.77%, and the total polysaccharide yield was 0.482 kg / kg biomass. The resulting polysaccharide solution had a volume of 42.62 L at a pH of 1.5 and a polysaccharide concentration of 11.318 g / L.

[0066] ④ Combine the acid-containing liquid phases obtained after the three solid-liquid separations in step ② and add water for back extraction. Allow to stand and then separate the layers. Repeat this process three times, with the total mass of water being three times the total mass of the acid-containing liquid phases. This yields a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solutions was measured, and the results showed that after three back extractions, an 84.88% recovery rate of the input acid was achieved. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0067] Example 3

[0068] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0069] ① Wheat straw is swelled with 70 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:1.

[0070] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with the organic solvent methanol and subjected to solid-liquid separation, with the mass ratio of biomass sugar residue to methanol being 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is then subjected to repeated extraction with the organic solvent twice, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0071] The acid content in the third low-acid biomass sugar residue was determined, and the results showed that 75.46% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0072] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 75.24%, the xylan yield was 66.19%, and the total polysaccharide yield was 0.462 kg / kg biomass. The resulting polysaccharide solution had a volume of 98.160 L at a pH of 1.5 and a polysaccharide concentration of 4.704 g / L.

[0073] ④ The acid-containing liquid phases obtained after the three solid-liquid separations in step ② were combined and stripped with water. After standing, the phases were separated and separated. This process was repeated three times, with the total mass of water being three times the total mass of the acid-containing liquid phases. This yielded a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content of the acid solution was determined. The results showed that after three stripping cycles, a 52.82% recovery rate of the input acid was achieved.

[0074] The obtained third organic phase is purified and returned to step ② for use as an organic solvent; the obtained acid solution is concentrated or diluted to the acid concentration of step ① and then returned to step ① for use as an acid solution.

[0075] Example 4

[0076] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0077] ① Wheat straw is swelled with 70 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:1.

[0078] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with ethanol, an organic solvent, and then subjected to solid-liquid separation. The mass ratio of biomass sugar residue to ethanol is 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with an organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0079] The acid content in the third low-acid biomass sugar residue was determined, and the results showed that 76.49% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0080] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 73.36%, the xylan yield was 59.22%, and the total polysaccharide yield was 0.437 kg / kg biomass. The resulting polysaccharide solution had a volume of 94.04 L at a pH of 1.5 and a polysaccharide concentration of 4.643 g / L.

[0081] ④ Combine the acid-containing liquid phases obtained after the three solid-liquid separations in step ② and add water for back extraction. After standing, allow the phases to separate into separate layers, yielding a first acid solution and a first organic phase. Repeat this process three times, with the total mass of water being three times the total mass of the acid-containing liquid phases, to yield a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solution was measured, and the results showed a 53.54% recovery of the input acid mass after three back extractions. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the acid concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0082] Example 5

[0083] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0084] ① Wheat straw is swelled with 90 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:2.

[0085] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with an organic solvent and subjected to solid-liquid separation. The mass ratio of the biomass sugar residue to isobutanol is 1:1. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with an organic solvent, with the mass ratio of the low-acid biomass sugar residue to the organic solvent being 1:1 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0086] The acid content in the third low-acid biomass sugar residue was determined, and the results showed that 91.32% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0087] ③ After extraction, the third low-acid biomass sugar residue was added to water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 70.37%, the xylan yield was 61.52%, and the total polysaccharide yield was 0.431 kg / kg biomass. The resulting polysaccharide solution had a volume of 69.44 L at a pH of 1.5 and a polysaccharide concentration of 6.205 g / L.

[0088] ④ Combine the acid-containing solutions obtained after the three solid-liquid separations in step ② and add water for back extraction. Allow to stand and allow the phases to separate into separate layers, yielding a first acid solution and a first organic phase. Repeat this process three times, with the total mass of water being 1 times the total mass of the acid-containing solution phase, to yield a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solution was measured, and the results showed that after three back extractions, an 86.75% recovery rate of the input acid mass was achieved. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0089] Example 6

[0090] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0091] ① Wheat straw is swelled with 90 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:2.

[0092] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with an organic solvent and subjected to solid-liquid separation. The mass ratio of biomass sugar residue to isobutanol is 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with an organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0093] The acid content in the third low-acid biomass sugar residue was measured, and the results showed that 97.17% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0094] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 67.07%, the xylan yield was 53.73%, and the total polysaccharide yield was 0.398 kg / kg biomass. The resulting polysaccharide solution had a volume of 22.64 L and a polysaccharide concentration of 17.584 g / L at a pH of 1.5.

[0095] ④ Combine the acid-containing liquid phases obtained after the three solid-liquid separations in step ② and add water for back extraction. After standing, allow the phases to separate into separate layers, yielding a first acid solution and a first organic phase. Repeat this process three times, with the total mass of water being three times the total mass of the acid-containing liquid phases, to yield a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solution was measured, and the results showed a 92.31% recovery of the input acid mass after three back extractions. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0096] Example 7

[0097] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0098] ① Wheat straw is swelled with 90 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:2.

[0099] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with an organic solvent and subjected to solid-liquid separation. The mass ratio of biomass sugar residue to isobutanol is 1:5. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with an organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:5 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0100] The acid content in the third low-acid biomass sugar residue was measured, and the results showed that 98.26% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0101] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 76.49%, the xylan yield was 67.55%, and the total polysaccharide yield was 0.470 kg / kg biomass. The resulting polysaccharide solution had a volume of 13.92 L and a polysaccharide concentration of 33.773 g / L at a pH of 1.5.

[0102] ④ Combine the acid-containing liquid phases obtained after the three solid-liquid separations in step ② and add water for back extraction. After standing, allow the phases to separate into separate layers, yielding a first acid solution and a first organic phase. Repeat this process three times, with the total mass of water being three times the total mass of the acid-containing liquid phases, to yield a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solution was measured, and the results showed a 93.35% recovery of the input acid mass after three back extractions. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the acid concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0103] Example 8

[0104] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0105] ① Wheat straw is swelled with 90 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:2.

[0106] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with an organic solvent and subjected to solid-liquid separation. The mass ratio of biomass sugar residue to isobutanol is 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted four times with an organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After five extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, a fourth acidic organic phase, a fifth acidic organic phase, and a fifth low-acid biomass sugar residue are obtained.

[0107] The acid content in the third low-acid biomass sugar residue was measured, and the results showed that 98.35% of the input acid mass was extracted from the biomass sugar residue through 5 extractions.

[0108] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 89.83%, the xylan yield was 82.69%, and the total polysaccharide yield was 0.561 kg / kg biomass. The resulting polysaccharide solution had a volume of 13.28 L and a polysaccharide concentration of 42.224 g / L at a pH of 1.5.

[0109] ④ Combine the acidic solutions obtained after the five solid-liquid separations in step ② and add water for back extraction. After standing, allow the solution to separate into separate layers, yielding a first acid solution and a first organic phase. Repeat this process five times, with the total mass of water being three times the total mass of the acidic solution phase, to yield a first acid solution, a second acid solution, a third acid solution, a fourth acid solution, a fifth acid solution, and a fifth organic phase. The acid content in the acid solutions was measured, and the results showed a 93.42% recovery of the input acid mass after five back extractions. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was concentrated or diluted to the acid concentration obtained in step ① and then returned to step ① for use as the acid solution.

[0110] Example 9

[0111] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0112] ① Wheat straw is swelled with 80 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:1.5.

[0113] ② The high-acid biomass sugar residue obtained in step 1 is uniformly mixed with an organic solvent and subjected to solid-liquid separation. The mass ratio of biomass sugar residue to isobutanol is 1:3. This results in a single extraction to obtain a first acidic organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with an organic solvent, with the mass ratio of low-acid biomass sugar residue to organic solvent being 1:3 during each extraction. After three extractions, a first acidic organic phase, a second acidic organic phase, a third acidic organic phase, and a third low-acid biomass sugar residue are obtained.

[0114] The acid content in the third low-acid biomass sugar residue was determined, and the results showed that 97.49% of the input acid mass was extracted from the biomass sugar residue through three extractions.

[0115] ③ After extraction, the third low-acid biomass residue was added with water and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 93.87%, the xylan yield was 88.69%, and the total polysaccharide yield was 0.592 kg / kg biomass. The resulting polysaccharide solution had a volume of 15.06 L and a polysaccharide concentration of 39.297 g / L at a pH of 1.5.

[0116] ④ Combine the acid-containing liquid phases obtained after solid-liquid separation in step ② and add water for back extraction. Allow to stand and allow the phases to separate, yielding a first acid solution and a first organic phase. Repeat this process three times, with the total mass of water being three times the total mass of the acid-containing liquid phases, to yield a first acid solution, a second acid solution, a third acid solution, and a third organic phase. The acid content in the acid solution was measured, and the results showed a 92.62% recovery of the input acid mass after three back extractions. The resulting third organic phase was purified and returned to step ② for use as an organic solvent. The resulting acid solution was then concentrated or diluted to the acid concentration obtained in step ① and returned to step ① for use as the acid solution.

[0117] The two-dimensional NMR spectrum of the oligosaccharide obtained in this example is as follows Figure 2 shown.

[0118] Example 10

[0119] A straw-based lignocellulose oligosaccharide production and acid circulation process comprises the following steps:

[0120] ① Wheat straw is swelled with 80 wt% acid solution at room temperature and normal pressure until it has good fluidity to obtain high-acid biomass sugar residue. Wheat straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid is 1:1.5.

[0121] ② The high-acid biomass sugar residue obtained in step ① is evenly mixed with the organic solvent isobutanol and then subjected to solid-liquid separation. The mass ratio of the biomass sugar residue to the isobutanol is 1:3, thereby obtaining an acid-containing organic phase and a low-acid biomass sugar residue. Through one extraction, 70.25% of the input acid mass is extracted from the biomass sugar residue.

[0122] ③ The extracted low-acid biomass sugar residue was added to an aqueous solution and centrifuged to remove the insoluble lignin component. The supernatant containing the soluble total polysaccharides was collected. The glucan yield was 92.16%, the xylan yield was 86.75%, and the total polysaccharide yield was 0.580 kg / kg biomass. The resulting polysaccharide solution had a volume of 178.50 L at a pH of 1.5 and a polysaccharide concentration of 3.250 g / L.

[0123] ④ The acid-containing liquid phase obtained after the solid-liquid separation in step ② was stripped with water, and the phases were separated after standing to obtain an acid solution and an organic phase. The total mass of water was 3 times the total mass of the acid-containing liquid phase, and a recovery rate of 63.23% of the input acid mass was achieved; the obtained organic phase was purified and returned to step ② for use as an organic solvent; the obtained acid solution was concentrated and returned to step ① for use as an acid solution.

[0124] Example 11

[0125] Same as Example 9, except that different lignocellulose raw materials are used.

[0126]

[0127] Among them, the cellulose content in xylose residue is 88.42%, and the hemicellulose content is 0%; the cellulose content in furfural residue is 60.60%, and the hemicellulose content is 0%; the cellulose content in corn straw is 31.02%, and the hemicellulose content is 18.26%; the cellulose content in cellulose powder is 98.36%; and the hemicellulose content in hemicellulose powder is 96.72%.

[0128] Example 12

[0129] Same as Example 9, except that a different organic phase was used.

[0130]

[0131]

[0132] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A process for producing oligosaccharides using lignocellulose, characterized in that: The steps include: (1) subjecting lignocellulose to a swelling reaction with an inorganic acid solution of 70 wt % or more to obtain a high-acid biomass sugar residue; (2) extracting the high-acid biomass sugar residue with an organic solvent to obtain a low-acid biomass sugar residue and an acid-containing organic phase; (3) Removing insoluble matter from low-acid biomass sugar residue to obtain oligosaccharide solution.

2. The method according to claim 1, characterized in that In step (1), the lignocellulose is any one or a combination of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed, rapeseed, sawdust, fruit shell, furfural residue, xylose residue, cellulose powder and hemicellulose powder.

3. The method according to claim 1, characterized in that In step (1), the inorganic acid is any one of sulfuric acid, hydrochloric acid and phosphoric acid or a combination thereof, and / or the concentration of the acid in the inorganic acid solution is 70 wt % to 90 wt %.

4. The method according to claim 1, wherein In step (1), the mass ratio of the lignocellulose to the acid in the acid solution is 1:0.5-3, preferably 1:1-2.

5. The method according to claim 1, wherein In step (1), the temperature of the swelling reaction is 20-30°C, preferably room temperature.

6. The method according to claim 1, wherein In step (2), the organic solvent is any one or a combination of an alcohol organic solvent, a ketone organic solvent and a tertiary amine organic solvent, preferably an alcohol organic solvent, preferably isobutanol and / or sec-octanol.

7. The method according to claim 1, characterized in that In step (2), the mass ratio of the high-acid biomass sugar residue to the organic solvent is 1:1-5.

8. The method according to claim 1, characterized in that The method further comprises: (4) adding water to the acid-containing liquid phase obtained in step (2) for back extraction, allowing it to stand and then separating the layers to obtain an acid solution and an organic phase.

9. The method according to claim 8, characterized in that The number of times of the back extraction is 1-7 times, and in the back extraction, the total mass of water is 1-5 times the mass of the acid-containing organic phase.

10. The method according to claim 8, characterized in that The organic phase obtained in step (4) is purified and returned to step (2) for use as an organic solvent; the acid solution obtained in step (4) is concentrated or diluted and returned to step (1) for use as an inorganic acid solution.

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