A method for producing acetic acid by solvent fractionation of a whole lignocellulosic feedstock

Abstract

This invention discloses a method for producing acetic acid from lignocellulose raw materials by solvent fractionation. Using non-grain biomass as raw material, the method achieves efficient separation of lignin from cellulose and hemicellulose through pretreatment with hydrogen peroxide-acetic acid aqueous solution. The lignin is then gasified with oxygen and steam to obtain syngas, eliminating the need for a water-gas conversion process. After selectively separating some carbon monoxide, the remaining gas is used to synthesize methanol, which is then dehydrated to obtain dimethyl ether. This dimethyl ether is then reacted with carbon monoxide for carbonylation and hydrolysis to obtain acetic acid and methanol. The methanol and acetic acid are recycled in a closed loop. The molecular sieve used in the carbonylation reaction is modified with alkali and phosphorus to improve the catalyst's lifespan. This method completely eliminates fossil raw materials in the production of acetic acid, resulting in a green and low-carbon chain with high raw material utilization.

Description

Technical Field

[0001] This invention relates to the field of biomass energy chemical technology, specifically to a method for producing acetic acid by solvent fractionation of a completely lignocellulose feedstock. Background Technology

[0002] Acetic acid, as a core raw material in strategic fields such as chemicals, materials, and pharmaceuticals, directly impacts the decarbonization process and sustainable development of the chemical industry through its green production model. Driven by both "dual carbon" goals and resource security strategies, breaking free from dependence on fossil fuels such as coal and natural gas and building a green production system with no fossil involvement throughout the entire chain has become the core direction for the upgrading of the acetic acid industry. However, the limitations of traditional technologies and the inherent shortcomings of new solutions constitute the core contradiction in the industry's development.

[0003] Currently, there are two main production routes for acetic acid: the methanol carbonylation route, which uses non-renewable fossil resources as raw materials to produce methanol, which is then reacted with carbon monoxide. This process has high carbon emissions, relies on precious metal catalysts such as rhodium and iridium, and toxic iodide co-catalysts. The catalysts are expensive and pose a risk of poisoning. Furthermore, the catalysts have short lifespans and require frequent replacement, further increasing production and maintenance costs and limiting production efficiency. Iodides are also highly corrosive, increasing equipment investment and maintenance costs, and posing potential environmental risks. While the bio-fermentation route has carbon-neutral potential, it relies on grain-based raw materials, facing ethical controversies regarding land use. Additionally, the fermentation cycle is long, the product concentration is low, and separation energy consumption is high, resulting in high product costs.

[0004] Non-grain biomass such as straw, as abundant and low-cost renewable carbon resources, are ideal raw materials for decarbonization in the acetic acid industry. Currently, however, they are not used to produce acetic acid. Furthermore, existing biomass pretreatment technologies consume large amounts of reagents, involve cumbersome processes, and rely heavily on fossil fuels, further diminishing the green nature of the process. Therefore, developing a purely green acetic acid production process that uses non-grain biomass as the sole carbon source, achieves efficient utilization of the three elements (carbon, oxygen, and fuel), enables in-situ control of syngas, eliminates precious metals and toxic additives, and completely avoids fossil fuel involvement, has become a core breakthrough for addressing industry pain points and promoting industrial transformation. It is also a crucial technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a method for producing acetic acid from a completely lignocellulose raw material through solvent fractionation. By performing alkali and phosphorus composite modification on the molecular sieve, it acquires stronger resistance to deactivation and optimized mass transfer performance. Furthermore, by using non-grain biomass such as straw as raw materials, it eliminates dependence on fossil raw materials and achieves low carbon, low consumption, and high raw material utilization.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for producing acetic acid by solvent fractionation of a completely lignocellulose feedstock includes the following steps:

[0008] S1. Non-grain biomass is placed in a biomass acid treatment unit to obtain a mixture;

[0009] S2. The mixture is placed in a filtration and separation unit for filtration to obtain solid and liquid components;

[0010] S3. The liquid component is placed in the acetic acid recovery unit for atmospheric distillation to obtain crude lignin;

[0011] S4. Crude lignin is placed in a biomass gasification unit with water vapor and oxygen for a combined gasification reaction to generate crude syngas. After dust removal and desulfurization treatment, the crude syngas is purified to obtain syngas.

[0012] S5. The purified syngas is placed in the CO separation unit for carbon dioxide removal and then separated to obtain carbon monoxide and syngas.

[0013] S6. The synthesis gas is placed in the methanol synthesis unit to carry out the synthesis reaction to obtain crude methanol;

[0014] S7. Crude methanol is placed in the methanol dehydration to dimethyl ether unit and dehydrated under the action of a catalyst to obtain dimethyl ether.

[0015] S8. Dimethyl ether and carbon monoxide obtained from S5 are placed in the carbonylation unit for the carbonylation reaction to produce acetic acid and methanol to obtain methyl acetate.

[0016] S9. Methyl acetate and deionized water are placed in the methyl acetate hydrolysis unit and hydrolyzed under the action of a catalyst to obtain a mixture of acetic acid and methanol.

[0017] S10. The mixture is placed in the acetic acid and methanol separation unit for distillation separation to obtain high-purity acetic acid and methanol.

[0018] More preferably, the non-grain biomass mentioned in step S1 is one or more agricultural and forestry wastes such as trees and straw.

[0019] More preferably, in step S1, the biomass acid treatment unit uses an aqueous solution of acetic acid containing hydrogen peroxide as the treatment solution to treat the biomass. The treatment temperature is 60-80℃ and the time is 2-10h. The mass fraction of hydrogen peroxide is 5%-15%, the mass fraction of acetic acid is 20%-60%, and the solid-liquid mass ratio of non-grain biomass to the hydrogen peroxide-acetic acid aqueous solution is 1:8-1:15. Before treatment with the treatment solution, physical sorting, impurity removal, crushing, and drying are required.

[0020] More preferably, in step S2, the pressure condition during filtration in the filtration separation unit is 0.3-0.6 MPa, and the time condition is 15-60 min.

[0021] More preferably, the filtration and separation unit in step S2 adopts plate and frame filtration, wherein the solid component mainly contains cellulose and hemicellulose, and the liquid component mainly contains lignin and acetic acid aqueous solution.

[0022] More preferably, in step S3, the temperature at the top of the atmospheric distillation column is controlled at 110-120°C and the temperature at the bottom of the column is controlled at 130-140°C. The concentrate in the bottom of the distillation column needs to be washed with water and dried.

[0023] More preferably, in step S4, the mass ratio of water vapor to lignin in the combined gasification reaction is 0.8:1-1.2:1, the oxygen-carbon molar ratio of oxygen to crude lignin is 0.8:1-1:1, the temperature of the combined gasification reaction is 800-1200℃, the pressure is 0.1-0.3MPa, and the molar ratio of hydrogen to carbon monoxide in the crude synthesis gas is 1:1-1.2:1.

[0024] More preferably, in step S5, the molar ratio of hydrogen to carbon monoxide in the syngas is 2:1 to 2.15:1, and the purity of the separated carbon monoxide is ≥98%.

[0025] More preferably, the synthesis reaction in step S6 requires the use of a CuO / ZnO / Al2O3 ternary catalyst, and the temperature conditions for the synthesis reaction are 220-280℃ and the pressure conditions are 5-10MPa.

[0026] More preferably, the crude methanol in step S7 needs to be purified by a dual-tower distillation system, and the purified methanol has a purity of ≥99.9%.

[0027] More preferably, the catalyst in step S7 is HZSM-5 molecular sieve or γ-Al2O3.

[0028] More preferably, the temperature conditions for the carbonyl insertion reaction in step S8 are 220-280℃, the pressure conditions are 2.0-5.0MPa, and the molar ratio of dimethyl ether to carbon monoxide is 1:1-1:1.15.

[0029] More preferably, the catalyst in step S9 is an A-15 acidic ion exchange resin catalyst, the reaction temperature is 60-80℃, the pressure is 0.1-0.3MPa, the time is 2-4h, and the molar ratio of methyl acetate to deionized water is 1:1-1:3.

[0030] More preferably, in step S10, the separated methanol is recycled back to the reactive distillation column in S7 for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is used as the target product.

[0031] More preferably, the preparation method of the modified molecular sieve catalyst includes the following steps:

[0032] (1) Alkali-modified mordenite molecular sieve was obtained by calcining after being alkali-modified by sodium hydroxide aqueous solution.

[0033] (2) After ion exchange and phosphorus loading of alkali-modified mordenite molecular sieve under the action of ammonium dihydrogen phosphate aqueous solution, the modified molecular sieve catalyst is obtained by calcination.

[0034] More preferably, the temperature conditions for alkali treatment in step (1) are 50-70℃ and the time conditions are 1-5h. After alkali treatment, water washing, filtration and drying are required.

[0035] More preferably, the concentration of the sodium hydroxide aqueous solution in step (1) is 0.2-0.6 mol / L, and the solid-liquid mass ratio of the silicate zeolite molecular sieve to the sodium hydroxide aqueous solution is 1:5-1:10.

[0036] More preferably, in step (1), the calcination is carried out by heating to 500-550℃ at a rate of 1-3℃ / min and holding the temperature for 4-6 hours.

[0037] More preferably, in step (2), the temperature condition for phosphorus loading is room temperature, the time condition is 4-5 h, the concentration of ammonium dihydrogen phosphate aqueous solution is 0.1-0.5 mol / L, the solid-liquid mass ratio of alkali-modified mordenite molecular sieve to ammonium dihydrogen phosphate aqueous solution is 1:5-1:10, the number of ion exchanges is 2-4, and the phosphorus loading on the modified molecular sieve is 2%-3%.

[0038] More preferably, in step (2), the calcination is carried out by heating to 500-550℃ at a rate of 1-3℃ / min and holding the temperature for 4-6 hours.

[0039] The beneficial effects of this invention are:

[0040] This invention utilizes acetic acid as a solvent for separating lignin from cellulose and hemicellulose, and produces acetic acid on-site. It is a fully biomass solvent fractionation process that is green and environmentally friendly and does not involve any fossil-based chemicals.

[0041] This invention uses non-grain biomass such as straw as the sole carbon source, making it green, low-carbon, renewable, and not competing with grain for land. It eliminates dependence on fossil fuels and aligns with the "dual carbon" goal. The hydrogen-to-carbon ratio of the lignin gasification syngas can be directly adjusted to be suitable for methanol synthesis through selective separation of carbon monoxide, eliminating the need for a water-gas conversion process, reducing carbon dioxide emissions, raw material consumption, and energy consumption, achieving low-carbon, energy-saving, and raw material-saving results. The carbonyl insertion reaction uses a non-precious metal catalyst, eliminating precious metals and toxic additives such as iodomethane, allowing the use of conventional carbon steel equipment, significantly reducing catalyst and equipment investment, operation and maintenance costs, and environmental risks, achieving cost reduction, corrosion reduction, and greater environmental protection. At the same time, it utilizes biomass components in a tiered manner to co-produce high-value-added products, combining environmental benefits, cost advantages, and market resilience.

[0042] This invention modifies molecular sieves using a combination of alkali and phosphorus. Phosphorus stabilizes the framework, enhancing the hydrothermal stability of the modified molecular sieve. The interaction between phosphorus and aluminum in the framework selectively modulates acid strength and density, reducing strong acid sites and suppressing side reactions such as dimethyl ether decomposition and olefin formation, thereby improving the selectivity of methyl acetate. Alkali treatment introduces mesoporous structures into the crystal structure through controlled desilication, effectively improving the diffusion and mass transfer properties of macromolecules and optimizing the enrichment and transformation of reactants near active sites. The alkali-phosphorus modified molecular sieve exhibits stronger resistance to deactivation, significantly extending catalyst lifespan and improving overall process stability and the yield of the target product. Attached Figure Description

[0043] The invention will now be further described with reference to the accompanying drawings.

[0044] Figure 1 This is a schematic diagram of a process for producing acetic acid from a completely lignocellulose raw material through solvent fractionation. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, a method for producing acetic acid from a completely lignocellulose feedstock by solvent fractionation includes the following steps:

[0048] S1. Select corn stalks as raw materials, remove impurities such as soil and stones through physical sorting, crush them to a particle size of 9-12 mm, and dry them to a moisture content of 9% to obtain pretreated biomass; prepare a hydrogen peroxide-acetic acid aqueous solution (hydrogen peroxide mass fraction 8%, acetic acid mass fraction 40%, acetic acid is recycled material produced by this method) according to a solid-liquid mass ratio of non-grain biomass to hydrogen peroxide-acetic acid aqueous solution of 1:12; mix the pretreated biomass with the above aqueous solution and send it into a reactor; react at 70℃ for 6 hours to fully exfoliate lignin into the liquid phase, while cellulose and hemicellulose remain in the solid phase to obtain a mixture;

[0049] S2. The mixture is fed into a plate and frame filter press, and the separation pressure is controlled at 0.5 MPa and the separation time is 30 min to obtain solid components and liquid components. The solid components mainly contain cellulose and hemicellulose, and the liquid components mainly contain lignin and acetic acid aqueous solution.

[0050] S3. The liquid component is fed into an atmospheric distillation column, and the top temperature of the column is controlled at 115℃ and the bottom temperature at 135℃. Acetic acid is recovered by distillation. The recovered acetic acid is recycled back to S1 for the preparation of aqueous solution. The concentrate discharged from the bottom of the distillation column is washed twice with water and then dried at 110℃ for 3 hours to obtain crude lignin.

[0051] S4. Crude lignin is fed into a gasifier, while steam is introduced at a mass ratio of 1:1 to lignin and oxygen at a molar ratio of 0.9:1. The temperature inside the gasifier is controlled at 900℃ and the pressure at 0.2MPa to carry out a combined gasification reaction, producing crude syngas with a hydrogen to carbon monoxide molar ratio of 1:1. After dust removal by a cyclone separator and desulfurization by a desulfurization tower, purified syngas is obtained.

[0052] S5. Membrane separation technology is used to separate the purified syngas, separating 50% of the carbon monoxide, and obtaining a syngas with a purity of 98.5% carbon monoxide and a hydrogen to carbon monoxide molar ratio of 2:1.

[0053] S6. Synthesis gas is directly fed into the methanol synthesis reactor. Under the action of CuO / ZnO / Al2O3 ternary catalyst, the reaction temperature is controlled at 250℃ and the pressure at 8MPa to synthesize crude methanol.

[0054] S7. The crude methanol is purified by a double-tower distillation system to obtain purified methanol with a purity of 99.92%. The purified methanol is sent to a reactive distillation column, which is filled with HZSM-5 molecular sieves. The column is dehydrated to produce dimethyl ether, and the dimethyl ether is directly collected from the top of the column.

[0055] S8. The dimethyl ether extracted from S7 and the carbon monoxide separated from S5 are mixed in a molar ratio of 1:1 and introduced into a fixed-bed reactor. Using modified molecular sieve as a catalyst, the reaction temperature is controlled at 250℃ and the pressure at 3.5MPa to carry out the carbonylation reaction to produce methyl acetate.

[0056] S9. Methyl acetate is fed into the methyl acetate hydrolysis unit, and deionized water is added at a molar ratio of methyl acetate to water of 1:2. A-15 acidic ion exchange resin is used as a catalyst, and the reaction temperature is controlled at 70℃, the pressure at 0.2MPa, and the reaction time at 3h to obtain a mixture of acetic acid and methanol.

[0057] S10. The mixture is separated by distillation to obtain acetic acid with a purity of 99.9% and methanol with a purity of 99.5%. The methanol is recycled back to the S7 reactive distillation column for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is collected as the target product.

[0058] The preparation method of the modified molecular sieve catalyst includes the following steps:

[0059] (1) The mordenite molecular sieve was stirred with 0.2 mol / L sodium hydroxide aqueous solution at 60°C for 3 h. The solid-liquid mass ratio of the mordenite molecular sieve to the sodium hydroxide aqueous solution was 1:10. Then it was washed with water, filtered and dried. Then it was transferred to a muffle furnace and heated to 500°C at a rate of 2°C / min. After calcination for 6 h, it was cooled with the furnace and then ground thoroughly to obtain alkali-modified mordenite molecular sieve.

[0060] (2) The alkali-modified mordenite molecular sieve was added to an aqueous solution of ammonium dihydrogen phosphate with a concentration of 0.5 mol / L. The solid-liquid mass ratio of the alkali-modified mordenite molecular sieve to the aqueous solution of ammonium dihydrogen phosphate was 1:10. After stirring at room temperature for 4 hours, the mixture was dried and the operation was repeated twice under the same conditions. Then, it was transferred to a muffle furnace and calcined at 500°C for 6 hours at a rate of 1°C / min. After cooling in the furnace, the mixture was thoroughly ground to obtain the modified molecular sieve catalyst, wherein the phosphorus loading on the molecular sieve was 3%.

[0061] Example 2

[0062] like Figure 1 As shown, a method for producing acetic acid from a completely lignocellulose feedstock by solvent fractionation includes the following steps:

[0063] S1. Using a mixture of wheat straw and agricultural and forestry waste as raw material, after physical sorting and impurity removal, the mixture is pulverized to a particle size of 5-7 mm and dried to a moisture content of 8% to obtain pretreated biomass; a hydrogen peroxide-acetic acid aqueous solution is prepared by mixing non-grain biomass with a hydrogen peroxide-acetic acid aqueous solution at a solid-liquid mass ratio of 1:8 (wherein the mass fraction of hydrogen peroxide is 12% and the mass fraction of acetic acid is 50%, and the acetic acid is a self-produced recycled material of this method). The pretreated biomass is mixed with the above aqueous solution and fed into a reactor, where it is reacted at 80°C for 10 hours to achieve efficient separation of lignin from cellulose and hemicellulose, resulting in a mixture;

[0064] S2. The mixture is fed into a centrifuge, and the separation pressure is controlled at 0.6 MPa and the separation time is 60 min to obtain solid components and liquid components. The solid components mainly contain cellulose and hemicellulose, and the liquid components mainly contain lignin and acetic acid aqueous solution.

[0065] S3. The liquid component is fed into an atmospheric distillation column, and the top temperature of the column is controlled at 120℃ and the bottom temperature at 140℃. Acetic acid is recovered by distillation. The recovered acetic acid is recycled back to S1 for the preparation of aqueous solution. The concentrate in the bottom of the distillation column is washed with water three times and then dried at 105℃ for 4 hours to obtain crude lignin.

[0066] S4. The crude lignin is fed into the gasifier. Steam is introduced at a mass ratio of 1.2:1 to lignin, and oxygen is introduced at a molar ratio of 1:1 to carbon. The gasification temperature is controlled at 1000℃ and the pressure at 0.3MPa to produce crude syngas with a molar ratio of 1:1 to hydrogen and carbon monoxide. The crude syngas is then purified by dust removal in a cyclone separator and desulfurization in a desulfurization tower.

[0067] S5. Membrane separation technology is used to separate the purified syngas, separating 50% of carbon monoxide, and obtaining a syngas with a purity of 98.2% carbon monoxide and a hydrogen to carbon monoxide molar ratio of 2:1.

[0068] S6. The synthesis gas is fed into the methanol synthesis reactor. Under the action of the CuO / ZnO / Al2O3 ternary catalyst, the reaction temperature is controlled at 280℃ and the pressure at 10MPa to synthesize crude methanol.

[0069] S7. Crude methanol is purified by double-tower distillation to obtain refined methanol with a purity of 99.95%. The refined methanol is fed into a reactive distillation column, which is filled with γ-Al2O3 catalyst to dehydrate and generate dimethyl ether. The dimethyl ether is directly collected from the top of the column.

[0070] S8. The dimethyl ether generated in S7 is mixed with the carbon monoxide separated in S5 at a molar ratio of 1:1 and introduced into a fixed-bed reactor. Using modified molecular sieve as a catalyst, the reaction temperature is controlled at 280℃ and the pressure at 5.0MPa to carry out the carbonylation reaction to produce methyl acetate.

[0071] S9. Methyl acetate is fed into the methyl acetate hydrolysis unit, and deionized water is added at a molar ratio of methyl acetate to water of 1:3. A-15 acidic ion exchange resin catalyst is used, and the reaction temperature is controlled at 80℃, the pressure at 0.3MPa, and the reaction time at 4h to obtain a mixed solution.

[0072] S10. The mixture is separated by distillation to obtain acetic acid with a purity of 99.9% and methanol with a purity of 99.6%. The methanol is recycled back to the S7 reactive distillation column for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is collected as the target product.

[0073] The preparation method of the modified molecular sieve catalyst includes the following steps:

[0074] (1) The mordenite molecular sieve was stirred with 0.4 mol / L sodium hydroxide aqueous solution at 70°C for 3 h. The solid-liquid mass ratio of the mordenite molecular sieve to the sodium hydroxide aqueous solution was 1:10. Then it was washed with water, filtered and dried. Then it was transferred to a muffle furnace and heated to 550°C at a rate of 2°C / min. After constant temperature calcination for 4 h, it was cooled with the furnace and then fully ground to obtain alkali modified mordenite molecular sieve.

[0075] (2) The alkali-modified mordenite molecular sieve was added to an aqueous solution of ammonium dihydrogen phosphate with a concentration of 0.5 mol / L. The solid-liquid mass ratio of the alkali-modified mordenite molecular sieve to the aqueous solution of ammonium dihydrogen phosphate was 1:10. After stirring at room temperature for 5 h, the mixture was dried and the same operation was repeated 3 times. Then, it was transferred to a muffle furnace and heated to 550 °C at a rate of 2 °C / min. After constant temperature calcination for 4 h, it was cooled with the furnace and then thoroughly ground to obtain the modified molecular sieve catalyst, wherein the phosphorus loading on the molecular sieve was 3%.

[0076] Example 3

[0077] like Figure 1 As shown, a method for producing acetic acid from a completely lignocellulose feedstock by solvent fractionation includes the following steps:

[0078] S1. Using corn stalks as raw material, after physical sorting and impurity removal, the stalks are crushed to a particle size of 7-9 mm and dried to a moisture content of 10% to obtain pretreated biomass. A hydrogen peroxide-acetic acid aqueous solution is prepared at a solid-liquid mass ratio of 1:10 (wherein the mass fraction of hydrogen peroxide is 10% and the mass fraction of acetic acid is 45%, and the acetic acid is a self-produced recycled material of this method). The pretreated biomass is mixed with the above aqueous solution and fed into a reactor. The reaction is carried out at 75°C for 8 hours to achieve efficient separation of lignin from cellulose and hemicellulose, resulting in a mixture.

[0079] S2. The mixture is fed into a centrifuge, and the separation pressure is controlled at 0.4 MPa and the separation time is 40 min to obtain solid components and liquid components. The solid components mainly contain cellulose and hemicellulose, and the liquid components mainly contain lignin and acetic acid aqueous solution.

[0080] S3. The liquid component is fed into an atmospheric distillation column, and the top temperature of the column is controlled at 110℃ and the bottom temperature at 130℃. Acetic acid is recovered by distillation. The recovered acetic acid is recycled back to S1 for the preparation of aqueous solution. The concentrate in the bottom of the distillation column is washed with water three times and then dried at 100℃ for 5 hours to obtain crude lignin.

[0081] S4. The crude lignin is fed into the gasifier. Steam is introduced at a mass ratio of 1.2:1 to lignin, and oxygen is introduced at a molar ratio of 0.8:1. The gasification temperature is controlled at 800℃ and the pressure at 0.2MPa to produce crude syngas with a molar ratio of 1:1 of hydrogen to carbon monoxide. The crude syngas is then purified by dust removal in a cyclone separator and desulfurization in a desulfurization tower.

[0082] S5. Membrane separation technology is used to separate the purified syngas, separating 50% of carbon monoxide, and obtaining a syngas with a purity of 98.3% carbon monoxide stream and a hydrogen to carbon monoxide molar ratio of 2:1.

[0083] S6. Synthesis gas is fed into methanol synthesis reactor. Under the action of CuO / ZnO / Al2O3 ternary catalyst, the reaction temperature is controlled at 275℃ and the pressure at 9MPa to synthesize crude methanol.

[0084] S7. Crude methanol is purified by double-tower distillation to obtain refined methanol with a purity of 99.93%. The refined methanol is sent to a reactive distillation column, which is filled with HZSM-5 molecular sieve catalyst, and dehydrated to produce dimethyl ether. The dimethyl ether is directly collected from the top of the column.

[0085] S8. The dimethyl ether generated in S7 and the carbon monoxide separated in S5 are mixed in a molar ratio of 1:1 and introduced into a fixed-bed reactor. Using modified molecular sieve as a catalyst, the reaction temperature is controlled at 275℃ and the pressure at 4.0MPa to carry out the carbonylation reaction to produce methyl acetate.

[0086] S9. Methyl acetate is fed into the methyl acetate hydrolysis unit, and deionized water is added at a molar ratio of methyl acetate to water of 1:3. A-15 acidic ion exchange resin catalyst is used, and the reaction temperature is controlled at 75℃, the pressure at 0.3MPa, and the reaction time at 4h to obtain a mixed solution.

[0087] S10. The mixture is separated by distillation to obtain acetic acid with a purity of 99.9% and methanol with a purity of 99.5%. The methanol is recycled back to the S7 reactive distillation column for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is collected as the target product.

[0088] The preparation method of the modified molecular sieve catalyst includes the following steps:

[0089] (1) The mordenite molecular sieve was stirred with 0.6 mol / L sodium hydroxide aqueous solution at 70°C for 3 h. The solid-liquid mass ratio of the mordenite molecular sieve to the sodium hydroxide aqueous solution was 1:10. Then it was washed with water, filtered and dried. Then it was transferred to a muffle furnace and heated to 530°C at a rate of 3°C / min. After constant temperature calcination for 5 h, it was cooled with the furnace and then fully ground to obtain alkali modified mordenite molecular sieve.

[0090] (2) Add alkali-modified mordenite molecular sieve to a 0.5 mol / L ammonium dihydrogen phosphate aqueous solution. The solid-liquid mass ratio of alkali-modified mordenite molecular sieve to ammonium dihydrogen phosphate aqueous solution is 1:10. Stir at room temperature for 4.5 h and then dry. Repeat the operation 3 times under the same conditions. Then transfer it to a muffle furnace and heat it to 530 °C at a rate of 3 °C / min. After constant temperature calcination for 5 h, cool it with the furnace and then grind it thoroughly to obtain the modified molecular sieve catalyst, wherein the phosphorus loading on the molecular sieve is 3%.

[0091] Comparative Example 1

[0092] like Figure 1 As shown, a method for producing acetic acid from a completely lignocellulose feedstock by solvent fractionation includes the following steps:

[0093] S1. Using corn stalks as raw material, after physical sorting to remove impurities such as soil and stones, the stalks are crushed to a particle size of 8-12 mm and dried to a moisture content of 9% to obtain pretreated biomass. A hydrogen peroxide-acetic acid aqueous solution is prepared at a solid-liquid mass ratio of 1:12 (where the mass fraction of hydrogen peroxide is 8% and the mass fraction of acetic acid is 40%, and the acetic acid is recycled material produced by this method). The pretreated biomass is mixed with the above aqueous solution and fed into a reactor. The reaction is carried out at 70°C for 6 hours to allow lignin to be fully exfoliated into the liquid phase, while cellulose and hemicellulose remain in the solid phase, resulting in a mixture.

[0094] S2. The mixture is fed into a plate and frame filter press, and the separation pressure is controlled at 0.5 MPa and the separation time is 30 min to obtain solid components and liquid components. The solid components mainly contain cellulose and hemicellulose, and the liquid components mainly contain lignin and acetic acid aqueous solution.

[0095] S3. The liquid component is fed into an atmospheric distillation column, and the top temperature of the column is controlled at 115℃ and the bottom temperature at 135℃. Acetic acid is recovered by distillation. The recovered acetic acid is recycled back to S1 for the preparation of aqueous solution. The concentrate discharged from the bottom of the distillation column is washed twice with water and then dried at 110℃ for 3 hours to obtain crude lignin.

[0096] S4. Crude lignin is fed into a gasifier, while steam is introduced at a mass ratio of 1:1 to lignin and oxygen at a molar ratio of 0.9:1. The temperature inside the gasifier is controlled at 900℃ and the pressure at 0.2MPa to carry out a combined gasification reaction, producing crude syngas with a hydrogen to carbon monoxide molar ratio of 1:1. After dust removal by a cyclone separator and desulfurization by a desulfurization tower, purified syngas is obtained.

[0097] S5. The purified syngas is sent into the pressure swing adsorption separation unit to separate 50% of the carbon monoxide, and a syngas with a purity of 98.5% carbon monoxide and a hydrogen to carbon monoxide molar ratio of 2:1 is obtained.

[0098] S6. The synthesis gas is directly fed into the methanol synthesis reactor. Under the action of the CuO / ZnO / Al2O3 ternary catalyst, the reaction temperature is controlled at 250℃ and the pressure at 8MPa to synthesize crude methanol.

[0099] S7. The crude methanol is purified by a double-tower distillation system to obtain purified methanol with a purity of 99.92%. The purified methanol is fed into a reactive distillation column, which is filled with HZSM-5 molecular sieve catalyst. The methanol is dehydrated to produce dimethyl ether, and the dimethyl ether is directly collected from the top of the column.

[0100] S8. The dimethyl ether extracted from S7 and the carbon monoxide separated from S5 are mixed in a molar ratio of 1:1 and introduced into a fixed-bed reactor. Using mordenite molecular sieve as a catalyst, the reaction temperature is controlled at 250℃ and the pressure at 3.5MPa to carry out the carbonylation reaction to produce methyl acetate.

[0101] S9. Methyl acetate is fed into the methyl acetate hydrolysis unit, and deionized water is added at a molar ratio of methyl acetate to water of 1:2. A-15 acidic ion exchange resin is used as a catalyst, and the reaction temperature is controlled at 70℃, the pressure at 0.2MPa, and the reaction time at 3h to obtain a mixture containing acetic acid and methanol.

[0102] S10. The mixture is separated by distillation to obtain acetic acid with a purity of 99.8% and methanol with a purity of 99.5%. The methanol is recycled back to the reactive distillation column in S7 for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is collected as the target product.

[0103] Performance testing

[0104] The modified molecular sieve catalysts in Examples 1-3 and the mordenite molecular sieve catalyst in Comparative Example 1 were subjected to performance tests: the activity retention rate was tested according to GB / T18881-2017; the acetic acid purity of Examples 1-3 and Comparative Example 1 was tested according to GB / T22099-2008; the acetic acid recycling rate and methanol recycling rate of Examples 1-3 and Comparative Example 1 were tested according to GB / T27531-2011; and the comprehensive utilization rate of non-grain biomass raw materials of Examples 1-3 and Comparative Example 1 was tested according to GB / T42679-2023. The obtained process index test data are shown in Table 1.

[0105] Table 1: Statistical Table of Process Indicator Testing Data

[0106] As can be seen from the data in Table 1, compared with Comparative Example 1, the modified molecular sieves in Examples 1-3 have a higher activity retention rate, indicating that the composite modification of molecular sieves with alkali and phosphorus can effectively improve the service life of molecular sieves. Compared with Comparative Example 1, the acetic acid purity, acetic acid recycling rate, methanol recycling rate, and comprehensive utilization rate of non-grain biomass raw materials in Examples 1-3 have all improved to a certain extent, but are all at a high level.

[0107] The foregoing detailed description of one embodiment of the present invention is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the patent coverage of the present invention. It should be emphasized that the present invention is a process for the on-site production of acetic acid using all-biomass solvent fractionation. The production of cellulose, hemicellulose, pulp, solvent pulp, and cellulosic ethanol (including the production of lactic acid and other fermentation products from cellulose sugars) using all-solvent fractionation processes are all within the scope of patent protection.

Claims

1. A method for producing acetic acid by solvent fractionation of a completely lignocellulose feedstock, characterized in that, Includes the following steps: S1. Non-grain biomass is placed in a biomass acid treatment unit to obtain a mixture; S2. The mixture is placed in a filtration and separation unit for filtration to obtain solid and liquid components; S3. The liquid component is placed in the acetic acid recovery unit for atmospheric distillation to obtain crude lignin; S4. Crude lignin is placed in a biomass gasification unit with water vapor and oxygen for a combined gasification reaction to generate crude syngas. After dust removal and desulfurization treatment, the crude syngas is purified to obtain syngas. S5. The purified syngas is placed in the CO separation unit for carbon dioxide removal and then separated to obtain carbon monoxide and syngas. S6. The synthesis gas is placed in the methanol synthesis unit to carry out the synthesis reaction to obtain crude methanol; S7. Crude methanol is placed in the methanol dehydration to dimethyl ether unit and dehydrated under the action of a catalyst to obtain dimethyl ether. S8. Dimethyl ether and carbon monoxide obtained from S5 are placed in the carbonylation unit for the carbonylation reaction to produce acetic acid and methanol to obtain methyl acetate. S9. Methyl acetate and deionized water are placed in the methyl acetate hydrolysis unit and hydrolyzed under the action of a catalyst to obtain a mixture of acetic acid and methanol. S10. The mixture is placed in the acetic acid and methanol separation unit for distillation separation to obtain high-purity acetic acid and methanol.

2. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, In step S1, the biomass acid treatment unit uses an aqueous solution of acetic acid containing hydrogen peroxide as the treatment solution to treat the biomass, wherein the mass fraction of hydrogen peroxide is 5%-15%, the mass fraction of acetic acid is 20%-60%, and the solid-liquid mass ratio of non-grain biomass to the hydrogen peroxide-acetic acid aqueous solution is 1:8-1:

15.

3. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, In step S3, the temperature at the top of the atmospheric distillation column is controlled at 110-120℃, and the temperature at the bottom of the column is controlled at 130-140℃.

4. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, In step S4, the mass ratio of water vapor to lignin in the combined gasification reaction is 0.8:1-1.2:1, the oxygen-carbon molar ratio of oxygen to crude lignin is 0.8:1-1:1, the temperature of the combined gasification reaction is 800-1200℃, the pressure is 0.1-0.3MPa, and the molar ratio of hydrogen to carbon monoxide in the crude syngas is 1:1-1.2:

1. In step S5, the purity of the separated carbon monoxide is ≥98%, and the molar ratio of hydrogen to carbon monoxide in the syngas is 2:1-2.15:

1.

5. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, In step S7, the catalyst is HZSM-5 molecular sieve or γ-Al2O3; in step S8, the molar ratio of dimethyl ether to carbon monoxide is 1:1 to 1:1.15; in step S9, the catalyst is A-15 acidic ion exchange resin catalyst, and the molar ratio of methyl acetate to deionized water is 1:1 to 1:

3.

6. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, In step S10, the separated methanol is recycled back to the reactive distillation column in S7 for reuse, part of the acetic acid is recycled back to S1, and the remaining acetic acid is collected as the target product.

7. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 1, characterized in that, The preparation method of modified molecular sieve catalysts includes the following steps: (1) Alkali-modified mordenite molecular sieve was obtained by calcining after being alkali-modified by sodium hydroxide aqueous solution. (2) After ion exchange and phosphorus loading of alkali-modified mordenite molecular sieve under the action of ammonium dihydrogen phosphate aqueous solution, the modified molecular sieve catalyst is obtained by calcination.

8. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 7, characterized in that, The concentration of the sodium hydroxide aqueous solution in step (1) is 0.2-0.6 mol / L, the solid-liquid mass ratio of the silicate zeolite molecular sieve to the sodium hydroxide aqueous solution is 1:5-1:10, the reaction temperature is 50-70℃, and the reaction time is 1-5h.

9. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 7, characterized in that, In step (1), the calcination is carried out by heating the temperature to 500-550℃ at a rate of 1-3℃ / min and holding the temperature for 4-6 hours.

10. The method for producing acetic acid from a completely lignocellulose raw material by solvent fractionation according to claim 7, characterized in that, In step (2), the concentration of the ammonium dihydrogen phosphate aqueous solution is 0.1-0.5 mol / L, the solid-liquid mass ratio of the alkali-modified mordenite molecular sieve to the ammonium dihydrogen phosphate aqueous solution is 1:5-1:10, the number of ion exchanges is 2-4 times, and the calcination is carried out by heating to 500-550℃ at a rate of 1-3℃ / min and holding for calcination for 4-6 hours.

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