Purification method for preparing natural gas from biomass

Abstract

The invention belongs to the field of biological fermentation, and particularly relates to a purification method for preparing natural gas from biomass, which comprises the following steps: preparing a porous hydrophobic carrier, and preparing the carrier into porous particles by using a long-chain branched polymer; performing hydrophilic modification on the surfaces of the porous particles to obtain an amphiphilic carrier; then carrying out hydrogen storage on the amphiphilic carrier in a hydrogen atmosphere to obtain hydrogen-carrying particles; the hydrogen-carrying particles and an inoculum containing hydrogen nutritional methanogens are fermented together with biomass in a water phase system to produce natural gas, and purification is formed. The gas prepared by the method is high in methane content and low in carbon dioxide content which is equivalent to that of natural gas, and can be put into use as natural gas.

Description

Technical Field

[0001] The present invention belongs to the field of biological fermentation, and particularly relates to a method for purifying biogas produced from biomass. Background Art

[0002] In the past few decades, the development of the world has been highly dependent on fossil energy. However, fossil energy is limited, and a large amount of carbon dioxide that causes global warming and climate change is released during the combustion process. To alleviate the consumption rate of fossil energy and significantly reduce global carbon emissions at the same time, it is extremely urgent to develop renewable energy and apply it in practice during the development process. Biomass is a clean and renewable energy source with huge reserves, but most biomass exists in the form of waste including sewage, food waste, straw, and livestock manure. Anaerobic fermentation is a widely used biological process for recovering energy from biomass. It converts waste organic carbon into biogas, and biogas is an important biofuel mainly composed of methane. However, biogas not only contains methane but also carbon dioxide. Methane is the energy-rich compound in biogas, and the carbon dioxide accounting for 15-60% in the composition will significantly dilute the methane content in biogas and reduce the calorific value of biogas, limiting the utilization of biogas as a fuel and making biogas only suitable for simple cooking, etc. And when biogas is compressed, carbon dioxide is easily converted into dry ice under high pressure, so it is also difficult for biogas to achieve long-distance transportation.

[0003] Currently, methods including water washing, adsorption, and membrane separation are maturely applied to industrial biogas purification. However, these methods have high operation and equipment costs, and there are problems such as the need to use inert gases and a large amount of water, difficult preparation of adsorbents, high regeneration costs, and easy generation of environmentally harmful by-products. Microbial technology provides a method that can be carried out under environmental conditions without using expensive catalysts and chemicals to purify biogas sustainably. Compared with the original biogas, the gas purified by biotechnology has a higher methane concentration and can reach the natural gas concentration standard, and can be directly injected into the existing natural gas network as natural gas. The purification of biogas by microbial technology is based on the method of hydrogenotrophic methanogens using hydrogen and carbon dioxide to produce methane to reduce carbon dioxide and increase methane. However, this method requires hydrogen, and compared with carbon dioxide and methane, hydrogen has a very low solubility in water, which will affect its mass transfer behavior in the system. The methods to alleviate the gas-liquid mass transfer of hydrogen mainly include stirring, adding fillers to make the bubble size smaller, gas circulation, and increasing the pressure of the reactor. These methods will have problems such as having an adverse impact on the microbial community structure, high requirements for equipment, high resources and energy consumption, etc. The defect of low hydrogen solubility severely restricts the development of the technology for converting biogas into natural gas. Summary of the Invention

[0004] The present invention mainly provides a method for hydrogen storage using a carrier with a high affinity for hydrogen and strong adsorption capacity, and then continuously releasing and supplying it for the fermentation and purification of biomass to produce natural gas. The technical solution is as follows:

[0005] A purification method for producing natural gas from biomass, which prepares a porous hydrophobic carrier, and uses a long-chain and branched polymer to make the carrier into porous particles; hydrophilic modification is carried out on the surface of the porous particles to obtain an amphiphilic carrier; then the amphiphilic carrier is hydrogen-stored in a hydrogen atmosphere to obtain hydrogen-carrying particles; an inoculum containing hydrogenotrophic methanogens ferments with biomass in an aqueous phase system, and after the microorganisms adapt, hydrogen-carrying particles are added to the system for continuous fermentation.

[0006] Further, the mass ratio of the hydrogen-carrying particles to the inoculum is 0.5-5:1; the mass ratio of the inoculum to the biomass is 1:2-4; the thickness of the porous particles is 0.5-5 cm.

[0007] Further, the inoculum contains 0.2-1 g / L of nitrogen, 0.8-3.5 g / L of phosphorus, and 3-6 mg / L of magnesium.

[0008] Further, it includes the following steps: After crushing the straw, it is mixed with an inoculum containing hydrogenotrophic methanogens, hydrogen-carrying particles are added, and water is added to make the solid content of the system reach 5-25%, and anaerobic digestion is carried out at 35-38 °C for 6-24 days.

[0009] Further, the preparation method of the amphiphilic carrier includes the following steps:

[0010] a. Dissolve sodium aluminate in water, then add cetyltrimethylammonium bromide and mix well, continue to add sodium hydroxide and silica gel, and mix evenly to obtain a mixed solution; crystallize the mixed solution at 140-160 °C for 24-42 h, and after washing the obtained crystals thoroughly, perform heat treatment at 100-150 °C for 6-12 h to obtain a hydrophobic carrier;

[0011] b. Mix methyl methacrylate polymer, dichloromethane, carbon tetrachloride and ethanol well, and after mixing evenly, pour it into a mold, let it stand at 40-55 °C for 0.5-1 h, then evacuate and continue to stand for 3-6 h, and take it out to obtain porous particles;

[0012] c. Prepare an acrylic acid solution, add benzophenone and mix, use the acrylic acid solution to infiltrate the outer surface of the porous particles, exclude the oxygen in the system, and carry out a UV light reaction for 5-15 min under closed conditions, and take it out and wash and dry it thoroughly.

[0013] Further, the silica-alumina ratio in step a is 300-500; the molar ratio of silica gel to sodium hydroxide is 5-18:1; the molar ratio of silica gel to cetyltrimethylammonium bromide is 2-3.5:1.

[0014] Furthermore, in step b, the mass ratio of the sum of the mass of dichloromethane and carbon tetrachloride to methyl methacrylate is 8-3:1; the mass ratio of methyl methacrylate to ethanol is 1:0.8-1.5; and the mass ratio of dichloromethane to carbon tetrachloride is 2-3:1.

[0015] Furthermore, the preparation of methyl methacrylate comprises the following steps: fully mixing methyl methacrylate and a hydrophobic carrier, adding azobisisobutyronitrile, mixing evenly, and then polymerizing at 60-75° C. for 2-4 hours.

[0016] Furthermore, the mass ratio of the methyl methacrylate to the hydrophobic carrier is 0.5-5:1; and the azobisisobutyronitrile accounts for 1-3% of the mass of the methyl methacrylate.

[0017] Furthermore, the porous particles are soaked in ethanol, then rinsed with ethanol or water, and placed on an acrylic acid solution after drying; the benzophenone in step c accounts for 2-4% of the mass of the acrylic acid.

[0018] By adopting the above scheme, the method of the present invention has the following advantages:

[0019] 1. After the hydrogen-carrying particles of the present invention are placed in the fermentation liquid in the aqueous phase, the pores of the carrier and the polymer have a high affinity for hydrogen, which attracts hydrogen, while the hydrophilic groups on the surface of the particles and the water in the external fermentation liquid that has a poor affinity for hydrogen will have a certain inhibitory effect on the overflow of hydrogen, thereby extending the release period of hydrogen to solve the problem that hydrogen is easily and quickly released into the upper gas phase.

[0020] 2. The hydrogen-carrying particles of the present invention are filled with pores and gas, and can float on the liquid surface under natural conditions. The gas generated by fermentation rises to the liquid surface and combines with the hydrogen at the liquid surface, which has high mass transfer efficiency and helps the fermentation bacteria to convert the high-concentration carbon dioxide gas at the liquid surface, thereby improving the conversion efficiency. It also prevents the hydrogen-carrying particles from falling into the deep of the fermentation liquid and being squeezed out of the carrier under the action of the pressure difference, thereby achieving effective storage and utilization of hydrogen.

[0021] 3. The surface of the amphiphilic carrier of the present invention is hydrophilic, which is conducive to the interface bonding between the aqueous phase system containing hydrogenotrophic methanogens and the carrier, thereby achieving effective utilization of hydrogen.

[0022] 4. The present invention uses hexadecyltrimethylammonium bromide as a template. After the carrier crystals are formed, the system is fully dried and heat-treated to promote the close connection between the hexadecyltrimethylammonium bromide in the carrier pores and the inner wall to reduce its escape.

[0023] 5. The carrier of the present invention adsorbs hydrogen in the pores through van der Waals forces, and after the carrier is formed, it is not subjected to conventional calcination. By utilizing the characteristics of cetyltrimethylammonium bromide having a long chain and the high affinity of hydrogen with long-chain alkanes, the adsorption of hydrogen in the carrier pores is improved.

[0024] 6. The present invention uses polymethyl methacrylate with a high degree of branching on the main chain to connect and fix the carrier. On the one hand, it can increase the volume without affecting the adsorption properties of the carrier, making it easier to separate and recover in practical applications. On the other hand, the main chain with a high degree of branching has a higher affinity for hydrogen, and the pores formed by the polymer itself can also form adsorption for hydrogen.

[0025] 7. The present invention fills the amphiphilic carrier with hydrogen, and the hydrogen is uniformly released in the carrier, solving the problems of waste of hydrogen resources caused by pressurization and cyclic intake of gas, as well as the excessively high equipment and preparation costs. It also solves the problem that stirring to improve mass transfer efficiency is likely to affect the microbial community structure. Description of the Drawings

[0026] Figure 1 : Comparative chart of the average carbon dioxide concentration of the gas produced in each example and comparative example;

[0027] Figure 2 : Comparative chart of the average methane concentration of the gas produced in each example and comparative example. Detailed Embodiments

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1: (1) Dissolve 1 mmol of sodium aluminate in water, then add 0.12 mol of cetyltrimethylammonium bromide and mix well. Continue to add 30 mmol of sodium hydroxide and 0.3 mol of silica gel, and mix evenly to obtain a mixed solution; crystallize the mixed solution at 150 °C for 36 h. After washing the obtained crystals thoroughly, heat-treat them at 120 °C for 8 h to obtain a hydrophobic carrier;

[0030] (2) Mix 10 g of methyl methacrylate and 25 g of the hydrophobic carrier thoroughly, add 0.2 g of azobisisobutyronitrile, mix evenly, and then carry out a polymerization reaction at 65 °C for 3 h; mix the methyl methacrylate polymer, 45 mL of dichloromethane, 20 mL of carbon tetrachloride, and 12 mL of ethanol thoroughly. After mixing evenly, pour the mixed liquid with a thickness of 2 - 3 cm into a mold with a pore size of 5×5 cm, place it in a vacuum box, let it stand at 40 °C for 1 h, and then evacuate and continue to stand for 6 h to obtain porous particles;

[0031] (3) Prepare an acrylic acid solution, add benzophenone accounting for 3% of the mass of acrylic acid and mix. Soak the porous particles with ethanol, then rinse with ethanol or water, dry, and displace the gas adsorbed in the porous particles by passing nitrogen. Put the porous particles back into the mold, pour the acrylic acid solution onto the porous particles in the mold to make the porous particles float and wet the outer surface. After removing the oxygen in the system, carry out a UV light reaction for 10 min under closed conditions, take out and wash thoroughly and dry to obtain an amphiphilic carrier;

[0032] (4) Then pressurize the amphiphilic carrier for hydrogen storage in a hydrogen atmosphere to fill the amphiphilic carrier with hydrogen to obtain hydrogen-carrying particles; Prepare fresh cow dung containing 0.5 - 1 g / L of nitrogen, 2 - 3 g / L of phosphorus, 4 - 5 mg / L of magnesium, and rich in hydrogenotrophic methanogens as an inoculum. Mix the inoculum and crushed straw in a mass ratio of 1:3, add water to make the solid content of the system reach 10%, carry out anaerobic digestion at 7 °C for 6 days, put hydrogen-carrying particles 3 times the mass of the inoculum on the surface of the mixture, and continue fermentation for 12 days.

[0033] Example 2: The difference from Example 1 is that:

[0034] (1) Dissolve 1 mmol of sodium aluminate in water, then add 0.15 mol of cetyltrimethylammonium bromide and mix thoroughly. Continue to add 30 mmol of sodium hydroxide and 0.3 mol of silica gel, mix evenly to obtain a mixed solution; crystallize the mixed solution at 150 °C for 36 h, wash the obtained crystals thoroughly, and then carry out heat treatment at 120 °C for 8 h to obtain a hydrophobic carrier.

[0035] Example 3: The difference from Example 1 is that:

[0036] (1) Dissolve 1 mmol of sodium aluminate in water, then add 0.085 mol of cetyltrimethylammonium bromide and mix thoroughly. Continue to add 30 mmol of sodium hydroxide and 0.3 mol of silica gel, mix evenly to obtain a mixed solution; crystallize the mixed solution at 150 °C for 36 h, wash the obtained crystals thoroughly, and then carry out heat treatment at 120 °C for 8 h to obtain a hydrophobic carrier.

[0037] Example 4: The difference from Example 1 is that:

[0038] (2) 10 g of methyl methacrylate and 5 g of a hydrophobic carrier were fully mixed, 0.2 g of azobisisobutyronitrile was added, the mixture was mixed evenly, and then a polymerization reaction was carried out at 65° C. for 3 h; methyl methacrylate polymer, 45 mL of dichloromethane, 20 mL of carbon tetrachloride and 12 mL of ethanol were fully mixed, and after mixing evenly, the mixed liquid was poured into a mold with a pore size of 5×5 cm to a thickness of 2 to 3 cm, placed in a vacuum box, and allowed to stand at 40° C. for 1 h, and then vacuumed and allowed to stand for another 6 h to obtain porous particles.

[0039] Embodiment 5: The difference from Embodiment 1 is that:

[0040] (2) 10 g of methyl methacrylate and 50 g of a hydrophobic carrier were fully mixed, 0.2 g of azobisisobutyronitrile was added, the mixture was mixed evenly, and then a polymerization reaction was carried out at 65° C. for 3 h; methyl methacrylate polymer, 45 mL of dichloromethane, 20 mL of carbon tetrachloride and 12 mL of ethanol were fully mixed, and after mixing evenly, the mixed liquid was poured into a mold with a pore size of 5×5 cm to a thickness of 2 to 3 cm, placed in a vacuum box, and allowed to stand at 40° C. for 1 h, and then vacuumed and allowed to stand for another 6 h to obtain porous particles.

[0041] Embodiment 6: The difference from Embodiment 1 is that:

[0042] (2) 10 g of methyl methacrylate and 25 g of a hydrophobic carrier were fully mixed, 0.2 g of azobisisobutyronitrile was added, the mixture was mixed evenly, and then a polymerization reaction was carried out at 65° C. for 3 h; methyl methacrylate polymer, 60 mL of dichloromethane, 20 mL of carbon tetrachloride and 12 mL of ethanol were fully mixed, and after mixing evenly, the mixed liquid was poured into a mold with a pore size of 5×5 cm to a thickness of 2 to 3 cm, placed in a vacuum box, and allowed to stand at 40° C. for 1 h, and then vacuumed and allowed to stand for another 6 h to obtain porous particles.

[0043] Embodiment 7: The difference from Embodiment 1 is that:

[0044] (2) 10 g of methyl methacrylate and 25 g of a hydrophobic carrier were fully mixed, 0.2 g of azobisisobutyronitrile was added, the mixture was mixed evenly, and then a polymerization reaction was carried out at 65° C. for 3 h; methyl methacrylate polymer, 20 mL of dichloromethane, 10 mL of carbon tetrachloride and 12 mL of ethanol were fully mixed, and after mixing evenly, the mixed liquid was poured into a mold with a pore size of 5×5 cm to a thickness of 2 to 3 cm, placed in a vacuum box, and allowed to stand at 40° C. for 1 h, and then vacuumed and allowed to stand for another 6 h to obtain porous particles.

[0045] Embodiment 8: The difference from Embodiment 1 is that:

[0046] (4) Then, the amphiphilic carrier is pressurized in a hydrogen atmosphere for hydrogen storage, so that the amphiphilic carrier is filled with hydrogen to obtain hydrogen-loaded particles; Fresh cow dung containing 0.5 - 1 g / L of nitrogen, 2 - 3 g / L of phosphorus, 4 - 5 mg / L of magnesium, and rich in hydrogenotrophic methanogens is prepared as an inoculum. The inoculum and crushed straw are mixed at a mass ratio of 1:3, and water is added to make the solid content of the system reach 10%. After anaerobic digestion at 7°C for 6 days, hydrogen-loaded particles 5 times the mass of the inoculum are added to the surface of the mixture, and fermentation continues for 12 days.

[0047] Example 9: The difference from Example 1 is that:

[0048] (4) Then, the amphiphilic carrier is pressurized in a hydrogen atmosphere for hydrogen storage, so that the amphiphilic carrier is filled with hydrogen to obtain hydrogen-loaded particles; Fresh cow dung containing 0.5 - 1 g / L of nitrogen, 2 - 3 g / L of phosphorus, 4 - 5 mg / L of magnesium, and rich in hydrogenotrophic methanogens is prepared as an inoculum. The inoculum and crushed straw are mixed at a mass ratio of 1:3, and water is added to make the solid content of the system reach 10%. After anaerobic digestion at 7°C for 6 days, hydrogen-loaded particles 0.5 times the mass of the inoculum are added to the surface of the mixture, and fermentation continues for 12 days.

[0049] Comparative Example 1: The difference from Example 1 is that:

[0050] (1) Dissolve 1 mmol of sodium aluminate in water, then add 0.12 mol of cetyltrimethylammonium bromide and mix well. Continue to add 30 mmol of sodium hydroxide and 0.3 mol of silica gel, and mix evenly to obtain a mixed solution; The mixed solution is crystallized at 150°C for 36 h. After the obtained crystals are washed thoroughly, they are calcined at 550°C for 3 h to obtain a hydrophobic carrier.

[0051] Comparative Example 2: The difference from Example 1 is that:

[0052] Acrylic acid is not used for hydrophilic modification.

[0053] Testing of example samples:

[0054] The gas production volume per day from the 12th day to the 18th day of the total fermentation process is measured by the water displacement gas collection method. Carbon dioxide and methane in the gas are determined by gas chromatography, and the contents of carbon dioxide and methane are calculated in combination with the gas production volume, and the average value from the 12th day to the 18th day is calculated. The results are as follows:

[0055]

[0056] As can be seen from the above table, the content of carbon dioxide in each embodiment is significantly lower than the comparative example, and the content of methane is significantly higher than the comparative example, and the methane content of most embodiments is greater than 90%, indicating that the use of hydrogen-carrying particles of the present invention has a significant promoting effect on the conversion of carbon dioxide into methane. Compared with Example 1, the average carbon dioxide content of Example 2 and Example 3 adding more and less hexadecyltrimethylammonium bromide increases, and the average content of methane also decreases, indicating that more hexadecyltrimethylammonium bromide is conducive to the adsorption of hydrogen, but its content is too much and may affect the formation of carrier pores, and too large pores are also not conducive to the adsorption of hydrogen. And the carrier is calcined, the carbon dioxide content of Comparative Example 1 with hexadecyltrimethylammonium bromide removed reaches 10.4%, and the methane content is only 81.7%, indicating that the presence of hexadecyltrimethylammonium bromide has a significant impact on the load of hydrogen.

[0057] The carbon dioxide content of embodiment 4 obviously rises, and methane content decreases, while the carbon dioxide content of embodiment 5 decreases, and methane content increases, indicating that when preparing porous particles, the more carrier of polymer load is conducive to the adsorption of hydrogen, thereby promoting the conversion of carbon dioxide to methane.But the carbon dioxide content reduction degree of embodiment 5 does not match the increase degree of hydrophobic carrier, and the cost increases relatively, and the excessive hydrophobic carrier also easily affects the structural integrity of porous particles.When preparing porous particles, the dichloromethane content of embodiment 6 increases, and carbon tetrachloride decreases relatively, and the addition of dichloromethane and carbon tetrachloride of embodiment 7 decreases, but in dichloromethane and carbon tetrachloride, the ratio of carbon tetrachloride increases, but the carbon dioxide content of embodiment 6 and embodiment 7 is all increased compared with embodiment 1, indicating that the content of dichloromethane and carbon tetrachloride and polymer is maintained in the relative balanced ratio interval, which is beneficial to promoting the adsorption of hydrogen-carrying particles.

[0058] In Comparative Example 2, the porous particles were not hydrophilically modified, and the surface hydrophobicity was relatively strong. The aqueous fermentation liquid was difficult to directly contact the porous particles, which hindered the mass transfer of hydrogen and the fermentation liquid, and affected the speed at which the microorganisms directly consumed carbon dioxide and hydrogen at the liquid surface, thereby affecting the concentration difference of hydrogen generated by the liquid surface and the consumption of microorganisms, and the rate at which hydrogen continued to dissolve in the fermentation liquid. Therefore, the carbon dioxide content in Comparative Example 2 increased significantly, and the methane content dropped to below 80%.

[0059] In the actual fermentation process, compared with Example 1, the carbon dioxide content of Example 8, which added more hydrogen-carrying particles, was significantly reduced, and the methane content was significantly increased, while the opposite was true for Example 9, which added less hydrogen-carrying particles, indicating that the content of hydrogen-carrying particles is directly related to the efficiency of converting carbon dioxide to methane. The method of the present invention can significantly purify the biogas produced by biomass fermentation and realize the preparation of natural gas from biomass.

[0060] Those skilled in the art can make various corresponding changes and deformations according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A purification method for biomass-derived natural gas, characterized in that, Prepare a porous hydrophobic carrier, and use a long-chain and branched polymer to make the carrier into porous particles; perform hydrophilic modification on the surface of the porous particles to obtain an amphiphilic carrier; then store hydrogen in the amphiphilic carrier in a hydrogen atmosphere to obtain hydrogen-loaded particles; an inoculum containing hydrogenotrophic methanogens ferments with biomass in an aqueous phase system. After the microorganisms adapt, hydrogen-loaded particles are added to the system for continued fermentation.

2. The purification method of biomass-derived natural gas according to claim 1, wherein The mass ratio of the hydrogen-loaded particles to the inoculum is 0.5 - 5:1; the mass ratio of the inoculum to the biomass is 1:2 - 4; the thickness of the porous particles is 0.5 - 5 cm.

3. The purification method of biomass-derived natural gas according to claim 1, wherein The inoculum contains 0.2 - 1 g / L of nitrogen, 0.8 - 3.5 g / L of phosphorus, and 3 - 6 mg / L of magnesium.

4. The purification method of biomass-derived natural gas according to claim 1, wherein, It includes the following steps: Crush the straw and mix it with an inoculum containing hydrogenotrophic methanogens, add hydrogen-loaded particles, add water to make the solid content of the system reach 5 - 25%, and perform anaerobic digestion at 35 - 38 °C for 6 - 24 days.

5. The purification method of biomass-derived natural gas according to claim 1, characterized in that, The preparation method of the amphiphilic carrier includes the following steps: a. Dissolve sodium aluminate in water, then add cetyltrimethylammonium bromide and mix well. Continue to add sodium hydroxide and silica gel and mix evenly to obtain a mixed solution; crystallize the mixed solution at 140 - 160 °C for 24 - 42 h. After washing the obtained crystals thoroughly, perform heat treatment at 100 - 150 °C for 6 - 12 h to obtain a hydrophobic carrier; b. Mix methyl methacrylate polymer, dichloromethane, carbon tetrachloride, and ethanol well. After mixing evenly, pour it into a mold, let it stand at 40 - 55 °C for 0.5 - 1 h, then evacuate and continue to stand for 3 - 6 h, and take it out to obtain porous particles; c. Prepare an acrylic acid solution, add benzophenone and mix. Use the acrylic acid solution to infiltrate the outer surface of the porous particles. After removing the oxygen in the system, perform a UV light reaction under closed conditions for 5 - 15 min. Take it out, wash it thoroughly, and dry it.

6. The purification method of biomass-derived natural gas according to claim 5, characterized in that, The silicon-aluminum ratio in step a is 300 - 500; the molar ratio of silica gel to sodium hydroxide is 5 - 18:1; the molar ratio of silica gel to cetyltrimethylammonium bromide is 2 - 3.5:

1.

7. The purification method of biomass-derived natural gas according to claim 5, characterized in that, In step b, the mass sum of dichloromethane and carbon tetrachloride and the mass ratio of methyl methacrylate is 8 - 3:1; the mass ratio of methyl methacrylate to ethanol is 1:0.8 - 1.5; the mass ratio of dichloromethane to carbon tetrachloride is 2 - 3:

1.

8. The purification method of biomass-derived natural gas according to claim 5, characterized in that, The preparation of the methyl methacrylate includes the following steps: Mix methyl methacrylate and the hydrophobic carrier well, add azobisisobutyronitrile, mix evenly, and then perform a polymerization reaction at 60 - 75 °C for 2 - 4 h.

9. The purification method of biomass-derived natural gas according to claim 8, wherein The mass ratio of methyl methacrylate to the hydrophobic carrier is 0.5 - 5:1; azobisisobutyronitrile accounts for 1 - 3% of the mass of methyl methacrylate.

10. The purification method of biomass-derived natural gas according to claim 5, wherein Soak the porous particles in ethanol, then rinse with ethanol or water, dry and place them on the acrylic acid solution; in step c, benzophenone accounts for 2 - 4% of the mass of acrylic acid.

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