A process for preparing monosaccharide solution by acid gradient treatment of straw-based lignocellulose

Abstract

The present invention discloses a process for preparing a monosaccharide solution by acid gradient treatment of straw-type lignocellulose, comprising the following steps: S1: lignocellulose biomass is subjected to a first acid hydrolysis reaction catalyzed by an acid solution with a concentration of 50wt% or more to obtain a first acid hydrolysis solution; S2: the first acid hydrolysis solution is mixed with an organic solvent, and solid-liquid separation is performed to obtain a polysaccharide-containing residue; S3: the polysaccharide-containing residue is added with water and / or an acid solution to obtain a mixed solution with an acid concentration of less than 45wt%, and a second acid hydrolysis reaction is performed to obtain a monosaccharide-containing reaction solution. The pretreatment of the present invention is carried out at room temperature and pressure, and no additional energy is required, and various reagents used in the pretreatment process can be recycled, which greatly reduces the production cost. At the same time, the present invention adopts a lower liquid-to-solid ratio, and monosaccharides can be directly obtained after pretreatment, and finally a high-concentration and controllable monosaccharide solution is obtained, avoiding the investment of a large amount of enzyme costs.

Description

Technical Field

[0001] The invention belongs to the field of biochemical engineering and bioenergy, and relates to a process for preparing a monosaccharide solution by acid gradient treatment of straw-type lignocellulose. Background Art

[0002] Bioenergy from lignocellulosic biomass is considered a suitable and potential alternative to fossil fuels due to their high greenhouse gas emissions. Agriculture, forestry, and industrial sectors are the major contributors to the availability of lignocellulosic biomass, with the most promising feedstocks being crop residues and forest residues. Lignocellulosic biomass is a potential source for the production of biofuels and biochemicals due to its abundance and low cost.

[0003] Lignocellulosic biomass materials are composed of three polymer layers, including cellulose, hemicellulose and lignin. Because lignin is composed of complex aromatic polymers, it hinders the process efficiency in biofuel and biochemical production. Pretreatment technology can effectively remove the lignin component to reduce its negative impact, but traditional pretreatment will inevitably lead to problems such as carbohydrate loss, and the residue obtained after pretreatment still requires the introduction of enzymes to obtain monosaccharide components, making the cost of biorefining still high. In traditional pretreatment processes, physical pretreatment has little effect when used alone and has high operating costs, while physical and chemical pretreatment requires high temperature, special reactors and expensive instruments. The biological pretreatment cycle is long, and the process will lead to the consumption of some carbohydrates due to the growth and utilization of microorganisms themselves.

[0004] In order to overcome the key problems faced in the process of preparing monosaccharides from lignocellulosic biomass, many researchers have proposed corresponding solutions. For example, Chinese invention CN115341004A discloses a method for preparing monosaccharides from biomass raw materials, but this method requires two stages of enzyme preparation for monosaccharide preparation, and at least one of steam explosion, cooking and puffing is performed on the lignocellulosic biomass before the enzyme preparation is used. The overall process cost is high, the cycle is long, and the operation is cumbersome. Chinese invention CN101855368A discloses a method for preparing sugar products, but this method needs to maintain high temperature and high pressure during the acid treatment process, which brings a certain degree of challenge to the pretreatment process. Chinese invention CN114410850A discloses a comprehensive method for treating lignocellulosic materials, but this method requires a large amount of energy consumption and ignores the recycling and reuse of the acid used in the pretreatment process.

[0005] Therefore, developing economical, efficient and green methods to obtain monosaccharide solutions remains a key challenge for lignocellulose conversion technology. Summary of the invention

[0006] The technical problem to be solved by the present invention is to address the deficiencies in the prior art and to provide a process for preparing a monosaccharide solution by acid gradient treatment of straw-based lignocellulose so as to solve the problem of sugar degradation into by-products affecting saccharification yield and producing microbial fermentation inhibitors in the previous non-grain bio-based sugar production process, as well as the problem of energy consumption under harsh conditions of high temperature and high pressure.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] The present invention discloses a process for preparing a monosaccharide solution by acid gradient treatment of straw-based lignocellulose, comprising the following steps:

[0009] S1: The lignocellulosic biomass is subjected to a first acid hydrolysis reaction catalyzed by an acid solution having a concentration of 50 wt % or more to obtain a first acid hydrolysis solution;

[0010] S2: mixing the first acid hydrolysis solution with an organic solvent, separating the solid and the liquid, and obtaining a residue containing polysaccharides;

[0011] S3: adding water and / or an acid solution to the polysaccharide-containing residue to obtain a mixed solution having an acid concentration of less than 45 wt%, performing a second acid hydrolysis reaction to obtain a reaction solution containing monosaccharides, and performing solid-liquid separation to obtain a monosaccharide-containing solution and a lignin precipitate; the monosaccharide-containing solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution;

[0012] S4: The acid-containing liquid phase obtained after the solid-liquid separation in step S2 is stripped with water, and the phase is separated after standing to obtain an acid solution and an organic phase; the obtained organic phase is purified and returned to step S2 for use as an organic solvent; the obtained acid solution (which may include the acid solution in step S3) is concentrated to obtain an acid solution with a concentration of more than 50 wt% and condensed water or a low-concentration acid solution; the obtained acid solution with a concentration of more than 50 wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3.

[0013] In step S1, the lignocellulosic biomass includes straw-based lignocellulosic biomass; preferably, the straw-based lignocellulosic biomass is any one or a combination of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed and rapeseed, preferably wheat straw.

[0014] In step S1, the acidic aqueous solution is an aqueous solution of an inorganic acid; preferably, the inorganic acid is any one or a combination of sulfuric acid, hydrochloric acid and phosphoric acid; preferably, the concentration of the acid in the acidic solution is 55wt%-95wt%, preferably 60wt%-90wt%, preferably 80wt%.

[0015] In step S1, the mass ratio of the lignocellulosic biomass to the acid in the acid solution is 1:0.5-2.5, preferably 1:1-2, preferably 1:1.5.

[0016] In step S1, the reaction temperature of the first acid hydrolysis reaction is 20-30°C, preferably room temperature.

[0017] In step S1, the pressure of the first acid hydrolysis reaction is normal pressure.

[0018] In step S1, the first acid hydrolysis reaction is completed when the system has good fluidity. Taking 10 kg of straw as an example, the time required for the reaction to be completed is 1 hour.

[0019] In step S2, the organic solvent is any one or a combination of alcohol organic solvents, ketone organic solvents and tertiary amine organic solvents.

[0020] In step S2, the mass ratio of the first acid hydrolysis solution to the organic solvent is 1:1-5, preferably 1:2-4, preferably 1:2.5-3.5, preferably 1:3

[0021] In step S2, the purpose of mixing the first acid hydrolysis solution with the organic solvent is to extract and recover the acid in the first acid hydrolysis solution. The number of extractions is not limited and is adjusted according to actual conditions.

[0022] In step S3, the acid concentration of the mixed solution is 5wt%-35wt%, preferably 10wt%-30wt%, preferably 20wt%.

[0023] In step S3, the temperature of the second acid hydrolysis reaction is 60-120°C, preferably 70-110°C, preferably 80-100°C, preferably 90°C.

[0024] In step S3, the pressure of the second acid hydrolysis reaction is normal pressure.

[0025] In step S3, the second acid hydrolysis reaction time is 0.3 to 2.5 hours, preferably 0.4 to 2 hours, preferably 0.5 to 1.5 hours, preferably 1 hour.

[0026] The polysaccharides described in the present invention mainly include glucan and xylan.

[0027] Beneficial effects:

[0028] (1) The straw-based lignocellulosic biomass of the present invention is first pretreated at room temperature and pressure (i.e., the first acid hydrolysis reaction), which does not require additional energy, and all reagents used in the pretreatment process can be recycled, greatly reducing the production cost.

[0029] (2) The straw-based lignocellulosic biomass of the present invention is first pretreated (i.e., primary acid hydrolysis) at room temperature and pressure, and then subjected to secondary acid hydrolysis to obtain a monosaccharide conversion rate that is significantly improved compared to conventional heating treatment, providing a new option for the construction of a non-food bio-based sugar platform.

[0030] (3) The present invention adopts a lower liquid-to-solid ratio, and monosaccharides can be directly obtained after pretreatment, and finally a high-concentration and controllable monosaccharide solution is obtained, avoiding the investment of a large amount of enzyme costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0032] Figure 1 This is a flow chart of the pretreatment of straw-based lignocellulosic biomass in an embodiment of the present invention.

[0033] Figure 2 This is the aromatic two-dimensional NMR image of lignin obtained in Example 11 of the present invention.

[0034] Figure 3 The types and distribution of polysaccharides obtained by single acid hydrolysis in Example 11 of the present invention.

[0035] Figure 4 This is the monosaccharide solution obtained in Example 11 of the present invention. DETAILED DESCRIPTION

[0036] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0037] The straw-based lignocellulosic biomass raw material used in the following examples is wheat straw, in which the mass content of cellulose is 34.92%, the mass content of hemicellulose is 22.58%, and the mass content of lignin is 23.03%.

[0038] The simulated moving bed treatment conditions described in the following examples are: using strong acid styrene resin hydrogen type resin, the circulation flow rate is 75ml / min, the feed flow rate is 25ml / min, the elution reagent is water, and the elution flow rate is 75ml / min.

[0039] The calculation method of glucose conversion rate and xylose conversion rate in the embodiment of the present invention is as follows:

[0040] Glucose conversion rate % = C G *V / M G *100%

[0041] Xylose conversion rate % = CX *V / M X *100%

[0042] C G : The concentration of glucose in the monosaccharide solution; C X : xylose concentration in monosaccharide solution; V: volume of monosaccharide solution; M G : The mass of glucose in the straw put into the reaction; M X : The mass of xylose in the straw put into the reaction;

[0043] Example 1

[0044] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0045] S1: wheat straw (40-100 mesh) is mixed with a 60wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0046] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with heptanol, wherein the mass ratio of the first acid hydrolysis liquid to heptanol is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0047] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 10 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 80°C for 0.5 h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0048] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >60wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >60wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0049] After two stages of acid hydrolysis, the glucose conversion rate was 71.36% and the xylose conversion rate was 63.14%.

[0050] Example 2

[0051] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0052] S1: wheat straw (40-100 mesh) is mixed with a 60wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0053] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with methyl ethyl ketone, wherein the mass ratio of the first acid hydrolysis liquid to the methyl ethyl ketone is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0054] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 10 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 80°C for 0.5 h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0055] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >60wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >60wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0056] After two stages of acid hydrolysis, the glucose conversion rate was 66.89% and the xylose conversion rate was 52.66%.

[0057] Example 3

[0058] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0059] S1: wheat straw (40-100 mesh) is mixed with a 60wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0060] S2: The first acid hydrolysis liquid obtained in step S1 is fully mixed with tri(2-ethylhexyl)amine, wherein the mass ratio of the first acid hydrolysis liquid to tri(2-ethylhexyl)amine is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0061] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 10 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 80°C for 0.5 h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0062] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >60wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >60wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0063] After two stages of acid hydrolysis, the glucose conversion rate was 77.24% and the xylose conversion rate was 68.62%.

[0064] Example 4

[0065] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0066] S1: wheat straw (40-100 mesh) is mixed with a 90%wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:2, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0067] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with heptanol, wherein the mass ratio of the first acid hydrolysis liquid to heptanol is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0068] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 30 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 100°C for 1.5 hours. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0069] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >90wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >90wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0070] After two stages of acid hydrolysis, the glucose conversion rate was 68.56% and the xylose conversion rate was 54.38%.

[0071] Example 5

[0072] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0073] S1: wheat straw (40-100 mesh) is mixed with a 90%wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:2, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0074] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with methyl ethyl ketone, wherein the mass ratio of the first acid hydrolysis liquid to the methyl ethyl ketone is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0075] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 30 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 100°C for 1.5 hours. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0076] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >90wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >90wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0077] After two stages of acid hydrolysis, the glucose conversion rate was 62.37% and the xylose conversion rate was 50.14%.

[0078] Example 6

[0079] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0080] S1: wheat straw (40-100 mesh) is mixed with a 90%wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:2, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0081] S2: The first acid hydrolysis liquid obtained in step S1 is fully mixed with tri(2-ethylhexyl)amine, wherein the mass ratio of the first acid hydrolysis liquid to tri(2-ethylhexyl)amine is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0082] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 30 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 100°C for 1.5 hours. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0083] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >90wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >90wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0084] After two stages of acid hydrolysis, the glucose conversion rate was 72.76% and the xylose conversion rate was 61.74%.

[0085] Example 7

[0086] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0087] S1: wheat straw (40-100 mesh) is mixed with a 60wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0088] S2: The first acid hydrolysis liquid obtained in step S1 is fully mixed with tri(2-ethylhexyl)amine, wherein the mass ratio of the first acid hydrolysis liquid to tri(2-ethylhexyl)amine is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0089] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 30 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 100°C for 1.5 hours. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0090] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >60wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >60wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0091] After two stages of acid hydrolysis, the glucose conversion rate was 84.53% and the xylose conversion rate was 76.85%.

[0092] Example 8

[0093] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0094] S1: wheat straw (40-100 mesh) is mixed with a 90wt% sulfuric acid aqueous solution, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:2, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity, thereby obtaining a first acid hydrolysis solution.

[0095] S2: The first acid hydrolysis liquid obtained in step S1 is fully mixed with tri(2-ethylhexyl)amine, wherein the mass ratio of the first acid hydrolysis liquid to tri(2-ethylhexyl)amine is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0096] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 10 wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 80°C for 0.5 h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0097] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >90wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >90wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0098] After two stages of acid hydrolysis, the glucose conversion rate was 88.21% and the xylose conversion rate was 82.46%.

[0099] Example 9

[0100] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0101] S1: wheat straw (40-100 mesh) is mixed with a sulfuric acid aqueous solution with a mass percentage concentration of 80wt%, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1.5, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity to obtain a first acid hydrolysis solution.

[0102] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with heptanol, wherein the mass ratio of the first acid hydrolysis liquid to heptanol is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0103] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 20wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 90°C for 1h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0104] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >80wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >80wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0105] After two stages of acid hydrolysis, the glucose conversion rate was 85.64% and the xylose conversion rate was 78.49%.

[0106] Example 10

[0107] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0108] S1: wheat straw (40-100 mesh) is mixed with a sulfuric acid aqueous solution with a mass percentage concentration of 80wt%, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1.5, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity to obtain a first acid hydrolysis solution.

[0109] S2: the first acid hydrolysis liquid obtained in step S1 is fully mixed with methyl ethyl ketone, wherein the mass ratio of the first acid hydrolysis liquid to the methyl ethyl ketone is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0110] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 20wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 90°C for 1h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0111] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >80wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >80wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0112] After two stages of acid hydrolysis, the glucose conversion rate was 83.42% and the xylose conversion rate was 75.93%.

[0113] Embodiment 11

[0114] A method for obtaining an acid-containing monosaccharide solution by acid treatment of straw-like lignocellulosic biomass comprises the following steps:

[0115] S1: wheat straw (40-100 mesh) is mixed with a sulfuric acid aqueous solution with a mass percentage concentration of 80wt%, the straw can be added in batches or all at once, wherein the mass ratio of wheat straw to sulfuric acid aqueous solution is 1:1.5, and the reaction solution is subjected to a first acid hydrolysis reaction at room temperature and normal pressure until it has good fluidity to obtain a first acid hydrolysis solution.

[0116] S2: The first acid hydrolysis liquid obtained in step S1 is fully mixed with tri(2-ethylhexyl)amine, wherein the mass ratio of the first acid hydrolysis liquid to tri(2-ethylhexyl)amine is 1:3, and after mixing, solid-liquid separation is performed to obtain an acid-containing liquid phase and a residue containing polysaccharides and lignin.

[0117] S3: The residue containing polysaccharides and lignin obtained in step S2 is mixed with water and / or an acid solution to obtain a secondary acid hydrolysis mixed solution (acid concentration is 20wt%), and then a secondary acid hydrolysis reaction is carried out at normal pressure and 90°C for 1h. After the acid reaction is completed, the solid and liquid are separated to obtain an acid-containing monosaccharide solution and a lignin precipitate. The obtained acid-containing monosaccharide solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

[0118] S4: Add water to the acid-containing liquid phase obtained in step S2 for back extraction, and separate the layers after standing to obtain an acid solution and an organic phase. The obtained organic phase is purified and returned to step S2 for use as an organic solvent. The obtained acid solution (including the acid solution obtained in step S3) is concentrated to obtain an acid solution of >80wt% and condensed water or a low-concentration acid solution; the obtained acid solution of >80wt% is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3 for use as a secondary acid hydrolysis solvent.

[0119] After two stages of acid hydrolysis, the glucose conversion rate was 91.58%, the xylose conversion rate was 85.29%, and the total sugar concentration in the final monosaccharide solution could reach 109.61 g / L.

[0120] Example 12

[0121] A method for obtaining an acid-containing monosaccharide solution by acid-treating straw-like lignocellulosic biomass is the same as that of Example 1, except that a different solvent is used for the treatment.

[0122]

[0123]

[0124] Figure 2 It is the aromatic structure of the residual lignin component after the secondary acid hydrolysis, which can be recycled for the preparation of bio-based fertilizers.

[0125] Figure 3 The types and distribution of polysaccharides obtained from the first acid hydrolysis are mainly glucan and xylan.

[0126] Figure 4 The monosaccharide solution obtained by the present invention mainly contains glucose and xylose in the monosaccharides.

[0127] The present invention provides a method and idea for obtaining an acid-containing monosaccharide solution by acid treatment of straw-based lignocellulosic biomass. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for preparing monosaccharides from lignocellulosic biomass, characterized in that: The steps include: S1: The lignocellulosic biomass is subjected to a first acid hydrolysis reaction at 20-30° C. by catalysis of an acid solution having a concentration of 50 wt % or more to obtain a first acid hydrolysis solution; S2: mixing the first acid hydrolysis solution with an organic solvent, separating the solid and the liquid, and obtaining a residue containing polysaccharides; S3: adding water and / or an acid solution to the polysaccharide-containing residue to obtain a mixed solution having an acid concentration of less than 45 wt %, and performing a second acid hydrolysis reaction to obtain a reaction solution containing monosaccharides; In step S2, the organic solvent is any one of tri(2-ethylhexyl)amine, triethylamine and isopropylamine.

2. The method according to claim 1, characterized in that In step S1, the lignocellulosic biomass includes straw-based lignocellulosic biomass.

3. The method according to claim 2, characterized in that The straw-based lignocellulosic biomass is any one or a combination of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed and rapeseed.

4. The method according to claim 1, characterized in that: In step S1, the acid solution is an aqueous solution of an inorganic acid, and the concentration of the acid in the acid solution is 55wt%-95wt%.

5. The method according to claim 4, characterized in that The inorganic acid is any one of sulfuric acid, hydrochloric acid and phosphoric acid or a combination of several thereof.

6. The method according to claim 4, characterized in that In step S1, the acid concentration in the acid solution is 60wt%-90wt%.

7. The method according to claim 1, characterized in that In step S1, the mass ratio of the lignocellulosic biomass to the acid in the acid solution is 1:0.5-2.

5.

8. The method according to claim 1, characterized in that In step S1, the mass ratio of the lignocellulosic biomass to the acid in the acid solution is 1:1-2.

9. The method according to claim 1, characterized in that: In step S1, the reaction temperature of the first acid hydrolysis reaction is room temperature, and the pressure of the first acid hydrolysis reaction is normal pressure.

10. The method according to claim 1, characterized in that In step S2, the mass ratio of the first acid hydrolysis solution to the organic solvent is 1:1-5.

11. The method according to claim 1, characterized in that: In step S2, the mass ratio of the first acid hydrolysis solution to the organic solvent is 1:2.5-3.

5.

12. The method according to claim 1, characterized in that In step S3, the acid concentration of the mixed solution is 5wt%-35wt%.

13. The method according to claim 1, characterized in that In step S3, the acid concentration of the mixed solution is 10wt%-30wt%.

14. The method according to claim 1, characterized in that In step S3, the temperature of the second acid hydrolysis reaction is 60-120°C.

15. The method according to claim 1, characterized in that In step S3, the temperature of the second acid hydrolysis reaction is 80-100°C.

16. The method according to claim 1, characterized in that In step S3, the pressure of the second acid hydrolysis reaction is normal pressure.

17. The method according to claim 1, characterized in that In step S3, the second acid hydrolysis reaction time is 0.3 to 2.5 hours.

18. The method according to claim 1, characterized in that In step S3, the monosaccharide-containing reaction liquid is subjected to solid-liquid separation to obtain a monosaccharide-containing solution and a lignin precipitate; the monosaccharide-containing solution is treated by a simulated moving bed to obtain a monosaccharide solution and an acid solution.

19. The method according to claim 1, characterized in that The method further comprises: S4: adding water to the acid-containing liquid phase obtained after the solid-liquid separation in step S2 for back extraction, standing and separating the phases to obtain an acid solution and an organic phase.

20. The method according to claim 19, characterized in that The organic phase obtained in step S4 is purified and returned to step S2 for use as an organic solvent.

21. The method according to claim 19 or 20, characterized in that The acid solution obtained in step S4 is concentrated to obtain an acid solution with a concentration of more than 50 wt % and condensed water or a low-concentration acid solution.

22. The method according to claim 21, characterized in that The obtained acid solution with a concentration of 50 wt % or more is returned to step S1 for use as an acid solution; the obtained condensed water or low-concentration acid solution is returned to step S3.

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