A cobalt-based catalyst, its preparation and use in the co2 methanation reaction

Abstract

The present application belongs to the field of catalytic reaction, and relates to preparation of a high-loading Co-XC catalyst and application of the catalyst in CO2 methanation reaction. The catalyst loaded with carbon material is prepared by a calcination method, the loading of metal Co is 20-40wt% (calculated by metal), and the catalyst has good CO2 methanation activity. The present application utilizes the anchoring effect of elements such as N, B and P in the carrier on the metal active site, so that the metal Co is more uniformly dispersed, the metal loading can be greatly increased, and the catalyst has good thermal stability. Since the Co nanoparticles have higher dispersion and higher loading, the catalyst has excellent catalytic activity in the CO2 methanation reaction, and the generation of by-product CO is avoided. The present application develops a preparation method of a carbon material high-loading Co-based catalyst, and the catalyst is applied in the CO2 methanation reaction, so that the catalytic activity is greatly improved, and the catalyst has good CH4 selectivity.

Description

Technical Field

[0001] This invention belongs to the field of catalytic reactions and relates to the preparation of a high-loading Co-XC catalyst and its application in the CO2 methanation reaction. Technical Background

[0002] Since the Industrial Revolution, the accumulation of carbon dioxide (CO2) in the atmosphere has reached a critical level, exacerbating a series of problems such as global climate change, ocean acidification, and desertification. As a major greenhouse gas, CO2 is also an economical and abundant carbon source. CO2 methanation, also known as the Sabatier reaction, is an important process for the hydrogenation of CO2, possessing high academic research value and commercial prospects. In the industrial process of ammonia synthesis, CO2 methanation can remove trace amounts of CO from the gas, preventing catalyst poisoning. In space, CO2 methanation can convert CO2 produced by respiration into CH4 for fuel, and the generated H2O can be electrolyzed to produce O2, constructing a life support cycle system. Achieving high selectivity and high conversion rates in CO2 methanation has become a research hotspot.

[0003] Co coordination with N, P, B, etc. improves the dispersion and loading of Co in the catalyst. The calcined catalyst has self-reduction properties, and metallic Co exists stably on the catalyst. Due to the good H2 activation ability of metallic Co, the catalyst has good CH4 selectivity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a high-load Co-XC catalyst. The catalyst prepared by this invention has good methane selectivity under the reaction conditions of CO2 methanation (200-700℃, 0.1-5.0MPa).

[0005] To achieve the above objectives, the present invention adopts the following solution:

[0006] This invention provides a method for preparing a cobalt-based catalyst, the method comprising the following steps:

[0007] (1) The metal precursor, coordination precursor, solvent and inorganic carbon support are thoroughly mixed by stirring and / or ultrasound, and then dried under vacuum after standing (1-12h, preferably 2-6h) to prepare a supported catalyst precursor; (2) The catalyst precursor prepared above is calcined in a specific atmosphere to obtain a high-load Co-XC catalyst.

[0008] Based on the above technical solution, in step (1), the metal precursor is one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt formate, and cobalt acetate (preferably one or more of cobalt chloride, cobalt sulfate, and cobalt acetate); the coordination precursor is one or more of melamine, triethylamine, ethylenediamine, boron trichloride, boron carbide, boron phosphate, boron powder, triphenylphosphine, phenylphosphonic acid, and phenyldichlorophosphine (preferably one or more of melamine, boron carbide, boron phosphate, and phenyldichlorophosphine); the solvent is one or more of tetrahydrofuran, petroleum ether, water, methanol, and ethanol (preferably water, petroleum ether, water, and ethanol). The inorganic carbon support is one or more of the following: activated carbon, carbon nanotubes, carbon nanofibers, ordered mesoporous carbon, graphite carbon, carbon black, and carbon spheres (preferably one or more of carbon nanotubes, carbon nanofibers, and ordered mesoporous carbon); the ratio of metal precursor: coordination precursor: carbon support: solvent is 1-3:1-5:1-5:15-40 (mass ratio), preferably 1-3:1-2:1-2:15-30 (mass ratio); the vacuum drying temperature is 60-120℃, preferably 80-100℃, and the time is 1-24h, preferably 8-12h. Based on the above technical solution, in step (2), the calcination atmosphere is one or more of nitrogen, argon, and helium (preferably one or more of nitrogen and argon); the calcination gas flow rate is 50-1000 mL·min. -1 ·gcat -1 (Preferred concentration: 100–500 mL / min) -1 ·gcat -1 The roasting temperature is 500–1200℃ (preferably 500–1000℃); the constant temperature roasting time is 1.0–8.0h (preferably 2.0–4.0h);

[0009] Based on the above technical solution, the catalyst is the anchoring effect of elements such as N, B, and P in the support on the active sites of metal, so that the metal Co is more uniformly dispersed, the metal loading can be greatly increased and it has good thermal stability. The metal loading (based on metal) is 20-40 wt% (preferably 25-35 wt%).

[0010] Another aspect of the present invention provides the application of the above-mentioned high-loading Co-XC catalyst in the CO2 methane reaction.

[0011] Based on the above technical solution, in the aforementioned application, the reaction temperature is 300–700℃ (preferably 400–600℃), the reaction pressure is 0.1–5.0 MPa (preferably 2.0–4.0 MPa), and the gas hourly space velocity (based on catalyst mass) is 10,000–60,000 mL·gcat. -1 ·h -1 (Preferred concentration: 20,000–50,000 mL gcat) -1 ·h-1 The reaction feed gas is a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 1.0 to 4.0 (preferably 3.0 to 4.0). The reactor adopts a fixed bed, and the feeding method is continuous feeding. The product is first passed through a cold tank (0-5℃) to remove the generated water, and the tail gas is analyzed by gas chromatography.

[0012] This invention employs a calcination method to prepare a carbon-supported catalyst with a Co loading of 20–40 wt% (based on metal content), exhibiting excellent CO2 methanation activity. This invention utilizes the anchoring effect of N, B, and P elements in the support on the active sites of the metal, resulting in more uniform Co dispersion, significantly increased metal loading, and good thermal stability. Due to the higher dispersion and loading of Co nanoparticles, it exhibits excellent catalytic activity in the CO2 methanation reaction, avoiding the formation of the byproduct CO. This invention develops a method for preparing a highly loaded Co-based catalyst on carbon materials and applies it to the CO2 methanation reaction, significantly improving catalytic activity and exhibiting good CH4 selectivity. Attached Figure Description

[0013] Figure 1 This is a TEM image of the Co-NC-1 catalyst. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments, but this does not limit the scope of the invention in any way.

[0015] Example 1

[0016] 3.0 g cobalt nitrate, 4.0 g melamine, 1.0 g carbon nanotubes, and 25.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 2 h, the mixture was vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 900 °C in an argon atmosphere for 2 h at a gas flow rate of 100 mL·min. -1 A high-load Co-NC-1 catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP), with specific data shown in Table 1. The prepared high-load Co-NC-1 catalyst was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 300℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles. The Co particle size was small (1-5 nm), and the statistical average particle size was 3.1 nm. (See HRTEM image). Figure 1 As shown.

[0017] Example 2

[0018] 3.0 g cobalt nitrate, 2.0 g ethylenediamine, 1.5 g carbon nanofibers, and 30.0 g ethanol were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 3 h. The mixture was then vacuum dried at 100 °C for 12 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in an argon atmosphere for 2 h at a gas flow rate of 100 mL / min. -1 A high-load Co-NC-2 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0019] Evaluation experiments on CO2 methanation reaction were conducted using the prepared high-load Co-NC-2. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 20000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (1-5 nm). The statistical average particle size was 3.5 nm.

[0020] Example 3

[0021] 2.5 g cobalt nitrate, 3.5 g boron carbide, 2.0 g carbon black, and 25.0 g methanol were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 2 h, the mixture was dried under vacuum at 100 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was then calcined at 1000 °C in a nitrogen atmosphere for 2 h at a gas flow rate of 100 mL·min. -1A high-load Co-BC-1 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0022] The CO2 methanation reaction was evaluated using the prepared high-loading Co-BC-1. Specific evaluation conditions were as follows: reaction temperature 300℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (1-5 nm). The statistical average particle size was 3.5 nm.

[0023] Example 4

[0024] 3.0 g cobalt nitrate, 2.5 g boron powder, 1.5 g graphite carbon, and 23.0 g tetrahydrofuran were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 3 h. The mixture was then vacuum dried at 110 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in an argon atmosphere for 2 h at a gas flow rate of 300 mL / min. -1 A high-load Co-BC-2 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0025] Evaluation experiments on CO2 methanation reaction were conducted using the prepared high-loading Co-BC-2. Specific evaluation conditions were as follows: reaction temperature 350℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 20000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (2-5 nm). The statistical average particle size was 3.2 nm.

[0026] Example 5

[0027] 3.0 g cobalt nitrate, 1.8 g triphenylphosphine, 3.2 g activated carbon, and 28.0 g petroleum ether were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 4 h. The mixture was then vacuum dried at 65 °C for 12 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 950 °C in a helium atmosphere for 2 h at a gas flow rate of 100 mL / min. -1 A high-load Co-PC-1 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0028] The CO2 methanation reaction was evaluated using the prepared high-loading Co-PC-1. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 40000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (3-6 nm). The statistical average particle size was 4.2 nm.

[0029] Example 6

[0030] 3.0 g cobalt nitrate, 2.0 g phenyl dichlorophosphine, 2.0 g ordered mesoporous carbon, and 30.0 g methanol were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 6 h. The mixture was then vacuum dried at 80 °C for 12 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 1000 °C in an argon atmosphere for 2 h at a gas flow rate of 300 mL·min. -1 A high-load Co-PC-2 catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP) analysis. Specific data are shown in Table 1. The prepared high-load Co-PC-2 was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 50000 mL·gcat. -1 ·h -1The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (1-4 nm). The statistical average particle size was 2.3 nm.

[0031] Example 7

[0032] 3.0 g cobalt nitrate, 4.5 g melamine, 2.0 g carbon nanotubes, and 26.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 5 h, the mixture was vacuum dried at 85 °C for 12 h to obtain the catalyst. The prepared catalyst precursor was calcined at 900 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL·min. -1 A high-load Co-NC-1 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0033] The CO2 methanation reaction was evaluated using the prepared high-loading Co-NC-1. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (4-7 nm). The statistical average particle size was 4.8 nm.

[0034] Example 8

[0035] 3.0 g cobalt nitrate, 3.8 g ethylenediamine, 2.0 g graphite carbon, and 21.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 3 h, the mixture was vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 800 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL·min. -1 A high-load Co-NC-2 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0036] Evaluation experiments on CO2 methanation reaction were conducted using the prepared high-loading Co-NC-2. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 2.5 MPa, and gas hourly space velocity (based on catalyst mass) 18000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (2-6 nm). The statistical average particle size was 3.9 nm.

[0037] Example 9

[0038] 3.0 g cobalt nitrate, 2.0 g boron carbide, 2.0 g carbon nanofibers, and 25.0 g ethanol were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 6 h. The mixture was then vacuum dried at 100 °C for 8 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 950 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL / min. -1 A high-load Co-BC-1 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0039] Evaluation experiments on CO2 methanation reaction were conducted using the prepared high-loading Co-BC-1. Specific evaluation conditions were as follows: reaction temperature 350℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 50000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (2-6 nm). The statistical average particle size was 3.8 nm.

[0040] Example 10

[0041] 3.0 g cobalt nitrate, 2.7 g boron powder, 1.0 g ordered mesoporous carbon, and 25.0 g petroleum ether were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 2 h. The mixture was then vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 850 °C in an argon atmosphere for 5 h at a gas flow rate of 500 mL·min. -1 A high-load Co-BC-2 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0042] The CO2 methanation reaction was evaluated using the prepared high-loading Co-BC-2. Specific evaluation conditions were as follows: reaction temperature 350℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (2-6 nm). The statistical average particle size was 3.9 nm.

[0043] Example 11

[0044] 3.0 g cobalt nitrate, 3.5 g triphenylphosphine, 1.5 g carbon nanotubes, and 25.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 4 h. The mixture was then vacuum dried at 80 °C for 8 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 950 °C in an argon atmosphere for 4 h at a gas flow rate of 100 mL / min. -1 A high-load Co-PC-1 catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP) analysis. Specific data are shown in Table 1. The prepared high-load Co-PC-1 catalyst was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 300℃, reaction pressure 2.5 MPa, and gas hourly space velocity (based on catalyst mass) 28000 mL·gcat. -1 ·h -1The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (3-7 nm). The statistical average particle size was 4.2 nm.

[0045] Example 12

[0046] 3.0 g cobalt nitrate, 3.2 g phenyl dichlorophosphine, 1.5 g graphite carbon, and 23.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 6 h. The mixture was then vacuum dried at 100 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 600 °C in an argon atmosphere for 5 h at a gas flow rate of 100 mL / min. -1 A high-load Co-PC-2 catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP) analysis. Specific data are shown in Table 1. The prepared high-load Co-PC-2 was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The prepared catalyst was characterized by TEM and found to be uniformly dispersed, existing in the form of Co nanoparticles with a small particle size (1-4 nm). The statistical average particle size was 2.2 nm.

[0047] Comparative Example 1

[0048] 3.0 g of cobalt nitrate, 3.0 g of carbon nanotubes, and 20.0 g of water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 2 h. The mixture was then vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 700 °C in an argon atmosphere for 2 h at a gas flow rate of 100 mL / min. -1A Co-C catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP), with specific data shown in Table 1. The prepared high-load Co-C was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, revealing that it existed in the form of Co nanoparticles, with a statistically average particle size of 8.2 nm.

[0049] Comparative Example 2

[0050] 3.0 g cobalt nitrate, 0.5 g melamine, 0.5 g carbon nanotubes, and 26.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 5 h, the mixture was vacuum dried at 85 °C for 12 h to obtain the catalyst. The prepared catalyst precursor was calcined at 900 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL·min. -1 Comparative Example 2 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0051] The prepared catalyst from Comparative Example 2 was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 500℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, and it was found to exist in the form of Co nanoparticles. The average particle size was 15.2 nm.

[0052] Comparative Example 3

[0053] 3.0 g cobalt nitrate, 3.8 g ethylenediamine, 2.0 g graphite carbon, and 21.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated. After standing for 3 h, the mixture was vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 400 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL·min. -1 Comparative Example 3 catalyst was prepared, and the Co loading in the catalyst was determined by inductively coupled plasma (ICP), with specific data shown in Table 1. The morphology of the prepared catalyst was observed by TEM characterization, revealing that it existed in the form of Co nanoparticles, with a statistically average particle size of 3.2 nm.

[0054] The prepared catalyst (Comparative Example 3) was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 2.5 MPa, and gas hourly space velocity (based on catalyst mass) 18000 mL·gcat. -1 ·h -1 The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, and the feed was continuous. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1.

[0055] Comparative Example 4

[0056] 3.0 g cobalt nitrate, 6.0 g boron carbide, 10 g carbon nanofibers, and 25.0 g ethanol were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 6 h. The mixture was then vacuum dried at 100 °C for 8 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 400 °C in an argon atmosphere for 4 h at a gas flow rate of 300 mL / min. -1 Comparative Example 4 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0057] The prepared catalyst (Comparative Example 4) was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 350℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 50000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, and it was found to exist in the form of Co nanoparticles. The average particle size was 4.9 nm.

[0058] Comparative Example 5

[0059] 3.0 g cobalt nitrate, 0.7 g boron powder, 0.4 g ordered mesoporous carbon, and 25.0 g petroleum ether were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 2 h. The mixture was then vacuum dried at 80 °C for 10 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 450 °C in an argon atmosphere for 5 h at a gas flow rate of 500 mL·min. -1 Comparative Example 5 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0060] The prepared catalyst (Comparative Example 5) was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 350℃, reaction pressure 2.0 MPa, and gas hourly space velocity (based on catalyst mass) 15000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 2. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, and it was found to exist in the form of Co nanoparticles. The average particle size was 20.5 nm.

[0061] Comparative Example 6

[0062] 3.0 g cobalt nitrate, 5.5 g triphenylphosphine, 8.5 g carbon nanotubes, and 25.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 4 h. The mixture was then vacuum dried at 80 °C for 8 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 350 °C in an argon atmosphere for 4 h at a gas flow rate of 100 mL / min. -1 Comparative Example 6 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0063] The prepared catalyst (Comparative Example 6) was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 300℃, reaction pressure 2.5 MPa, and gas hourly space velocity (based on catalyst mass) 28000 mL·gcat. -1 ·h -1The reaction feed gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 4. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (at 0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, and it was found to exist in the form of Co nanoparticles. The average particle size was 5.0 nm.

[0064] Comparative Example 7

[0065] 3.0 g cobalt nitrate, 0.2 g phenyl dichlorophosphine, 0.5 g graphite carbon, and 23.0 g water were placed in a 50 mL beaker, thoroughly stirred and mixed, then sonicated, and allowed to stand for 6 h. The mixture was then vacuum dried at 100 °C for 3 h to obtain the catalyst precursor. The prepared catalyst precursor was calcined at 600 °C in an argon atmosphere for 5 h at a gas flow rate of 100 mL / min. -1 Comparative Example 7 catalyst was prepared. The Co loading in the catalyst was determined by inductively coupled plasma (ICP), and the specific data are shown in Table 1.

[0066] The prepared catalyst (Comparative Example 7) was used to evaluate the CO2 methanation reaction. Specific evaluation conditions were as follows: reaction temperature 400℃, reaction pressure 4.0 MPa, and gas hourly space velocity (based on catalyst mass) 10000 mL·gcat. -1 ·h -1 The reactant gas was a mixture of CO2 and H2, with a molar ratio of H2 to CO2 of 3. A fixed-bed reactor was used, with continuous feeding. The product was first cooled (0°C) to remove the generated water, and the tail gas was analyzed by gas chromatography. The carbon dioxide conversion rate and the selectivity of each product are listed in Table 1. The morphology of the prepared catalyst was observed by TEM, and it was found to exist in the form of Co nanoparticles. The average particle size was 12.3 nm.

[0067] Comparative Example 8

[0068] CN113546627A discloses a low-temperature carbon dioxide methanation catalyst and its preparation method. The catalyst is Co / Al2O3 synthesized by hydrothermal synthesis, and its catalytic performance is significantly better than that of Co / Al2O3 catalysts prepared by traditional impregnation method. The catalytic activity of the catalyst at 1.5 MPa and 300℃ is shown in Table 1.

[0069] Table 1 Performance of CO2 methanation reaction with different Co-XC catalysts

[0070]

[0071]

[0072] Table 1 shows that the catalyst after coordination pyrolysis exhibits better CO2 conversion and excellent CH4 selectivity. This is because the catalyst undergoes self-reduction during pyrolysis, resulting in higher dispersion and smaller particle size, which contributes to its good activity and selectivity. When the mass ratio of metal precursor: coordination precursor: carbon support: solvent is not met (3:1:1:15-3:5:5:40), the catalyst distribution is uneven, leading to decreased CH4 selectivity. When the calcination temperature of the catalyst precursor is too low, part of the catalyst is coated with the coordination material, reducing catalytic activity.

[0073] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. The application of a cobalt-based catalyst in the CO2 methanation reaction, characterized in that, The preparation method of cobalt-based catalysts includes the following steps: (1) The metal precursor, coordination precursor, solvent and inorganic carbon support are thoroughly mixed by stirring and / or sonication, and then vacuum dried after standing for 1-12 h to prepare the supported catalyst precursor. (2) The catalyst precursor prepared above is calcined in a specific atmosphere to obtain a high-load Co-XC catalyst, wherein X is one or more of N, B and P elements; In step (1), the mass ratio of metal precursor: coordination precursor: carbon support: solvent is 1-3:1-5:1-5:15-40; The metal precursor is one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt formate, and cobalt acetate; The coordination precursor is one or more of the following: melamine, triethylamine, ethylenediamine, boron trichloride, boron carbide, boron phosphate, boron powder, triphenylphosphine, phenylphosphonic acid, and phenyldichlorophosphine. In step (2), the roasting temperature is 600~1200 ℃; the roasting time is 1.0~8.0 h.

2. The application according to claim 1, characterized in that, In step (1), the metal precursor is one or more of cobalt chloride, cobalt sulfate, and cobalt acetate; The coordination precursor is one or more of melamine, boron carbide, boron phosphate, and phenyl dichlorophosphine; The solvent is one or more of tetrahydrofuran, petroleum ether, water, methanol, and ethanol; The inorganic carbon carrier is one or more of the following: activated carbon, carbon nanotubes, carbon nanofibers, ordered mesoporous carbon, graphitic carbon, carbon black, and carbon spheres. The mass ratio of metal precursor: coordination precursor: carbon support: solvent is 1-3:1-2:1-2:15-30; Vacuum drying temperature is 60~120 ℃, time is 1-24 h.

3. The application according to claim 1, characterized in that, In step (2), the calcination atmosphere is one or more of nitrogen, argon, and helium; the flow rate of the calcination gas is 50~1000 mL·min. -1 ·gcat -1 The roasting temperature is 600~1000 ℃; the roasting time is 2.0~4.0 h.

4. The application according to claim 1 or 2, characterized in that, In step (1), the solvent is one or more of water, methanol, and ethanol; The inorganic carbon support is one or more of carbon nanotubes, carbon nanofibers, and ordered mesoporous carbon. Vacuum drying temperature is 80~100 ℃, time is 8-12 h; In step (2), the roasting temperature is 600~1000 ℃; the constant temperature roasting time is 2.0~4.0 h.

5. The application according to claim 1 or 3, characterized in that, In step (2), the calcination atmosphere is one or both of nitrogen and argon; the flow rate of the calcination gas is 100~500 mL·min. -1 ·gcat -1 .

6. The application according to claim 1, characterized in that, One or more of the N, B, and P elements in the carrier have an anchoring effect on the metal active sites, making the metal Co more uniformly dispersed, significantly increasing the metal loading and having good thermal stability. The metal loading is 20~40 wt% based on the metal content.

7. The application according to claim 1, characterized in that, The metal loading in the catalyst is 25-35 wt% (based on metal content).

8. The application according to claim 1, characterized in that, In the aforementioned applications, the reaction temperature is 200–700 °C, the reaction pressure is 0.1–5.0 MPa, and the gas space velocity (gas hourly velocity) is 10,000–60,000 mL·gcat (catalyst mass). -1 ·h -1 The molar ratio of H2 to CO2 in the feed gas is 1.0 to 4.0; the feed gas is a gas containing H2 and CO2.

9. The application according to claim 1 or 8, characterized in that, In the aforementioned applications, the reaction temperature is 400–600 °C, the reaction pressure is 2.0–4.0 MPa, and the gas space velocity (gas hourly velocity) is 20,000–50,000 mL·gcat (catalyst mass). -1 ·h -1 The molar ratio of H2 to CO2 in the feed gas is 3.0~4.0; the feed gas is a gas containing H2 and CO2.

10. The application according to claim 1, characterized in that, In the application described, the reactor uses a fixed bed, the feeding method is continuous feeding, the product first passes through a 0-5 ℃ cold tank to remove the generated water, and the tail gas is analyzed by gas chromatography.

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