A method for improving the production of aromatic compounds and / or biomethane from lignite

Abstract

The present application provides a method for improving the efficiency of selective depolymerization of lignite to produce aromatic compounds and / or biomethane. The method comprises the following steps: crushing and sieving lignite to obtain lignite powder; placing the lignite powder in a closed device, adding activated sludge, and adjusting the pH of the reaction system to 6.8-7.2; placing the device in a constant temperature condition to perform selective degradation reaction, thereby producing high-yield aromatic compounds and / or biomethane. A promoter can be added before adjusting the pH of the reaction system. The promoter includes one or more of formic acid, acetic acid, oleic acid, glucose, fructose, xylose, arabinose, galactose, maltose, sucrose, lactose, trehalose, dextrin, cellulose, corn straw powder, soluble starch, and aqueous solutions thereof. The present application provides a method for synergistically and selectively depolymerizing lignite with microbial flora and / or a promoter to efficiently co-produce humic acid, benzyl alcohol, benzaldehyde, benzoic acid, phenol, and by-product methane.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coal resource utilization, and particularly relates to a method for improving the efficiency of selective depolymerization of lignite to obtain aromatic compounds and / or biomethane. BACKGROUND

[0002] Lignite is a low-rank coal with a low degree of coalification. Lignite is mainly used for power generation in pithead power plants, but it produces NOx, SO2 and dust during combustion, which can cause serious environmental pollution. Especially in Inner Mongolia, Yunnan and Northeast China, lignite has high moisture content and high oxygen content, and contains rich benzene rings, oxygen-containing functional groups (-COOH, -CHO, -OH) and side chains, which provide a theoretical basis and resource basis for the preparation of aromatic compounds. Lignite is a fuel, but also an important chemical raw material. The essence of extracting aromatic compounds from lignite and returning lignite from fuel to chemical raw material is an important way of lignite resource utilization. In the world, 15-25% of light aromatic hydrocarbons and about 95% of polycyclic aromatic compounds are obtained from the degradation products of coal, and the products and derivative products prepared from aromatic compounds have been widely used in the fields of medicine, dye, plasticizer, food preservative, etc.

[0003] Due to the complexity and diversity of the network structure of lignite macromolecules, the high-value utilization of lignite for the preparation of chemicals is hindered to some extent. In the prior art, lignite can be broken and depolymerized by pyrolysis, hot dissolution and oxidation. Among them, chemical oxidants such as HNO3, NaClO and H2O2 can break covalent bonds under mild conditions, and oxidize and degrade the macromolecular structure of lignite into oxygen-containing compounds such as humic acid, aromatic compounds and small molecule fatty acids, and the oxidation degradation products mainly depend on the oxidant and oxidation conditions. Solvents such as cyclohexane, benzene, toluene and methanol can effectively destroy the molecular structure of lignite during the process of hot dissolution and depolymerization, and a series of free radical reactions occur, lignite is hot dissolved and depolymerized to generate aromatic compounds. Different depolymerization methods result in different structures and properties of the components of the depolymerization products, which make their application fields different.

[0004] However, the above methods have the following problems: 1. The preparation of aromatic compounds has the problems of large organic solvent pollution, high energy consumption, complex product separation process and poor controllability; 2. The reagent for depolymerizing lignite to prepare aromatic compounds is a chemical reagent, which has the problem of waste liquid treatment, and cannot achieve green and environmental protection; 3. The preparation process is complex, harsh reaction conditions are required, and the requirements for equipment and energy consumption are high. Therefore, from the aspects of resource utilization rate, environmental protection and economic feasibility, it is necessary to continue to explore new green and efficient depolymerization processes for lignite, and to establish a process route with industrial scale production value, which is the development trend of lignite production of chemicals under the situation of carbon neutralization.

[0005] In summary, how to produce aromatic compounds and / or biomethane efficiently and in an environmentally friendly manner using safe and environmentally friendly raw materials is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the efficiency of selective depolymerization of lignite in the production of aromatic compounds and / or biomethane. This method utilizes microbial communities and / or promoters to synergistically degrade lignite, thereby achieving high-efficiency co-production of multiple aromatic compounds. This preparation method is simple, highly feasible, energy-efficient, uses inexpensive raw materials, and is environmentally friendly, making it particularly suitable for large-scale industrial production.

[0007] To achieve the above objectives, the present invention provides a method for improving the efficiency of selective depolymerization of lignite in the production of aromatic compounds and / or biomethane, specifically comprising the following steps:

[0008] S1 involves crushing and sieving lignite to obtain lignite powder;

[0009] S2 involves placing lignite powder in a closed device, adding activated sludge, and adjusting the pH of the reaction system to 6.8~7.2;

[0010] S3 involves placing a sealed device under constant temperature conditions and selectively degrading the reaction for a certain period of time to produce high yields of aromatic compounds and / or biomethane.

[0011] In a preferred embodiment, in step S1, the pulverization method can be a conventional method known to those skilled in the art, and the sieve used for sieving is 40 mesh or more; more preferably, the sieve used for sieving is 40 mesh, 60 mesh, or 80 mesh.

[0012] In a preferred embodiment, in step S2, the activated sludge is anaerobic activated sludge with a total solids (TS) content of 0.15%-0.23% and a volatile solids (VS) content of 0.08%-0.11%.

[0013] In a preferred embodiment, in step S2, the mass-to-volume ratio of lignite to activated sludge is (1~2) g:10 ml; preferably, the mass-to-volume ratio of lignite to activated sludge is (1.3~1.7) g:10 ml; more preferably, the mass-to-volume ratio of lignite to activated sludge is 1.5 g:10 ml.

[0014] In a preferred embodiment, in step S2, the pH of the reaction system is adjusted to 7.0.

[0015] In a preferred embodiment, in step S2, the pH adjusting reagent is a sodium hydroxide solution and / or a sulfuric acid solution, preferably, the mass concentration of the sodium hydroxide solution and / or the sulfuric acid solution is 2-8%, more preferably, the mass concentration of the sodium hydroxide solution and / or the sulfuric acid solution is 5%.

[0016] In a preferred embodiment, in step S3, the constant temperature is 50-54°C, and the reaction time is 1-6 days; preferably, the constant temperature is 52°C, and the reaction time is 4 days.

[0017] In a preferred embodiment, in step S3, the concentrations of benzyl alcohol, benzaldehyde and benzoic acid produced can reach 5.82 mg / L, 59.02 mg / L and 6.05 mg / L, respectively; and the concentration of phenol produced can reach 3.40 mg / L.

[0018] In a preferred embodiment, in step S2, a reaction promoter is further added before adjusting the pH.

[0019] In a preferred embodiment, the promoter includes one or more of formic acid, acetic acid, oleic acid, glucose, fructose, xylose, arabinose, galactose, maltose, sucrose, lactose, trehalose, dextrin, cellulose, corn straw powder, soluble starch, and an aqueous solution thereof.

[0020] In a preferred embodiment, the concentration of the promoter is 0.5-1.5 g / L; preferably, the concentration of the promoter is 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1.0 g / L, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L.

[0021] In a preferred embodiment, the mass-volume ratio of the lignite, activated sludge and promoter is (1-2) g:10 ml:(0.25-0.5) ml; preferably, the mass-volume ratio of the lignite, activated sludge and promoter is (1.3-1.7) g:10 ml:(0.25-0.5) ml; more preferably, the mass-volume ratio of the lignite, activated sludge and promoter is 1.5 g:10 ml:(0.25-0.5) ml.

[0022] In a preferred embodiment, when the promoter is 0.25 mL of a 1 g / L glucose solution, the amount of methane produced can reach 7.44 mL / g, the concentration of humic acid produced can reach 864.1202 mg / L, and the concentration of benzoic acid produced can reach 0.5243 mg / L.

[0023] In a preferred embodiment, when the accelerator is 0.45 mL of 1 g / L oleic acid, the humic acid concentration can reach 2214.3810 mg / L, and the benzoic acid concentration can reach 1.5082 mg / L.

[0024] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0025] 1. Unlike the prior art, which degrades lignite with chemical reagents or single microorganisms, the technical scheme of the present application uses activated sludge as a source of microbial flora, explores a method for improving the efficiency of lignite selective depolymerization to produce aromatic compounds, and obtains high yields of humic acid, benzyl alcohol, benzaldehyde, benzoic acid, phenol, and by-products such as methane.

[0026] 2. In the present application, lignite is degraded cooperatively by microbial flora and accelerators. The principle is based on the Huttinger-Michenfelder model of coal chemical lignite macromolecular structure. By regulating the directional mild depolymerization of lignite macromolecules, selective preparation of aromatic compounds such as benzoic acid, benzaldehyde, and benzyl alcohol, or further conversion to biomethane, is achieved. The growth, reproduction, and metabolism of microbial flora are regulated by accelerators, which strengthen the efficiency of directional mild depolymerization of lignite macromolecules. After cooperative treatment, the microbial flora and accelerators can effectively degrade lignite, improve the strength and force of lignite macromolecular structure and groups, shorten the reaction time, and obtain high concentrations of directional aromatic compounds and high yields of biomethane.

[0027] 3. In the present application, traditional acid and alkali treatment agents are not used. Under relatively mild reaction conditions, lignite is biologically and chemically depolymerized using microbial flora in activated sludge, overcoming the shortcomings of existing processes such as large waste liquid discharge and harsh reaction conditions. A new green production method is provided for selective depolymerization of lignite to produce corresponding aromatic compounds and biomethane products. The raw materials used are safe, environmentally friendly, and low-cost. Compared with traditional lignite degradation processes, the technical scheme provided by the present application is easy to operate, has low energy consumption, has fewer limitations on equipment and operators, and is more suitable for industrialized production. It also expands the utilization of lignite, allowing for the targeted production of various high-yield aromatic compounds and clean energy biomethane from lignite. BRIEF DESCRIPTION OF DRAWINGS

[0028] These and / or other aspects and advantages of the present application will become more apparent and more readily appreciated from the following detailed description of the exemplary embodiments of the present application, taken in conjunction with the accompanying drawings in which:

[0029] Figure 1Scanning electron microscope images of lignite before and after microbial inoculation in Example 1, where a. 380 μm lignite as received; b. 380 μm lignite after microbial inoculation; c. 250 μm lignite as received; d. 250 μm lignite after microbial inoculation; e. 13.28 μm lignite as received; f. 13.28 μm lignite after microbial inoculation; g. quartz sand as received; h. quartz sand in humic acid control after microbial inoculation; i. quartz sand in fulvic acid control after microbial inoculation;

[0030] Figure 2 Effect of microbial inoculation on pH of lignite reaction system in Example 1;

[0031] Figure 3 Effect of microbial inoculation on humic acid production from lignite in Example 1;

[0032] Figure 4 Effect of microbial inoculation on benzyl alcohol production from lignite in Example 1;

[0033] Figure 5 Effect of microbial inoculation on benzaldehyde production from lignite in Example 1;

[0034] Figure 6 Effect of microbial inoculation on benzoic acid production from lignite in Example 1;

[0035] Figure 7 Effect of microbial inoculation on phenol production from lignite in Example 1;

[0036] Figure 8 Effect of microbial inoculation on daily methane production from lignite reaction byproducts in Example 1;

[0037] Figure 9 Effect of microbial inoculation on total methane production from lignite reaction byproducts in Example 1;

[0038] Figure 10 Effect of facilitator addition on methane production in reaction system in Example 2;

[0039] Figure 11 Effect of facilitator addition on humic acid concentration in reaction system in Example 2;

[0040] Figure 12 Effect of facilitator addition on benzoic acid concentration in reaction system in Example 2;

[0041] Figure 13 Effect of reaction temperature on gas production in effective facilitator addition reaction system in Example 2;

[0042] Figure 14Effect of reaction temperature on humic acid concentration in reaction system with effective promoter added in Example 2;

[0043] Figure 15 Effect of reaction temperature on benzoic acid concentration in reaction system with effective promoter added in Example 2;

[0044] Figure 16 Effect of glucose addition on humic acid and benzoic acid concentration in reaction system in Example 2;

[0045] Figure 17 Effect of xylose addition on humic acid and benzoic acid concentration in reaction system in Example 2;

[0046] Figure 18 Effect of corn stalk powder addition on humic acid and benzoic acid concentration in reaction system in Example 2;

[0047] Figure 19 Effect of cellulose addition on humic acid and benzoic acid concentration in reaction system in Example 2;

[0048] Figure 20 Effect of oleic acid addition on humic acid and benzoic acid concentration in reaction system in Example 2;

[0049] Figure 21 Effect of soluble starch addition on humic acid and benzoic acid concentration in reaction system in Example 2

[0050] Figure 22 Standard curve of humic acid concentration in Example 2. DETAILED DESCRIPTION

[0051] In order to make the skilled in the art better understand the present application, the following further detailed description of the present application is combined with the drawings and specific embodiments, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0052] If not specifically indicated, the technical means used in the present application are the conventional means well known to those skilled in the art, and various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing method. The reagent parameters used in the examples of the present application are shown in Table 1.

[0053] Table 1

[0054] Reagent Category Manufacturer Lignite - Baotou Activated sludge Total solid TS 0.19%, volatile solid VS content 0.09% Baotou City South Suburban Sewage Treatment Plant Sodium hydroxide AR Tianjin Guangfu Science and Technology Development Company Sulfuric acid AR Beijing North Chemical Fine Chemicals Co., Ltd. Formic acid AR Tianjin Chemical Reagent Factory No. 3 Acetic acid AR Nanjing Chemical Reagent Co., Ltd. Oleic acid AR Tianjin Guangcheng Chemical Reagent Co., Ltd. Glucose AR Tianjin Damao Chemical Reagent Factory Fructose AR Beijing Solabio Co., Ltd. Xylose AR Beijing Solabio Co., Ltd. Arabinose AR Beijing Solabio Co., Ltd. Galactose AR Beijing Solabio Co., Ltd. Maltose AR Beijing Solabio Co., Ltd. Sucrose AR Beijing Solabio Co., Ltd. Lactose AR Beijing Solabio Co., Ltd. Trehalose AR Beijing Solabio Co., Ltd. Dextrin AR Beijing Solabio Co., Ltd. Cellulose AR Beijing Solabio Co., Ltd. Corn straw powder 100 mesh Baotou Soluble starch AR Tianjin Bailing Biological Technology Co., Ltd. Anhydrous ethanol AR Tianjin Huadong Reagent Factory Ammonium acetate AR Tianjin Damao Chemical Reagent Factory Methanol AR Tianjin Damao Chemical Reagent Factory Acetonitrile AR Tianjin Damao Chemical Reagent Factory

[0055] The microbial flora of the activated sludge used in the embodiment includes bacteria and archaea. The bacteria specifically include Trichococcus, Tepidiphilus, Clostridium, and Norank-SBR1031. Verification of the effects shows that Trichococcus can produce metabolic products such as acetic acid and D-lactic acid. Tepidiphilus promotes the generation of soluble organic matter into acetic acid, H2, and CO2. Clostridium is a strict anaerobic acid-producing bacterium such as acetic acid and butyric acid. Norank-SBR1031 has a good degradation effect on aromatic hydrocarbons and naphthenic aromatic hydrocarbons of lignite.

[0056] The archaea specifically include Methanosarcina, Methanothermobacter, and Methanosaeta. Verification of the effects shows that Methanosarcina is a hydrogenotrophic, methylotrophic, and acetotrophic mixed methanogen, which can convert H2 / CO2, acetic acid, and methyl compounds into CH4. Methanothermobacter is a hydrogenotrophic methanogen that produces methane through a CO2 reduction pathway, using H2 as an electron donor to reduce CO2 under the action of hydrogenase and then convert it into CH4. Methanosaeta only uses acetic acid to produce CH4, and can convert the methyl group of the acetic acid molecule into methane.

[0057] In the present application, the above-mentioned multiple microbial genera are used synergistically in an anaerobic environment, and by adjusting parameters such as temperature, pH, and nutrients in the environmental conditions, the relationship between the microbial flora is effectively coordinated to reach the optimal ecological level, promote the material metabolism and energy metabolism of the microbial flora, and thus improve the efficiency of selective depolymerization of lignite to obtain aromatic compounds and / or biological methane. Compared with the use of a single genus, the present application scheme will face more challenges in coordinating different characteristic microbial flora to enhance their metabolic capacity.

[0058] Embodiment 1

[0059] Method for obtaining high-yield aromatic compounds by pretreating lignite with a microbial flora

[0060] (I) Formulation design:

[0061] 30 g of lignite was mechanically pulverized and sieved through a 40-mesh sieve and a 60-mesh sieve, respectively, to obtain lignite powder with particle sizes of 380 μm and 250 μm, which are denoted as experimental group one and experimental group two, respectively.

[0062] 30 g of lignite was ultra-finely pulverized to obtain lignite powder with an average particle size of 13.28 μm, which was recorded as experimental group three;

[0063] The humic acid content in the lignite used for determination was 33%, 9.9 g; the fulvic acid content was 3%, 0.9 g, therefore, 9.9 g of humic acid and 20.1 g of quartz sand were mixed and recorded as control group one;

[0064] 0.9 g of fulvic acid and 29.1 g of quartz sand were mixed and recorded as control group two.

[0065] (II) Experimental steps:

[0066] The raw materials of experimental groups one to three and control groups one to two were respectively added to the reaction bottles, 200 mL of activated sludge was measured and added to the reaction bottles, the reaction bottles were immediately sealed and water was added to a constant volume of 400 mL, the pH was adjusted to 7.0, the sealed reaction bottles were placed in a constant temperature water bath at a temperature of 50°C, and the reaction bottles were shaken at irregular times every day to make the lignite and the microbial flora fully react with each other, 10 mL of sample was taken at regular times every day, and the daily gas production, pH, and the contents of humic acid, benzyl alcohol, benzaldehyde, benzoic acid, and phenol in the sample were determined, three parallel experiments were performed for each group, and the average value was taken as the result.

[0067] (III) Experimental results and discussion:

[0068] 1. Effect of microbial flora pretreatment on the morphology of lignite

[0069] The results are shown in Table 1. Figure 1As shown, Figures a and b are scanning electron microscope (SEM) images of 380 μm lignite before and after microbial pretreatment. The lignite after microbial pretreatment shows a significantly porous structure, indicating substantial degradation, and the surface becomes rougher. Figures c and d are SEM images of 250 μm lignite before and after microbial pretreatment. In Figure c, the lignite surface is relatively smooth, while in Figure d, compared to Figure c, the lignite structure shows obvious small pores, resembling corrosion, with significantly increased pore size and porosity, cracks, and increased roughness. Figures e and f are images of 13.28 μm lignite before and after microbial pretreatment. The scanning electron microscope (SEM) images of μm lignite in Figure e show that the molecular structure of lignite has sharp edges and obvious stratification. Figure f clearly shows that the lignite is degraded layer by layer by microorganisms. The edges of the treated lignite become uneven, and the surface becomes rougher, showing obvious signs of microbial degradation and fragmentation. This indicates that the microbial community degrades the lignite, selectively pyrolyzing large particles to prepare aromatic compounds. Compared with Figures a and c, Figure e shows that after ultrafine grinding, the pore structure and surface area of ​​the lignite increase due to strong shearing and grinding effects, making the stratification and fragmentation of lignite more significant. Figures g, h, and i show the changes in the morphology of quartz sand before and after microbial pretreatment. Compared with Figures h, i, and g, the morphology of quartz sand does not change significantly, and the edges and stratification are more obvious. This indicates that the addition of quartz sand as a weight to the humic acid and fulvic acid reaction system has a weak effect on the reaction system, and the microbial community does not pyrolyze the quartz sand.

[0070] 2. Effects of microbial community on pH of lignite reaction system

[0071] The result is as follows Figure 2As shown, the pH of lignite at sizes of 13.28, 250, and 380 μm initially decreased and then increased with increasing reaction days. This is because the microbial community consumes organic matter in the lignite during depolymerization, converting it into volatile fatty acids, leading to a decrease in the pH of the reaction system. As the reaction days increase, the volatile fatty acids are further degraded by the microbial community into methane, causing the pH to slowly increase. Existing research indicates that the degradation efficiency of lignite is related to pH changes; higher pH results in higher lignite degradation efficiency. The pH values ​​of the humic acid and fulvic acid control groups initially increased and then decreased with increasing reaction days, reaching their highest values ​​of 7.01 and 7.24 respectively on day 4. The pH value of the humic acid control group fluctuated between 6.97 and 7.01, while the pH value of the fulvic acid control group remained consistently higher than the initial pH of 7.0. This indicates that humic acid and fulvic acid are easily decomposed during microbial treatment, leading to a reduction in carboxyl functional groups and an increase in pH. This confirms that the concentration of benzoic acid in the aforementioned reaction systems of humic acid and fulvic acid control groups showed a continuous decreasing trend with increasing reaction days. In the reaction systems of 13.28, 250, and 380 μm lignite, the pH of 13.28 and 250 μm lignite decreased more rapidly than that of 380 μm lignite in the first two days. After day 2, the pH of 13.28 and 250 μm lignite was higher than that of 380 μm lignite, indicating that smaller lignite particles are more easily selectively degraded and decomposed by microbial communities to produce aromatic compounds.

[0072] 3. The Influence of Microbial Community on Humic Acid Production from Lignite

[0073] The result is as follows Figure 3 As shown in the figure, the humic acid concentrations in the 13.28, 250, and 380 μm lignite, humic acid, and fulvic acid control groups all exhibit a trend of first increasing and then decreasing. The humic acid concentrations in the 13.28, 380 μm lignite, and humic acid control groups all reached their maximum values ​​on day 2, at 1505.56, 1181.34, 1118.82, and 2584.89 mg / L, respectively. The humic acid concentration in the 250 μm lignite reached its maximum value of 1181.53 mg / L on day 3. Combining the changes in humic acid concentrations in the 13.28, 250, and 380 μm lignite, it can be seen that the smaller the particle size, the weaker the cohesion between the small lignite molecules, increasing the contact area between the microbial community and the lignite, and more easily promoting the depolymerization and degradation of lignite by microorganisms to produce humic acid. This further verifies that the 13.28 μm lignite produced the highest concentration of humic acid. The fulvic acid control group was added to the reaction system instead of lignite. Since fulvic acid is water-soluble, the humic acid concentration in the fulvic acid control group was higher than that in both the humic acid control group and the lignite experimental group. As the reaction time increased, the humic acid concentration decreased in both groups. This is because microbial degradation of humic acid causes a large number of hydroxyl and carboxyl functional groups to dissociate and degrade into different types of aromatic compounds.

[0074] 4Effect of Microbial Flora on the Production of Benzyl Alcohol from Lignite

[0075] The results are shown in Figure 4 Figure 4. The benzyl alcohol concentration in the 13.28, 250, 380 μm lignite and humic acid control groups showed a continuous decreasing trend with increasing reaction time, and the highest benzyl alcohol concentration was achieved on the first day, at 5.30, 4.89, 5.82 and 5.51 mg / L, respectively. The benzyl alcohol concentration in the fulvic acid control group showed an increasing trend first and then a decreasing trend, and the highest concentration was achieved on the third day, at 5.39 mg / L. Compared with the 13.28 and 380 μm lignite, the benzyl alcohol concentration in the 250 μm lignite decreased more greatly, and the benzyl alcohol concentration in the 13.28 μm lignite tended to be stable after the third day. This is because the small particle size of lignite helps the microbial flora to degrade the organic matter in the lignite, providing the necessary nutrients for the microbial flora and promoting the reproduction and metabolic degradation of the microbial flora to obtain benzyl alcohol. Compared with the lignite and humic acid control groups, the molecular weight of the fulvic acid is smaller and the molecular structure is simpler, so it is easier to be degraded by the microbial flora to produce benzyl alcohol.

[0076] 5Effect of Microbial Flora on the Production of Benzaldehyde from Lignite

[0077] The results are shown in Figure 5 Figure 5. The benzaldehyde concentration in the 13.28, 250, 380 μm and humic acid control groups showed an increasing trend first and then a decreasing trend, and the benzaldehyde concentration in the fulvic acid control group showed a continuous decreasing trend. The highest benzaldehyde concentration in the 13.28, 250, 380 μm and humic acid control groups was achieved on the second day, at 36.91, 57.34, 59.02 and 42.22 mg / L, respectively, and the highest benzaldehyde concentration in the fulvic acid control group was achieved on the first day, at 31.91 mg / L. The benzaldehyde concentration in the 380 μm lignite was the highest, and the benzaldehyde concentration in the 13.28 μm lignite was the lowest, indicating that too small a particle size can cause the aldehyde group or carbon-carbon single bond in the lignite to be destroyed, which is not conducive to the production of benzaldehyde from lignite by the microbial flora. As can be seen from Figure 6 , the benzaldehyde content in the lignite reaction system was higher than that in the humic acid and fulvic acid control groups at the beginning of the reaction, and more aldehyde groups were oxidized by the microorganisms to carboxyl groups, which reduced the benzaldehyde content in the humic acid and fulvic acid control groups. Compared with the fulvic acid, the aromaticity of the humic acid is stronger and similar to the structure of lignite, so the change trend of the lignite and humic acid degradation by the microbial flora is nearly the same. The structure of the fulvic acid is relatively simple, and it can be directly cleaved by the microorganisms in the reaction system, so it shows a continuous decreasing trend.

[0078] 6Effect of microbial flora on benzene carboxylic acid production from lignite

[0079] The results are shown in Figure 6 The benzene carboxylic acid concentration of 13.28, 250, and 380 μm lignite showed a trend of first increasing and then decreasing. The benzene carboxylic acid concentration of 13.28 μm lignite reached the highest value of 5.17 mg / L on the 4th day, and the benzene carboxylic acid concentration of 250 and 380 μm lignite reached the highest value on the 5th day, which were 6.05 and 5.71 mg / L, respectively. The benzene carboxylic acid concentration of 380 μm lignite was the highest, and the benzene carboxylic acid concentration of 13.28 μm lignite was the lowest, which was contrary to the change trend of benzene formaldehyde concentration, because the microorganisms would oxidize the aldehyde group to make the aldehyde group oxidized to carboxyl group. The benzene carboxylic acid of 13.28 μm lignite reached the peak value on the 4th day, which was 1 day earlier than 250 and 380 μm lignite, indicating that the smaller the particle size of lignite, the easier the structure of lignite was cracked by the microbial flora, which increased the oxidation efficiency of aldehyde group and made the benzene carboxylic acid concentration reach the peak value in advance. The benzene carboxylic acid concentration of humic acid and fulvic acid control groups showed a decreasing trend with the increase of reaction days, and the highest benzene carboxylic acid concentration on the 1st day was 5.48 and 5.68 mg / L, respectively. Compared with the humic acid and fulvic acid control groups, the benzene carboxylic acid of 380 μm lignite was more easily degraded by the microbial flora from humic acid and fulvic acid, and with the progress of the reaction, the benzene carboxylic acid in the humic acid and fulvic acid reaction system was decomposed by the microorganisms, which continuously reduced the benzene carboxylic acid concentration.

[0080] 7Effect of microbial flora on benzene carboxylic acid production from lignite

[0081] The results are shown in Figure 7As shown, with the increase of reaction days, the phenol concentration in 13.28, 250, and 380 μm lignite showed a trend of first decreasing, then increasing, and then decreasing again, reaching its highest value on day 6, at 3.40, 3.35, and 3.34 mg / L, respectively. This indicates that microorganisms oxidize some phenolic hydroxyl groups in the first 3 days. As the microbial community continuously degrades the lignite, some aromatic rings and phenolic hydroxyl groups are dissociated from the polycyclic aromatic hydrocarbon macromolecules of lignite, causing the phenol concentration in the reaction system to gradually increase. However, as the degree of aromatization in the condensed aromatic ring structure of lignite increases, the difficulty of aromatic ring dissociation increases, leading to a gradual decrease in the final phenol concentration. Compared with the control group of fulvic acid and humic acid and the experimental group of lignite, the phenol concentration in the fulvic acid control group showed a trend of first increasing and then decreasing, while the phenol concentration in the humic acid control group showed a trend of first decreasing and then increasing. This is because fulvic acid has a simple structure and is more easily decomposed by microbial communities compared to humic acid and lignite, making it easier for phenol to dissociate from the macromolecular structure of fulvic acid. Humic acid is more difficult to be degraded by microorganisms, but compared to lignite, phenol dissociates more easily from humic acid, resulting in a higher phenol concentration in the humic acid control group than in lignite. However, as the reaction proceeds, microorganisms continuously oxidize the hydroxyl groups, and the phenol concentration in both reaction systems eventually shows a decreasing trend.

[0082] 8. The impact of microbial communities on the daily methane production from lignite reaction byproducts

[0083] The result is as follows Figure 8 As shown, the methane production of 13.28, 250, and 380 μm lignite initially decreased and then increased with the increase of reaction days. Furthermore, the methane production of 13.28 and 250 μm lignite was higher than that of 380 μm lignite, further verifying that smaller particle sizes of lignite are more easily degraded by microbial communities, providing the necessary nutrients for methanogenic bacteria and leading to the production of biomethane. The methane production of humic acid and fulvic acid showed a continuous decreasing trend with the increase of reaction days. In the first 5 days, the methane production in the reaction system was consistently higher than that of 380 μm lignite, indicating that humic acid and fulvic acid are more easily degraded and utilized by microbial communities. The methane production continuously decreased in the first 4 days of the reaction. As the reaction days increased, the microorganisms in the reaction system consumed volatile fatty acids, converting them into acetic acid, which in turn was converted into methane, thus promoting the depolymerization of lignite by microbial communities to produce methane.

[0084] 9. The Influence of Microbial Community on the Total Methane Production from Lignite Reactor Byproducts

[0085] The result is as follows Figure 9As shown, for the lignite experimental group, the total gas production shows an upward trend with the continuous decrease of the particle size of lignite, and the total gas production of 380, 250 and 13.28 μm lignite is 30.19, 31.31 and 35.18 mL respectively, which indicates that the smaller the particle size of lignite, the more conducive to the production of methane by the microbial flora. Compared with the humic acid and fulvic acid control groups, the total gas production of the humic acid control group is 24.02 mg / L, and the total gas production of the fulvic acid control group is the highest, which is 38.26 mL, higher than that of the humic acid control group and the lignite experimental group, further indicating that the fulvic acid is more easily degraded and converted by the microorganisms.

[0086] From the above experimental results, it can be seen that,

[0087] (1) The microbial flora has a certain cracking effect on lignite. Compared with the lignite before pretreatment, the microbial pretreatment makes the surface of the lignite rough, the pore structure increases, and the fragmentation is obvious.

[0088] (2) The microbial flora has different abilities to produce aromatic compounds from lignite of different particle sizes. The concentrations of benzyl alcohol, benzaldehyde and benzoic acid in the 380 μm lignite reaction system are the highest, which are 5.82, 59.02 and 6.05 mg / L respectively; the concentration of phenol in the 13.28 μm lignite reaction system is the highest, which is 3.40 mg / L. Phenol is only obtained in the production of aromatic compounds by the microbial flora pretreatment of lignite, and is not found in the physical pretreatment such as crushing. Therefore, the present application can explore a high-yield method for producing aromatic compounds from lignite, especially phenol.

[0089] (3) The microbial flora degrades lignite to produce aromatic compounds. Compared with single microbial degradation of lignite, the reaction system can produce biological methane while obtaining aromatic compounds, realizing a multi-coproduction production mode of aromatic compounds benzyl alcohol, benzoic acid, benzaldehyde, phenol and clean energy biological methane.

[0090] Example 2

[0091] Method for producing high-yield aromatic compounds by synergistically treating lignite with microbial flora and accelerant

[0092] On the basis of Example 1, the best lignite powder particle size of 380 microns (passing through a 40 mesh sieve) and the best reaction time of 4 days are selected to explore the effect of different accelerants on improving the yield:

[0093] (I) Preparation of experimental raw materials and experimental reagents:

[0094] (1) 1 g / L formic acid solution, 1 g / L acetic acid solution, 1 g / L oleic acid solution:

[0095] Accurately pipette 0.1 g of formic acid solution with a disposable dropper, then accurately measure 50 mL of distilled water with a measuring cylinder, and slowly pour it into a 100 mL beaker and constantly stir with a glass rod rinsed with distilled water. After the solution is mixed evenly, transfer it to a 100 mL volumetric flask rinsed with distilled water, and dilute to the calibration line with distilled water. Shake well. (The remaining solution is placed in two 10 ml centrifuge tubes, labeled and stored in the refrigerator for future use.)

[0096] According to the above experimental procedure, 1 g / L acetic acid solution and 1 g / L oleic acid solution are prepared respectively.

[0097] (2) 1 g / L glucose solution, 1 g / L fructose solution, 1 g / L xylose solution, 1 g / L arabinose solution, 1 g / L galactose solution, 1 g / L maltose solution 1 g / L sucrose solution, 1 g / L lactose solution, 1 g / L trehalose solution, 1 g / L dextrin solution, 1 g / L cellulose solution, 1 g / L corn straw powder solution, 1 g / L soluble starch solution:

[0098] Accurately weigh 0.1 g of glucose, then accurately measure 50 mL of distilled water with a measuring cylinder and pour it into a small beaker and stir with a glass rod rinsed with distilled water. After the solid is completely dissolved, transfer it to a 100 mL volumetric flask rinsed with distilled water, and dilute to the calibration line with distilled water. Shake well. (The remaining solution is stored in two 10 ml centrifuge tubes, labeled and stored in the refrigerator for future use.)

[0099] According to the above experimental procedure, 1 g / L fructose solution, 1 g / L xylose solution, 1 g / L arabinose solution, 1 g / L galactose solution, 1 g / L maltose solution 1 g / L sucrose solution, 1 g / L lactose solution, 1 g / L trehalose solution, 1 g / L dextrin solution, 1 g / L cellulose solution, 1 g / L corn straw powder solution, 1 g / L soluble starch solution are prepared respectively.

[0100] (3) 5% dilute sulfuric acid solution:

[0101] Accurately weigh 5.0 mL of 98% concentrated sulfuric acid solution with a measuring cylinder, and slowly pour it into a 50 mL beaker along the wall of the beaker. Then accurately measure 40 mL of distilled water with another measuring cylinder and slowly pour it into the beaker and constantly stir with a glass cup. After the solution cools to room temperature, transfer the solution to a 100 mL volumetric flask rinsed with distilled water, dilute to the calibration line, and shake well.

[0102] (4) 5% sodium hydroxide solution:

[0103] Take 5.0 g of solid particles of sodium hydroxide with a laboratory precision electronic balance, then slowly pour it into a 50 mL beaker, then accurately measure 40 mL of distilled water with a measuring cylinder and slowly pour it into the beaker and constantly stir with a glass cup until the solid particles are completely melted. After the solution cools to room temperature, transfer the solution to a rinsed 100 mL volumetric flask, dilute to the calibration line, shake well.

[0104] (5) Humic acid solution preparation:

[0105] Take 6 clean 100mL capacity bottles, rinse with distilled water and number them as capacity bottle one, capacity bottle two, capacity bottle three, capacity bottle four, capacity bottle five, capacity bottle six. Accurately weigh 0.1 g of refined humic acid (yellow humic acid) with a laboratory precision electronic balance, then slowly pour it into a 50 mL beaker, then accurately measure 40 mL of distilled water with a measuring cylinder and slowly pour it into the beaker, constantly stirring with a glass cup during the process. Then transfer the solution to capacity bottle one, and finally dilute the solution to the calibration line with distilled water to prepare a humic acid solution with a mass concentration of 1000 mg / L. Then use a 20 mL pipette to remove 20 mL of the prepared humic acid solution with a mass concentration of 1000 mg / L and place it in a 50 mL beaker. Add an appropriate amount of distilled water to dilute the original solution, constantly stirring with a glass cup during the process. Then transfer the diluted solution to capacity bottle two and dilute the solution to the calibration line again with distilled water. At this time, the mass concentration of the humic acid solution in capacity bottle two is 200 mg / L. Then use a pipette to remove 50 mL of humic acid solution from capacity bottle one and inject it into capacity bottle three. Then dilute capacity bottle three to 100 mL. At this time, the mass concentration of the humic acid solution in capacity bottle three is 100 mg / L. Follow this method to prepare the humic acid solutions in capacity bottle four, capacity bottle five, and capacity bottle six with mass concentrations of 50 mg / L, 25 mg / L, and 12.5 mg / L, respectively.

[0106] (6) Preparation of benzene acid mobile phase:

[0107] Take 1000ml liquid chromatography special methanol into the vacuum pump beaker, then the methanol is filtered by AP-01P vacuum pump (microporous filtration membrane is 0.45um organic membrane), after filtration, then pour into the liquid phase special bottle filled with methanol, then put into SB-80 ultrasonic cleaner for ultrasonic degassing 10-15 min. Accurately weigh 1.5416 g of ammonium acetate particles with a laboratory precision electronic balance, then slowly pour into a 50mL beaker, then accurately measure 40mL of pure water with a graduated cylinder and slowly pour into the beaker, constantly stir with a glass cup during the process until the solid is completely melted, finally transfer the solution to a 1000mL clean volumetric flask, and finally use pure water to make the solution to the calibration line. Then the ammonium acetate solution is filtered by AP-01P vacuum pump (microporous filtration membrane is 0.45um water membrane), after filtration, then pour into the special bottle of liquid chromatography buffer salt, then put into the ultrasonic cleaner for ultrasonic degassing 10-15 min. Then filter 500mL of pure water, pour into the liquid phase water special bottle, and put into the SB-80 ultrasonic cleaner for ultrasonic degassing 10-15 min.

[0108] (II) Experimental steps:

[0109] Take an appropriate amount of lignite and crush it, pass it through a 40-mesh sieve, and store it for future use. First, prepare a clean 100ml syringe and enough three-way valves. Connect the three-way valves to the 100ml syringe respectively, and check if the air tightness is normal. Then accurately weigh 1.5g of lignite respectively with a laboratory precision electronic balance, and add them to the 100ml syringe respectively. Add 10ml of activated sludge to each syringe, and divide them into 17 groups. Each group has three parallel control experiments. The first group is a blank control experiment. The remaining 16 groups are added with 1g / L formic acid solution, acetic acid solution, oleic acid solution, glucose solution, fructose solution, xylose solution, arabinose solution, galactose solution, maltose solution, sucrose solution, lactose solution, trehalose solution, dextrin solution, cellulose solution, corn straw powder solution, and soluble starch solution respectively, each 0.25ml. Shake well and label for easy identification. Then adjust the pH to 7.0 with 5% sodium hydroxide solution and a Leici pH meter, and dilute to 20ml. Shake well. Transfer all of them to a 52℃ constant temperature water bath for reaction. Shake the syringes regularly every day to ensure full reaction. On the fourth day of reaction, measure the concentration of benzoic acid and humic acid, and record the gas production. Calculate the average value of each group with three parallel control experiments.

[0110] (1) Measurement of gas production

[0111] First, the length L of the 100ml syringe is measured accurately with a ruler. Record the initial position of each syringe piston and mark it, and then record the position after the reaction is completed. The distance L' between the two positions is measured accurately with a ruler, and the gas production V is calculated using the formula L / L' = 100 / V.

[0112] (2) Determination of humic acid concentration

[0113] After the fourth day reaction is completed, the syringe is taken out of the water bath. Shake each syringe thoroughly, then open the three-way valve connected to the syringe to transfer all the sample to a large centrifuge tube. After cooling to room temperature, shake again, and use a disposable rubber head dropper to take an appropriate amount of sample into a 5ml centrifuge tube (the remaining sample is placed in the refrigerator for storage). Label the sample and weigh it to ensure uniform weight before placing it in the HC-2062 high-speed refrigerated centrifuge at 12000 rpm for 10 minutes. After centrifugation, take the supernatant from the centrifuge tube. If the liquid is too turbid, it needs to be centrifuged again. Accurately take 1mL of supernatant without loss and inject it into a 100mL volumetric flask rinsed with distilled water. Then, add distilled water to 100mL. Scan the prepared sample solution with CARY-5000 UV-visible near-infrared spectrophotometer (256nm-400 nm) to obtain the absorbance value and calculate the average. Then, put the value into the humic acid standard curve formula to obtain the humic acid concentration of the sample solution. Finally, multiply the humic acid concentration of the sample solution by the dilution factor 100 to obtain the humic acid concentration of the sample.

[0114] (3) Determination of benzoic acid concentration

[0115] After the fourth day reaction is completed, the syringe is taken out of the water bath. Shake each syringe thoroughly, then open the three-way valve connected to the syringe to transfer all the sample to a large centrifuge tube. After cooling to room temperature, shake again, and use a disposable rubber head dropper to take an appropriate amount of sample into a 5ml centrifuge tube (the remaining sample is placed in the refrigerator for storage). Label the sample and weigh it to ensure uniform weight before placing it in the HC-2062 high-speed refrigerated centrifuge at 12000 rpm for 10 minutes. After centrifugation, take the supernatant from the centrifuge tube. If the liquid is too turbid, it needs to be centrifuged again. Take a clean liquid phase vial and label it with the serial number. Then, inject the centrifuged supernatant into the corresponding liquid phase vial through a 0.22 um filter (organic). Use high performance liquid chromatography to measure the concentration of benzoic acid in the liquid phase vial.

[0116] (Three) Experimental results and discussion:

[0117] 1. The effect of accelerator addition on the production of methane in the reaction system

[0118] The results are shown in Figure 10 The gas production of the blank control group was 3.52 mL / g, the gas production after adding formic acid solution was 4.25 mL / g, the gas production after adding acetic acid solution was 4.87 mL / g, the gas production after adding oleic acid solution was 4.53 mL / g, the gas production after adding glucose solution was 7.44 mL / g, the gas production after adding fructose solution was 6.67 mL / g, the gas production after adding xylose solution was 6.33 mL / g, the gas production after adding arabinose solution was 5.82 mL / g, the gas production after adding galactose solution was 5.67 mL / g, the gas production after adding maltose solution was 5.33 mL / g, the gas production after adding sucrose solution was 4.69 mL / g, the gas production after adding lactose solution was 4.06 mL / g, the gas production after adding trehalose solution was 5.22 mL / g, the gas production after adding dextrin solution was 5.67 mL / g, the gas production after adding cellulose solution was 6.22 mL / g, the gas production after adding corn straw powder solution was 7.08 mL / g, and the gas production after adding soluble starch solution was 4.54 mL / g. The gas production from high to low was glucose corn straw powder solution, fructose solution, xylose solution, cellulose solution, arabinose solution, dextrin solution, galactose solution, maltose solution, trehalose solution, acetic acid solution, sucrose solution, soluble starch solution, oleic acid solution, formic acid solution, lactose solution. Under this condition, the gas production was the highest when 1 g / L of glucose solution was added to treat the sample, which was 7.44 mL / g.

[0119] 2 Effect of accelerator addition on humic acid concentration of reaction system

[0120] The results are shown in Figure 11As shown, the humic acid concentration of the blank control group was 249.5370 mg / L, the humic acid concentration under the addition of formic acid solution was 410.7619 mg / L, the humic acid concentration under the addition of acetic acid solution was 385.3505 mg / L, the humic acid concentration under the addition of oleic acid solution was 747.2222 mg / L, the humic acid concentration under the addition of glucose solution was 864.1202 mg / L, the humic acid concentration under the addition of fructose solution was 611.3695 mg / L, the humic acid concentration under the addition of xylose solution was 700.6332 mg / L, the humic acid concentration under the addition of arabinose solution was 661.2011 mg / L, the humic acid concentration under the addition of galactose solution was 694.3122 mg / L, the humic acid concentration under the addition of maltose solution was 600.0298 mg / L, the humic acid concentration under the addition of sucrose solution was 597.0899 mg / L, the humic acid concentration under the addition of lactose solution was 533.9286 mg / L, the humic acid concentration under the addition of trehalose solution was 674.1598 mg / L, the humic acid concentration under the addition of dextrin solution was 651.3266 mg / L, the humic acid concentration under the addition of cellulose solution was 642.7120 mg / L, the humic acid concentration under the addition of corn straw powder solution was 681.5476 mg / L, and the humic acid concentration under the addition of soluble starch solution was 733.2876 mg / L. The humic acid concentration in the reaction system was the highest when 1 g / L of glucose solution was added, which was 864.1202 mg / L.

[0121] 3 Effect of accelerator addition on the concentration of benzoic acid in the reaction system

[0122] The results are as follows Figure 12As shown in the table, the benzoic acid concentration of the blank control group was 0.2696 mg / L, the benzoic acid concentration after adding formic acid solution was 0.2894 mg / L, the benzoic acid concentration after adding acetic acid solution was 0.2539 mg / L, the benzoic acid concentration after adding oleic acid solution was 0.4030 mg / L, the benzoic acid concentration after adding glucose solution was 0.5243 mg / L, the benzoic acid concentration after adding fructose solution was 0.4305 mg / L, the benzoic acid concentration after adding xylose solution was 0.4713 mg / L, the benzoic acid concentration after adding arabinose solution was 0.4450 mg / L, the benzoic acid concentration after adding galactose solution was 0.4272 mg / L, the benzoic acid concentration after adding maltose solution was 0.4010 mg / L, the benzoic acid concentration after adding sucrose solution was 0.3953 mg / L, the benzoic acid concentration after adding lactose solution was 0.3889 mg / L, the benzoic acid concentration after adding trehalose solution was 0.4163 mg / L, the benzoic acid concentration after adding dextrin solution was 0.4247 mg / L, the benzoic acid concentration after adding cellulose solution was 0.4464 mg / L, the benzoic acid concentration after adding corn straw powder solution was 0.4681 mg / L, and the benzoic acid concentration after adding soluble starch solution was 0.4343 mg / L. The benzoic acid concentration was the highest when 1 g / L of glucose solution was added, which was 0.5243 mg / L.

[0123] 4Effect of reaction temperature on the gas production of the effective promoter added reaction system

[0124] The results are shown in the table below. Figure 13 As shown in the table, after the reaction temperature was increased by 10℃, the gas production of the reaction was increased, among which the gas production was the highest when glucose solution was added, which was 14.67 mL / g. The second was soluble starch (10.67 mL / g), oleic acid (10.33 mL / g), xylose (10.25 mL / g), cellulose (9.75 mL / g), and corn straw powder (8.33 mL / g). At the same time, the increment of gas production was also the largest when glucose solution was added, which was 7.23 mL / g. The smallest increment was when corn straw powder solution was added, which was 1.25 mL / g.

[0125] 5Effect of reaction temperature on the humic acid concentration of the effective promoter added reaction system

[0126] The results are shown in the table below. Figure 14As shown in the table, after the reaction temperature was increased by 10°C, the humic acid concentrations in the reaction systems treated with glucose solution, xylose solution, corn straw powder solution, cellulose solution, oleic acid solution, and soluble starch solution were 423.6321 mg / L, 491.6943 mg / L, 533.1002 mg / L, 403.1496 mg / L, 509.6352 mg / L, and 527.0241 mg / L, respectively. The humic acid concentrations in the reaction systems were all reduced, with the largest reduction of 440.4881 mg / L in the glucose solution and the smallest reduction of 148.4474 mg / L in the corn straw powder solution.

[0127] 6. Effect of reaction temperature on benzoic acid concentration in the reaction system with effective accelerators

[0128] The results are shown in the table below. Figure 15 As shown in the table, after the reaction temperature was increased by 10°C, the benzoic acid concentrations in the reaction systems treated with glucose solution, xylose solution, corn straw powder solution, cellulose solution, oleic acid solution, and soluble starch solution were 0.3685 mg / L, 0.4004 mg / L, 0.4010 mg / L, 0.3698 mg / L, 0.3566 mg / L, and 0.3721 mg / L, respectively. The benzoic acid concentrations in the reaction systems were all reduced, with the largest reduction of 0.1558 mg / L in the glucose solution and the smallest reduction of 0.0464 mg / L in the oleic acid solution.

[0129] 7. The particle size of lignite powder was set to 380 microns (passed through a 40-mesh sieve), and the optimal reaction time was 4 days, the reaction temperature was 52°C. The effects of different accelerators and different volumes of added accelerators on the humic acid and benzoic acid concentrations in the reaction system were explored, and the results are as follows:

[0130] 7.1. Effect of glucose addition on humic acid and benzoic acid concentrations in the reaction system

[0131] The results are shown in the table below. Figure 16As shown in the diagram, the concentrations of humic acid solution at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 864.1202 mg / L, 322.0916 mg / L, 471.1789 mg / L, 263.1481 mg / L, 391.3178 mg / L, and 631.2176 mg / L, respectively. Therefore, the highest humic acid concentration, 864.1202 mg / L, is achieved when 0.25 mL of glucose solution is added. From the right-hand coordinate axis (red illustration), the concentrations of benzoic acid solution under the volume gradient of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.5242 mg / L, 0.2976 mg / L, 0.3277 mg / L, 0.2798 mg / L, 0.2664 mg / L, and 0.4789 mg / L, respectively. Therefore, the highest benzoic acid concentration, 0.5242 mg / L, is achieved when 0.25 mL of glucose solution is added. Figure 16 It can be seen that the concentrations of humic acid and benzoic acid show roughly the same trend, with the highest concentration achieved by adding 0.25 mL of glucose solution.

[0132] 7.2 Effect of xylose addition on the concentrations of humic acid and benzoic acid in the reaction system

[0133] The result is as follows Figure 17 As shown in the diagram, the concentrations of the humic acid solution in the reaction system under the volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 700.6332 mg / L, 742.3221 mg / L, 501.3720 mg / L, 447.2156 mg / L, 630.2991 mg / L, and 919.8112 mg / L, respectively. Therefore, the highest humic acid concentration, 919.8112 mg / L, is achieved when 0.50 mL of xylose solution is added. From the right-hand coordinate axis (red illustration), the benzoic acid concentrations at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.4713 mg / L, 0.4469 mg / L, 0.6184 mg / L, 0.3610 mg / L, 0.5161 mg / L, and 0.7103 mg / L, respectively. Therefore, the highest benzoic acid concentration, 0.7103 mg / L, is achieved when 0.50 mL of xylose solution is added. Figure 17 It can be seen that the concentrations of humic acid and benzoic acid change in roughly the same way, with the highest concentration achieved by adding 0.50 mL of xylose solution.

[0134] 7.3 Effect of corn straw powder addition on the concentrations of humic acid and benzoic acid in the reaction system

[0135] The result is as follows Figure 18 As shown in the diagram, the concentrations of the humic acid solution in the reaction system under the volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 681.5476 mg / L, 420.7539 mg / L, 912.3633 mg / L, 522.0930 mg / L, 595.0423 mg / L, and 548.5117 mg / L, respectively. Therefore, the highest humic acid concentration, 912.3633 mg / L, is achieved when 0.35 mL of corn straw powder solution is added. From the right-hand coordinate axis (red illustration), the benzoic acid concentrations at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.4483 mg / L, 0.3430 mg / L, 0.5077 mg / L, 0.3621 mg / L, 0.2696 mg / L, and 0.4004 mg / L, respectively. Therefore, the highest benzoic acid concentration, 0.5077 mg / L, is achieved when 0.35 mL of corn straw powder solution is added. Figure 18 It can be seen that the trends of humic acid concentration and benzoic acid concentration are roughly the same, and the volume of corn straw powder solution added at the highest concentration is 0.35 mL.

[0136] 7.4 Effect of cellulose addition on the concentrations of humic acid and benzoic acid in the reaction system

[0137] The result is as follows Figure 19As shown in the diagram, the concentrations of the humic acid solution in the reaction system under the volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 642.7120 mg / L, 898.3174 mg / L, 946.8741 mg / L, 586.1590 mg / L, 475.3988 mg / L, and 600.9314 mg / L, respectively. Therefore, the highest humic acid concentration, 946.8741 mg / L, is achieved when 0.35 mL of cellulose solution is added. From the right-hand coordinate axis (red illustration), the benzoic acid concentrations at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.4464 mg / L, 0.6139 mg / L, 0.7388 mg / L, 0.3654 mg / L, 0.4802 mg / L, and 0.5003 mg / L, respectively. Therefore, the highest benzoic acid concentration, 0.7388 mg / L, is achieved when 0.35 mL of cellulose solution is added. Figure 19 It can be seen that the concentrations of humic acid and benzoic acid change in roughly the same direction, with the highest concentration achieved by adding 0.35 mL of cellulose solution to both solutions.

[0138] 7.5 Effect of Oleic Acid Addition on the Concentrations of Humic Acid and Benzoic Acid in the Reaction System

[0139] The result is as follows Figure 20 As shown in the diagram, the concentrations of benzoic acid solution in the reaction system under volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 747.2222 mg / L, 986.3991 mg / L, 1621.2767 mg / L, 1722.9816 mg / L, 2214.3810 mg / L, and 1106.7398 mg / L, respectively. Therefore, the highest humic acid concentration, 2214.3810 mg / L, is achieved when 0.45 mL of oleic acid solution is added. From the right-hand coordinate axis (red illustration), the concentrations of benzoic acid solution at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.4100 mg / L, 0.6270 mg / L, 1.1261 mg / L, 1.4488 mg / L, 1.5082 mg / L, and 0.6685 mg / L, respectively. Therefore, the highest benzoic acid concentration, 1.5082 mg / L, is achieved when 0.45 mL of oleic acid solution is added. Figure 20 It can be seen that the concentrations of humic acid and benzoic acid change in roughly the same way, with the highest concentration achieved by adding 0.45 mL of oleic acid solution.

[0140] 7.6 Effect of Soluble Starch Addition on the Concentrations of Humic Acid and Benzoic Acid in the Reaction System

[0141] The result is as follows Figure 21 As shown in the diagram, the concentrations of the humic acid solution in the reaction system under the volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 733.2876 mg / L, 921.3419 mg / L, 1002.8711 mg / L, 901.1223 mg / L, 1411.3451 mg / L, and 723.5608 mg / L, respectively. Therefore, the highest humic acid concentration, 1411.3451 mg / L, is achieved when 0.45 mL of soluble starch solution is added. From the right-hand coordinate axis (red illustration), the concentrations of benzoic acid solution at volume gradients of 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL, 0.45 mL, and 0.50 mL are 0.4449 mg / L, 0.5963 mg / L, 0.5875 mg / L, 0.5766 mg / L, 0.7886 mg / L, and 0.5881 mg / L, respectively. Therefore, the highest benzoic acid concentration, 0.7886 mg / L, is achieved when 0.45 mL of soluble starch solution is added. Figure 21 It can be seen that the trends of humic acid concentration and benzoic acid concentration are roughly the same, and the volume of soluble starch solution added at the highest concentration is 0.45 mL.

[0142] The experimental results above show that

[0143] (1) Under the conditions of a concentration of 1 g / L, a microbial community treatment reaction time of 4 days, and a water bath temperature of 52℃, the concentrations of humic acid and benzoic acid were highest when the volume of glucose solution added was 0.25 mL, which were 864.1202 mg / L and 0.5242 mg / L, respectively.

[0144] (2) Under the conditions of a concentration of 1 g / L, a microbial community treatment reaction time of 4 days, and a water bath temperature of 52℃, the concentrations of humic acid and benzoic acid were highest when the volume of corn straw powder solution added was 0.35 mL, which were 912.3633 mg / L and 0.5077 mg / L, respectively.

[0145] (3) Under the conditions of a concentration of 1 g / L, a microbial community treatment reaction time of 4 days, and a water bath temperature of 52℃, the concentrations of humic acid and benzoic acid were highest when the volume of xylose solution added was 0.50 mL, which were 919.8112 mg / L and 0.7103 mg / L, respectively.

[0146] (4) Under the conditions of 1 g / L of concentration, 4 d of microbial flora treatment reaction time, 52 DEG C of water bath temperature, and 0.35 mL of the added volume of the cellulose solution, the humic acid concentration and the benzoic acid concentration are the highest, being 946.8741 mg / L and 0.7388 mg / L respectively.

[0147] (5) Under the conditions of 1 g / L of concentration, 4 d of microbial flora treatment reaction time, 52 DEG C of water bath temperature, and 0.45 mL of the added volume of the soluble starch solution, the humic acid concentration and the benzoic acid concentration are the highest, being 1411.3451 mg / L and 0.7886 mg / L respectively.

[0148] (6) Under the conditions of 1 g / L of concentration, 4 d of microbial flora treatment reaction time, 52 DEG C of water bath temperature, and 0.45 mL of the added volume of the oleic acid solution, the humic acid concentration and the benzoic acid concentration are the highest, being 2214.3810 mg / L and 1.5082 mg / L respectively.

[0149] Based on the experimental data, it can be illustrated that the accelerator and the microbial flora provided by the scheme can effectively improve the effect of producing humic acid, benzoic acid and biomethane from lignite, thereby expanding the utilization mode of lignite co-production of aromatic compounds and biomethane. The overall method is simple, the raw materials are safe and environmentally friendly, and the dependence on energy consumption and equipment is low, which is especially suitable for large-scale industrial production.

[0150] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms described. Many modifications and variations are possible in light of the above teachings without departing from the spirit or essential characteristics of the application. The exemplary embodiments are chosen and described in order to explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A method for improving the efficiency of selective depolymerization of lignite in the production of aromatic compounds, characterized in that, Includes the following steps: S1 involves crushing and sieving lignite to obtain lignite powder; S2 involves placing lignite powder in a closed device, adding activated sludge, and adjusting the pH of the reaction system to 6.8~7.2; S3 involves placing a sealed device under constant temperature conditions and selectively degrading the reaction for a certain period of time to produce high yields of aromatic compounds and / or biomethane. In step S1, the sieve used for sieving has a mesh size of 40 or higher. In step S2, the activated sludge is anaerobic activated sludge with a total solids (TS) content of 0.15%-0.23% and a volatile solids (VS) content of 0.08%-0.11%. In step S3, the constant temperature is 50~54℃, and the reaction time is 1~6 days; Step S2 further includes adding an accelerator before adjusting the pH of the system; the accelerator includes one or more of formic acid, acetic acid, oleic acid, glucose, fructose, xylose, arabinose, galactose, maltose, sucrose, lactose, trehalose, dextrin, cellulose, corn stalk powder, soluble starch, and their aqueous solutions; the concentration of the accelerator is 0.5~1.5 g / L; The mass-volume ratio of the lignite, activated sludge, and accelerator is (1~2) g: 10 ml: (0.25~0.5) ml.

2. The method for improving the efficiency of selective depolymerization of lignite to produce aromatic compounds as described in claim 1, characterized in that, When the promoter is 0.25 mL of 1 g / L glucose solution, the amount of methane produced reaches 7.44 mL / g, the concentration of humic acid produced reaches 864.1202 mg / L, and the concentration of benzoic acid produced reaches 0.5243 mg / L. When the promoter is 0.45 mL of 1 g / L oleic acid, the concentration of humic acid produced reaches 2214.3810 mg / L and the concentration of benzoic acid produced reaches 1.5082 mg / L.

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