Method for preparing monosaccharide from lignocellulose biomass and recycling acid

Abstract

The invention discloses a method for preparing monosaccharide from lignocellulose biomass and acid circulation, which comprises the following steps of: (1) performing swelling reaction on the lignocellulose biomass by using more than 70 weight percent of inorganic acid solution to obtain high-acid biomass candy pomace; (2) extracting the obtained high-acid biomass candy pomace with an organic solvent to obtain low-acid biomass candy pomace and an acid-containing organic phase; and (3) adding the low-acid biomass candy pomace into water and / or an acid solution to prepare a mixed solution with the acid concentration of below 30wt%, and carrying out hydrolysis reaction to obtain a reaction solution containing monosaccharide. The process provided by the invention not only can effectively solve the problems, including invalid degradation of carbohydrates, small molecular byproducts and complex and harsh reaction conditions, existing in the process of preparing sugar from lignocellulose, but also can effectively improve the acid recovery rate while keeping relatively high glucose yield and xylose yield.

Description

Technical Field

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

[0002] Lignocellulosic biomass, due to its abundant reserves and low cost, is considered a potential alternative to fossil fuels, particularly amid growing concerns about greenhouse gas emissions. The agriculture, forestry, and industrial sectors are the primary sources of lignocellulosic biomass, with crop residues and forest residues representing the most promising feedstocks. This biomass can be used as a sugar platform feedstock to produce biofuels and biochemical products, demonstrating promising applications.

[0003] Current research has found that lignin is a complex aromatic polymer present in plant cell walls, which gives plant cell walls hardness and corrosion resistance. The complex structure limits the accessibility of enzymes to carbohydrates, which inhibits process efficiency in biofuel and biochemical production. Although pretreatment technology can effectively remove lignin and reduce its negative effects, traditional pretreatment methods have many problems. For example, physical pretreatment has limited effects when used alone and has high operating costs; chemical pretreatment has better effects, but may cause equipment corrosion and the production of toxic byproducts; biological pretreatment has a longer cycle, and microorganisms consume some carbohydrates during growth. None of the above methods can efficiently achieve sugar production from lignocellulose alone, and even require additional hydrolytic enzymes to assist, which greatly increases production costs.

[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. For example, Chinese invention patent CN201711361294.0 discloses a pretreatment method and application for improving the efficiency of enzymatic saccharification of lignocellulose in an efficient and green manner, but this method will cause ineffective degradation of some hemicelluloses. Chinese invention patent CN202310517256.9 discloses a pretreatment method for densifying lignocellulose raw materials, inorganic salts and acidic reagents together, but this method also requires biodegradation conversion or further treatment before biodegradation conversion. Chinese invention patent CN202410309666.9 discloses a combined pretreatment method for improving lignocellulose degradation and sugar conversion rate, but this method has problems such as complex process and long production cycle.

[0005] In addition, the acid-based sugar production process faces the problem of acid recovery and reuse. Currently, the main methods include ion exchange resins, solvent extraction, electrodialysis, and alkali salt neutralization, but all of the above methods have certain advantages and disadvantages. Ion exchange resins can be recycled through repeated regeneration, but are only suitable for conditions with relatively low acid concentrations and have a certain dilution effect on the recovered acid concentration; electrodialysis has a good sugar-acid separation effect at low concentrations, but the separation efficiency decreases at higher concentrations; ammonia or sodium hydroxide is easy to operate when partially neutralizing the acidic medium, but other auxiliary treatments may be required to avoid the generation and accumulation of harmful compounds in the system; solvent extraction can effectively solve the above-mentioned high acid concentration recovery problem, but it is necessary to effectively avoid chemical reactions between the organic reagent and the acid.

[0006] Therefore, it is urgent to develop an economical, efficient and green process to obtain monosaccharide solution to solve and develop key problems in lignocellulose conversion. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a two-step acid production process of monosaccharides from straw-based lignocellulose and an acid circulation process in response to 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 method for preparing monosaccharides from lignocellulosic biomass comprises the following steps:

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

[0011] (2) extracting the high-acid biomass sugar residue obtained in step (1) with an organic solvent to obtain a low-acid biomass sugar residue and an acid-containing organic phase;

[0012] (3) adding water and / or an acid solution to the low-acid biomass sugar residue obtained in step (2) to prepare a mixed solution having an acid concentration of less than 30 wt%, and performing a hydrolysis reaction to obtain a reaction solution containing monosaccharides; and sequentially performing pigment removal and sugar-acid separation on the obtained reaction solution containing monosaccharides through a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0013] (4) adding water or an acid solution to the acid-containing organic phase obtained in step (2) and back-extracting for 1-4 times to obtain an acid solution and an organic phase.

[0014] In step (1), the lignocellulosic biomass includes straw-based lignocellulosic biomass, specifically 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 and xylose residue.

[0015] In step (1), the inorganic acid is any one or a combination of sulfuric acid, hydrochloric acid and phosphoric acid, and / or the concentration of the acid in the inorganic acid solution is 70wt%-90wt%, preferably 80wt%.

[0016] In step (1), the mass ratio of the lignocellulosic biomass to the acid in the inorganic acid solution is 1:0.5-3, preferably 1:1-2, preferably 1:1.3-1.7, and preferably 1:1.5.

[0017] 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.

[0018] In step (1), the swelling reaction is completed until the reaction system has a good mobile phase. Taking 10 kg of straw as an example, the reaction takes about 1 hour to complete.

[0019] In step (2), the organic solvent is an alcohol organic solvent and / or an amine organic solvent; the alcohol organic solvent includes C1-C8 alcohol, preferably sec-octanol and / or isobutanol; the amine organic solvent includes tri(2-hexylhexyl)amine.

[0020] In step (2), during the extraction process, the mass of the organic solvent is 1-5 times, such as 3 times, the mass of the high-acid biomass sugar residue during each extraction. That is, the mass ratio of the high-acid biomass sugar residue to the organic solvent is 1:1-5, such as 1:3.

[0021] 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 1-5 extractions, such as 3 extractions and 4 extractions.

[0022] In step (2), the extraction is performed by mixing uniformly and then performing solid-liquid separation; the mixing is performed by stirring uniformly at room temperature and a rotation speed of 50-200 rpm.

[0023] In step (3), the acid concentration of the mixed solution is 5 wt%-30 wt%, such as 5 wt%-15 wt%, preferably 10 wt%.

[0024] In step (3), the temperature of the hydrolysis reaction is 80-120°C, such as 90-100°C.

[0025] In step (3), the pressure of the hydrolysis reaction is normal pressure.

[0026] In step (3), the hydrolysis reaction time is 0.3-1.0h, preferably 0.5h.

[0027] In step (4), in the stripping, the total mass of water and acid solution is 1-5 times, such as 3 times, the mass of the acid-containing organic phase.

[0028] In step (4), the number of back extraction is 1-5 times, such as back extraction 3 times, back extraction 4 times.

[0029] like Figure 1 As shown, 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 to the acid concentration of step (1) and returned to step (1) for use as a substitute for the inorganic acid solution, or as a substitute for the acid solution in the back extraction; the condensed water obtained by the concentration is returned to step (4) for use.

[0030] 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 %.

[0031] The process provided by the present invention can not only effectively solve the problems existing in the sugar production process of lignocellulose, including the ineffective degradation of carbohydrates, small molecule by-products, and complex and harsh reaction conditions, but also effectively improve the acid recovery rate while maintaining high glucose and xylose yields.

[0032] Beneficial effects:

[0033] (1) The present invention realizes the separation of chemical reagents at low cost under mild conditions in the swelling reaction stage of lignocellulosic biomass.

[0034] (2) The present invention uses an organic solvent to achieve high-concentration acid recovery, effectively resolving the problem of industrial simulated moving bed (SMB) processes being unable to achieve high-concentration acid recovery. The acid recovery rate reaches 83.93%. This effectively addresses the prior art problem of biomass residues being high in acid concentration and in a solid form, making continuous simulated moving bed (SMB) processes incapable of continuous sugar-acid separation.

[0035] (3) The monosaccharide conversion rate and production cycle obtained during the hydrolysis reaction of the present invention are shorter, higher in conversion rate, and lower in production cost than those of traditional treatments (pretreatment and pretreatment-assisted enzymatic hydrolysis), providing a new option for the construction of a biomass sugar platform.

[0036] (4) The present invention adopts a lower liquid-to-solid ratio to achieve the adjustability of monosaccharide concentration and high concentration acquisition, effectively solving the feedback inhibition in the enzymatic hydrolysis process and providing targeted concentration monosaccharide solution for downstream products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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.

[0038] Figure 1 This is a flow chart for preparing monosaccharides from lignocellulosic biomass in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0041] 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.

[0042] The obtained acid-containing monosaccharide solution described in the following examples is treated with a simulated moving bed to obtain a monosaccharide solution and an acid solution. Specifically, the obtained acid-containing monosaccharide solution is decolorized by passing it through a simulated moving bed composed of 10 chromatographic columns filled with plant carbon-based decolorizing fillers, and the decolorized acid-containing monosaccharide solution is collected; the decolorized acid-containing monosaccharide solution is separated into sugars and acids by passing it through a simulated moving bed composed of 8 chromatographic columns filled with strong acid styrene-based resin hydrogen type resin, thereby obtaining a monosaccharide solution and an acid solution. The specific treatment conditions of the two simulated moving beds are as follows:

[0043] Decolorization: The simulated moving bed decolorization system consists of 10 columns (each filled with 400 ml and with a radius of 3.4 cm) divided into four zones (Zones I, II, III, and IV). Columns 1 through 4 constitute the pigment adsorption zone (Zone I), columns 5 through 7 form the regeneration zone (Zone IV), columns 8 through 9 form the pigment desorption zone (Zone III), and column 10 constitutes the sugar washing zone (Zone II). The columns are packed with plant-based carbon-based decolorization filler (L-AC) (iodine value: ≥400 mg / g; particle size: 0.5-1.5 mm; ash content: ≤3%). During the initial phase, the inlet of Zone I (column 1) is fed to remove pigments. Eluent water is introduced into the inlets of Zone II (column 10) and Zone IV (column 5) to remove residual acidic sugars and residual alkaline solution, respectively. Sodium hydroxide solution is introduced into the inlet of Zone III (column 8) to remove pigments adsorbed on the resin. The decolorized acidic monosaccharide solution is collected at the outlet of Zone I (column 4). During operation, the resin columns switch in a clockwise direction (zone I → zone II → zone III → zone IV). Zone I (pigment adsorption zone): The acidic monosaccharide solution is fed at a rate of 2 BV / h. Countercurrent contact with the L-AC promotes pigment fixation. Terminal column 4 discharges the decolorized acidic monosaccharide solution, processing 12 BV per cycle. Zone II (sugar wash zone): Deionized water (1 BV / h, 2 BV / cycle) is used to elute residual sugars from the L-AC pores via displacement chromatography. Zone III (Pigment Desorption Zone): 0.1 M sodium hydroxide solution (1 BV / h, 2 BV / cycle) is passed through. Column 9 discharges the concentrated pigment eluate. Zone IV (Alkali Wash Zone): Residual alkali is removed (deionized water, 1 BV / h, 5 BV / cycle) to prevent pH interference with subsequent cycles. Column 7 maintains the pH below 8.0 before re-entering Zone I.

[0044] Sugar-acid separation: The simulated moving bed for sugar-acid separation consists of eight 50mm x 1700mm chromatographic columns connected in series in a ring, divided into four zones (Zones I, II, III, and IV), with even distribution within each zone. The columns are packed with strong acid styrene-based hydrogen-type resin (functional group: -SO3H; total exchange capacity (mmol / g) ≥ 4.35, water content %: 45.0-55.0). In the initial stage, feed is fed from the inlet of Zone III, eluent is fed from the inlet of Zone I, monosaccharide solution is collected at the outlet of Zone III, and acid solution is collected at the outlet of Zone I. During operation, the resin columns switch from Zone III to Zone IV to Zone I to Zone II. The feed flow rate is 25ml / min, the elution reagent is water, and the elution flow rate is 75ml / min. The simulated moving bed column switching time is 30 minutes, and the monosaccharide solution outlet flow rate is 30-40ml / min.

[0045] In the following examples, the acid content can be determined by acid-base titration.

[0046] In the following examples, the percentage of the input acid extracted from the biomass sugar residue by mass = (the mass of the input acid - the mass of the acid in the third low-acid biomass sugar residue) / the mass of the input acid × 100%.

[0047] In the following examples, the acid recovery rate = mass of acid in the acid solution / mass of input acid × 100%.

[0048] The calculation methods of glucose yield and xylose yield in the following examples are as follows:

[0049] Glucose yield % = C G *V / M G *100%

[0050] Xylose yield % = C X *V / M X *100%

[0051] C G : The concentration of glucose in the monosaccharide solution; C X : xylose concentration in monosaccharide solution; V: volume of monosaccharide solution; M G : Glucose mass in the straw input into the reaction; M X : The mass of xylose in the straw input into the reaction.

[0052] In the following examples, the sugar solution yield = mass of monosaccharide solution / mass of lignocellulose. In the following examples, the total sugar concentration = mass of total sugar / mass of sugar solution; the total sugar mass = mass of lignocellulose × cellulose content × glucose yield + mass of lignocellulose × hemicellulose content × xylose yield.

[0053] Example 1

[0054] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0055] 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:1.

[0056] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:3 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0057] 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 after three extractions, 87.18% of the input acid mass could be extracted from the biomass sugar residue.

[0058] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 5 wt%. The mixture is then hydrolyzed at 80°C under normal pressure for 0.3 h, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0059] After the reaction was completed, the glucose yield was 74.27%, the xylose yield was 66.28%, the available sugar solution yield was 2.56 kg / kg wheat straw, and the total sugar concentration was 15.952 wt%.

[0060] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0061] 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.

[0062] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 70 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0063] Example 2

[0064] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0065] ① Wheat straw is swelled with 90 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:2.

[0066] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:1 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction is performed 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0067] Through three extractions, 89.24% of the input acid mass was extracted from the biomass sugar residue.

[0068] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 15 wt%. The mixture is then hydrolyzed at atmospheric pressure and 100°C for 1.0 hour, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0069] After the reaction was completed, the glucose yield was 66.85%, the xylose yield was 58.43%, the available sugar solution yield was 1.43 kg / kg wheat straw, and the total sugar concentration was 25.468 wt%.

[0070] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 1 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0071] 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 80.32% of the input acid mass could be achieved.

[0072] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 90 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0073] Example 3

[0074] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0075] ① Wheat straw is swelled with 90 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:2.

[0076] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:3 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction is performed 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0077] Through three extractions, 93.26% of the input acid mass was extracted from the biomass sugar residue.

[0078] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 15 wt%. The mixture is then hydrolyzed at atmospheric pressure and 100°C for 1.0 hour, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0079] After the reaction was completed, the glucose yield was 63.72%, the xylose yield was 51.04%, the sugar solution yield was 0.90 kg / kg wheat straw, and the corresponding total sugar concentration was 37.584 wt%.

[0080] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0081] 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 83.93% of the input acid mass could be achieved.

[0082] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 90 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0083] Example 4

[0084] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0085] ① Wheat straw is swelled with 90 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:2.

[0086] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:5 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction, to obtain a first acid-containing organic phase and a first low-acid biomass sugar residue. The first low-acid biomass sugar residue is extracted twice with sec-octanol, with the mass ratio of low-acid biomass sugar residue to sec-octanol being 1:5 during each extraction. After three extractions, a first acid-containing organic phase, a second acid-containing organic phase, a third acid-containing organic phase, and a third low-acid biomass sugar residue are obtained.

[0087] Through three extractions, 92.78% of the input acid mass was extracted from the biomass sugar residue.

[0088] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 15 wt%. The mixture is then hydrolyzed at atmospheric pressure and 100°C for 1.0 hour, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0089] After the reaction was completed, the glucose yield was 72.67%, the xylose yield was 64.17%, the available sugar solution yield was 0.96 kg / kg wheat straw, and the corresponding total sugar concentration was 41.412 wt%.

[0090] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 5 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0091] 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 83.50% of the input acid mass could be achieved.

[0092] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 90 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0093] Example 5

[0094] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0095] 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:1.

[0096] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:3 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction is performed 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0097] Through three extractions, 85.19% of the input acid mass was extracted from the biomass sugar residue.

[0098] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 15 wt%. The mixture is then hydrolyzed at atmospheric pressure and 100°C for 1.0 hour, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0099] After the reaction was completed, the glucose yield was 75.56%, the xylose yield was 67.48%, the sugar solution yield was 0.99 kg / kg wheat straw, and the corresponding total sugar concentration was 42.157 wt%.

[0100] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0101] 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 76.67% of the input acid mass could be achieved.

[0102] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 70 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0103] Example 6

[0104] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

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

[0106] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:3 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction is performed 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0107] The extraction of 92.89% of the input acid mass from the biomass sugar residue was achieved through three extractions.

[0108] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixed solution with an acid concentration of 5 wt%. The mixture is then hydrolyzed at 80°C under normal pressure for 0.3 h, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0109] After the reaction was completed, the glucose yield was 85.34%, the xylose yield was 78.56%, the sugar solution yield was 2.84 kg / kg wheat straw, and the corresponding total sugar concentration was 16.716 wt%.

[0110] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0111] 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 83.60% of the input acid mass could be achieved.

[0112] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 90 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0113] Example 7

[0114] A two-step process for producing monosaccharides from straw-based lignocellulose acid and acid circulation, comprising the following steps:

[0115] ① Wheat straw is swelled with 80 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 can be added in batches or all at once, with a mass ratio of wheat straw to sulfuric acid of 1:1.5.

[0116] ② The high-acid biomass sugar residue obtained in step 1 is mixed with sec-octanol in a mass ratio of 1:3 at room temperature and 100 rpm, and the solid-liquid separation is performed, i.e., a single extraction is performed 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, with the mass ratio of low-acid biomass sugar residue to sec-octanol 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.

[0117] The extraction of 90.17% of the input acid mass from the biomass sugar residue was achieved through three extractions.

[0118] ③ The third low-acid biomass sugar residue from step ②, after three extractions, is added to water and / or an acid solution to produce a mixture with an acid concentration of 10 wt%. The mixture is then hydrolyzed at 90°C under normal pressure for 0.5 h, followed by solid-liquid separation to produce an acid-containing monosaccharide solution and a lignin precipitate. The resulting acid-containing monosaccharide solution is treated in a simulated moving bed to produce a monosaccharide solution and an acid solution.

[0119] After the reaction was completed, the glucose yield was 89.18%, the xylose yield was 84.26%, the sugar solution yield was 1.47 kg / kg wheat straw, and the corresponding total sugar concentration was 34.023 wt%.

[0120] ④ Combine the acid-containing organic phases extracted 3 times 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 the acid solution or water obtained in step ③ for back extraction, let stand and separate to obtain a first acid solution and a first organic phase. The first organic phase obtained has some residual acid, and water is further added to repeat back extraction 2 times. The total mass of water and acid solution used in the 3 back extractions is 3 times the total mass of the acid-containing organic phases extracted 3 times in step ② 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.

[0121] 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 81.15% of the input acid mass could be achieved.

[0122] The obtained third organic phase is purified by rotary evaporation and returned to step ② for use as an organic solvent; the obtained acid solution (i.e., the first acid solution, the second acid solution, and the third acid solution) is concentrated or diluted to a concentration of about 80 wt% and returned to step ① for use as an acid solution, and the second acid solution and the third acid solution can also be returned to step ④ to replace the acid solution or water used in the first stripping; the concentrated condensed water is returned to step ④ to replace the water used in the first stripping.

[0123] Example 8

[0124] A two-step process for producing monosaccharides from straw-based lignocellulose and acid circulation is the same as Example 7, except that different lignocellulose raw materials are used.

[0125] Table 1

[0126]

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

[0128] Example 9

[0129] A two-step process for producing monosaccharides from straw-based lignocellulose and acid circulation is the same as Example 7, except that different solvents and different extraction times are used for the extraction process.

[0130] Table 2

[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 method for preparing monosaccharides from lignocellulosic biomass, characterized in that The steps include: (1) subjecting lignocellulosic biomass to a swelling reaction with a 70 wt % or greater inorganic acid solution to obtain a high-acid biomass sugar residue; (2) extracting the obtained high-acid biomass sugar residue with an organic solvent to obtain a low-acid biomass sugar residue and an acid-containing organic phase; (3) adding water and / or acid solution to the low-acid biomass sugar residue to prepare a mixed solution having an acid concentration of less than 30 wt %, and performing a hydrolysis reaction to obtain a reaction solution containing monosaccharides.

2. The method according to claim 1, characterized in that In step (1), the lignocellulosic biomass is any one or a combination of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed, rapeseed, wood chips, fruit shells, furfural residue and xylose residue.

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 lignocellulosic biomass to the acid in the inorganic acid solution is 1:0.5-3, preferably 1:1-2; the temperature of the swelling reaction is 20-30°C, preferably room temperature.

5. The method according to claim 1, wherein In step (2), the organic solvent is an alcohol organic solvent and / or an amine organic solvent, preferably octanol and / or isobutanol; preferably, the mass ratio of the high-acid biomass sugar residue to the organic solvent is 1:1-5.

6. The method according to claim 1, characterized in that In step (3), the acid concentration of the mixed solution is 5wt%-30wt%, and the temperature of the hydrolysis reaction is 80-120°C.

7. The method according to claim 1, characterized in that In step (3), the obtained monosaccharide-containing reaction liquid is decolorized and the sugar and acid are separated in a simulated moving bed to obtain a monosaccharide solution and an acid solution.

8. The method according to claim 1, characterized in that The method further comprises: (4) adding water or an acid solution to the acid-containing organic phase obtained in step (2) and back-extracting for 1-4 times to obtain an acid solution and an organic phase.

9. The method according to claim 8, characterized in that In the stripping, the total mass of water and acid solution 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 to the acid concentration of step (1) and returned to step (1) for use as a substitute for the inorganic acid solution, or as a substitute for the acid solution in the stripping; the condensed water obtained by the concentration is returned to step (4) for use.

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