Laal03 modified supported ni-based catalyst, and preparation method and application thereof

Abstract

The application provides a LaAlO3 modified supported Ni-based catalyst and a preparation method and application thereof; the catalyst composition is Ni-LaAlO3 / Al2O3, wherein Ni is an active component of the catalyst, the mass fraction is 5-20%; LaAlO3 is a perovskite structure, the mass fraction is 6.5-45%. The preparation method of the LaAlO3 modified supported Ni-based catalyst through the equal-volume impregnation method combined with high-temperature calcination is simple and easy to operate; through the surface solid-phase reaction, the active component, the additive and the carrier form the perovskite structure, the formation of the difficult-to-reduce NiAl2O4 spinel is effectively inhibited, meanwhile, the perovskite is highly dispersed on the carrier surface, the Ni element is uniformly dispersed in the perovskite, and after reduction, it is beneficial to prepare the Ni nanoparticles (NPs) with small crystal grains, and is beneficial to improve the catalytic activity. The catalyst is applied to the pressurized carbon dioxide methanation reaction, and good activity and stability are exhibited.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a LaAlO3 supported Ni-based catalyst, its preparation method, and its application in the field of CO2 methanation. Background Technology

[0002] The use of fossil fuels has greatly improved labor productivity, but it has also generated serious environmental problems. As a greenhouse gas, excessive CO2 emissions lead to global warming and climate change. Among the various methods explored for controlling carbon dioxide emissions, the hydrogenation of CO2 to produce high-value-added chemicals, such as methane, methanol, ethanol, diethyl ether, formic acid, and dimethyl carbonate, is considered the most promising approach. Methane, in particular, is a major component of natural gas fuel and an important basic chemical raw material with huge market demand.

[0003] Renewable energy sources such as solar, wind, and hydropower are considered ideal alternatives to fossil fuels. However, solar and wind power fluctuate seasonally, making energy storage crucial. Yet, battery-based energy storage technologies still face numerous challenges. Hydrogen production via water electrolysis is a mature technology, and photocatalytic water splitting (photocatalysis) for hydrogen production is also maturing, making electro-to-hydrogen conversion relatively easy. However, hydrogen has a low bulk density and is prone to leakage, making its storage and transportation difficult. Converting electrical energy into methane for chemical energy storage is more feasible. In conclusion, against the backdrop of rapid development in renewable energy and hydrogen energy, CO2 hydrogenation to methane, as a technology that can simultaneously utilize greenhouse gas resources and store renewable energy, has promising application prospects and research value.

[0004] Catalysts with Ni, Fe, Co, Ru, Rh, Pt, and Pd as active components have been reported for CO2 methanation. Among them, Ru and Rh-based noble metal catalysts have high activity and CH4 selectivity, but their high price limits their industrial application. Among non-noble metal catalysts, Ni-based catalysts have relatively high activity and selectivity, and are inexpensive and readily available, thus showing potential for industrial application.

[0005] Among numerous support materials, Al₂O₃, as a conventional support with excellent performance, is widely used in the research of CO₂ methanation catalysts. Al₂O₃ as a support has the following characteristics: First, Al₂O₃ has a high melting point and good thermal stability, enabling it to maintain the stability and activity of the catalyst under high temperatures and even harsh reaction conditions. Second, Al₂O₃ is widely available, inexpensive, and easy to shape and process, which is beneficial for the industrial production and application of the catalyst. Furthermore, Al₂O₃ has a large porosity and specific surface area, which is conducive to the adsorption and diffusion of reactants, improving catalytic efficiency. More importantly, its surface unsaturated Al... 3+A strong interaction exists between Ni and the active component of the catalyst, which can firmly anchor the active component to the surface of the support, preventing the loss and agglomeration of the active component and improving the stability and service life of the catalyst. However, during the research, it was found that, on the one hand, metallic Ni particles supported on the Al2O3 surface are prone to sintering during high-temperature and long-term reaction; on the other hand, at high temperatures, the interaction between Ni and Al2O3 is too strong, which will form a difficult-to-reducible NiAl2O4 spinel phase, leading to a decrease in catalyst activity.

[0006] Perovskite-type oxides (PTOs), typically represented by the structural formula ABO3, exhibit good thermal and chemical stability. Their chemical composition and crystal structure can be flexibly adjusted; by modifying the A-site and B-site elements, the structure and properties of the perovskite can be controlled to better meet catalytic requirements. Furthermore, the metal ions in ABO3 are uniformly mixed at the atomic level, leading to strong interactions between the metals after reduction. Additionally, oxygen vacancies readily form on the perovskite surface, which is beneficial for CO2 activation. In summary, perovskite oxides can be considered excellent catalyst materials and precursors for CO2 catalytic conversion.

[0007] Pure perovskites synthesized by conventional methods such as citric acid complexation and autogenous combustion typically have a small specific surface area, which is detrimental to the dispersion of surface-active components. To address this issue, perovskites are usually loaded onto the surface of a support with a higher specific surface area. Li et al. prepared SiO2-supported perovskite LaNi 1-x Mo x O3 precursor, after reduction, Ni nanoparticles are in close contact and highly dispersed with La2O3 and MoO3, exhibiting good CO2 methanation activity as well as good anti-sintering ability [Li S, Guo S, Gong D, et al. Nano composite composed of MoO3]. x -La2O3-Ni on SiO2 for storing hydrogen into CH4 via CO2methanation[J]. International Journal of HydrogenEnergy, 2019, 44(3):1597-1609.]; Song et al. 1-x Co xO3 was supported on the ZrO2 surface, and the resulting Co nanoparticles and LaAlO3 were highly dispersed on the support surface after reduction. The catalyst exhibited good activity in the hydrogenation of CO to lower alcohols [Song P, Fang Y, Liu X, et al. LaAlO3-Tailored Active Pairs of Co]. 0 –Co δ+ Supported on ZrO2 for Higher Alcohol Synthesis from Syngas[J].Ind.Eng.Chem.Res.,2023,62:16696-16706.]. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low activity and poor stability of existing CO2 methanation catalysts, and to provide a LaAlO3-modified supported Ni-based catalyst and its preparation method. When used in CO2 methanation reaction, it exhibits good activity and anti-sintering properties.

[0009] To improve the low-temperature activity and stability of the catalyst, this invention employs a stepwise impregnation method. In the first step, the La₂O₃ loaded onto the support surface covers the catalyst, suppressing excessive interaction between the subsequently loaded Ni and Al₂O₃. Simultaneously, a surface solid-phase reaction occurs between the active component, the promoter, and the support, forming a perovskite precursor, La(AlNi)O₃, on the support surface. After reduction, a supported metal catalyst with perovskite as the promoter is obtained. When applied to a pressurized carbon dioxide methanation reaction, it exhibits excellent activity and stability.

[0010] This invention provides the following technical solution:

[0011] A LaAlO3-modified supported Ni-based catalyst, characterized in that the catalyst has a composition of Ni-LaAlO3 / Al2O3, wherein Ni is the active component of the catalyst with a mass fraction of 5-20%; LaAlO3 has a perovskite structure with a mass fraction of 6.5-45%; and the support is Al2O3.

[0012] The method for preparing the LaAlO3-modified supported Ni-based catalyst of the present invention includes the following steps:

[0013] 1) Dissolve lanthanum nitrate in distilled water to obtain a solution, and immerse an equal volume of the dissolved solution on a carrier, then seal and leave for 12–48 hours;

[0014] 2) Unseal the carrier placed in step 1) and dry it overnight in a constant temperature drying oven at 100-150°C to obtain the dried product;

[0015] 3) Calcine the dried product obtained in step 2) at 300-700℃ for 1-6 hours to obtain La2O3 / Al2O3;

[0016] 4) Dissolve nickel nitrate and citric acid in distilled water to obtain a solution with a nickel nitrate concentration of 0.9-4.2 mol / L and a nickel nitrate to citric acid molar ratio of 1:(1-3). Impregnate an equal volume of the dissolved solution onto the La2O3 / Al2O3 support obtained in step 3) and seal for 12-48 h.

[0017] 5) Unseal the carrier placed in step 4), place it in a constant temperature drying oven at 60-90℃ for 1-6 hours, and then dry it overnight at 100-150℃ to obtain the dried product;

[0018] 6) Calcine the dried product obtained in step 5) at 250-400℃ for 1-6 hours, and then continue to calcine at 600-900℃ for 3-10 hours to obtain the catalyst precursor;

[0019] 7) Place the catalyst precursor obtained in step 5) in a reactor, introduce reducing gas into the reactor to reduce the catalyst precursor and obtain the catalyst Ni-LaAlO3 / Al2O3.

[0020] The product dried in step 3) is calcined at 300-700℃ for 1-6 hours, with a heating rate of 1-10℃ / min.

[0021] The product dried in step 6) is calcined at 250-500℃ for 1-6 hours, and then calcined at 500-900℃ for 3-10 hours at a rate of 1-10℃ / min.

[0022] In step 7), a reducing gas flow rate of 10–30 mL / min is introduced, and the reduction time is 1–3 h; the reduction temperature is 500–800 °C, and the heating rate is 1–10 °C / min. The reducing gas is hydrogen, carbon monoxide, or a mixture of an inert gas and one or two of hydrogen and carbon monoxide; the volume percentage of the inert gas in the mixed gas atmosphere is 1%–99%.

[0023] The LaAlO3-modified supported Ni-based catalyst of this invention is applied to CO2 methanation. The catalyst is added to a fixed-bed reactor at a temperature of 200-600℃ and a pressure of 1-5 MPa, with a volume hourly space velocity (VHSV) of 15000-60000 mL / (g). cat h) Carbon dioxide and hydrogen are introduced, with a molar ratio of carbon dioxide to hydrogen of 1:(1-5), to obtain the target product, methane. The CO2 conversion rate can reach 90%, and the methane selectivity is 100%.

[0024] The present invention has the following beneficial effects:

[0025] (1) The preparation method of the LaAlO3 modified supported Ni-based catalyst of the present invention by means of equal volume impregnation combined with high temperature calcination is simple and easy to operate;

[0026] (2) The present invention forms a perovskite structure by surface solid-phase reaction, active components, additives and carrier, which effectively inhibits the formation of difficult-to-reduce NiAl2O4 spinel. Ni element is uniformly dispersed in perovskite, and after reduction, Ni nanoparticles (NPs) with smaller grain size are obtained, which is beneficial to improving catalytic activity.

[0027] (3) The close contact between Ni metal particles and perovskite additives is beneficial to the synergistic catalytic effect of Ni metal sites and perovskite alkaline sites; the interaction between Ni metal particles and perovskite is strong, Ni NPs can be fixed by the perovskite phase and are not easy to migrate, thus improving the anti-sintering performance. The CO2 conversion rate can reach 90%, and it does not deactivate in the 100h stability test, which has certain industrialization prospects. Attached Figure Description

[0028] Figure 1 The images show the X-ray diffraction (XRD) patterns of the catalyst after the first calcination, the second calcination, and the reduction in Example 1.

[0029] Figure 2 This is a high-resolution TEM image of the catalyst after reduction in Example 1.

[0030] Figure 3 These are the stability test results for the CO2 methanation reaction catalyzed by the catalyst. The reaction conditions were: H2:CO2 composition = 4:1, reaction pressure 3 MPa, temperature 450℃, and reaction space velocity 15000 mL g cat. -1 h -1 . Detailed Implementation

[0031] Example 1

[0032] 1) Dissolve 0.930g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.650g of Al2O3 and seal for 24h.

[0033] 2) Dry the product overnight at 120°C in a constant temperature drying oven to obtain the dried product;

[0034] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 35% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0035] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 24h.

[0036] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0037] 6) The dried product was calcined at 350℃ for 2h by increasing the temperature by 2℃ / min, and then calcined at 700℃ for 5h to obtain the catalyst precursor.

[0038] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700℃ for 2.5 h in H2 at a flow rate of 30 mL / min and a heating rate of 2℃ / min to obtain a 10% Ni-LaAlO3 / Al2O3 catalyst, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 45%. Figure 1The XRD pattern shows that the catalyst precursor obtained after calcination formed a perovskite structure, and no diffraction peaks of NiAl2O4 spinel were observed. The perovskite peaks in the reduced catalyst were shifted to the right compared to those after calcination. This is attributed to the solid-state reaction between Ni, La2O3 and the support during calcination to form a perovskite structure. After the reduction step, Ni was reduced from the perovskite lattice, resulting in a smaller interplanar spacing of the perovskite. The grain size of Ni calculated using the Scherrer equation is approximately 6 nm, which is smaller than the grain size of Ni in conventional Ni / Al2O3 (8-10 nm) [Fei Han, Qinghe Liu, Daokui Li, et al. An emerging and high-performance sepiolite-supported Ni catalyst for low-temperature CO2methanation: The critical role of hydroxyl groups[J]. Journal of Environmental Chemical Engineering, 2023, 11(5): 110331][Jitendra Kumar Prabhakar, Pankaj A. Apte, Goutam Deo, The kinetics of Ni / Al2O3 and Ni-Fe / Al2O3 catalysts for the CO2 methanation reaction and the reasons for promotion[J]. Chemical Engineering Journal, 2023, 471: 144252]. Figure 2 The high-resolution TEM images also show the lattice fringes of metallic Ni, LaAlO3, and Al2O3.

[0039] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0040] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0041] At 250℃, the CO2 conversion rate was 12.1%; at 300℃, the CO2 conversion rate was 66.1%; and at 350℃, the CO2 conversion rate was 83.1%. At all these temperatures, the CH4 selectivity was 100%.

[0042] Stability test results are as follows Figure 3As shown, at 450℃ and 15000mL / (g) cat Under h), the CO2 conversion rate did not decrease during the 100h test.

[0043] Example 2

[0044] 1) Dissolve 0.797g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.700g of Al2O3 and seal for 24h.

[0045] 2) Dry the product overnight at 120°C in a constant temperature drying oven to obtain the dried product;

[0046] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 30% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0047] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 24h.

[0048] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0049] 6) The dried product was calcined at 250℃ for 1 hour after the temperature was increased by 2℃ / min, and then calcined at 650℃ for 6 hours to obtain the catalyst precursor.

[0050] 7) The obtained catalyst precursor was placed in a reactor and reduced at 650°C for 3 h in H2 at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 39%.

[0051] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0052] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0053] At 250℃, the CO2 conversion rate was 8.3%; at 300℃, the CO2 conversion rate was 44.8%; and at 350℃, the CO2 conversion rate was 72.6%. At all these temperatures, the CH4 selectivity was 100%.

[0054] Example 3

[0055] 1) Dissolve 0.532g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.800g of Al2O3 and seal for 24h.

[0056] 2) Dry the product overnight at 150°C in a constant temperature drying oven to obtain the dried product;

[0057] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 20% La2O3 / Al2O3, with a La2O3 mass fraction of 20%.

[0058] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 24h.

[0059] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 90°C for 3 hours, and then dry it overnight at 150°C to obtain the dried product.

[0060] 6) The dried product was heated at 5℃ / min and then calcined at 450℃ for 2 hours, and then heated to 800℃ for 4 hours to obtain the catalyst precursor.

[0061] 7) The obtained catalyst precursor was placed in a reactor and reduced at 750°C for 2 h in H2 at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 26%.

[0062] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0063] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0064] At 250℃, the CO2 conversion rate was 13.8%; at 300℃, the CO2 conversion rate was 69.4%; and at 350℃, the CO2 conversion rate was 79.8%. At all these temperatures, the CH4 selectivity was 100%.

[0065] Example 4

[0066] 1) Dissolve 0.266g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.900g of Al2O3 and seal for 24h.

[0067] 2) Dry the product overnight at 120°C in a constant temperature drying oven to obtain the dried product;

[0068] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 10% La2O3 / Al2O3, with a La2O3 mass fraction of 10%.

[0069] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 24h.

[0070] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0071] 6) The dried product was calcined at 350℃ for 2h by increasing the temperature by 2℃ / min, and then calcined at 700℃ for 5h to obtain the catalyst precursor.

[0072] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700℃ for 2.5h in H2 at a flow rate of 30mL / min and a heating rate of 2℃ / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 13%.

[0073] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0074] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0075] At 250℃, the CO2 conversion rate was 22.5%; at 300℃, the CO2 conversion rate was 66.1%; and at 350℃, the CO2 conversion rate was 83.1%. At all these temperatures, the CH4 selectivity was 100%.

[0076] Example 5

[0077] 1) Dissolve 0.133g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.950g of Al2O3 and seal for 12 hours.

[0078] 2) Dry the product overnight at 100°C in a constant temperature drying oven to obtain the dried product;

[0079] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 5% La2O3 / Al2O3, with a La2O3 mass fraction of 5%.

[0080] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 12h.

[0081] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 90°C for 3 hours, and then dry it overnight at 150°C to obtain the dried product.

[0082] 6) The dried product was calcined at 250℃ for 2 hours after the temperature was increased by 2℃ / min, and then calcined at 700℃ for 5 hours to obtain the catalyst precursor.

[0083] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700℃ for 2.5h in H2 at a flow rate of 30mL / min with a heating rate of 2℃ / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 6.5%.

[0084] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0085] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0086] At 250℃, the CO2 conversion rate was 32.9%; at 300℃, the CO2 conversion rate was 79.6%; and at 350℃, the CO2 conversion rate was 91.6%. At all these temperatures, the CH4 selectivity was 100%.

[0087] Example 6

[0088] 1) Dissolve 0.797g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.700g of Al2O3 and seal for 24h.

[0089] 2) Dry the product overnight at 120°C in a constant temperature drying oven to obtain the dried product;

[0090] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 30% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0091] 4) Dissolve 0.248g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.950g La2O3 / Al2O3 support and seal for 24h.

[0092] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0093] 6) The dried product was calcined at 350℃ for 2h by increasing the temperature by 2℃ / min, and then calcined at 700℃ for 5h to obtain the catalyst precursor.

[0094] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700℃ for 2.5h in H2 at a flow rate of 30mL / min and a heating rate of 2℃ / min to obtain a catalyst of 5% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni is 5% and the mass fraction of LaAlO3 is 39%.

[0095] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0096] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0097] At 250℃, the CO2 conversion rate was 6.2%; at 300℃, the CO2 conversion rate was 40.7%; and at 350℃, the CO2 conversion rate was 71.8%. At all these temperatures, the CH4 selectivity was 100%.

[0098] Example 7

[0099] 1) Dissolve 0.797g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.700g of Al2O3 and seal for 24h.

[0100] 2) Dry the product overnight at 120°C in a constant temperature drying oven to obtain the dried product;

[0101] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 30% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0102] 4) Dissolve 0.991g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.800g La2O3 / Al2O3 support and seal it for 24h.

[0103] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0104] 6) The dried product was calcined at 350℃ for 2h by increasing the temperature by 2℃ / min, and then calcined at 700℃ for 5h to obtain the catalyst precursor.

[0105] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700℃ for 2.5h in H2 at a flow rate of 30mL / min and a heating rate of 2℃ / min to obtain a catalyst of 20% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 20% and the mass fraction of LaAlO3 was 39%.

[0106] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0107] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0108] At 250℃, the CO2 conversion rate was 10.8%; at 300℃, the CO2 conversion rate was 51.4%; and at 350℃, the CO2 conversion rate was 78.9%. At all these temperatures, the CH4 selectivity was 100%.

[0109] Example 8

[0110] 1) Dissolve 0.797g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.700g of Al2O3 and seal for 24h.

[0111] 2) Dry the product overnight at 100°C in a constant temperature drying oven to obtain the dried product;

[0112] 3) The dried product was heated at 1℃ / min and then calcined at 400℃ for 1h to obtain 30% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0113] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1. Impregnate an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal for 24h.

[0114] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 60°C for 6 hours, and then dry it at 100°C overnight to obtain the dried product.

[0115] 6) The dried product was calcined at 250℃ for 1 h after the temperature was increased by 1℃ / min, and then calcined at 500℃ for 3 h to obtain the catalyst precursor.

[0116] 7) The obtained catalyst precursor was placed in a reactor and reduced at 500°C for 1 h in 1% H2 / He at a flow rate of 10 mL / min and a heating rate of 1 °C / min to obtain the catalyst 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni is 10% and the mass fraction of LaAlO3 is 39%.

[0117] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0118] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0119] At 250℃, the CO2 conversion rate was 10.3%; at 300℃, the CO2 conversion rate was 52.7%; and at 350℃, the CO2 conversion rate was 79.8%. At all these temperatures, the CH4 selectivity was 100%.

[0120] Example 9

[0121] 1) Dissolve 0.797g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.700g of Al2O3 and seal for 48h.

[0122] 2) Dry the product overnight at 150°C in a constant temperature drying oven to obtain the dried product;

[0123] 3) The dried product was heated at 10℃ / min and then calcined at 700℃ for 1h to obtain 30% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0124] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:3. Impregnate an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal for 24h.

[0125] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 90°C for 6 hours, and then dry it overnight at 150°C to obtain the dried product.

[0126] 6) The dried product was heated at 10℃ / min and then calcined at 400℃ for 3 hours, and then heated to 900℃ for 6 hours to obtain the catalyst precursor.

[0127] 7) The obtained catalyst precursor was placed in a reactor and reduced at 800°C for 3 h in 99% H2 / He at a flow rate of 30 mL / min and a heating rate of 10 °C / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 39%.

[0128] 8) Under a pressure of 3 MPa, the contents of the reactor are increased at a volumetric space velocity of 15000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:4.

[0129] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0130] At 250℃, the CO2 conversion rate was 12.5%; at 300℃, the CO2 conversion rate was 57.7%; and at 350℃, the CO2 conversion rate was 75.2%. At all these temperatures, the CH4 selectivity was 100%.

[0131] Example 10

[0132] 1) Dissolve 0.930g of lanthanum nitrate in distilled water to obtain a solution. Immerse an equal volume of the dissolved solution onto 0.650g of Al2O3 and seal for 12 hours.

[0133] 2) Dry the product overnight at 100°C in a constant temperature drying oven to obtain the dried product;

[0134] 3) The dried product was heated at 2℃ / min and then calcined at 550℃ for 4h to obtain 35% La2O3 / Al2O3, with a La2O3 mass fraction of 35%.

[0135] 4) Dissolve 0.495g of nickel nitrate and citric acid in distilled water to obtain a solution, wherein the molar ratio of nickel nitrate to citric acid is 1:1.2. Immerse an equal volume of the dissolved solution onto a 0.900g La2O3 / Al2O3 support and seal it for 24h.

[0136] 5) Place the mixture obtained in step 4) in a constant temperature drying oven at 80°C for 6 hours, and then dry it overnight at 120°C to obtain the dried product.

[0137] 6) The dried product was calcined at 350℃ for 2h by increasing the temperature by 2℃ / min, and then calcined at 700℃ for 5h to obtain the catalyst precursor.

[0138] 7) The obtained catalyst precursor was placed in a reactor and reduced at 700°C for 2.5 h in CO at a flow rate of 30 mL / min with a heating rate of 2 °C / min to obtain a catalyst of 10% Ni-LaAlO3 / Al2O3, wherein the mass fraction of Ni was 10% and the mass fraction of LaAlO3 was 45%.

[0139] 8) Under a pressure of 1 MPa, the contents of the reactor are increased at a volumetric space velocity of 60,000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:1.

[0140] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0141] At 250℃, the CO2 conversion rate was 8.2%; at 300℃, the CO2 conversion rate was 43.5%; and at 350℃, the CO2 conversion rate was 70.2%. At all these temperatures, the CH4 selectivity was 100%.

[0142] Under a pressure of 5 MPa, the contents were introduced into the reactor at a volumetric space velocity of 30000 mL / (g). cat h) A CO2 methanation test was performed by introducing CO2 and hydrogen in a molar ratio of 1:5.

[0143] Under the above conditions, the catalytic performance of the CO2 hydrogenation methanation reaction is as follows:

[0144] At 250℃, the CO2 conversion rate was 13.3%; at 300℃, the CO2 conversion rate was 59.3%; and at 350℃, the CO2 conversion rate was 76.8%. At all these temperatures, the CH4 selectivity was 100%.

[0145] All embodiments involved in this invention exhibit good catalytic performance in CO2 methanation reactions, and after long-term stability testing, the selectivity of the products remains stable without significant deactivation, demonstrating excellent stability and high application value.

[0146] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A LaAlO3-modified supported Ni-based catalyst, characterized in that, The catalyst has a composition of Ni-LaAlO3 / Al2O3, where Ni is the active component of the catalyst, with a mass fraction of 5-20%; LaAlO3 has a perovskite structure, with a mass fraction of 6.5-45%; and the support is Al2O3. The preparation method of the LaAlO3-modified supported Ni-based catalyst includes the following steps: 1) Dissolve lanthanum nitrate in distilled water to obtain a solution, and immerse an equal volume of the dissolved solution on a carrier, then seal and leave for 12-48 hours; 2) Unseal the carrier placed in step 1) and dry it overnight in a constant temperature drying oven at 100-150 °C to obtain the dried product; 3) Calcine the dried product obtained in step 2) at 300-700ºC for 1-6 hours to obtain La2O3 / Al2O3; 4) Dissolve nickel nitrate and citric acid in distilled water to obtain a solution with a nickel nitrate concentration of 0.9–4.2 mol / L and a nickel nitrate to citric acid molar ratio of 1:(1–3). Impregnate an equal volume of the dissolved solution onto the La2O3 / Al2O3 support obtained in step 3) and seal for 12–48 h. 5) Unseal the carrier placed in step 4), place it in a constant temperature drying oven at 60-90℃ for 1-6 hours, and then dry it overnight at 100-150℃ to obtain the dried product; 6) Calcine the dried product obtained in step 5) at 250-400ºC for 1-6 hours, and then continue to calcine at 600-900ºC for 3-10 hours to obtain the catalyst precursor; 7) Place the catalyst precursor obtained in step 6) into a reactor, introduce reducing gas into the reactor, reduce the catalyst precursor to obtain the catalyst Ni-LaAlO3 / Al2O3.

2. The method for preparing the LaAlO3-modified supported Ni-based catalyst of claim 1, characterized in that, Includes the following steps: 1) Dissolve lanthanum nitrate in distilled water to obtain a solution, and immerse an equal volume of the dissolved solution on a carrier, then seal and leave for 12-48 hours; 2) Unseal the carrier placed in step 1) and dry it overnight in a constant temperature drying oven at 100-150 °C to obtain the dried product; 3) Calcine the dried product obtained in step 2) at 300-700ºC for 1-6 hours to obtain La2O3 / Al2O3; 4) Dissolve nickel nitrate and citric acid in distilled water to obtain a solution with a nickel nitrate concentration of 0.9–4.2 mol / L and a nickel nitrate to citric acid molar ratio of 1:(1–3). Impregnate an equal volume of the dissolved solution onto the La2O3 / Al2O3 support obtained in step 3) and seal for 12–48 h. 5) Unseal the carrier placed in step 4), place it in a constant temperature drying oven at 60-90℃ for 1-6 hours, and then dry it overnight at 100-150℃ to obtain the dried product; 6) Calcine the dried product obtained in step 5) at 250-400ºC for 1-6 hours, and then continue to calcine at 600-900ºC for 3-10 hours to obtain the catalyst precursor; 7) Place the catalyst precursor obtained in step 6) into a reactor, introduce reducing gas into the reactor, reduce the catalyst precursor to obtain the catalyst Ni-LaAlO3 / Al2O3.

3. The preparation method according to claim 2, characterized in that, Step 3) The dried product is calcined at 300-700ºC for 1-6 hours, with a heating rate of 1-10℃ / min.

4. The preparation method according to claim 2, characterized in that, Step 6) Calcine the dried product at 250-500ºC for 1-6 hours, and continue to calcine at 500-900ºC for 3-10 hours, with a heating rate of 1-10°C / min.

5. The preparation method according to claim 2, characterized in that, In step 7), a reducing gas flow rate of 10–30 mL / min is introduced, and the reduction time is 1–3 h; the reduction temperature is 500–800 ℃, and the heating rate is 1–10 ℃ / min.

6. The preparation method according to claim 2, characterized in that, The reducing gas is hydrogen, carbon monoxide, or a mixture of an inert gas and one or two of hydrogen and carbon monoxide; the volume percentage of the inert gas in the mixed gas atmosphere is 1%-99%.

7. The LaAlO3-modified supported Ni-based catalyst of claim 1 is applied to the CO2 methanation process.

8. The application as described in claim 7, characterized in that, The catalyst was added to a fixed-bed reactor at a temperature of 200-600℃ and a pressure of 1-5 MPa, with a volume hourly space velocity (VHSV) of 15000-60000 mL / (g). cat h) Introduce carbon dioxide and hydrogen gas, wherein the molar ratio of carbon dioxide to hydrogen gas is 1:(1-5), to obtain the target product methane.

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