Low-carbon preparation method of bio-based acetic acid

Abstract

The invention discloses a low-carbon preparation method of bio-based acetic acid, and relates to the technical field of biomass energy and chemical industry. The method provided by the invention comprises the following steps: adding non-grain biomass into a pyrolysis unit for pyrolysis and carbonization to obtain biochar and biological combustible gas; the biochar is added into a gasification unit for gasification, and synthesis gas is obtained; adding the synthesis gas to a separation unit to obtain a carbon monoxide stream and a reaction gas; reaction gas is added into a synthesis unit for synthesis and then added into a rectification unit for rectification and purification, and refined methanol is obtained; adding the refined methanol into a dehydration unit for dehydration to obtain dimethyl ether; adding the carbon monoxide flow and dimethyl ether into a carbonyl insertion unit for carbonyl insertion to obtain methyl acetate; methyl acetate is added into the hydrolysis unit for hydrolysis, and a mixed solution is obtained; and adding the mixed solution into a purification unit for separation and purification to obtain refined acetic acid. The method for preparing acetic acid provided by the invention is low-carbon and environment-friendly in process, high in raw material utilization rate and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of biomass energy chemical technology, specifically to a low-carbon preparation method for bio-based acetic acid. Background Technology

[0002] Guided by the "dual carbon" goals, the green and low-carbon transformation of the chemical industry has become an inevitable trend. Acetic acid, as one of the world's most widely used organic acids, is extensively used in the production of key chemical products such as vinyl acetate, purified terephthalic acid (PTA), and acetate esters. The decarbonization of its production process and the greening of raw materials have become the core directions for technological innovation in the industry. Currently, the industrial production of acetic acid mainly relies on two mainstream routes:

[0003] The methanol carbonylation method uses fossil-based methanol as a raw material and relies on precious metal catalysts such as rhodium and iridium, as well as iodide co-catalysts. This not only results in high costs for catalyst procurement and recycling, but also in the severe corrosion of equipment caused by iodides, necessitating the use of high-end corrosion-resistant materials such as Hastelloy and titanium alloys, significantly increasing initial investment and maintenance costs. Furthermore, the use of fossil raw materials leads to a high carbon footprint, and the recycling and treatment of iodides poses environmental risks, failing to meet the requirements of green chemical development. While the bio-fermentation method uses biomass as a raw material and has some carbon neutrality advantages, the fermentation feedstock is mostly grain-based resources, raising potential conflicts with grain production regarding land use. Additionally, the reaction cycle is long, the product concentration is low, and subsequent separation and purification are energy-intensive, limiting large-scale production and making it difficult to meet the high-efficiency supply requirements of industrial-grade acetic acid.

[0004] Biomass, as an abundant, carbon-neutral, and renewable resource, especially non-grain biomass (such as straw and agricultural and forestry waste), can be converted and utilized without consuming food resources. This presents an ideal path to reduce dependence on fossil fuels and achieve a deep low-carbon transformation of the acetic acid industry. However, current technologies have not yet developed mature industrial-scale preparation schemes for non-grain biomass-based acetic acid, and related research still faces several critical challenges requiring breakthroughs.

[0005] First, the utilization rate of biomass is low, and its low-carbon potential has not been fully realized. Existing biomass utilization technologies mostly focus on the conversion of single products, failing to develop non-grain biomass in a "energy-raw material" cascade manner. This results in the inefficient separation and utilization of carbon and hydrogen resources in biomass, with some energy wasted as waste heat, failing to achieve full-chain low-carbonization and falling short of the resource efficiency requirements under the "dual carbon" goal. Second, the compatibility problem of syngas components restricts the implementation of the process. If syngas generated from the gasification of non-grain biomass is used as an intermediate feedstock to prepare acetic acid, the hydrogen-carbon ratio of the syngas must first be addressed. The molar ratio of hydrogen to carbon monoxide in the syngas obtained from biomass gasification is usually around 1:1, while methanol synthesis (a key intermediate step in acetic acid preparation) requires a strictly controlled hydrogen-carbon ratio of 2:1. The industry's conventional solution is to use a water-gas shift reaction to adjust the composition, but this reaction is accompanied by a large amount of carbon dioxide emissions and requires additional biomass feedstock to compensate for carbon loss. This increases energy consumption and carbon emissions, reduces feedstock utilization, and violates the core logic of low-carbon production. Third, the high cost and high risk inherent in traditional acetic acid synthesis processes are difficult to avoid. Even if the syngas stage is skipped and acetic acid is produced directly from biomass-derived methanol, the traditional methanol carbonylation technology is still required, relying on precious metal catalysts such as rhodium and iridium, as well as iodide co-catalysts. This cannot overcome the bottlenecks of high cost and high corrosion, limiting the economic viability of non-grain biomass-based acetic acid. Fourth, there is a lack of integrated processes that balance low carbon emissions and economic efficiency. Currently, no integrated solution exists that combines the cascade conversion of non-grain biomass, precise control of syngas components, green synthesis of acetic acid, and recycling of raw materials. Either the carbon emission problem caused by syngas conversion is not solved, or the dual high-efficiency utilization of biomass energy and raw materials is not achieved, or the high cost bottleneck of traditional processes hinders the industrial-scale promotion of non-grain biomass-based acetic acid.

[0006] Therefore, developing a bio-based acetic acid preparation process that uses non-grain biomass as raw material, achieves cascade utilization of "energy-raw material", eliminates the need for syngas conversion process, discards precious metals and corrosive additives, and can construct a low-carbon closed loop throughout the entire process has become the key to breaking through the limitations of existing technologies and promoting the deep low-carbon transformation of the acetic acid industry. It is also a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a low-carbon preparation method for bio-based acetic acid, solving the following technical problems:

[0008] Existing methods for preparing acetic acid suffer from high costs, environmental pollution, and low resource utilization.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A low-carbon method for preparing bio-based acetic acid, comprising at least the following steps:

[0011] Non-grain biomass is added to a pyrolysis unit for pyrolysis and carbonization to obtain biochar and biocombustible gas.

[0012] The biochar is added to a gasification unit for gasification to obtain syngas;

[0013] The synthesis gas is added to a separation unit to remove carbon dioxide and separate a portion of carbon monoxide, resulting in a carbon monoxide stream and a reaction gas.

[0014] The reaction gas is added to the synthesis unit for synthesis reaction, and then added to the distillation unit for distillation purification to obtain refined methanol;

[0015] The refined methanol is added to a dehydration unit for a dehydration reaction to obtain dimethyl ether;

[0016] The carbon monoxide stream and the dimethyl ether are added to the carbonylation unit to carry out the carbonylation reaction to obtain methyl acetate.

[0017] The methyl acetate was added to the hydrolysis unit for hydrolysis to obtain a mixture;

[0018] The mixture is added to a purification unit for separation and purification to obtain refined acetic acid.

[0019] As a further aspect of the present invention: the biogas is used at least for heating the pyrolysis unit, the gasification unit, the distillation unit, the dehydration unit, and the purification unit.

[0020] As a further aspect of the present invention, the synthesis gas contains hydrogen and carbon monoxide in a molar ratio of 1:1.

[0021] As a further aspect of the present invention: the reaction gas contains hydrogen and carbon monoxide in a molar ratio of 2:1, and the purity of the carbon monoxide stream is not less than 98%.

[0022] As a further aspect of the present invention: the separation unit first performs the carbon dioxide removal operation, and then performs the partial carbon monoxide separation operation.

[0023] As a further aspect of the present invention, the dehydration unit simultaneously performs the methanol dehydration reaction and the dimethyl ether separation operation.

[0024] As a further aspect of the present invention: the molar ratio of the carbon monoxide stream to the dimethyl ether is 1:1.

[0025] As a further aspect of the present invention: the mixture is a mixture of acetic acid and methanol, the separation and purification removes the methanol from the mixture, and the methanol is recovered to the distillation unit.

[0026] As a further aspect of the present invention, the purity of the refined acetic acid is not less than 99.8%.

[0027] The beneficial effects of this invention are:

[0028] The biomass acetic acid preparation method provided by this invention has significant low-carbon advantages. Relying on the non-grain biomass cascade conversion and precise syngas separation design, it eliminates the water-gas conversion process. Combined with biogas combustible gas to replace fossil energy and methanol closed-loop recovery, it greatly reduces carbon emissions throughout the process, which is in line with the "dual carbon" goal.

[0029] The method for preparing biomass acetic acid provided by this invention adopts an industrially mature non-precious metal catalytic system, avoiding the use of precious metals and corrosive additives. The equipment can be made of conventional carbon steel. Combined with widely available and low-cost non-grain biomass raw materials, it significantly reduces catalyst costs and initial investment, resulting in outstanding economic efficiency.

[0030] The method for preparing biomass acetic acid provided by this invention achieves efficient resource utilization and green production. It realizes material recycling through multi-unit closed-loop design, has high biomass carbon utilization rate, and produces refined bio-based acetic acid with a purity of not less than 99.8%, which meets the needs of industrial applications. Moreover, the process has no solid waste discharge, does not use toxic and harmful additives, and the wastewater is easy to treat, making it suitable for large-scale promotion. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a process flow diagram of the low-carbon preparation of acetic acid from bio-based acetic acid in one embodiment. Detailed Implementation

[0033] 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.

[0034] Please see Figure 1As shown, this invention proposes a low-carbon preparation method for bio-based acetic acid. Non-grain biomass such as straw and agricultural / forestry waste are selected as raw materials. First, impurities such as soil, metal, and stones are removed from the raw materials through physical sorting. Then, the raw materials are sent to a drying device for dehydration, controlling the moisture content of the non-grain biomass to below 10%, and then pulverized to a particle size of 80-120 mesh to ensure uniform and efficient pyrolysis. The dried and crushed non-grain biomass is then fed into a pyrolysis unit, and nitrogen or argon gas is introduced into the unit to create an inert atmosphere to prevent oxidation of the raw materials. Pyrolysis carbonization is carried out by controlling the pyrolysis temperature through programmed temperature control, for example, 400-600℃, with a holding time of for example, 1-3 hours, causing the biomass to undergo a pyrolysis carbonization reaction, simultaneously producing biochar and biocombustible gas. The biogas, after being purified through desulfurization, dust removal, and tar removal, is fed into the system's energy supply module for combustion, providing green steam for heat-requiring processes such as pyrolysis, gasification, distillation, and dehydration. The biochar serves as the raw material for the subsequent gasification reaction.

[0035] Please see Figure 1 As shown, the biochar obtained after pyrolysis is cooled and collected, then added to the gasification unit. Simultaneously, a mixture of oxygen-enriched air and water vapor is introduced as a gasifying agent in a preset ratio to initiate the gasification reaction. The biochar is fed into the gasification unit via a sealed screw conveyor, with the oxygen concentration controlled at, for example, 25%-35%, and the mass ratio of water vapor to biochar at, for example, 0.8-1.2:1. The reaction conditions in the gasification unit are adjusted, controlling the gasification temperature at, for example, 800-1000℃ and the pressure at, for example, 0.1-0.3 MPa, to allow the biochar and gasifying agent to undergo incomplete oxidation and reduction reactions, generating syngas with hydrogen and carbon monoxide as the main components. The molar ratio of hydrogen to carbon monoxide in the syngas remains stable at approximately 1:1, eliminating the need for an additional water-gas shift process to adjust the composition, and the syngas is directly transported to the separation unit. In this invention, the syngas generated by gasification is also purified. For example, it first enters a cyclone separator to remove dust particles, then passes through a desulfurization tower to remove sulfides, and finally is cooled to below 40°C by a cooler to obtain purified syngas.

[0036] Please see Figure 1As shown, the obtained syngas is introduced into a separation unit to remove carbon dioxide and separate a portion of carbon monoxide. In this invention, selective separation is performed, for example, using pressure swing adsorption (PSA) or membrane separation technology. Carbon dioxide is removed first, and then a portion of carbon monoxide is separated. During the separation process, by adjusting the adsorption pressure of the adsorbent or the operating parameters of the membrane module, 50% of the carbon monoxide in the syngas is precisely separated, resulting in a carbon monoxide stream with a purity ≥98%. This stream serves as the feedstock for the dimethyl ether carbonylation reaction, and the reaction gas, containing hydrogen and carbon monoxide in a molar ratio of 2:1, serves as the reaction feedstock for methanol synthesis. A small amount of tail gas generated during the separation process is discharged after passing inspection, or mixed with biogas for recovery and combustion, maximizing energy utilization. The high-purity carbon monoxide stream and the reaction gas are transported to the carbonylation unit and the synthesis unit respectively through dedicated pipelines. Insulation measures are used during the transportation process to prevent gas temperature fluctuations from affecting subsequent reactions.

[0037] Please see Figure 1 As shown, the reactant gas is fed into the synthesis unit, which is equipped with a copper-based composite catalyst, such as a Cu-Zn-Al-O series catalyst. The catalyst needs to be activated at 200-250℃ for 2-4 hours under a hydrogen atmosphere before use. The reaction conditions are adjusted to control the temperature within the synthesis unit, for example, at 220-280℃, the pressure, for example, at 5-10 MPa, and the gas space velocity, for example, at 5000-10000 h⁻¹. -1 Hydrogen and carbon monoxide undergo a synthesis reaction under the action of a catalyst to produce crude methanol. The crude methanol is then transported via pipeline to a distillation unit, which employs a dual-tower distillation process, including a pre-distillation tower and a pressurized distillation tower. The methanol first enters the pre-distillation tower, where the bottom temperature is controlled at, for example, 70-80°C and the top temperature at, for example, 64-66°C, to remove light impurities such as methane, carbon monoxide, and carbon dioxide. The bottom liquid from the pre-distillation tower is then fed into the pressurized distillation tower, where the bottom pressure is controlled at, for example, 0.6-0.8 MPa and the top temperature at, for example, 120-130°C, to obtain refined methanol with a purity ≥99.9%. The light component tail gas recovered during the distillation process is sent to the energy supply module for combustion, while unreacted syngas is returned to the synthesis unit for recycling via a reflux pipeline.

[0038] Please see Figure 1 As shown, purified methanol is fed into a dehydration unit to undergo a dehydration reaction to produce dimethyl ether, as shown in the following reaction formula: The reaction yields dimethyl ether, which can be directly used for subsequent carbonyl insertion reactions without additional purification. The dehydration unit, for example, employs a reactive distillation reactor. Refined methanol is fed into the column, which is packed with a methanol dehydration molecular sieve catalyst. The methanol enters the column and is dehydrated to produce dimethyl ether and water. Dimethyl ether is obtained from the top of the reactive distillation column, while the water is discharged from the bottom. The bottom temperature is, for example, set to 170-180°C, the reaction pressure is, for example, set to 40-45°C, and the reaction pressure is, for example, set to 1-1.2 MPa.

[0039] Please see Figure 1 As shown, the high-purity carbon monoxide stream obtained from the separation unit is mixed with dimethyl ether obtained from the dehydration unit at a preset molar ratio of 1:1. After being heated to, for example, 200-280°C, it is added to the carbonylation unit for a carbonylation reaction. The carbon monoxide stream and dimethyl ether are preheated using biogas combustion heat, thus reducing production costs. In this invention, the carbonylation unit is equipped with a mordenite molecular sieve catalyst, and the carbonylation reaction pressure is set to, for example, 2.0-5.0 MPa, and the space velocity of the mixed gas of carbon monoxide and dimethyl ether is set to, for example, 1000-3000 ml / (g·h), so that dimethyl ether reacts with carbon monoxide to obtain crude methyl acetate. The obtained crude methyl acetate is first cooled to below 40°C in a cooler, and then enters a gas-liquid separator to separate the unreacted mixed gas and liquid crude methyl acetate. The unreacted carbon monoxide is returned to the carbonyl unit for recycling through a recovery pipeline. The purity of the liquid crude methyl acetate is at least 90%, and it is directly transported to the hydrolysis unit.

[0040] Please see Figure 1 As shown, crude methyl acetate is fed into a hydrolysis unit, and deionized water is added at a molar ratio of methyl acetate to water of 1:1-1:3. Simultaneously, acidic ion exchange resin is added as a catalyst, with the catalyst amount being 5%-10% of the total mass of crude methyl acetate and water. The hydrolysis reaction conditions are adjusted, controlling the reaction temperature at, for example, 60-80℃, the pressure at, for example, 0.1-0.3 MPa, the stirring rate at, for example, 100-200 r / min, and the reaction residence time at, for example, 2-4 h, to ensure complete hydrolysis of methyl acetate to generate a mixture containing acetic acid and methanol, with a hydrolysis conversion rate ≥99%. After the hydrolysis reaction is complete, the mixture is sent to a solid-liquid separator to separate and recover the catalyst. The recovered catalyst can be reused after activation treatment.

[0041] Please see Figure 1The mixture containing acetic acid and methanol is fed into a purification unit for separation and purification, separating methanol. The purification unit is, for example, a distillation column, and, for example, an atmospheric distillation process is used to separate acetic acid and methanol. In this invention, the bottom temperature of the distillation column is controlled, for example, at 118-120°C, and the top temperature is, for example, at 64-66°C. Methanol is recovered by condensation using a top condenser to obtain methanol with a purity ≥99.5%. The recovered methanol is returned to the dehydration unit for recycling via a dedicated pipeline. The product from the bottom of the column is collected after cooling to obtain refined acetic acid product with a purity ≥99.8%, which is then packaged and stored after passing inspection.

[0042] This invention also provides an apparatus for realizing the above-mentioned low-carbon preparation method of bio-based acetic acid. The apparatus strictly matches the process logic of "non-grain biomass pyrolysis carbonization → biomass gasification → carbon monoxide separation → methanol refining and synthesis → methanol distillation → methanol dehydration to prepare dimethyl ether → carbon monoxide and dimethyl ether carbonylation → methyl acetate hydrolysis → acetic acid and methanol separation and purification". The apparatus includes, for example, a pyrolysis unit, a gasification unit, a separation unit, a synthesis unit, a distillation unit, a dehydration unit, a carbonylation unit, a hydrolysis unit, and a purification unit. Each unit is connected sequentially through pipelines to form a closed-loop synergistic production system.

[0043] The low-carbon preparation method of bio-based acetic acid in this example includes the following steps:

[0044] like Figure 1 As shown, a mixture of corn stalks and wheat stalks with a mass ratio of 1:1 and a particle size ≤30mm was selected as the non-grain biomass raw material. The raw material had a moisture content of 12%, an ash content of 5.8%, and a lower heating value of 18.2 MJ / kg. After physical sorting to remove impurities such as soil and metal, it was fed into a pulverizing device to be processed into 80-100 mesh particles and dried to a moisture content of 8%. Then, it was continuously fed into a pyrolysis unit for pyrolysis carbonization treatment. In this embodiment, the pyrolysis unit is a vertical pyrolysis carbonization reactor, which is purged with nitrogen to maintain an inert atmosphere (oxygen content ≤0.5%). The preheating temperature of the upper section of the reactor is controlled at 400℃, the reaction temperature of the middle section at 550℃, and the cooling temperature of the lower section at 150℃. The material residence time is 2.5 hours, and biochar and biocombustible gas are produced simultaneously. The biochar yield is 32% of the total mass of the raw material, with a fixed carbon content ≥78%. The biocombustible gas is desulfurized (hydrogen sulfide ≤10mg / Nm³). 3 Dust removal (dust content ≤ 5 mg / Nm³) 3 ), tar removal (tar content ≤20mg / Nm 3 After purification, the calorific value reaches 12.6 MJ / Nm³. 3 It is directly connected to the process steam boiler for heating the entire process.

[0045] like Figure 1As shown, the biochar obtained from the pyrolysis unit is fed into the gasification unit via a sealed screw conveyor for gasification. In this embodiment, the gasification unit is a combined spray gasification device, using a mixture of oxygen-enriched air and water vapor as the gasifying agent. The oxygen concentration in the oxygen-enriched air is 30%, and the mass ratio of water vapor to biochar is 1.0:1. The gasification furnace is operated at a temperature of 850°C and a pressure of 0.2 MPa to obtain syngas with a hydrogen to carbon monoxide molar ratio of 1:1. In this embodiment, the obtained syngas is further purified by a cyclone separator for dust removal and an alkaline scrubbing tower for desulfurization, and then cooled to below 40°C. The content of effective gases (hydrogen and carbon monoxide) in the syngas is ≥72%, meeting the requirements for subsequent separation.

[0046] like Figure 1 As shown, the purified syngas obtained from the gasification unit is introduced into the separation unit to remove carbon dioxide and separate a portion of carbon monoxide, obtaining the reaction gas. In this embodiment, carbon dioxide is first removed by an amine absorption module with a removal rate ≥99%. Then, pressure swing adsorption (PSA) technology is used for selective separation of carbon monoxide. The adsorption pressure is adjusted to 2.5 MPa and the desorption pressure to 0.15 MPa, separating 50% of the carbon monoxide from the syngas. The separated carbon monoxide forms a carbon monoxide stream for subsequent carbonylation reactions, and the purity of the carbon monoxide stream is 99.2%. In this embodiment, the molar ratio of hydrogen to carbon monoxide in the obtained reaction gas is 2:1. The tail gas generated during the separation process is mixed with the purified biogas and sent to the boiler for supplementary combustion, achieving energy recovery.

[0047] like Figure 1 As shown, the reaction gas obtained after the separation unit is compressed to 5 MPa and then fed into the synthesis unit to synthesize methanol. In this embodiment, the synthesis unit is a tubular methanol synthesis reactor, which is filled with a Cu-Zn-Al-O composite catalyst. After activation in a hydrogen atmosphere at 230°C for 3 hours, the reaction is started. The synthesis reaction temperature is controlled at 250°C and the gas space velocity is controlled at 5000 h⁻¹. -1 The final syngas conversion rate is ≥85%, producing crude methanol with a purity of 92%. The crude methanol is then fed into a distillation unit for purification. In this embodiment, the distillation unit is a dual-tower system, including a pre-distillation tower and a pressurized distillation tower. The pre-distillation tower is set with a top temperature of 65°C and a bottom temperature of 75°C to remove light component impurities. The pressurized distillation tower is set with a top pressure of 0.7 MPa and a top temperature of 125°C, ultimately producing refined methanol with a purity of 99.95%.

[0048] like Figure 1As shown, the refined methanol obtained from the distillation unit is fed into the dehydration unit for dehydration reaction to prepare dimethyl ether. In this embodiment, the dehydration unit is a reactive distillation column, which is filled with ZSM-5 molecular sieve catalyst. A mid-section feed mode is adopted, and the bottom temperature is controlled at 175°C, the top temperature at 42°C, and the operating pressure at 1.1 MPa. Methanol undergoes a dehydration reaction and product separation simultaneously in the column. Dimethyl ether with a purity of 99.5% is directly collected from the top of the column without additional purification process. The reaction conversion rate reaches 98%, and the wastewater discharged from the bottom of the column is treated to meet the discharge standards.

[0049] like Figure 1 As shown, dimethyl ether obtained from the dehydration unit and carbon monoxide obtained from the separation unit are mixed at a molar ratio of 1:1, preheated to 230°C, and then fed into a carbonylation reactor to prepare methyl acetate via a carbonylation reaction. In this embodiment, the carbonylation unit is a fixed-bed carbonylation reactor, which is filled with mordenite molecular sieve catalyst. The reaction pressure is controlled at 3.5 MPa, the space velocity of the mixed gas of carbon monoxide and dimethyl ether is 2000 ml / (g·h), the dimethyl ether conversion rate is ≥90%, and the purity of the product is 91%. After being placed into crude methyl acetate and cooled to 40°C, it is sent to a gas-liquid separator. The unreacted carbon monoxide and dimethyl ether separated are recycled back to the carbonylation unit to participate in the reaction again.

[0050] like Figure 1 As shown, crude methyl acetate obtained through the carbonylation unit is fed into a hydrolysis unit for hydrolysis to prepare acetic acid. In this embodiment, the hydrolysis unit is a stirred hydrolysis reactor. Deionized water is added at a methyl acetate to water molar ratio of 1:2, and 8% (by mass) of acidic ion exchange resin catalyst is added simultaneously. The reaction temperature is controlled at 70°C, the pressure at 0.2 MPa, the stirring rate at 150 r / min, and the reaction residence time at 3 h, resulting in a mixture of acetic acid and methanol. The hydrolysis conversion rate of methyl acetate is 99.3%.

[0051] like Figure 1 As shown, the mixture obtained from the hydrolysis unit is sent to the purification unit for separation and purification to obtain refined acetic acid. In this embodiment, the purification unit is an atmospheric distillation column, with the top temperature set at 64°C, to collect recovered methanol with a purity of 99.6%, which is then recycled back to the dehydration unit. The bottom temperature is set at 119°C, to collect refined acetic acid with a purity of 99.85%, which is then cooled and sent to the finished product storage tank.

[0052] In summary, the low-carbon preparation method for bio-based acetic acid provided by this invention achieves efficient conversion of non-grain biomass into acetic acid through the coupling and synergy of various units and material recycling. The process is low-carbon and environmentally friendly, with high raw material utilization, making it suitable for large-scale industrial production. Using this method, the annual consumption of non-grain biomass raw materials is 0.42 million tons, producing 0.102 million tons of refined bio-based acetic acid. Methanol recycling rate is ≥95%, and biomass carbon utilization rate reaches 78%. The overall energy consumption per ton of product is reduced by 32% compared to traditional fossil-based processes, catalyst costs are reduced by more than 60%, there is no solid waste discharge, and wastewater discharge is reduced by 55% compared to the industry average. This achieves a balance between low carbon emissions, economic efficiency, and environmental friendliness, making it valuable for large-scale promotion.

[0053] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] The foregoing has provided a detailed description of one embodiment of the present invention, but this description 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 claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A low-carbon preparation method for bio-based acetic acid, characterized in that, At least the following steps are included: Non-grain biomass is added to a pyrolysis unit for pyrolysis and carbonization to obtain biochar and biocombustible gas. The biochar is added to a gasification unit for gasification to obtain syngas; The synthesis gas is added to a separation unit to remove carbon dioxide and separate a portion of carbon monoxide, resulting in a carbon monoxide stream and a reaction gas. The reaction gas is added to the synthesis unit for synthesis reaction, and then added to the distillation unit for distillation purification to obtain refined methanol; The refined methanol is added to a dehydration unit for a dehydration reaction to obtain dimethyl ether; The carbon monoxide stream and the dimethyl ether are added to the carbonylation unit to carry out the carbonylation reaction to obtain methyl acetate. The methyl acetate was added to the hydrolysis unit for hydrolysis to obtain a mixture; The mixture is added to a purification unit for separation and purification to obtain refined acetic acid.

2. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The biogas is used to heat at least the pyrolysis unit, the gasification unit, the distillation unit, the dehydration unit, and the purification unit.

3. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The synthesis gas contains hydrogen and carbon monoxide in a molar ratio of 1:

1.

4. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The reaction gas contains hydrogen and carbon monoxide in a molar ratio of 2:1, and the purity of the carbon monoxide stream is not less than 98%.

5. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The separation unit first performs the carbon dioxide removal operation, and then performs the partial carbon monoxide separation operation.

6. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The dehydration unit simultaneously performs the methanol dehydration reaction and the dimethyl ether separation operation.

7. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The molar ratio of the carbon monoxide stream to the dimethyl ether is 1:

1.

8. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The mixture is a mixture of acetic acid and methanol. The separation and purification removes the methanol from the mixture, and the methanol is recovered to the distillation unit.

9. The low-carbon preparation method of bio-based acetic acid according to claim 1, characterized in that, The purity of the refined acetic acid is not less than 99.8%.

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