Method for preparing organic acid through biomass pyrolysis catalyzed by cobalt oxide

Abstract

The invention discloses a method for preparing organic acid through biomass pyrolysis catalyzed by cobalt oxide, which comprises the following steps: pyrolyzing a first mixture containing a biomass raw material, cobalt oxide and alkali metal hydroxide in an oxygen-free atmosphere to obtain a solid-phase organic acid salt mixture; dissolving the solid-phase organic acid salt mixture with water, and carrying out solid-liquid separation to obtain filtrate A and filter residues B; mixing the filtrate A with ethanol, and carrying out solid-liquid separation to obtain filter residues C and filtrate B; and dissolving the filter residue C with water, acidifying and extracting to obtain first organic acid and raffinate. The method for preparing the organic acid by catalyzing biomass pyrolysis through the cobalt oxide provides an efficient, green and sustainable biomass conversion path, high-selectivity synthesis of the organic acid is achieved through a cobalt oxide catalysis system, and the method has the multiple advantages of being simple and convenient in process, mild in condition, high in resource utilization rate, capable of achieving environment positive benefits and the like; the method has important industrial application prospect and ecological value.

Description

Technical Field

[0001] This application relates to the field of biomass pyrolysis technology, and more specifically, to a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. Background Technology

[0002] With the advancement of the global "dual carbon" strategy, utilizing renewable biomass to produce high-value-added chemicals is a key path to maximizing its resource value. Biomass, as the only renewable carbon resource in nature, is an ideal precursor for the preparation of oxygen-containing organic acids. Among them, glycolic acid and succinic acid, as extremely important platform compounds, are experiencing continuous market demand growth. Currently, the production of organic acids mainly relies on petrochemical routes or bio-fermentation methods. In the petrochemical route, glycolic acid is usually produced by the carbonylation of formaldehyde, which suffers from problems such as high raw material toxicity, harsh reaction conditions (high temperature and high pressure), and dependence on fossil resources. While bio-fermentation methods offer milder reaction conditions, they face challenges such as long fermentation cycles, low substrate concentrations, significant product inhibition effects, and sensitivity to microbial contamination, making large-scale continuous production difficult. In recent years, chemical conversion methods have attracted much attention due to their fast reaction rates and large processing capacities. Among these, biomass alkaline thermal treatment technology can depolymerize large-molecule biomass at relatively mild temperatures.

[0003] Studies have shown that strong bases (such as NaOH and KOH) can effectively reduce the activation energy of reactions, promote deprotonation and reverse aldol condensation, and generate lactic acid, formic acid, acetic acid, etc. (Reference: Esipovich AL, Zlobin SY, Shirshin KK, et al. "Catalytic conversion of glycerol to lactic acid over Cu-based catalysts" [J]. Catalysts, 2024, 14(4): 231.). Liu Guojie et al. disclosed a two-stage biomass alkaline thermal treatment method for hydrogen production in patent (CN116654867A), which achieved efficient hydrogen production from cellulose at a relatively low temperature. However, such technologies currently mainly focus on improving hydrogen yield, and lack effective means to control the distribution of organic acids in the solid-phase products.

[0004] Therefore, a method is particularly necessary to prepare high-value organic acids from biomass while maintaining the selectivity of high-value organic acids in the product. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxides, which is beneficial for improving the selectivity of high-value organic acids.

[0006] This application is implemented as follows: In a first aspect, this application provides a method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, comprising: A first mixture containing biomass raw materials, cobalt oxide and alkali metal hydroxide was pyrolyzed in an oxygen-free atmosphere to obtain a solid-phase organic acid salt mixture. The solid-phase organic acid salt mixture was dissolved in water and then subjected to solid-liquid separation to obtain filtrate A and filter residue B. The filtrate A was mixed with ethanol and then subjected to solid-liquid separation to obtain filter residue C and filtrate B. The filter residue C is dissolved in water and then acidified and extracted to obtain a first organic acid whose main component is glycolic acid and a raffinate; and / or the filtrate B is cooled and subjected to solid-liquid separation to obtain filter residue D and filtrate C, and the filter residue D is acidified and fractionated to obtain a third organic acid containing propionic acid.

[0007] In an optional embodiment, the cobalt oxide is selected from at least one of CoO and Co3O4; And / or, the mass ratio of the cobalt oxide to the biomass feedstock is 0.05~0.15:1; And / or, the biomass raw material is selected from at least one of fructose, glucose, sucrose, cellobiose, cellulose, hemicellulose, starch, and chitosan.

[0008] In an optional embodiment, the alkali metal hydroxide is selected from at least one of NaOH and KOH; And / or, the mass ratio of the alkali metal hydroxide to the biomass feedstock is 2.0~4.5:1; And / or, the pyrolysis reaction temperature is 190~250 ℃, and the time is 20~90 min.

[0009] In an optional embodiment, the mass ratio of the solid-phase organic acid salt mixture to water is 1:150~300; And / or, it also includes: sequentially acid washing, drying and calcining the filter residue B to obtain regenerated cobalt oxide.

[0010] In an optional embodiment, the acid used to acid wash the filter residue B is dilute nitric acid with a mass fraction of 1% to 5%, and the acid washing is performed 2 to 3 times. And / or, the drying temperature is 110~150 ℃; And / or, the calcination temperature is 800~1000 ℃, and the calcination time is 1~3 h.

[0011] In an optional embodiment, the volume ratio of filtrate A to ethanol is 1:2~3; And / or, the mass ratio of water to filter cake C is 1:50~100; And / or, the acidification includes adjusting the pH of the aqueous solution of filter residue C to 2-3 using dilute sulfuric acid with a mass fraction of 2-10%; And / or, the extractant used for the extraction is selected from at least one of ethyl acetate, butyl acetate, toluene, or butanone; And / or, the volume ratio of the extractant used in the extraction to the acidified aqueous solution is 1:0.5~1.0, and the number of extractions is 2~3.

[0012] In an optional embodiment, the method further includes adding a precipitant to the filtrate C and performing a precipitation reaction and solid-liquid separation to obtain filter residue E and filtrate D; then dissolving the filter residue E with acid and performing solid-liquid separation to obtain filter residue F and filtrate E; and fractionating the filtrate E to obtain a second organic acid whose main component is succinic acid.

[0013] In an optional implementation, the cooling temperature is 0~5 ℃; And / or, the precipitant is selected from calcium hydroxide; And / or, the mass ratio of the precipitant to filtrate C is 1:50~100; And / or, the precipitation reaction temperature is 50~80 ℃; And / or, the acid solution is dilute sulfuric acid with a mass fraction of 2-10%, and the mass ratio of the filter residue E to the acid solution is 1:50-100.

[0014] In an optional embodiment, the method further includes: subjecting the mixed solution obtained by mixing the raffinate and filter residue D to causticization and solid-liquid separation in sequence to obtain filtrate F and filter residue G; combining filtrate F and filtrate D for evaporation and concentration to recover alkali metal hydroxide.

[0015] In an optional embodiment, the causticizing step includes mixing calcium hydroxide with a mixed solution at a mass ratio of 1:30 to 80 and reacting the mixture. And / or, the causticizing reaction temperature is 50~80 ℃, and the causticizing reaction is carried out 2~3 times.

[0016] This application has the following beneficial effects: The application provides an efficient, green, and sustainable biomass conversion pathway that achieves highly selective synthesis of organic acids through a cobalt oxide catalytic system. It has multiple advantages, including simple process, mild conditions, high resource utilization, and positive environmental benefits, and has significant industrial application prospects and ecological value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the application; Figure 2 The yield of organic acids prepared by cellulose pyrolysis involving CoO and NaOH under different reaction conditions ((a) reaction time; (b) reaction temperature; (c) alkali-to-material ratio). Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This application provides a method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, such as... Figure 1 As shown, it includes: A first mixture containing biomass raw materials, cobalt oxide and alkali metal hydroxide was pyrolyzed in an oxygen-free atmosphere to obtain a solid-phase organic acid salt mixture. The solid-phase organic acid salt mixture was dissolved in water and then subjected to solid-liquid separation to obtain filtrate A and filter residue B. The filtrate A was mixed with ethanol and then subjected to solid-liquid separation to obtain filter residue C and filtrate B. The filter residue C is dissolved in water and then acidified and extracted to obtain a first organic acid whose main component is glycolic acid and a raffinate; and / or the filtrate B is cooled and subjected to solid-liquid separation to obtain filter residue D and filtrate C, and the filter residue D is acidified and fractionated to obtain a third organic acid containing propionic acid.

[0021] The application provides an efficient, green, and sustainable biomass conversion pathway that achieves highly selective synthesis of organic acids through a cobalt oxide catalytic system. It has multiple advantages, including simple process, mild conditions, high resource utilization, and positive environmental benefits, and has significant industrial application prospects and ecological value.

[0022] In an optional embodiment, the cobalt oxide is selected from at least one of CoO and Co3O4; it can be a cobalt oxide with high purity, or it can be derived from cobalt-containing industrial solid waste, waste cobalt-based catalysts, and waste cobalt-containing electrode materials, etc.

[0023] And / or, the mass ratio of the cobalt oxide to the biomass feedstock is 0.05~0.15:1; And / or, the biomass raw material is selected from at least one of fructose, glucose, sucrose, cellobiose, cellulose, hemicellulose, starch, and chitosan.

[0024] In an optional embodiment, the alkali metal hydroxide is selected from at least one of NaOH and KOH; And / or, the mass ratio of the alkali metal hydroxide to the biomass feedstock is 2.0~4.5:1; And / or, the pyrolysis reaction temperature is 190~250 ℃, and the time is 20~90 min.

[0025] In an optional embodiment, the mass ratio of the solid-phase organic acid salt mixture to water is 1:150~300; the water involved in this application can be distilled water or ultrapure water; And / or, it also includes: sequentially acid washing, drying and calcining the filter residue B to obtain regenerated cobalt oxide.

[0026] In an optional embodiment, the acid used to acid wash the filter residue B is dilute nitric acid with a mass fraction of 1% to 5%, and the acid washing is performed 2 to 3 times. And / or, the drying temperature is 110~150 ℃; And / or, the calcination temperature is 800~1000 ℃, and the calcination time is 1~3 h.

[0027] In an optional embodiment, the volume ratio of filtrate A to ethanol is 1:2~3; And / or, the mass ratio of water to filter cake C is 1:50~100; And / or, the acidification includes adjusting the pH of the aqueous solution of filter residue C to 2-3 using dilute sulfuric acid with a mass fraction of 2-10%; And / or, the extractant used for the extraction is selected from at least one of ethyl acetate, butyl acetate, toluene, or butanone; And / or, the volume ratio of the extractant used in the extraction to the acidified aqueous solution is 1:0.5~1.0, and the number of extractions is 2~3.

[0028] In an optional embodiment, the method further includes adding a precipitant to the filtrate C and performing a precipitation reaction and solid-liquid separation to obtain filter residue E and filtrate D; then dissolving the filter residue E with acid and performing solid-liquid separation to obtain filter residue F and filtrate E; and fractionating the filtrate E to obtain a second organic acid whose main component is succinic acid.

[0029] In an optional implementation, the cooling temperature is 0~5 ℃; And / or, the precipitant is selected from calcium hydroxide; And / or, the mass ratio of the precipitant to filtrate C is 1:50~100; And / or, the precipitation reaction temperature is 50~80 ℃; And / or, the acid solution is dilute sulfuric acid with a mass fraction of 2-10%, and the mass ratio of the filter residue E to the acid solution is 1:50-100.

[0030] In an optional embodiment, the method further includes: subjecting the mixed solution obtained by mixing the raffinate and filter residue D to causticization and solid-liquid separation in sequence to obtain filtrate F and filter residue G; combining filtrate F and filtrate D for evaporation and concentration to recover alkali metal hydroxide.

[0031] In an optional embodiment, the causticizing step includes mixing calcium hydroxide with a mixed solution at a mass ratio of 1:30 to 80 and reacting the mixture. And / or, the causticizing reaction temperature is 50~80 ℃, and the causticizing reaction is carried out 2~3 times.

[0032] This application discloses a method for preparing organic acids from biomass pyrolysis catalyzed by cobalt oxide. By introducing a cobalt oxide catalyst, efficient and directional conversion of biomass is achieved under relatively mild reaction conditions, significantly improving the yield and selectivity of organic acids. Specific advantages include: 1. Mild reaction conditions: Compared with traditional high-temperature and high-pressure thermochemical conversion processes, this method can be carried out at lower temperatures and atmospheric or near-atmospheric pressure, reducing energy consumption and equipment requirements, which is conducive to industrial promotion.

[0033] 2. Simple preparation process: The process is simple, requiring no complex pretreatment or multi-stage reaction system, and is easy to operate and control, with good repeatability and stability.

[0034] 3. High yield and selectivity of organic acids: Compared with catalyst-free or non-cobalt-based systems, the introduction of cobalt oxides can increase the total yield of organic acids by more than 50%, significantly enhance the selectivity of target products, effectively reduce the generation of by-products, and improve separation and purification efficiency.

[0035] 4. High raw material conversion rate: Under the catalysis of cobalt oxide, the conversion rate of biomass raw materials can be increased by more than 19%.

[0036] 5. Wide adaptability of raw materials: It is suitable for biomass raw materials from a variety of sources, including agricultural waste (such as straw and rice husks), forestry residues, energy plants and organic solid waste, etc., and has a wide range of resource applicability.

[0037] 6. Superior catalyst performance: Cobalt oxide has good thermal stability and catalytic activity, and the catalyst is easy to recover and can be recycled multiple times, with high recovery rate and reduced operating costs.

[0038] 7. Solid waste resource utilization: Realize the high-value transformation of organic solid waste and promote the development of "waste treatment" and circular economy models.

[0039] 8. Negative carbon emission characteristics: The entire preparation process is accompanied by a net carbon sequestration effect, which helps to reduce greenhouse gas emissions, conforms to the "dual carbon" strategic goal, and has the dual advantages of environmental friendliness and sustainable development.

[0040] In summary, this application provides an efficient, green, and sustainable biomass conversion pathway that achieves highly selective synthesis of organic acids through a cobalt oxide catalytic system. It has multiple advantages, including simple process, mild conditions, high resource utilization, and positive environmental benefits, and has significant industrial application prospects and ecological value.

[0041] The features and performance of this application are further described in detail below with reference to the embodiments. Unless otherwise specified, the temperature involved in each embodiment and comparative example is 25°C, the pressure is atmospheric pressure, and the content is mass fraction.

[0042] Example 1 This embodiment provides a method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, specifically including the following steps: (1) The biomass raw materials, cobalt oxide and alkali metal hydroxide are mixed, ground thoroughly, and then pyrolyzed under an oxygen-free atmosphere to obtain a solid-phase organic acid salt mixture; specifically including: 162.7 mg of microcrystalline cellulose, 16.5 mg of CoO and 401.7 mg of NaOH were mixed evenly and placed in a quartz boat. The mixture was then placed in the heating zone of a tube furnace and purged with argon gas at a rate of 40 mL / min for 20 min. The heating program was then set.

[0043] Keeping the purge gas flow rate constant, the mixture was heated from room temperature to 110 °C at a heating rate of 5 °C / min and dried at a constant temperature for 30 min. Then, it was heated from 110 °C to 210 °C at a heating rate of 5 °C / min and dried at a constant temperature for 60 min. After the reaction was completed, the solid organic acid salt mixture was collected and hydrogen was produced.

[0044] (2) The solid-phase organic acid salt mixture was dissolved in distilled water at a mass ratio of 1:200, and then filtered to obtain filtrate A and filter residue B. Filter residue B was washed thoroughly three times with 5% dilute nitric acid, dried at 150 °C, and then calcined at 900 °C for 2 h to obtain regenerated cobalt oxide. The recovery rate of cobalt oxide was calculated according to formula (1-1):

[0045] Where ε is the recovery rate of cobalt oxide, %; m recycled metal oxide The mass of regenerated cobalt oxide is expressed in g; m metal oxide in feedstockd The mass of cobalt oxide in the raw material is expressed in grams.

[0046] (3) Filtrate A is mixed with anhydrous ethanol at a volume ratio of 1:2 and then filtered to obtain filter residue C and filtrate B. Distilled water and filter residue C are mixed at a mass ratio of 1:75 and the pH is adjusted to 2-3 with dilute sulfuric acid before extraction. The volume ratio of extractant to acidified aqueous solution is 1:1 and the extraction is performed twice. The extractant is ethyl acetate. Then, ethyl acetate is used to extract and separate the first organic acid (mainly glycolic acid) and the raffinate. (4) Cool filtrate B at 5 °C, filter to separate residue D and filtrate C, add calcium hydroxide as a precipitant to filtrate C, filter to obtain residue E and filtrate D, the mass ratio of the precipitant to filtrate C is 1:75, and the precipitation reaction temperature is 50 °C; then dissolve residue E with 5% dilute sulfuric acid, the mass ratio of residue E to the acid solution is 1:50, filter to separate residue F and filtrate E, collect the fraction at 180 °C from filtrate E by fractional distillation to obtain the second organic acid (mainly succinic acid); add dilute sulfuric acid to filtrate D to adjust the pH to 2~3 and then fractional distill to collect the fractions at 120 °C (acetic acid) and 140 °C (propionic acid); calculate the yield and selectivity of the organic acid according to formulas (1-2) and (1-3):

[0047] Where Yield represents the yield of organic acids, in % (total organic acids include glycolic acid, succinic acid, acetic acid, and propionic acid); m carbon in organic acid The content of carbon (C) in organic acids, in g; m carbon in feedstockd The content of carbon (C) in the raw material, in g; m i , represents the total C content in glycolic acid and succinic acid, in g.

[0048] (5) Mix the raffinate and filter residue D to obtain a mixed solution. Mix calcium hydroxide with the mixed solution at a mass ratio of 1:60 and carry out a causticization reaction. Filter and separate to obtain filtrate F and filter residue G. The causticization reaction temperature is 80 ℃ and the causticization reaction is carried out twice. Combine the causticization reaction solution of filtrate F and the fractionation residue of filtrate D and carry out evaporation and concentration to recover alkali metal hydroxide. Combine filter residue F and filter residue G, which can be used as building materials and fillers, etc.

[0049] In this embodiment, qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 96.86%, yielding an H2 yield of 18.46 mmol / g cellulose with a purity of 99.35%. The total organic acid yield was 84.55% (of which, the glycolic acid yield was 45.93% and the succinic acid yield was 21.67%). Specifically, the purity of glycolic acid in the first organic acid was 95.6%, and the purity of succinic acid in the second organic acid was 98.3%. The selectivity of glycolic acid and succinic acid (based on the total amount of glycolic acid and succinic acid contained in the first and second organic acids) was 79.95%, and the recovery rate of CoO was 90.21%.

[0050] Example 2 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is that the cobalt oxide in step (1) is replaced with Co3O4: 162.7 mg of microcrystalline cellulose, 16.4 mg of Co3O4 and 401.3 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0051] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 91.03%, yielding 17.16 mmol / g cellulose H2 with a purity of 99.11%. The total organic acid yield was 73.52% (of which, glycolic acid yield was 35.23% and succinic acid yield was 20.89%). Among the first organic acid, glycolic acid had a purity of 95.1%, and among the second organic acid, succinic acid had a purity of 97.6%. The selectivity for glycolic acid and succinic acid was 84.79%, and the recovery rate of Co3O4 was 89.35%.

[0052] Example 3 This embodiment provides a method for preparing organic acids by catalytic pyrolysis of biomass using cobalt oxide. The only difference from Example 1 is that the alkali metal hydroxide in step (1) is KOH: 162.2 mg of microcrystalline cellulose, 16.3 mg of CoO and 560.1 mg of KOH are mixed evenly and placed in a quartz boat.

[0053] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 98.96%, yielding 19.89 mmol / g cellulose H2 with a purity of 99.32%. The total organic acid yield was 87.56% (of which, glycolic acid yield was 49.30% and succinic acid yield was 25.71%). Among the first organic acid, glycolic acid had a purity of 96.6%, and among the second organic acid, succinic acid had a purity of 98.5%. The selectivity for glycolic acid and succinic acid was 85.67%, and the recovery rate of CoO was 85.43%.

[0054] Example 4 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is that the amount of NaOH used in step (1) is increased: 162.5 mg of microcrystalline cellulose, 16.4 mg of CoO and 481.6 mg of NaOH are mixed evenly and placed in a quartz boat.

[0055] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 97.52%, yielding 18.68 mmol / g cellulose H2 with a purity of 98.73%. The total organic acid yield was 84.36% (of which, glycolic acid yield was 47.28% and succinic acid yield was 20.16%). Among the first organic acid, glycolic acid had a purity of 95.2%, and among the second organic acid, succinic acid had a purity of 98.8%. The selectivity for glycolic acid and succinic acid was 79.94%, and the recovery rate of CoO was 87.02%.

[0056] Example 5 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 2 is that the amount of Co3O4 used in step (1) is increased: 163.5 mg of microcrystalline cellulose, 24.6 mg of Co3O4 and 402.7 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0057] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 92.51%, yielding 17.37 mmol / g cellulose H2 with a purity of 97.26%. The total organic acid yield was 74.77% (of which, glycolic acid yield was 39.12% and succinic acid yield was 22.16%). Among the first organic acid, glycolic acid had a purity of 96.1%, and among the second organic acid, succinic acid had a purity of 97.6%. The selectivity for glycolic acid and succinic acid was 81.96%, and the recovery rate of Co3O4 was 92.14%.

[0058] Example 6 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is step (1): 133.1 mg of xylan, 13.4 mg of CoO and 400.2 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0059] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The xylan conversion rate was 95.25%, yielding 23.06 mmol / g cellulose H2 with a purity of 95.16%. The total organic acid yield was 82.17% (of which, propionic acid yield was 39.48% and succinic acid yield was 20.07%). Specifically, the purity of propionic acid obtained by fractionation after acidification of filtrate D was 97.5%, and the purity of succinic acid, the second organic acid, was 98.9%. The selectivity for propionic acid and succinic acid was 72.47%, and the recovery rate of CoO was 87.93%.

[0060] Example 7 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is step (1): 162.9 mg of microcrystalline cellulose, 33.2 mg of waste carbon-based cobalt catalyst (main component is CoO, effective content is 52%, and the remainder is activated carbon) and 400.9 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0061] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 89.41%, yielding 16.13 mmol / g cellulose H2 with a purity of 95.14%. The total organic acid yield was 71.32% (of which, glycolic acid yield was 36.97% and succinic acid yield was 17.51%). Among the first organic acid, glycolic acid had a purity of 96.5%, and among the second organic acid, succinic acid had a purity of 98.6%. The selectivity for glycolic acid and succinic acid was 76.39%, and the recovery rate of cobalt oxide was 89.12%, making it suitable for direct use in recycling experiments.

[0062] Example 8 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is step (1): 164.0 mg of microcrystalline cellulose, 36.6 mg of lithium-air electrode cathode material (mainly Co3O4 with an effective content of 45%, and the remainder mainly graphene) and 401.5 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0063] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 87.25%, yielding 15.71 mmol / g cellulose H2 with a purity of 96.87%. The total organic acid yield was 67.03% (of which, glycolic acid yield was 32.29% and succinic acid yield was 19.28%). Among the first organic acid, glycolic acid had a purity of 95.9%, and among the second organic acid, succinic acid had a purity of 97.8%. The selectivity for glycolic acid and succinic acid was 76.94%, and the recovery rate of cobalt oxide was 90.02%, which was directly used in the recycling experiment.

[0064] Example 9 This embodiment provides a method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, which differs from Example 1 only in step (1): Specifically, approximately 162.0 mg of microcrystalline cellulose, approximately 16.2 mg of CoO, and approximately 400 mg of NaOH are uniformly mixed and placed in a quartz boat. The boat is then placed in the heating zone of a tube furnace and purged with an argon gas system at a rate of 40 mL / min for 20 min. The heating program is then set. Maintaining a constant purging gas flow rate, the mixture is heated from room temperature to 110 °C at a heating rate of 5 °C / min and dried at this constant temperature for 30 min. Then, it is heated from 110 °C to 210 °C at a heating rate of 5 °C / min and kept at this constant temperature for 40, 60, and 90 min respectively. After the reaction is complete, the solid organic acid salt mixture is collected, and the yields of different organic acids are obtained as follows: Figure 2 As shown in (a).

[0065] Example 10 This embodiment provides a method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, which differs from Example 1 only in step (1): Specifically, approximately 162.0 mg of microcrystalline cellulose, approximately 16.2 mg of CoO, and approximately 400 mg of NaOH are uniformly mixed and placed in a quartz boat. The boat is then placed in the heating zone of a tube furnace and purged with an argon gas system at a rate of 40 mL / min for 20 min. The heating program is then set. Maintaining a constant purging gas flow rate, the mixture is heated from room temperature to 110 °C at a heating rate of 5 °C / min and dried at this constant temperature for 30 min. Then, it is heated from 110 °C to 190, 210, and 230 °C respectively at a heating rate of 5 °C / min and held at these temperatures for 60 min. After the reaction is complete, the solid-phase organic acid salt mixture is collected, and the yields of different organic acids are obtained as follows: Figure 2 As shown in (b).

[0066] Example 11 This embodiment provides a method for preparing organic acids by catalytic biomass pyrolysis using cobalt oxide. The only difference from Example 1 is step (1): Specifically, approximately 162.0 mg of microcrystalline cellulose, approximately 16.2 mg of CoO, and NaOH are uniformly mixed and placed in a quartz boat. The mass ratios of microcrystalline cellulose and sodium hydroxide are 1:2, 1:2.5, and 1:3, respectively. After being fed into the heating zone of a tube furnace, an argon gas purging system at 40 mL / min is introduced for 20 min, and the heating program is set. The purging gas flow rate is kept constant, and the temperature is increased from room temperature to 110 °C at a heating rate of 5 °C / min and dried at a constant temperature for 30 min. Then, the temperature is increased from 110 °C to 210 °C at a heating rate of 5 °C / min and dried at a constant temperature for 60 min. After the reaction is completed, the solid organic acid salt mixture is collected, and the yields of different organic acids are obtained as follows: Figure 2 As shown in (c).

[0067] Comparative Example 1 This comparative example provides a method for preparing organic acids by biomass pyrolysis. The only difference from Example 1 is that CoO is not added in step (1): 162.4 mg of microcrystalline cellulose and 401.7 mg of NaOH are mixed evenly and placed in a quartz boat.

[0068] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 81.05%, yielding 15.02 mmol / g cellulose H2 with a purity of 99.04%. The total organic acid yield was 53.89% (of which, glycolic acid yield was 26.41% and succinic acid yield was 4.81%). Among the first organic acid, glycolic acid had a purity of 95.2%, and among the second organic acid, succinic acid had a purity of 96.8%. The selectivity for glycolic acid and succinic acid was 57.73%.

[0069] Comparative Example 2 This comparative example provides a method for preparing organic acids by catalytic pyrolysis of biomass using cobalt oxide. The only difference from Example 1 is that NaOH is not added in step (1): 162.9 mg of microcrystalline cellulose and 16.3 mg of CoO are uniformly mixed and placed in a quartz boat.

[0070] The results showed that the cellulose conversion rate was extremely low (<10%). Within the product detection range, no target gaseous components such as H2 were detected, and no organic acid generation was observed.

[0071] Comparative Example 3 This comparative example provides a method for preparing organic acids by biomass pyrolysis. The only difference from Example 1 is in step (1): 132.4 mg of xylan and 560.6 mg of KOH are mixed evenly and placed in a quartz boat.

[0072] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The xylan conversion rate was 86.48%, yielding an H2 yield of 18.20 mmol / g cellulose with a purity of 96.04%. The total organic acid yield was 69.84% (of which, propionic acid yield was 30.32% and succinic acid yield was 9.71%). Specifically, the purity of propionic acid obtained by fractionation after acidification of filtrate D was 98.8%, and the purity of succinic acid in the second organic acid was 98.5%. The selectivity for propionic acid and succinic acid was 57.32%.

[0073] Comparative Example 4 This comparative example provides a method for preparing organic acids by pyrolysis of biomass using oxide catalysis. The only difference from Example 1 is step (1): 162.8 mg of microcrystalline cellulose, 16.6 mg of CuO and 401.7 mg of NaOH are uniformly mixed and placed in a quartz boat.

[0074] Qualitative and quantitative analyses were performed on H2, CH4, CO, CO2, and major organic acids. The cellulose conversion rate was 90.80%, yielding 16.79 mmol / g cellulose H2 with a purity of 98.99%. The total organic acid yield was 70.29% (of which, glycolic acid yield was 37.88% and succinic acid yield was 7.31%). Among the first organic acid, glycolic acid had a purity of 96.1%, and among the second organic acid, succinic acid had a purity of 98.4%. The selectivity for glycolic acid and succinic acid was 64.29%, and the recovery rate of metal oxides was 86.22%.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis, characterized in that, include: A first mixture containing biomass raw materials, cobalt oxide and alkali metal hydroxide was pyrolyzed in an oxygen-free atmosphere to obtain a solid-phase organic acid salt mixture. The solid-phase organic acid salt mixture was dissolved in water and then subjected to solid-liquid separation to obtain filtrate A and filter residue B. The filtrate A was mixed with ethanol and then subjected to solid-liquid separation to obtain filter residue C and filtrate B. The filter residue C is dissolved in water and then acidified and extracted to obtain a first organic acid whose main component is glycolic acid and a raffinate; and / or the filtrate B is cooled and subjected to solid-liquid separation to obtain filter residue D and filtrate C, and the filter residue D is acidified and fractionated to obtain a third organic acid containing propionic acid.

2. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, The cobalt oxide is selected from at least one of CoO and Co3O4; And / or, the mass ratio of the cobalt oxide to the biomass feedstock is 0.05~0.15:1; And / or, the biomass raw material is selected from at least one of fructose, glucose, sucrose, cellobiose, cellulose, hemicellulose, starch, and chitosan.

3. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, The alkali metal hydroxide is selected from at least one of NaOH and KOH; And / or, the mass ratio of the alkali metal hydroxide to the biomass feedstock is 2.0~4.5:1; And / or, the pyrolysis reaction temperature is 190~250 ℃, and the time is 20~90 min.

4. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, The mass ratio of the solid-phase organic acid salt mixture to water is 1:150~300; And / or, it also includes: sequentially acid washing, drying and calcining the filter residue B to obtain regenerated cobalt oxide.

5. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 4, characterized in that, The acid used for acid washing of the filter residue B is dilute nitric acid with a mass fraction of 1% to 5%, and the acid washing is performed 2 to 3 times. And / or, the drying temperature is 110~150 ℃; And / or, the calcination temperature is 800~1000 ℃, and the calcination time is 1~3 h.

6. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, The volume ratio of filtrate A to ethanol is 1:2~3; And / or, the mass ratio of water to filter cake C is 1:50~100; And / or, the acidification includes adjusting the pH of the aqueous solution of filter residue C to 2-3 using dilute sulfuric acid with a mass fraction of 2-10%; And / or, the extractant used for the extraction is selected from at least one of ethyl acetate, butyl acetate, toluene, or butanone; And / or, the volume ratio of the extractant used in the extraction to the acidified aqueous solution is 1:0.5~1.0, and the number of extractions is 2~3.

7. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, It also includes adding a precipitant to filtrate C and carrying out a precipitation reaction and solid-liquid separation to obtain filter residue E and filtrate D; then using acid to dissolve filter residue E and carrying out solid-liquid separation to obtain filter residue F and filtrate E, and fractionating filtrate E to obtain a second organic acid whose main component is succinic acid.

8. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 7, characterized in that, Cooling temperature is 0~5℃; And / or, the precipitant is selected from calcium hydroxide; And / or, the mass ratio of the precipitant to filtrate C is 1:50~100; And / or, the precipitation reaction temperature is 50~80 ℃; And / or, the acid solution is dilute sulfuric acid with a mass fraction of 2-10%, and the mass ratio of the filter residue E to the acid solution is 1:50-100.

9. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 1, characterized in that, Also includes: The mixed solution obtained by mixing the raffinate and filter residue D is subjected to causticization and solid-liquid separation in sequence to obtain filtrate F and filter residue G; filtrate F and filtrate D are combined and evaporated and concentrated to recover alkali metal hydroxide.

10. The method for preparing organic acids by cobalt oxide-catalyzed biomass pyrolysis according to claim 9, characterized in that, The causticizing step includes mixing calcium hydroxide with a mixed solution at a mass ratio of 1:30~80 and reacting the mixture. And / or, the causticizing reaction temperature is 50~80 ℃, and the causticizing reaction is carried out 2~3 times.

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