Method for preparing multi-level hole magnetic catalyst for in-situ heating of bio-natural gas

Abstract

The application discloses a preparation method of a multi-level hole magnetic catalyst for in-situ heating of biological natural gas, and relates to the technical field of hydrogen production by dry reforming of biological natural gas. The preparation method comprises the following steps: adding microcrystalline cellulose, polyether P123 and aluminum isopropoxide into deionized water, heating and stirring, adjusting the pH value until a gel solution is formed, drying after filtration, grinding into powder and calcining to obtain macroporous carrier particles; dispersing the macroporous carrier particles in a nickel acetate aqueous solution, drying and calcining the obtained slurry, crushing and sieving, and pressing to obtain the multi-level hole magnetic catalyst for in-situ heating of biological natural gas. The multi-level hole magnetic catalyst prepared by the method has the advantages of increased specific surface area, increased active site loading, reduced mass transfer resistance, renewability and biodegradability, and effectively solves the problems of easy carbon deposition, low magnetic heat efficiency and single pore structure of the catalyst used in the existing hydrogen production by dry reforming of biological natural gas.

Description

Technical Field

[0001] The present invention relates to the technical field of biogas dry reforming hydrogen production, and in particular to a method for preparing a multi-level porous magnetic catalyst for in-situ heating of biogas. Background Art

[0002] Hydrogen energy, as a key means of large-scale deep decarbonization, is an important part of accelerating the cultivation of new quality productivity. my country is in a critical period of hydrogen energy development, and national policies are frequently introduced. The "Energy Technology Revolution Innovation Action Plan (2016-2030)" positions the research and development of large-scale hydrogen production technology as a strategic direction for hydrogen energy and fuel cell technology innovation. Against this background, the technological demand for my country's hydrogen production industry is experiencing explosive growth. Biogas, as a potential source of hydrogen, has a main component of 35-75% methane and 25-55% carbon dioxide, and has lower carbon emission potential. However, traditional steam reforming hydrogen production releases a large amount of carbon dioxide, and requires a series of processing steps to increase the methane content in biogas, which in turn poses a greater challenge to my country's dual-carbon strategic goals. Therefore, finding a zero-carbon or even negative carbon emission method for hydrogen production is of urgent practical significance.

[0003] Biogas dry reforming to produce hydrogen is a green, carbon-negative hydrogen production technology that can simultaneously utilize methane and carbon dioxide, two major greenhouse gases. It can also achieve high-quality utilization of biogas without the need for a prior purification step, and has the dual advantages of environmental protection and energy utilization. However, this technology also has challenges, namely the high-temperature reaction conditions determined by the nature of thermodynamics. For traditional external heating methods, industrial porous catalysts have slow dynamic responses, and the "cold spots" in the bed cause carbon deposition and deactivation of the catalyst. Carbon accumulation on the catalyst surface not only covers the active centers, causing the intrinsic activity to decay, but also causes the pores to narrow or even clog, hindering the mass transfer process, resulting in a rapid decrease in macroscopic activity and limiting the industrialization of dry reforming technology. The development of anti-carbon deposition catalysts is key to promoting the large-scale application of biogas dry reforming to produce carbon-negative hydrogen.

[0004] Developing magnetic-catalytic bifunctional particles that tightly contact heat sources with active sites to achieve in-situ electromagnetic induction heating is an effective means to solve the above problems of uneven heating and difficult temperature control. Therefore, a ferromagnetic micron material Ni60Co40 is prepared, and its heating mechanism is mainly eddy current, which can easily reach a temperature higher than 850℃ by providing energy through an alternating magnetic field. However, the specific surface area of micron metal powder is very low, which limits the catalytic activity. The rhodium single-atom magnetic catalyst prepared by the prior art can be used for catalyzing the hydrogen formylation reaction, and has high catalytic efficiency, excellent catalytic activity and strong stability, and can be separated. However, the magnetic catalyst has a single dispersed pore structure, and has problems of large heat and mass transfer resistance, low magnetic heat response efficiency, etc., which limits the reaction performance of the bifunctional magnetic porous catalyst. In addition, the magnetic solid acid catalyst has the advantages of good magnetic performance and stable physicochemical properties, but substances such as metal sulfate and ammonia are needed in the preparation process, and the preparation method has the disadvantages of high cost, non-biodegradability and harm to the environment.

[0005] In summary, the catalyst used in the hydrogen production technology by dry reforming of biogenic natural gas mainly has the disadvantages of high-temperature carbon deposition, low magnetic heat efficiency and single pore structure: (1) The traditional catalyst is prone to carbon deposition during high-temperature dry reforming, which covers the active center and causes a sharp decrease in catalytic efficiency. For example, the rhodium single-atom magnetic catalyst, although it has high catalytic efficiency, still faces the problems of carbon deposition and active center blockage after long-term use. (2) Low magnetic heat efficiency: in the prior art, for example, the magnetic solid acid catalyst has good physicochemical properties, but its magnetic heat response performance is insufficient, which cannot achieve efficient in-situ electromagnetic induction heating, resulting in difficulty in accurately controlling the reaction temperature and further limiting the universality of its industrial application. (3) Single pore structure: most existing catalysts, such as the ferromagnetic micron material Ni60Co40, can reach the required high temperature through the eddy current heating mechanism, but their low specific surface area limits the catalytic activity. The above technologies focus on the active site angle, while the design of the catalyst pore structure is the key to developing high-reactivity and anti-carbon catalysts. Therefore, it is urgent to design a multi-level pore magnetic anti-carbon catalyst with high specific surface area, high loading of active sites, small pore mass transfer resistance and no harm to the environment. SUMMARY

[0006] To solve the above technical problems, the present application provides a preparation method of a multi-level pore magnetic catalyst for in-situ heating of biogenic natural gas, which increases the specific surface area of the multi-level pore magnetic catalyst, increases the loading of active sites, reduces the mass transfer resistance, has renewability and biodegradability, and effectively solves the problems of easy carbon deposition, low magnetic heat efficiency and single pore structure of the catalyst used in the existing hydrogen production technology by dry reforming of biogenic natural gas.

[0007] To achieve the above object, the present invention solves the technical problem by adopting a technical solution: providing a method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas, comprising the following steps:

[0008] S1. Add microcrystalline cellulose, polyether P123, and aluminum isopropoxide to deionized water, heat and stir, and then adjust the pH value to promote hydrolysis until a gel solution is obtained;

[0009] S2, filtering and separating the gel solution obtained in step S1, grinding it into powder after drying, and then calcining it to obtain macroporous carrier particles;

[0010] S3, dissolving nickel acetate tetrahydrate and ferric chloride in deionized water to obtain a nickel acetate aqueous solution;

[0011] S4. Dispersing the macroporous carrier particles obtained in step S2 in the nickel acetate aqueous solution obtained in step S3, stirring at a constant temperature, drying, roasting, crushing, sieving, and pressing to obtain a multi-level porous magnetic catalyst for in-situ heating of biogas.

[0012] Furthermore, in step S1, the mass volume ratio of microcrystalline cellulose, polyether P123, aluminum isopropoxide and deionized water is 1.5-2.5 g:0.4-0.6 g:20-21 g:240-260 mL.

[0013] Furthermore, the mass volume ratio of microcrystalline cellulose, polyether P123, aluminum isopropoxide and deionized water is 2g:0.5g:20.42g:250mL.

[0014] Furthermore, the particle size of the microcrystalline cellulose is 20-30 μm.

[0015] Further, heat to 75-85°C and stir for 11-13 hours.

[0016] Further, the pH is adjusted to 4.5-5.5 using dilute nitric acid with a concentration of 5-15 vt%.

[0017] Furthermore, the pH was adjusted to 5 using 10vt% dilute nitric acid.

[0018] Furthermore, in step S2, the mixture is dried at 95-105° C. for 11-13 hours, and then calcined at 500-600° C. for 7-9 hours.

[0019] Furthermore, the obtained product was dried at 100°C for 12 h and then calcined at 550°C for 8 h.

[0020] Furthermore, in step S3, the mass of nickel acetate tetrahydrate and ferric chloride is 5-15% of the loading amount.

[0021] Furthermore, the mass of nickel acetate tetrahydrate and ferric chloride is 10% of the loading amount.

[0022] Furthermore, the molar ratio of nickel acetate tetrahydrate to ferric chloride is 0.5-1.5:1-3.

[0023] Furthermore, the molar ratio of nickel acetate tetrahydrate to ferric chloride is 1:2.

[0024] Furthermore, in step S4, the nickel acetate tetrahydrate is continuously heated at a constant temperature of 45-55° C. until the nickel acetate tetrahydrate is evenly distributed on the carrier, and then dried at 100-120° C. for 14-16 hours and calcined at 600-700° C. for 2-4 hours.

[0025] Furthermore, the reaction was continued at a constant temperature of 50° C. until nickel acetate was evenly distributed on the support, and then dried at 110° C. for 15 h and calcined at 650° C. for 3 h.

[0026] Further, the product is crushed into particles of 0.2-0.45 mm and pressed under a pressure of 5-7 MPa to form a cylinder with a diameter of 5-7 mm and a height of 2-4 mm.

[0027] Further, the mixture was crushed into particles of 0.2-0.45 mm and pressed under a pressure of 6 MPa into a cylinder with a diameter of 6 mm and a height of 3 mm.

[0028] The present invention has the following beneficial effects:

[0029] 1. The multi-level porous magnetic catalyst for in-situ heating of biogas prepared by the present invention significantly improves the specific surface area and the number of active sites of the catalyst through its unique pore structure design. Specifically, the macroporous structure promotes the rapid diffusion of macromolecular reactants, reduces the diffusion path, and reduces the pore mass transfer resistance. At the same time, the mesoporous structure provides sufficient surface area, enhancing the adsorption and conversion efficiency of reactants at the active sites. In addition, the multi-level porous structure also optimizes the magnetothermal response performance. The selection and distribution of magnetic materials are designed to respond quickly and evenly distribute heat energy under the action of a magnetic field, which is particularly critical for controlling chemical reactions at high temperatures. This design of the catalyst ensures the efficient transfer and utilization of heat energy throughout the reaction process, maximizes the reaction rate and selectivity, and reduces energy consumption and environmental impact. Compared with traditional monodispersed magnetic catalysts, the synergistic effect of the multi-level porous structure can promote the methane conversion rate to increase by more than 5% and reduce the carbon deposition deactivation rate by more than 10%.

[0030] 2、The present application uses microcrystalline cellulose as a reaming agent to prepare a mesoporous-macroporous bimodal dispersion carrier. Microcrystalline cellulose has a high specific surface area, can provide more active sites, and increase the activity of the catalyst; its microporous structure can be regulated, thereby affecting the pore structure and distribution of the catalyst; it is a naturally derived material, is renewable and biodegradable, and meets environmental protection requirements; microcrystalline cellulose can enhance the mechanical strength and thermal stability of the catalyst, and prolong the service life of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A catalyst sample is pressed into a physical model;

[0032] Figure 2 A comparison chart of methane conversion rate and hydrogen production;

[0033] Figure 3 A comparison chart of gas component volume content;

[0034] Figure 4 A result chart of the pore size distribution of the multi-level pore magnetic catalyst particles;

[0035] Figure 5 A result chart of the influence of the macropore fraction on the hydrogen production rate and the carbon deposition rate. DETAILED DESCRIPTION

[0036] The principles and characteristics of the present application are described below, and the examples are used only to explain the present application and are not intended to limit the scope of the present application. If no specific conditions are specified in the examples, conventional conditions or manufacturer-recommended conditions are used. If no manufacturer of the reagents or instruments used is specified, it is a conventional product that can be purchased on the market.

[0037] Example 1

[0038] A preparation method of a multi-level pore magnetic catalyst for in-situ heating of biogenic natural gas, comprising the following steps:

[0039] S1, 2g of microcrystalline cellulose with a particle size of 25um, 0.5g of polyether P123 and 20.42g (1mol) of aluminum isopropoxide are added to 250mL of deionized water, heated to 80℃ and continuously stirred for 12h to obtain a white emulsion, 5mL of dilute nitric acid with a concentration of 10vt% is added to the white emulsion to adjust the pH to 5 to promote hydrolysis, until a white gel solution is obtained;

[0040] S2, the gel solution obtained in step S1 is filtered and separated, dried at 100℃ for 12h, then ground into powder, and then calcined at 550℃ in a muffle furnace for 8h to obtain macroporous carrier particles;

[0041] S3. Dissolve 2 g of nickel acetate tetrahydrate and 2.6 g of ferric chloride in 40 mL of deionized water to obtain a nickel acetate aqueous solution;

[0042] S4, dispersing the macroporous carrier particles obtained in step S2 in the nickel acetate aqueous solution obtained in step S3, and continuously stirring at a constant temperature of 50°C until the nickel acetate is evenly distributed in the macroporous carrier particles, drying the slurry with the macroporous carrier particles in an air atmosphere of 110°C for 15 hours and calcining it in a muffle furnace at a temperature of 650°C for 3 hours, crushing the calcined sample and screening it to obtain particles with a particle size of 0.2-0.45 mm, and then pressing it under a pressure of 6 MPa into a cylinder with a diameter of 6 mm and a height of 3 mm to obtain a multi-level porous magnetic catalyst for in-situ heating of biogas, such as Figure 1 shown.

[0043] Example 2

[0044] A method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas comprises the following steps:

[0045] S1. Add 1.5 g of 20 μm microcrystalline cellulose, 0.4 g of polyether P123, and 20 g of aluminum isopropoxide to 240 mL of deionized water, heat to 75° C., and stir continuously for 11 h to obtain a white emulsion. Add 12 mL of 5% by volume dilute nitric acid to the white emulsion to adjust the pH to 4.5 to promote hydrolysis, until a white gel solution is obtained.

[0046] S2, filtering and separating the gel solution obtained in step S1, drying at 95° C. for 11 h, grinding the solution into powder, and then calcining the powder in a muffle furnace at 500° C. for 7 h to obtain macroporous carrier particles;

[0047] S3. Dissolve 4 g of nickel acetate tetrahydrate and 5.2 g of ferric chloride in 40 mL of deionized water to obtain a nickel acetate aqueous solution;

[0048] S4. Disperse the macroporous carrier particles obtained in step S2 in the nickel acetate aqueous solution obtained in step S3, and continuously stir at a constant temperature of 45°C until the nickel acetate is evenly distributed in the macroporous carrier particles. Dry the slurry with the macroporous carrier particles in an air atmosphere of 100°C for 14 hours and calcine in a muffle furnace at a temperature of 600°C for 2 hours. The calcined sample is crushed and sieved to obtain particles with a particle size of 0.2-0.45 mm, and then pressed into a cylinder with a diameter of 5 mm and a height of 2 mm under a pressure of 5 MPa to obtain a multi-level porous magnetic catalyst for in-situ heating of biogas.

[0049] Example 3

[0050] A method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas comprises the following steps:

[0051] S1. Add 2.5 g of 30 μm microcrystalline cellulose, 0.6 g of polyether P123, and 21 g of aluminum isopropoxide to 260 mL of deionized water, heat to 85° C., and stir continuously for 13 h to obtain a white emulsion. Add 3 mL of 15% by volume dilute nitric acid to the white emulsion to adjust the pH to 5.5 to promote hydrolysis, until a white gel solution is obtained.

[0052] S2, filtering and separating the gel solution obtained in step S1, drying at 105° C. for 13 h, grinding the resulting solution into powder, and then calcining the resulting solution in a muffle furnace at 600° C. for 9 h to obtain macroporous carrier particles;

[0053] S3. Dissolve 2 g of nickel acetate tetrahydrate and 1.3 g of ferric chloride in 40 mL of deionized water to obtain a nickel acetate aqueous solution;

[0054] S4. Disperse the macroporous carrier particles obtained in step S2 in the nickel acetate aqueous solution obtained in step S3, and continuously stir at a constant temperature of 55°C until the nickel acetate is evenly distributed in the macroporous carrier particles. Dry the slurry with the macroporous carrier particles in an air atmosphere of 120°C for 16 hours and calcine in a muffle furnace at a temperature of 700°C for 2-4 hours. The calcined sample is crushed and sieved to obtain particles with a particle size of 0.2-0.45 mm, and then pressed into a cylinder with a diameter of 7 mm and a height of 4 mm under a pressure of 7 MPa to obtain a multi-level porous magnetic catalyst for in-situ heating of biogas.

[0055] Comparative Example

[0056] A method for preparing a monodisperse porous magnetic catalyst comprises the following steps:

[0057] S1. Add 0.5 g of polyether P123 and 20.42 g (1 mol) of aluminum isopropoxide to 250 mL of deionized water, heat to 80° C., and stir continuously for 12 h to obtain a white emulsion. Add 5 mL of 10% by volume dilute nitric acid to the white emulsion to adjust the pH to 5 to promote hydrolysis, until a white gel solution is obtained.

[0058] S2, filtering and separating the gel solution obtained in step S1, drying at 100° C. for 12 h, grinding the solution into powder, and then calcining the powder in a muffle furnace at 550° C. for 8 h to obtain macroporous carrier particles;

[0059] S3. Dissolve 2 g of nickel acetate tetrahydrate and 2.6 g of ferric chloride in 40 mL of deionized water to obtain a nickel acetate aqueous solution;

[0060] S4. Disperse the macroporous carrier particles obtained in step S2 in the nickel acetate aqueous solution obtained in step S3, and continuously stir at a constant temperature of 50°C until the nickel acetate is evenly distributed in the macroporous carrier particles. Dry the slurry with the macroporous carrier particles in an air atmosphere of 110°C for 15 hours and calcine in a muffle furnace at a temperature of 650°C for 3 hours. The calcined sample is crushed and sieved to obtain particles with a particle size of 0.2-0.45 mm, and then pressed into a cylinder with a diameter of 6 mm and a height of 3 mm under a pressure of 6 MPa to obtain a monodisperse porous magnetic catalyst.

[0061] Test Example 1

[0062] The catalytic performance of the multi-level porous magnetic catalyst for in-situ heating of biogas prepared in Example 1 and the monodisperse porous magnetic catalyst prepared in the comparative example were tested. Specifically, a methane dry reforming reaction experiment was conducted. The reaction was operated at 973K and atmospheric pressure, with the inlet flow rates of 34mL / min methane and 34mL / min carbon dioxide, respectively. The outlet gas was characterized using an LC-200M gas phase mass spectrometer. The characterization results of the reactor outlet gas components are shown in Figure 2. Figure 2-3 As shown, Figure 2 The comparison chart of methane conversion rate and hydrogen production is shown in Figure 2. Figure 3 This is a comparison chart of the volume content of gas components.

[0063] Depend on Figure 2-3 It can be seen that the multi-level porous magnetic catalyst increases the methane conversion rate by 680% and the hydrogen yield by 150%.

[0064] Test Example 2

[0065] The catalytic performance of the multi-level porous magnetic catalyst for in-situ heating of biogas prepared in Example 1 was tested. Specifically, the pore volume distribution of the catalyst was measured using a mercury intrusion porosimeter according to the ASTM D4284-2012 standard test method. The results of the mercury intrusion porosimetry characterization of the multi-level porous magnetic catalyst are as follows: Figure 4 shown.

[0066] Depend on Figure 4 As can be seen, a large number of mesopores smaller than 10 nm are present, generated by the P123 small-pore pore former. Additionally, a certain amount of pores on the order of 10 μm are present, generated by the microcrystalline cellulose macroporous pore former. Finally, a small number of ultra-large pores larger than 100 μm are formed during the tableting process. As the amount of cellulose added increases, the cumulative pore volume, and therefore the porosity, increases.

[0067] Test Example 3

[0068] The multi-level porous magnetic catalyst for in-situ heating of biogas prepared in Example 1 was subjected to numerical simulations of chemical reaction and flow mass transfer coupling with the inlet flow of 750 mL / min methane and 2250 mL / min carbon dioxide using finite element CFD numerical simulation software. The effect of the macropore ratio on catalytic activity was theoretically evaluated. Figure 5 shown.

[0069] Depend on Figure 5 It can be seen that when the macropore fraction is 0.6, the hydrogen yield increases by 40% compared to pure mesopores (macropore fraction of 0, pores of 10nm), and by 99% compared to pure macropores (macropore fraction of 1, pores of 100nm). As the macropore fraction increases, the carbon deposit yield decreases.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas, characterized in that: The following steps are involved: S1. Add microcrystalline cellulose, polyether P123, and aluminum isopropoxide to deionized water, heat and stir, and then adjust the pH value to promote hydrolysis until a gel solution is obtained; S2, filtering and separating the gel solution obtained in step S1, grinding it into powder after drying, and then calcining it to obtain macroporous carrier particles; S3, dissolving nickel acetate tetrahydrate and ferric chloride in deionized water to obtain a product; S4. Dispersing the macroporous carrier particles obtained in step S2 in the product obtained in step S3, stirring at a constant temperature, drying, roasting, crushing, sieving, and pressing to obtain a multi-level porous magnetic catalyst for in-situ heating of biogas.

2. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S1, the mass volume ratio of the microcrystalline cellulose, polyether P123, aluminum isopropoxide and deionized water is 1.5-2.5 g:0.4-0.6 g:20-21 g:240-260 mL.

3. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1 or 2, characterized in that: The particle size of the microcrystalline cellulose is 20-30 μm.

4. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S1, heat to 75-85°C and stir for 11-13 hours.

5. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S2, the mixture is dried at 95-105° C. for 11-13 hours and then calcined at 500-600° C. for 7-9 hours.

6. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S3, the molar ratio of nickel acetate tetrahydrate to ferric chloride is 0.5-1.5:1-3.

7. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S4, the mixture is dried at 100-120° C. for 14-16 hours and calcined at 600-700° C. for 2-4 hours.

8. The method for preparing a hierarchically porous magnetic catalyst for in-situ heating of biogas according to claim 1, wherein: In step S4, the powder is crushed into particles of 0.2-0.45 mm and pressed under a pressure of 5-7 MPa into cylinders with a diameter of 5-7 mm and a height of 2-4 mm.

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