CO2 methanation catalyst as well as preparation method and application thereof

Abstract

The invention provides a CO2 methanation catalyst as well as a preparation method and application thereof. The CO2 methanation catalyst comprises an alpha-Al2O3 carrier and a Ni active component, the Ni active component is distributed on the surface of the alpha-Al2O3 carrier in the form of regular spherical particles. According to the method, the crystal form of Al2O3 is identified, alpha-Al2O3 is selected as a carrier, and Ni active components are distributed on the surface of the alpha-Al2O3 carrier in the form of regular spherical particles depending on the interaction between the alpha-Al2O3 carrier and Ni, so that the activity and product selectivity of CO2 methanation reaction are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, specifically to the field of CO2 hydrogenation catalysis technology, and particularly to a CO2 methanation catalyst, its preparation method and application. Background Art

[0002] In recent years, the extensive use of fossil fuels has greatly promoted the development of human society. However, the overexploitation and utilization of this non-renewable energy source have led to its increasing depletion, and at the same time, a large amount of carbon dioxide (CO2) emissions have been caused, exacerbating global warming and bringing great pressure to the ecological environment. Therefore, reducing CO2 emissions has become an urgent problem to be solved. As an abundant and low-cost carbon source, it is very necessary to recycle CO2 to mitigate the impact of excessive emissions. Among them, using hydrogen (H2) generated from renewable energy to react with CO2 to produce valuable chemicals is a solution with broad application prospects. Among many CO2 hydrogenation products, C1 products (such as CO and CH4) are important basic chemical raw materials, which can be converted into high-value-added chemicals or fuels through mature industrial processes. Highly selective hydrogenation of CO2 to specific products is of great significance for reducing separation and recycling costs and improving the production efficiency of the chemical industry. However, directional regulation of product selectivity is still quite challenging.

[0003] CN103721757A discloses a preparation method and application of a γ-Al2O3 support. By using the equal-volume co-impregnation method of an aqueous solution mixture of metal nitrates or chlorides, a Ni-Ru-Ce / γ-Al2O3 catalyst is prepared. The catalyst promoter loading of this invention is small. Under the conditions of a space velocity of 7200h -1 , 400 °C, 0.1 MPa, and H2 / CO2 = 4:1, the conversion rate of CO2 is above 80%, and the methane selectivity is close to 100%.

[0004] CN101884927A discloses a catalyst for the complete methanation of carbon dioxide. The catalyst uses spherical γ-Al2O3 as the support, Ni and Fe as the active components, and MgO, La2O3 or CeO2 as the promoters. The catalyst is prepared by the sequential impregnation method, followed by drying, calcination, and reduction. The mass percentages of each component are: γ-Al2O3: 60 - 80%; NiO: 10 - 20%; Fe2O3: 5 - 15%; MgO: 1 - 10%; La2O3 or CeO2: 1 - 10%. Under the reaction conditions of a pressure of 3.0 - 5.0 MPa, a raw material gas volume space velocity of 5000 - 10000h -1 and H2 / CO2 = 4.1, both the CO2 conversion rate and the CH4 selectivity can be close to 100%.

[0005] CN113368862A discloses a CO2 methanation catalyst, its preparation method and application. The catalyst uses γ-Al2O3 as the carrier, metal Ni as the active component, and Eu2O3 as the promoter. The mass of metal Ni is 3-25% of the mass of the carrier, and the mass of Eu2O3 is 1-8% of the mass of the carrier. The preparation method is as follows: Mix the Ni(NO3)2 aqueous solution and the Eu(NO3)2 aqueous solution and dropwise add them to the γ-Al2O3 powder, stir evenly, and then dry and calcine to obtain the catalyst, which is used for catalyzing the hydrogenation of CO2 to synthesize methane.

[0006] In the prior art, the CO2 methanation catalysts with alumina as the carrier usually need to introduce precious metals or rare earth elements as promoters. Although the selectivity of methane can be improved, the cost of the catalyst is significantly increased, which is not suitable for large-scale applications.

[0007] Therefore, it is of great significance to develop a catalyst with a simple preparation method, low price, high catalytic activity and CO2 hydrogenation selectivity. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a CO2 methanation catalyst, its preparation method and application. By identifying the crystal form of Al2O3, the present invention selects α-Al2O3 as the carrier. There are fewer five-coordinated aluminum sites on the α-Al2O3 carrier. When using it as the matrix, relying on the weak interaction between the α-Al2O3 carrier and Ni, the Ni active component is distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles. The regular spherical particle morphology of Ni can significantly increase the number of active sites for dissociating and activating H2 on the CO2 methanation catalyst, thereby improving the activity and product selectivity of the CO2 methanation reaction.

[0009] To achieve the purpose of the present invention, the following technical solutions are adopted:

[0010] In the first aspect, the present invention provides a CO2 methanation catalyst, and the CO2 methanation catalyst includes an α-Al2O3 carrier and a Ni active component;

[0011] The Ni active component is distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles.

[0012] The present invention selects α-Al2O3 as the carrier. By using the weak interaction between the α-Al2O3 carrier and Ni, the Ni active component is distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles, which significantly improves the product selectivity of the CO2 methanation reaction.

[0013] In the present invention, the Ni active component is distributed on the surface of the α-Al2O3 support in the form of regular spherical particles, which can provide more active sites and thus improve the activity of the CO2 methanation reaction.

[0014] The loading amount of the Ni active component affects the catalytic activity and CH4 selectivity of the CO2 methanation catalyst. If the loading amount is too low, the number of active centers is small, resulting in a relatively slow catalytic reaction, thus showing low catalytic activity and CH4 selectivity. If the loading amount is too high, agglomeration of the active component may occur, making the number of effective active sites no longer increase with the increase of the loading amount, but may even decrease, thereby reducing the activity and product selectivity of the CO2 methanation reaction.

[0015] Preferably, in the CO2 methanation catalyst, based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 6 wt.% to 15 wt.%, for example, it can be 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.% or 15 wt.%, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] In the present invention, the average particle size of the regular spherical particles of the Ni active component affects the performance of the CO2 methanation reaction. If the particle size is too large, the specific surface area is relatively small, and the number of active sites available for reaction molecule adsorption is relatively small, which will reduce the contact probability between the reaction molecules and the active sites, thus resulting in a decrease in the catalytic reaction activity. If the particle size is too small, although the specific surface area is large and the number of active sites is large, the too-small particles may agglomerate, resulting in some active sites being covered or inactivated. Moreover, the particles with too-small particle size may have too high surface energy during the reaction process, reducing the stability of the catalyst, which is also not conducive to the efficient progress of the catalytic reaction and the high selectivity for CH4.

[0017] Preferably, the average particle size of the regular spherical particles of the Ni active component is 4 nm - 10 nm, for example, it can be 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] In the second aspect, the present invention provides a preparation method of the CO2 methanation catalyst as described in the first aspect, and the preparation method includes:

[0019] The calcined Al2O3 precursor is used to prepare the α-Al2O3 support; the α-Al2O3 support is mixed with a soluble Ni salt to prepare a CO2 methanation catalyst precursor; the CO2 methanation catalyst precursor is sintered for the first time and then sintered for the second time to prepare the CO2 methanation catalyst.

[0020] In the present invention, the transition metal Ni is selected as the active component, and the crystal form of the Al2O3 support is regulated by controlling the calcination temperature of the Al2O3 precursor. By utilizing the weak interaction between the α-Al2O3 support and Ni, the activity and product selectivity of the CO2 methanation reaction are improved.

[0021] In the present invention, the temperature for calcining the Al2O3 precursor affects the crystal form of the prepared Al2O3. If the calcination temperature is too low, the α-Al2O3 crystal form cannot be prepared. Different crystal forms of the prepared Al2O3 have different interactions with the Ni active component, resulting in the Ni active component not being uniformly distributed on the surface of the Al2O3 support in the form of regular spherical particles. As a result, the catalytic activity of the prepared CO2 methanation catalyst decreases, and a high CH4 selectivity cannot be achieved. If the calcination temperature is too high, the energy consumption increases, which is not conducive to cost reduction.

[0022] Preferably, the temperature for calcining the Al2O3 precursor is 1100°C - 1300°C. For example, it can be 1100°C, 1120°C, 1140°C, 1160°C, 1180°C, 1200°C, 1220°C, 1240°C, 1260°C, 1280°C or 1300°C, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the Al2O3 precursor includes pseudoboehmite and / or boehmite.

[0024] Preferably, the method for mixing the α-Al2O3 support with the soluble Ni salt includes:

[0025] The α-Al2O3 support is impregnated in a soluble Ni salt solution and dried to obtain the CO2 methanation catalyst precursor.

[0026] Preferably, the drying temperature is 60°C - 100°C. For example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the soluble Ni salt includes any one or a combination of at least two of nickel nitrate, nickel acetate, nickel sulfate, or nickel chloride. Typical but non-limiting combinations include the combination of nickel nitrate and nickel acetate, the combination of nickel sulfate and nickel chloride, the combination of nickel acetate and nickel sulfate, or the combination of nickel chloride and nickel nitrate.

[0028] The present invention does not particularly limit the concentration of the soluble Ni salt in the soluble Ni salt solution, which can be set according to actual preparation needs. Exemplarily, the concentration of the soluble Ni salt can be 0.01 g / mL - 0.05 g / mL. For example, it can be 0.01 g / mL, 0.02 g / mL, 0.03 g / mL, 0.04 g / mL, or 0.05 g / mL, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0029] Preferably, when mixing the α-Al2O3 support with the soluble Ni salt, the mass ratio of Ni in the soluble Ni salt to the α-Al2O3 support is (6 - 15):100. For example, it can be 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, or 15:100, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the first sintering is carried out in an air atmosphere.

[0031] In the present invention, the first sintering of the CO2 methanation catalyst precursor is carried out in an air atmosphere. The temperature of the first sintering affects the formation of metal oxides. If the first sintering temperature is too high, the metal active components in the precursor will agglomerate, resulting in a reduction in active sites. If the first sintering temperature is too low, the impurities in the metal precursor cannot be effectively removed, leading to difficulty in forming metal oxides or incomplete formation.

[0032] Preferably, the temperature of the first sintering is 450°C - 600°C. For example, it can be 450°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, or 600°C, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the time of the first sintering is 2 h - 5 h. For example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, including but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the second sintering is carried out in a reducing atmosphere.

[0035] In the present invention, the second sintering of the CO2 methanation catalyst precursor is carried out in a reducing atmosphere, aiming to reduce the metal oxides in the CO2 methanation catalyst precursor to form active metal sites. If the second sintering temperature is too high, sintering and agglomeration of the active metal may occur, resulting in a decrease in the surface area of the active metal and a reduction in the number of active sites, thereby reducing the activity of the catalyst. If the second sintering temperature is too low, the metal oxides in the catalyst precursor cannot be fully reduced, and the formation of active metal centers is incomplete, resulting in insufficient activity of the catalyst.

[0036] Preferably, the temperature of the second sintering is 350°C - 550°C. For example, it can be 350°C, 400°C, 450°C, 500°C or 550°C, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the time of the second sintering is 0.5h - 3h. For example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or 3.5h, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the reducing gas in the reducing atmosphere includes H2.

[0039] Preferably, in the reducing atmosphere, the volume fraction of H2 is 5vol% - 20vol%. For example, it can be 5vol%, 7vol%, 9vol%, 11vol%, 13vol%, 15vol%, 17vol%, 19vol% or 20vol%, including but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0040] In the reducing atmosphere used in the present invention, in addition to the reducing gas, it also includes balance gas N2 and / or inert gas, and no special limitation is imposed on the gas composition other than the reducing gas in the reducing atmosphere.

[0041] Preferably, in the CO2 methanation catalyst, based on the mass of the Al2O3 support being 100wt.%, the loading amount of the transition metal active component is 6wt.% - 15wt.

[0042] In a third aspect, the present invention provides an application of the CO2 methanation catalyst as described in the first aspect, and the CO2 methanation catalyst is applied to the resource utilization of CO2.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] By identifying the crystal form of Al2O3, α-Al2O3 is selected as the carrier. Relying on the weak interaction between the α-Al2O3 carrier and Ni, the Ni active component is distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles. The regular spherical particle morphology of Ni can significantly increase the number of active sites for dissociating and activating H2 on the CO2 methanation catalyst, thereby improving the activity and product selectivity of the CO2 methanation reaction. Description of the Drawings

[0045] Figure 1 It is the TEM image of the CO2 methanation catalyst prepared in Example 1.

[0046] Figure 2 It is the TEM image of the CO2 methanation catalyst prepared in Comparative Example 1.

[0047] Figure 3 It is the comparison chart of the catalytic activity and CO / CH4 selectivity of the CO2 methanation catalysts prepared in Example 1 and Examples 3 - 6.

[0048] Figure 4 It is the comparison chart of the catalytic activity and CO / CH4 selectivity of the CO2 methanation catalysts prepared in Comparative Examples 1 - 6.

[0049] Figure 5 It is the H2-TPR curve of the α-Al2O3 carrier and the CO2 methanation catalyst prepared in Example 1 and the γ-Al2O3 carrier and the CO2 methanation catalyst prepared in Comparative Example 1.

[0050] Figure 6 It is the XRD pattern of the α-Al2O3 carrier and the CO2 methanation catalyst prepared in Example 1 and the γ-Al2O3 carrier and the CO2 methanation catalyst prepared in Comparative Example 1. Detailed Embodiments

[0051] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0052] Example 1

[0053] This example provides a CO2 methanation catalyst, including an α-Al2O3 carrier and a Ni active component. Based on the mass of the α-Al2O3 carrier being 100 wt.%, the loading amount of the Ni active component is 10 wt.%. As Figure 1 shown, the Ni active component is distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles.

[0054] The preparation method of the CO2 methanation catalyst includes:

[0055] (1) Calcining pseudo-boehmite at 1200 °C to prepare an α-Al2O3 support;

[0056] (2) Immersing the α-Al2O3 support prepared in step (1) in a nickel nitrate solution with a mass concentration of 0.1 g / mL, and the mass ratio of Ni in the nickel nitrate solution to the α-Al2O3 support is 10:100. Under continuous stirring, it is dried at 80 °C to obtain a CO2 methanation catalyst precursor;

[0057] (3) Performing a first sintering on the CO2 methanation catalyst precursor prepared in step (2) in a muffle furnace, the first sintering temperature is 550 °C, and the sintering time is 3 h. After the first sintering is completed, a second sintering is performed in a 10 vol% H2 atmosphere, the sintering temperature is 400 °C, and the sintering time is 1 h to prepare the CO2 methanation catalyst.

[0058] Example 2

[0059] This example provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 15 wt.%.

[0060] The preparation method of the CO2 methanation catalyst includes:

[0061] (1) Calcining pseudo-boehmite at 1100 °C to prepare an α-Al2O3 support;

[0062] (2) Immersing the α-Al2O3 support prepared in step (1) in a nickel nitrate solution with a mass concentration of 0.5 g / mL, and the mass ratio of Ni in the nickel nitrate solution to the α-Al2O3 support is 15:100. Under continuous stirring, it is dried at 60 °C to obtain a CO2 methanation catalyst precursor;

[0063] (3) Performing a first sintering on the CO2 methanation catalyst precursor prepared in step (2) in a muffle furnace, the first sintering temperature is 450 °C, and the sintering time is 5 h. After the first sintering is completed, a second sintering is performed in a 10 vol% H2 atmosphere, the sintering temperature is 350 °C, and the sintering time is 3 h to prepare the CO2 methanation catalyst.

[0064] Example 3

[0065] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 6 wt.%.

[0066] The preparation method of the CO2 methanation catalyst includes:

[0067] (1) Calcine pseudo-boehmite at 1300 °C to prepare the α-Al2O3 support;

[0068] (2) Immerse the α-Al2O3 support prepared in step (1) in a nickel nitrate solution with a mass concentration of 0.3 g / mL. The mass ratio of Ni in the nickel nitrate solution to the α-Al2O3 support is 6:100. Under continuous stirring, dry at 100 °C to obtain a CO2 methanation catalyst precursor;

[0069] (3) Conduct a first sintering on the CO2 methanation catalyst precursor prepared in step (2) in a muffle furnace. The first sintering temperature is 600 °C and the sintering time is 2 h. After the first sintering is completed, conduct a second sintering in a 10 vol% H2 atmosphere. The sintering temperature is 550 °C and the sintering time is 0.5 h to prepare the CO2 methanation catalyst.

[0070] Example 4

[0071] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 8 wt.%.

[0072] The preparation method of the CO2 methanation catalyst is the same as that of Example 1 except that the mass ratio of the Ni element to the α-Al2O3 support in step (2) is 8:100.

[0073] Example 5

[0074] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 1 wt.%.

[0075] The preparation method of the CO2 methanation catalyst is the same as that of Example 1 except that the mass ratio of the Ni element to the α-Al2O3 support in step (2) is 1:100.

[0076] Example 6

[0077] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 2 wt.%.

[0078] The preparation method of the CO2 methanation catalyst is the same as that of Example 1, except that the mass ratio of Ni element to the mass of the α-Al2O3 support in step (2) is 2:100.

[0079] Example 7

[0080] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 4 wt.%.

[0081] The preparation method of the CO2 methanation catalyst is the same as that of Example 1, except that the mass ratio of Ni element to the mass of the α-Al2O3 support in step (2) is 4:100.

[0082] Example 8

[0083] This embodiment provides a CO2 methanation catalyst, which includes an α-Al2O3 support and a Ni active component. Based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 18 wt.%.

[0084] The preparation method of the CO2 methanation catalyst is the same as that of Example 2, except that the mass ratio of Ni element to the mass of the α-Al2O3 support in step (2) is 18:100.

[0085] Example 9

[0086] This embodiment provides a preparation method of a CO2 methanation catalyst. The preparation method of the CO2 methanation catalyst is the same as that of Example 1, except that the first sintering temperature in step (3) is 350 °C.

[0087] Example 10

[0088] This embodiment provides a preparation method of a CO2 methanation catalyst. The preparation method of the CO2 methanation catalyst is the same as that of Example 1, except that the first sintering temperature in step (3) is 700 °C.

[0089] Example 11

[0090] This embodiment provides a preparation method of a CO2 methanation catalyst. The preparation method of the CO2 methanation catalyst is the same as that of Example 1, except that the second sintering temperature in step (3) is 300 °C.

[0091] Example 12

[0092] This example provides a method for preparing a CO2 methanation catalyst. The method for preparing the CO2 methanation catalyst is the same as that of Example 1, except that the second sintering temperature in step (3) is 650 °C.

[0093] Comparative Example 1

[0094] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 10 wt.%. As Figure 2 shown, the Ni active component is irregularly distributed on the surface of the γ-Al2O3 support.

[0095] The method for preparing the CO2 methanation catalyst provided in this comparative example is the same as that of Example 1, except that in step (1), pseudoboehmite is calcined at 600 °C to prepare the γ-Al2O3 support.

[0096] Comparative Example 2

[0097] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 6 wt.%.

[0098] The method for preparing the CO2 methanation catalyst provided in this comparative example is the same as that of Example 3, except that in step (1), pseudoboehmite is calcined at 700 °C to prepare the γ-Al2O3 support.

[0099] Comparative Example 3

[0100] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 8 wt.%.

[0101] The method for preparing the CO2 methanation catalyst provided in this comparative example is the same as that of Example 1, except that in step (1), pseudoboehmite is calcined at 700 °C to prepare the γ-Al2O3 support.

[0102] Comparative Example 4

[0103] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 1 wt.%.

[0104] The preparation method of the CO2 methanation catalyst provided in this comparative example is the same as that of Example 1 except that in step (1), pseudo-boehmite is calcined at 700 °C to prepare a γ-Al2O3 support.

[0105] Comparative Example 5

[0106] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 2 wt.%.

[0107] The preparation method of the CO2 methanation catalyst provided in this comparative example is the same as that of Example 1 except that in step (1), pseudo-boehmite is calcined at 700 °C to prepare a γ-Al2O3 support.

[0108] Comparative Example 6

[0109] This comparative example provides a CO2 methanation catalyst, including a γ-Al2O3 support and a Ni active component. Based on the mass of the γ-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 4 wt.%.

[0110] The preparation method of the CO2 methanation catalyst provided in this comparative example is the same as that of Example 1 except that in step (1), pseudo-boehmite is calcined at 700 °C to prepare a γ-Al2O3 support.

[0111] Performance test:

[0112] The activity and product selectivity of the CO2 methanation reaction of the CO2 methanation catalysts prepared in all the above examples and comparative examples were tested on a fixed-bed reactor. The test conditions were as follows:

[0113] At 400 °C, the reaction atmosphere passed through the catalyst in a flow-through manner. The reaction atmosphere composition was: 100000 ppm CO2, CO2 / H2 / N2 = 4:16:20 (N2 was the balance gas), the space velocity was 48000 mL·g -1 ·h -1 , the pressure was 0.1 MPa, and the total gas flow rate was 40 mL / min.

[0114] The test results of the CO2 conversion rate and CO / CH4 selectivity are shown in Table 1. The comparison of the catalytic activity and CO / CH4 selectivity of the CO2 methanation catalysts prepared in Example 1 and Examples 3 - 7 is shown in Figure 3 The comparison of the catalytic activity and CO / CH4 selectivity of the CO2 methanation catalysts prepared in Comparative Examples 1 - 6 is shown in Figure 4, the H2-TPR curves of the CO2 methanation catalysts prepared in Example 1 and Comparative Example 1 are shown in Figure 5 .

[0115] Table 1

[0116]

[0117] According to the data results of Examples 1 - 6 of the present invention, by identifying the crystal form of Al2O3, α-Al2O3 was selected as the carrier. Relying on the weaker interaction between the α-Al2O3 carrier and Ni, the Ni active component was distributed on the surface of the α-Al2O3 carrier in the form of regular spherical particles, significantly improving the activity and product selectivity of the CO2 methanation reaction.

[0118] As Figure 5 shown in the H2-TPR curve, there is no reduction peak on both the α-Al2O3 and γ-Al2O3 carriers. The reduction peaks in Example 1 and Comparative Example 1 were both attributed to the reduction of Ni species. The reduction temperature of Ni species in Example 1 was lower than that in Comparative Example 1, while the hydrogen consumption was higher than that in Comparative Example 1. This indicates that the interaction between Ni species and the carrier in Example 1 is weaker, which is more conducive to the formation of regular spherical particles of the Ni active component on the surface of the α-Al2O3 carrier, improving the reaction activity and product selectivity of the CO2 methanation catalyst.

[0119] As Figure 6 shown in the XRD patterns of the α-Al2O3 carrier and the CO2 methanation catalyst prepared in Example 1 and the γ-Al2O3 carrier and the CO2 methanation catalyst prepared in Comparative Example 1, there are differences in the diffraction peak positions and intensities of the α-Al2O3 and γ-Al2O3 carriers, indicating the differences in their structures. At the same time, the diffraction peaks in Example 1 and Comparative Example 1 can also correspond to the diffraction peaks of the two carriers respectively. The diffraction peak of metallic nickel is not obvious, which is related to the smaller particle size of the Ni active component.

[0120] According to the data results of Comparative Example 1 and Figure 2 , at the same Ni active component loading, when the carrier in Comparative Example 1 was γ-Al2O3, the interaction between γ-Al2O3 and the Ni active component was strong, resulting in an irregular distribution of Ni particles and the inability to form a regular spherical particle structure. The CO2 conversion rate and CH4 selectivity of the prepared CO2 methanation catalyst also decreased significantly.

[0121] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A CO2 methanation catalyst, characterized in that, The CO2 methanation catalyst includes an α-Al2O3 support and a Ni active component; The Ni active component is distributed on the surface of the α-Al2O3 support in the form of regular spherical particles.

2. The CO2 methanation catalyst according to claim 1, characterized in that, In the CO2 methanation catalyst, based on the mass of the α-Al2O3 support being 100 wt.%, the loading amount of the Ni active component is 6 wt.% to 15 wt.%; Preferably, the average particle size of the regular spherical particles of the Ni active component is 4 nm - 10 nm.

3. A method for preparing the CO2 methanation catalyst according to claim 1 or 2, characterized in that, The preparation method includes: Calcining the Al2O3 precursor to obtain the α-Al2O3 support; mixing the α-Al2O3 support with a soluble Ni salt to obtain a CO2 methanation catalyst precursor; subjecting the CO2 methanation catalyst precursor to a first sintering and a second sintering in sequence to obtain the CO2 methanation catalyst.

4. The preparation method according to claim 3, characterized in that, The temperature for calcining the Al2O3 precursor is 1100°C - 1300°C; Preferably, the Al2O3 precursor includes pseudoboehmite and / or boehmite.

5. The preparation method according to claim 3 or 4, characterized in that, The method for mixing the α-Al2O3 support with the soluble Ni salt includes: Immersing the α-Al2O3 support in a soluble Ni salt solution and drying to obtain the CO2 methanation catalyst precursor; Preferably, the drying temperature is 60°C - 100°C; Preferably, the soluble Ni salt includes any one or a combination of at least two of nickel nitrate, nickel acetate, nickel sulfate, or nickel chloride.

6. The preparation method according to any one of claims 3-5, characterized in that, When mixing the α-Al2O3 support with the soluble Ni salt, the mass ratio of Ni in the soluble Ni salt to the α-Al2O3 support is (6 - 15):

100.

7. The preparation method according to any one of claims 3-6, characterized in that, The first sintering is carried out in an air atmosphere; Preferably, the time for the first sintering is 2 h - 5 h; Preferably, the temperature for the first sintering is 450°C - 600°C.

8. The preparation method according to any one of claims 3-7, characterized in that, The temperature for the second sintering is 350 - 550°C; Preferably, the time for the second sintering is 0.5 h - 3 h.

9. The preparation method according to any one of claims 3-9, characterized in that, The second sintering is carried out in a reducing atmosphere; Preferably, the reducing gas in the reducing atmosphere includes H2; Preferably, in the reducing atmosphere, the volume fraction of H2 is 5 vol% - 20 vol%.

10. Use of the CO2 methanation catalyst according to claim 1 or 2, characterized in that, The CO2 methanation catalyst is applied to the resource utilization of CO2.

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