A co2 methanation catalyst, its preparation method and application

Abstract

The application belongs to the technical field of CO2 methanation catalysts, and particularly relates to a CO2 methanation catalyst, a preparation method and application thereof. The method uses an alkaline salt solution as a precipitant, and sequentially adds Ni and Zr salt solutions into a sodium hydroxide solution to obtain a precursor in which part of Zr replaces Ni in a carrier Ni(OH)2, and after calcination, a CO2 methanation catalyst with an integral wrapping structure formed by Ni metal particles wrapping the carrier Ni(OH)2 is obtained. The catalyst has good catalytic performance, high CO2 conversion rate at a low temperature, excellent catalytic activity, and advantages of oxidation resistance and anti-coking. Moreover, the preparation method of the catalyst is simple and very suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of CO2 methanation catalysts. More particularly, it relates to a CO2 methanation catalyst and a preparation method and application thereof. BACKGROUND

[0002] After the industrial revolution, the use of traditional energy greatly promoted the development of economy, society and technology, but also caused a large amount of CO2 emissions, making the concentration of CO2 in the atmosphere surge, affecting the ecological balance of the earth. The carbon dioxide methanation technology of synthesizing methane (CH4) from CO2 through hydrogenation technology not only can alleviate the problem of rapid increase of CO2 concentration in the atmosphere, but also can make full use of renewable resources of hydrogen and reduce the waste of existing renewable energy.

[0003] The carbon dioxide methanation technology is a technology of preparing methane from CO2 by hydrogenation under the catalysis of a specific catalyst. In theory, CO2 can be completely converted into methane, so that CO2 can be effectively utilized and converted into methane. For example, Chinese Patent Application CN103143364A discloses a highly dispersed nanocomposite catalyst, which has a high CO2 conversion rate, but it needs to be catalyzed at a temperature of 700-1000℃, which is extremely high and has a large energy consumption. Generally speaking, most of the existing catalysts for catalyzing CO2 methanation need to be catalyzed at a temperature of 350℃ or even above. Chinese Patent Application CN114870846A discloses a carbon dioxide methanation catalyst, which can play a catalytic role at a temperature of 250℃, but it needs to add biomass tar, and uses phenolic organic matter in the biomass tar as a dispersion medium. Tar is a mixture containing many components, and contains some carcinogenic components, and tar is difficult to completely burn, and the remaining residues can easily cause harm to human health and the environment.

[0004] Therefore, it is urgent to provide a green, mild and efficient CO2 methanation catalyst. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the defects and shortcomings of the existing CO2 methanation catalysts, which need to be catalyzed at a temperature of 700-800℃ or need to add organic matter that can easily cause harm to human health or environmental pollution, and to provide a preparation method of a green, mild and efficient CO2 methanation catalyst.

[0006] The purpose of the present application is to provide a CO2 methanation catalyst prepared by the preparation method.

[0007] Another purpose of the present application is to provide an application of the CO2 methanation catalyst.

[0008] The above object of the present application is achieved by the following technical solutions.

[0009] The present application protects a preparation method of a CO2 methanation catalyst, comprising the following steps:

[0010] The basic solution containing nickel salt is mixed with the zirconium salt solution uniformly, after the reaction is completed, post-treatment is performed, and a nickel-zirconium catalyst precursor is obtained. The nickel-zirconium catalyst precursor is calcined at 500-800 ℃ for 1-3 h, and the nickel-zirconium catalyst is obtained.

[0011] The method creatively uses a simple displacement method, so that part of the Ni ions in the nickel hydroxide precipitation is replaced by Zr ions. In the process of the displacement reaction, the Ni ions are firmly attached around the zirconium hydroxide carrier, thereby forming a stable precursor structure of the Ni ion wrapping the zirconium hydroxide precipitation. In the calcination process of the catalyst precursor, the Ni metal nanoparticles are gradually anchored around the zirconium hydroxide carrier, and the stable metal particles are obtained after hydrogen reduction.

[0012] The wrapping structure of the peripheral Ni ions formed by the displacement method can quickly wrap the metal salt precipitation, thereby limiting the size and size of the metal active component. After hydrogen reduction, the outer wrapping structure formed can disperse the metal active component, thereby realizing the multi-site catalytic characteristics. The outer Ni metal nanoparticle wrapping structure after anchoring presents a dispersed structure, which can more quickly and effectively exert the catalytic effect and has good stability and oxidation and coking resistance.

[0013] Further, the basic solution of the nickel salt is obtained by mixing a nickel salt solution with a basic solution, the obtained mixture is subjected to suction filtration, and the precipitate after suction filtration is dispersed by adding water.

[0014] Preferably, the solute of the basic solution is sodium hydroxide or potassium hydroxide.

[0015] Preferably, the molar concentration of the basic solution is 1-1.5 mol / L.

[0016] Preferably, the mass ratio of the water to the mass of the solute in the basic solution is 20-40:1.

[0017] Preferably, the zirconium salt is added to the basic solution containing the nickel salt in a dropwise manner to ensure sufficient mixing of the two solutes.

[0018] Preferably, the calcination temperature is 500-700 ℃.

[0019] Preferably, the nickel salt is nickel nitrate, nickel sulfate, nickel chloride, or a hydrate of any of the above nickel salts.

[0020] Preferably, the zirconium salt is zirconium nitrate, zirconium sulfate, zirconium chloride, or a hydrate of any of the above zirconium salts.

[0021] Preferably, the molar ratio of the nickel salt to the zirconium salt is 3-6:1, based on the molar amount of Ni in the nickel salt and the molar amount of Zr in the zirconium salt. The molar amount of the nickel salt based on Ni refers to the molar amount of Ni obtained by converting the molar amount of Ni element in the nickel salt, and the mass of the nickel salt is calculated based on the molar amount of Ni. That is, the molar amount of Ni element in elemental Ni is the same as the molar amount of Ni element in the nickel salt. For example, the nickel salt is nickel nitrate, the molar amount of nickel nitrate is 0.025 mol, the molar amount of Ni is 0.025 mol by keeping the molar amount of Ni element unchanged, and the mass of the nickel salt based on Ni is 4.57 g, based on the relative molecular mass of nickel nitrate of 182.70.

[0022] Preferably, the reaction is complete at a temperature of 20-40℃.

[0023] Preferably, the reaction is complete in 30-60 min.

[0024] Preferably, the reaction is carried out by stirring at a speed of 600-1000 r / min.

[0025] Preferably, the calcination further comprises pre-calcination at a temperature of 400-600℃ for 30-120 min.

[0026] Further, the post-treatment comprises filtration, washing, and drying.

[0027] Further, the filtration is carried out by adding water in batches.

[0028] Further, the drying is carried out in a blast drying oven at 65-105℃ for 6-12 h.

[0029] Further, the drying is carried out in a blast drying oven at 105℃ for 12 h.

[0030] The present application also protects a CO2 methanation catalyst prepared by the preparation method.

[0031] The present application also protects the use of the CO2 methanation catalyst in catalyzing the conversion of CO2 to CH4.

[0032] Preferably, the method for converting CO2 to methane comprises passing a mixed gas containing H2 and CO2 (H2:CO2=2-4:1) into a catalyst bed containing the CO2 methanation catalyst, and generating methane gas after heating.

[0033] More preferably, the heating reaction is carried out at a temperature of 200-500℃.

[0034] More preferably, the space velocity of the heating reaction is 15000-150000 mL.g -1 ·h -1 .

[0035] The present application has the following advantages:

[0036] The method uses a basic salt solution as a precipitant, and sequentially adds Ni and Zr salt solutions into a sodium hydroxide solution to obtain a precursor in which part of Zr replaces Ni in the carrier Ni(OH)2, and after calcination, a CO2 methanation catalyst with an integral wrapping structure formed by Ni metal particles wrapping the carrier Ni(OH)2 is obtained. The catalyst has good catalytic performance, high CO2 conversion rate at a low temperature, and excellent catalytic activity, and also has the advantages of oxidation resistance and coking resistance. Moreover, the preparation method of the catalyst is simple and very suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A data statistical graph for characterizing the oxidation resistance and coking resistance of the CO2 methanation catalyst obtained in Example 1 and Comparative Example 4.

[0038] Figure 2 An EDS spectrum for characterizing the dispersion characteristics of the CO2 methanation catalyst obtained in Example 1.

[0039] Figure 3 A STEM graph for characterizing the reverse wrapping characteristics of the CO2 methanation catalyst obtained in Example 1.

[0040] Figure 4 An EDS spectrum of the CO2 methanation catalyst obtained in Comparative Example 4.

[0041] Figure 5 An EDS spectrum for characterizing the wrapping form of the CO2 methanation catalyst obtained in Example 1.

[0042] Figure 6 A data statistical graph of X-ray diffraction data of the CO2 methanation catalysts obtained in Example 1 and Comparative Examples 2-4.

[0043] Figure 7 A data statistical graph of ICP element content analysis of the CO2 methanation catalysts obtained in Example 1, Comparative Example 2 and Comparative Example 4. DETAILED DESCRIPTION

[0044] The present application will be further described below in conjunction with the drawings and specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0045] Unless otherwise indicated, the reagents and materials used in the following examples were obtained from commercial suppliers and used without further purification.

[0046] Zirconium oxide (monoclinic phase) was 99% pure, 200 mesh, from Maclin Reagent;

[0047] Zirconium oxide (tetragonal phase) was 99.9% pure, 200 mesh, from Maclin Reagent.

[0048] Example 1 Preparation of a CO2 methanation catalyst

[0049] Take 0.1 mol of sodium hydroxide into 100 mL of water and stir for 10 min to obtain solution A, take 0.05 mol of nickel nitrate hexahydrate into 50 mL of deionized water and stir for 10 min to obtain solution B, first add solution B dropwise into solution A and stir for 30 min to obtain solution C, take solution C to suction filtration, add 600 mL of deionized water to rinse three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate back into a beaker, add 100 mL of water, stir for 30 min to evenly disperse the precipitate to obtain solution D, take 0.01 mol of zirconium nitrate pentahydrate into 50 mL of deionized water and stir for 10 min to obtain solution E, add solution E dropwise into solution D and stir for 30 min to obtain solution F, perform suction filtration on solution F, add 600 mL of deionized water to rinse three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate into a 105°C air drying oven to dry for 12 h, after drying, heat to 600°C at a rate of 10°C / min in an air furnace, and calcine at 600°C for 1 h to obtain the product.

[0050] Example 2 Preparation of a CO2 methanation catalyst

[0051] Take 0.1 mol of sodium hydroxide into 100 mL of water and stir for 10 min to obtain solution A, take 0.05 mol of nickel nitrate hexahydrate into 50 mL of deionized water and stir for 10 min to obtain solution B, first add solution B dropwise into solution A and stir for 30 min to obtain solution C, take solution C to suction filtration, add 600 mL of deionized water to rinse three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate back into a beaker, add 100 mL of water, stir for 30 min to evenly disperse the precipitate to obtain solution D, take 0.01 mol of zirconium nitrate pentahydrate into 50 mL of deionized water and stir for 10 min to obtain solution E, add solution E dropwise into solution D and stir for 30 min to obtain solution F, perform suction filtration on solution F, add 600 mL of deionized water to rinse three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate into a 105°C air drying oven to dry for 12 h, after drying, heat to 600°C at a rate of 10°C / min in an air furnace, and calcine at 600°C for 1 h to obtain the product.

[0052] The difference from Example 1 is that the amount of sodium hydroxide added is 0.12 mol, and the other raw material dosages and operation steps are the same as in Example 1.

[0053] Preparation of a CO2 methanation catalyst

[0054] Take 0.1 mol of sodium hydroxide and add it to 100 mL of water and stir for 10 min to obtain solution A. Take 0.05 mol of nickel nitrate hexahydrate and add it to 50 mL of deionized water and stir for 10 min to obtain solution B. First, add solution B dropwise to solution A and stir for 30 min to obtain solution C. Take solution C and perform suction filtration. During suction filtration, rinse with 600 mL of deionized water three times to remove sodium nitrate generated in the solution. After suction filtration is complete, place the precipitate back into a beaker, add 100 mL of water, and stir for 30 min to uniformly disperse the precipitate to obtain solution D. Take 0.01 mol of zirconium nitrate pentahydrate and add it to 50 mL of deionized water and stir for 10 min to obtain solution E. Add solution E dropwise to solution D and stir for 30 min to obtain solution F. Perform suction filtration on solution F. During suction filtration, rinse with 600 mL of deionized water three times to remove sodium nitrate generated in the solution. After suction filtration is complete, place the precipitate in a 105°C forced air drying oven and dry for 12 h. After drying, heat at a rate of 10°C / min to 500°C in an atmosphere furnace, and calcine at 500°C for 1 h to obtain the product.

[0055] Compared with Example 1, the calcination temperature is 500°C, and the other raw material dosages and operation steps are the same as in Example 1.

[0056] Preparation of a CO2 methanation catalyst

[0057] Take 0.1 mol of sodium hydroxide and add it to 100 mL of water and stir for 10 min to obtain solution A. Take 0.05 mol of nickel nitrate hexahydrate and add it to 50 mL of deionized water and stir for 10 min to obtain solution B. First, add solution B dropwise to solution A and stir for 30 min to obtain solution C. Take solution C and perform suction filtration. During suction filtration, rinse with 600 mL of deionized water three times to remove sodium nitrate generated in the solution. After suction filtration is complete, place the precipitate back into a beaker, add 100 mL of water, and stir for 30 min to uniformly disperse the precipitate to obtain solution D. Take 0.01 mol of zirconium nitrate pentahydrate and add it to 50 mL of deionized water and stir for 10 min to obtain solution E. Add solution E dropwise to solution D and stir for 30 min to obtain solution F. Perform suction filtration on solution F. During suction filtration, rinse with 600 mL of deionized water three times to remove sodium nitrate generated in the solution. After suction filtration is complete, place the precipitate in a 105°C forced air drying oven and dry for 12 h. After drying, heat at a rate of 10°C / min to 500°C in an atmosphere furnace, and calcine at 500°C for 1 h to obtain the product.

[0058] The difference from Example 1 is that the molar ratio of nickel nitrate to zirconium nitrate is 4:1, and the other raw material dosages and operation steps are the same as in Example 1.

[0059] Preparation of a Ni-based catalyst

[0060] A conventional Ni-based catalyst;

[0061] 0.05 mol of nickel nitrate and 0.01 mol of zirconium nitrate pentahydrate were dissolved in 50 mL of water, 0.1 mol of sodium hydroxide was dissolved in 100 mL of water, and the two solutions were mixed after stirring for 30 min. The mixed solution was dried in a blast drying oven at 105°C for 12 h, and then heated to 600°C at a heating rate of 10°C / min in an atmosphere furnace, and calcined at 600°C for 1 h.

[0062] Preparation of a CO2 methanation catalyst

[0063] 0.02 mol of zirconium oxide powder (monoclinic phase) and 0.06 mol of nickel nitrate hexahydrate were mixed, 100 mL of water was added and stirred for 30 min to obtain solution A. Solution A was placed in a water bath ultrasonic machine and ultrasonically treated for 10 min, and then stirred for another 30 min. The solution was directly placed in a blast drying oven at 105°C for drying for 12 h. After drying, the solution was heated to 600°C at a rate of 10°C / min in an atmosphere furnace, and calcined at 600°C for 1 h.

[0064] The difference between this example and Example 1 is that the oxide carrier in Comparative Example 2 is directly used to prepare the catalyst by the impregnation method.

[0065] Preparation of a CO2 methanation catalyst

[0066] 0.02 mol of zirconium oxide powder (tetragonal phase) and 0.06 mol of nickel nitrate hexahydrate were mixed, 100 mL of water was added and stirred for 30 min to obtain solution A. Solution A was placed in a water bath ultrasonic machine and ultrasonically treated for 10 min, and then stirred for another 30 min. The solution was directly placed in a blast drying oven at 105°C for drying for 12 h. After drying, the solution was heated to 600°C at a rate of 10°C / min in an atmosphere furnace, and calcined at 600°C for 1 h.

[0067] The difference from Comparative Example 2 is that the crystal phase of the zirconium oxide powder used is different, and the other raw material dosages and operation steps are the same as in Comparative Example 2.

[0068] Preparation of a CO2 methanation catalyst

[0069] Take 0.1 mol of sodium hydroxide solution into 100 mL of water and stir for 10 min to obtain solution A, take 0.01 mol of zirconium nitrate pentahydrate into 50 mL of deionized water and stir for 10 min to obtain solution B, first add solution B dropwise into solution A and stir for 30 min to obtain solution C, take solution C and perform suction filtration, add 600 mL of deionized water to wash three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate back into a beaker, add 100 mL of water, stir for 30 min to uniformly disperse the precipitate to obtain solution D, take 0.05 mol of nickel nitrate hexahydrate into 50 mL of deionized water and stir for 10 min to obtain solution E, add solution E dropwise into solution D and stir for 30 min to obtain solution F, perform suction filtration on solution F, add 600 mL of deionized water to wash three times during suction filtration to remove sodium nitrate generated in the solution, after suction filtration, put the precipitate into a 105℃ air drying oven and dry for 12 h, after drying, heat to 600℃ at a rate of 10℃ / min in an air furnace, and calcine at 600℃ for 1 h, to obtain the product.

[0070] Compared with Example 1, the addition order of nickel nitrate and zirconium nitrate in Comparative Example 4 is interchanged, and the dosages of other raw materials and the operation steps are the same as those in Example 1.

[0071] Performance test of experimental example

[0072] (1) Determination of CO2 conversion rate

[0073] 1. Experimental method

[0074] 0.1 g of the CO2 methanation catalyst prepared in Example 1 and the Ni-based catalyst prepared in Comparative Example 1 were respectively loaded into a fixed bed reactor, one end of the fixed bed was connected to a gas inlet, and a gas inlet pipe connected to a mixed gas with a H2 / CO2 ratio of 4, the reaction temperature was 250℃, and the reaction space velocity was 15000 mL·g -1 ·h -1 -1·h-1. The gas products after the reaction were tested by Agilent 6820, and the CO2 conversion rate in the gas was used as an index, the higher the conversion rate, the better the catalytic performance.

[0075] 2. Experimental results

[0076] The experimental results are shown in Table 1: the CO2 methanation catalyst prepared in Example 1 exhibited good catalytic activity and stability during the 16 h reaction process, and the CO2 conversion rate reached 71.74% at 250°C and 83.68% at 300°C. The CO2 conversion rate of the Ni-based catalyst prepared in Comparative Example 1 was only about 10% at 250°C. The CO2 conversion rates of Comparative Examples 2 and 3 were 0% and 14.65% at 250°C, respectively, which were much lower than the catalytic activity of the CO2 methanation catalyst prepared in Example 1. Although the CO2 conversion rate of Comparative Example 4 reached 55.77% at 250°C, it was still lower than the conversion rate of the catalyst prepared in Example 1.

[0077] Table 1 CO2 conversion rate

[0078]

[0079] (2) Measurement of oxidation resistance and coking resistance

[0080] 1. Experimental method

[0081] The difference from the above-mentioned method for measuring the CO2 conversion rate is that the reaction conditions are 300°C, 60000 mL·g-1·h-1, and other conditions and parameters remain unchanged. -1

[0082] 2. Experimental results

[0083] The measurement results are shown in Table 2, and the CO2 conversion rate of the catalyst prepared in Example 1 did not decrease after a long time of reaction, indicating that the catalyst has good oxidation resistance and coking resistance, and the conversion rate is >80%, which is greater than the conversion rate of Comparative Example 4 (about 55%). Figure 1

[0084] (3) Morphology measurement

[0085] The CO2 methanation catalysts prepared in Example 1 and Comparative Example 4 were measured using a TEM field emission transmission electron microscope combined with an energy spectrometer, and the results are shown in Table 3. Figures 2 to 5 Figure 2 The catalyst prepared in Example 1 contains Ni, Zr, C and O elements, wherein the Ni is distributed in the form of particles in the catalyst, and the Ni particles are uniformly distributed around the Zr, exhibiting the characteristics of uniform dispersion of the catalyst; it can be known from Table 3 that the catalyst prepared in Example 1 has the reverse wrapping structure; in combination with Figure 3 (Comparative Example 4) and Figure 4 (Example 1), it can be known that the catalyst prepared in Comparative Example 4 is a carrier (Zr) wrapping active metal particles (Ni), and the catalyst prepared in Example 1 is a Ni metal particle wrapping carrier (Zr). Figure 5 ​​​​

[0086] (4) X-ray diffraction

[0087] The measurement results of X-ray diffraction are shown in Table 2. Figure 6 As shown in Table 2, it can be seen that the crystal forms of the catalysts obtained in Comparative Example 2 and Comparative Example 3 are different.

[0088] (5) ICP elemental content analysis

[0089] The ICP elemental contents of Example 1, Comparative Example 2 and Comparative Example 4 were determined by an ICP analyzer, and the results are shown in Table 3. Figure 7 As shown in Table 3, it can be seen that the ratios of Ni and Zr elements of the catalysts obtained in Example 1, Comparative Example 2 and Comparative Example 4 are basically the same.

[0090] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

1. A method for the preparation of a CO2 methanation catalyst, characterized in that, The method comprises the following steps: mixing a basic solution containing a nickel salt with a zirconium salt solution, after the reaction is completed, post-treatment is performed, a nickel-zirconium catalyst precursor is obtained, and the nickel-zirconium catalyst precursor is calcined at 500-800 ℃ for 1-3 h to obtain the nickel-zirconium catalyst. The basic solution of the nickel salt is obtained by mixing a nickel salt solution with a basic solution, the obtained mixture is subjected to suction filtration, and the precipitate after suction filtration is dispersed by adding water. The solute in the basic solution is sodium hydroxide or potassium hydroxide.

2. The preparation method according to claim 1, characterized in that, The nickel salt is nickel nitrate, nickel sulfate, nickel chloride or a hydrate of any of the above nickel salts.

3. The preparation method according to claim 1, characterized in that, The zirconium salt is zirconium nitrate, zirconium sulfate, zirconium chloride or a hydrate of any of the above zirconium salts.

4. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The molar ratio of the nickel salt to the zirconium salt is 3-6:

1.

5. The method of claim 1, wherein The molar concentration of the basic solution is 1-1.5 mol / L.

6. The method of claim 1, wherein The temperature at which the reaction is completed is 20-40 ℃.

7. The method of claim 1, wherein The time for which the reaction is completed is 30-60 min.

8. A CO2 methanation catalyst characterized in that, The nickel-zirconium catalyst is prepared by the method of any one of claims 1-7.

9. Use of the CO2 methanation catalyst of claim 8 in catalyzing the conversion of CO2 into CH4.

Images