Nickel-based catalyst in-situ grown on surface of macroporous alumina, preparation method and application thereof

Abstract

The present application relates to a macroporous alumina surface in-situ growth nickel-based catalyst and its preparation method and application, the crystal form of the catalyst macroporous alumina is gamma-Al2O3, the specific surface area is 150~450m 2 / g, the average pore size of macroporous is 1~40μm;Structural formula is NiMgMAl-LDH / Al2O3;Overcome the existing CO2 methanation and reverse water gas shift catalyst activity is low, poor stability problem, provide a kind of macroporous alumina as carrier, in-situ growth hydrotalcite on surface, after reduction, obtain nickel-based catalyst method;For CO2 methanation reaction and reverse water gas shift reaction shows good activity and stability.CO2 conversion rate can reach 89.5% under high pressure 350℃, CH4 selectivity is 100%;CO2 conversion rate is 62.6% under normal pressure 700℃, CO selectivity can reach 90%;Stability test 200h does not deactivate, have certain industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a nickel-based catalyst grown in situ on the surface of macroporous alumina, its preparation method, and its application in the field of carbon dioxide hydrogenation to methane. Background Technology

[0002] Given the current energy shortage and environmental pollution problems facing my country, CO2 utilization has significant strategic importance and application prospects. CO2 conversion and utilization is an effective way to reduce CO2 emissions and mitigate the greenhouse effect. Among these methods, CO2 hydrogenation to methane has attracted increasing attention due to its high conversion rate and methane selectivity under mild conditions. Electricity generated from renewable energy sources such as solar and wind power can produce "green hydrogen" through water electrolysis. CO2 methanation not only achieves renewable energy fixation but also provides a practical solution for H2 storage and transportation. Furthermore, methane has a high calorific value and is easily and completely combusted, making it a high-quality fuel. As a one-carbon compound, it can also be used to synthesize important chemical raw materials and organic compounds. Similarly, CO produced by the reverse water-gas shift reaction (CO2 + H2 = CO + H2O) can be used to produce various chemicals through Fischer-Tropsch synthesis or other syngas processes, including the synthesis of higher alcohols and carboxylic acids. In summary, CO2 hydrogenation, as a technology that can simultaneously utilize greenhouse gases and store renewable energy, has promising application prospects and research value.

[0003] Among the reported CO2 methanation catalysts, those using Ni as the active metal are considered the most promising due to their excellent catalytic performance and low cost. Among the reported catalysts for reverse water-gas shift reaction, copper-based catalysts exhibit high activity and selectivity; however, the deactivation caused by copper's tendency to sinter at high temperatures limits their further application. Nickel-based catalysts offer higher CO2 conversion rates and slightly better stability than the former, but they are prone to methane production during the reaction.

[0004] The performance of a catalyst is inextricably linked to the properties of its support. Common supports for Ni-based CO2 methanation catalysts include SiO2, Al2O3, ZrO2, TiO2, and CeO2, among which Al2O3 is the most commonly used industrial support due to its high thermal stability and strong wear resistance. However, research has revealed that, on the one hand, metallic Ni particles supported on the Al2O3 surface are prone to sintering during long-term high-temperature reactions; on the other hand, at high temperatures, the interaction between Ni and Al2O3 becomes too strong, forming a difficult-to-reducible NiAl2O4 spinel phase, leading to a decrease in catalyst activity.

[0005] The large pores in macroporous alumina provide excellent mass transfer performance, making it suitable for operation under high space velocity conditions. High-velocity feed gas can improve heat and mass transfer efficiency, especially heat transfer, avoiding heat accumulation and hot spot formation during the reaction process. The micropores formed on the pore walls of macroporous alumina can increase the specific surface area, facilitating the high dispersion of active components. Currently, macroporous alumina has been studied in catalytic cracking and partial oxidation reactions, but its application in carbon dioxide methanation has not yet been reported.

[0006] Additives are commonly used to adjust the structure and performance of catalysts. Additives are mainly classified into two types: (1) electronic additives, used to alter the electron migration rate of the catalyst; and (2) structural additives, which improve the dispersibility and thermal stability of the catalyst by changing its chemical composition, crystal structure, pore structure, dispersion state, and mechanical strength. Currently, the widely studied additives mainly include two systems. One is alkaline additives, represented by alkaline earth metals and rare earth metals, used to improve the alkalinity of the catalyst to enhance its ability to adsorb and activate CO2; the other is additives, represented by transition metals, used to adjust the electronic state of nickel metal to improve the activity of nickel itself.

[0007] MgO, as an additive, can promote CO2 conversion by forming basic sites of varying strengths, improving Ni dispersion, and reducing carbon deposition. For example, Xin et al. prepared a Ni-Mg0.26 / CSC catalyst by co-impregnation of Ni-Mg onto a coconut shell carbon (CSC) support. This catalyst was successfully tested at 450 °C, atmospheric pressure, and a WHSV of 10000 mL / (g). cat Under the conditions of h), the CO2 conversion rate reached 90.1%, which was significantly higher than the CO2 conversion rate of the Ni / CSC catalyst without Mg additive (77.1%) [Li X.,Wang Y.,Zhang G.,et al.Influence of Mg-promoted Ni-based catalyst supported oncoconut shell carbon for CO2 methanation[J].Chemistry Select,2019,4:838–845.].

[0008] The preparation method of the catalyst is also a key factor affecting its structure and performance. Nano-metal catalysts supported on metal oxides prepared by traditional impregnation methods often suffer rapid deactivation due to sintering and aggregation during the reaction process (especially under high-temperature conditions). A key structural feature of hydrotalcite-like materials is the uniform dispersion of divalent and trivalent metal cations on the hydrotalcite layers. If hydrotalcite-like materials are used as catalyst precursors, the desired metal components can be reduced by heating under a reducing atmosphere to obtain metal oxide-supported nano-metal catalysts. The strong interaction between metal nanoparticles and metal oxides can prevent sintering and aggregation of nano-metal particles during use, thereby improving the catalyst's stability. In summary, hydrotalcite-like materials can be considered excellent catalyst precursors for CO2 catalytic conversion. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of low activity and poor stability of existing CO2 methanation and reverse water-gas shift catalysts, and to provide a method for obtaining a nickel-based catalyst by using macroporous alumina as a support, growing a hydrotalcite-like substance in situ on its surface, and reducing it. The obtained catalyst exhibits good activity and stability when used in CO2 methanation and reverse water-gas shift reactions.

[0010] Due to the trivalent metal cation Al commonly used in hydrotalcite-like materials 3+ Inspired by Al species activated on the surface of γ-Al₂O₃, this invention proposes a novel nickel-based catalyst grown in situ on the surface of macroporous alumina. The catalyst possesses a high specific surface area and large pore size, which is beneficial for the high dispersion of active metal Ni. When used in the CO₂ methanation reaction, it exhibits good activity and stability, with a WHSV of 40000 mL / (g) at 550 °C. cat In the 200-h stability test, the catalyst performed well, showing no significant deactivation. By adjusting the reaction conditions, the catalyst also exhibited good reverse water-gas shift performance, with a CO2 conversion rate of 62.6% and a CO selectivity of up to 90% at 700℃. (WHSV = 120000 mL / (g)) cat h) It can maintain a high CO2 conversion rate under test conditions and can adapt to high air speed operation.

[0011] To address the aforementioned objectives, the present invention provides the following technical solution:

[0012] A nickel-based catalyst is grown in situ on the surface of macroporous alumina, wherein the macroporous alumina has a crystal form of γ-Al₂O₃ and a specific surface area of ​​150–450 m². 2 / g, with an average macropore diameter of 1-40 μm; the structural formula is NiMgMAl-LDH / Al2O3; where M is an added additive, including Co, Fe, Zn, Ce or Mo; the catalyst has a molar ratio of Ni:Mg:M = 1:(1-4):(0-1); (Ni+Mg):Al = 1:(0.6-4); NiMgMAl-LDH has a hydrotalcite-like structure, and the reduced catalyst is a supported nickel-based catalyst.

[0013] With an additive M of 0, the catalyst structure is: NiMgAl-LDH / Al2O3.

[0014] Under the condition that the M additive is not 0, the catalyst structure is: NiMgMAl-LDH / Al2O3; wherein the preferred molar ratio is Ni:Mg:M = 1:(1~4):(0.1~1).

[0015] The reduction method of the present invention for preparing the supported nickel-based catalyst by in-situ growth on the macroporous alumina surface includes the following steps:

[0016] 1) Prepare a solution by mixing magnesium nitrate, nickel nitrate, the corresponding metal salt of the auxiliary agent, and urea, according to the molar ratio of nickel nitrate: magnesium nitrate: the corresponding metal salt of the auxiliary agent = 1:(1~4):(0~1); (magnesium nitrate + nickel nitrate + the corresponding metal salt of the auxiliary agent): urea = 1:(2~5);

[0017] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 0.5-2 hours. The molar ratio of (magnesium nitrate + nickel nitrate) to alumina is 1:(0.3-2). Then, place the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 100-150°C for 12-48 hours.

[0018] 3) After the reactor cools to room temperature, the macroporous alumina is removed, ultrasonically washed several times, and then dried in an oven at 60-100℃ overnight to obtain the catalyst precursor;

[0019] 4) Calcine the catalyst precursor obtained in step 3) at 400–700 °C;

[0020] 5) The calcined product obtained in step 4) is reduced at 550–700 °C to obtain a nickel-based catalyst.

[0021] The metal salt corresponding to the auxiliary agent in step 1) is one of cobalt nitrate, ferric nitrate, zinc nitrate, cerium nitrate, or ammonium molybdate.

[0022] The calcination conditions for step 4) are calcination at 400-700℃ for 2-6 hours, with a heating rate of 1-10℃ / min.

[0023] The reduction conditions for step 5) are as follows: the reducing gas flow rate is 10-30 mL / min, the reduction time is 1-3 h, the reduction temperature is 550-700 ℃, and the heating rate is 1-10 ℃ / min.

[0024] The reducing gas in step 5) 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%.

[0025] The nickel-based catalyst grown in situ on the macroporous alumina surface of the present invention can be applied to CO2 methanation reaction or reverse water-gas shift reaction.

[0026] The aforementioned in-situ grown nickel-based catalyst on the macroporous alumina surface is applied to the CO2 methanation reaction; the catalyst is added to a fixed-bed reactor, and under conditions of temperature 250–550℃ and pressure 0.1–5 MPa, it is added to the reactor at a volume hourly space velocity (VHSV) of 5000–120000 mL / (g). cat h) Carbon dioxide and hydrogen are introduced, wherein the molar ratio of carbon dioxide to hydrogen is 1:(1-5), to obtain the target product methane.

[0027] The aforementioned in-situ grown nickel-based catalyst on the macroporous alumina surface is applied to a reverse water-gas shift reaction. The catalyst is added to a fixed-bed reactor at a temperature of 450–750 °C and a pressure of 0.1–5 MPa, with a volume hourly space velocity (VHSV) of 5000–120000 mL / (g). cat h) Carbon dioxide and hydrogen are introduced, wherein the molar ratio of carbon dioxide to hydrogen is 1:(1~5), to obtain the target product carbon monoxide.

[0028] As described above, the in-situ growth of a nickel-based catalyst on the surface of macroporous alumina, its preparation method, and its application, according to the present invention, have the following beneficial effects:

[0029] (1) This invention uses macroporous alumina as a carrier to increase the specific surface area of ​​the catalyst, promote the dispersion of active metals, and provide excellent mass transfer performance, which is suitable for operation under high space velocity conditions and improves the production efficiency of methane and carbon monoxide.

[0030] (2) This invention employs in-situ growth to ensure that NiMgAl-LDHs grow uniformly on the surface of macroporous alumina. Utilizing the uniform dispersion of metal elements in a hydrotalcite-like structure, Ni nanoparticles are uniformly dispersed and loaded onto MgO nanosheets after appropriate calcination and reduction. The MgO nanosheets, in turn, grow uniformly on the support. Through this assembly of structures, the metal nanoparticles are ultimately uniformly loaded onto the support.

[0031] (3) When the catalyst prepared in this invention is applied to the hydrogenation of carbon dioxide, it exhibits good activity and stability. The CO2 conversion rate can reach 89.5% and the CH4 selectivity is 100% under high pressure at 350℃; the CO2 conversion rate is 62.6% and the CO selectivity can reach 90% under normal pressure at 700℃; the stability test shows no deactivation after 200h, which has certain industrialization prospects. Attached Figure Description

[0032] Figure 1 These are SEM images of (a) macroporous Al2O3 support, (b) NiMgAl-LDH / Al2O3, and (c) NiMgAl-LDH / Al2O3 after calcination in Example 1 of this invention.

[0033] Figure 2 These are the XRD patterns of the macroporous Al2O3 support and NiMgAl-LDH / Al2O3 in Example 1 of this invention.

[0034] Figure 3 These are the XRD patterns of the catalysts obtained after reduction in Examples 1-4 of this invention.

[0035] Figure 4 The catalyst prepared in Example 1 of this invention was subjected to atmospheric pressure, 550°C, and a space velocity of 40000 mL / (g) cat The results of the 200-hour stability test under the test conditions of h). Detailed Implementation

[0036] Example 1

[0037] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0038] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0039] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained. (See attached image) Figure 1 (a) is a scanning electron microscope image of the macroporous alumina support, showing that circular windows connect the various spherical pores, forming pores with diameters of 1-40 μm. These interconnected pores facilitate the transport and diffusion of reactants. (See attached image.) Figure 1 (b) is a scanning electron microscope image of a hydrothermally grown in-situ layered double hydroxide (LDH) sample after drying. It can be observed that the surface of the support wall is uniformly covered with sheet-like NiMgAl-LDH. Figure 2 The XRD patterns of macroporous alumina and hydrothermally grown hydrotalcite (LDH) samples after drying are shown. It can be observed that the macroporous alumina is γ-Al2O3. After hydrothermal treatment, a complete hydrotalcite phase is formed on the macroporous γ-Al2O3 support.

[0040] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4 hours, with a heating rate of 1℃ / min. (See attached image) Figure 1 (c) is a scanning electron microscope image of the sample after calcination, which shows that the NiMgAl-LDH nanosheets still maintain a sheet-like structure after calcination.

[0041] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as Ni1Mg3. (Appendix) Figure 3 The XRD pattern of the reduced sample shows that metallic Ni was formed in Ni1Mg3 after reduction.

[0042] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0043] At 250℃, the CO2 conversion rate was 15.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 65.4%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 53.7%, and the CH4 selectivity was 73.6%.

[0044] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 450-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0045] At 450℃, the CO2 conversion rate was 57.9% and the CO selectivity was 6.2%. At 700℃, the CO2 conversion rate was 62.6% and the CO selectivity was 89.9%. At 750℃, the CO2 conversion rate was 66.8% and the CO selectivity was 93.8%.

[0046] 7) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 5000 mL / (g). cath) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0047] At 250℃, the CO2 conversion rate was 15.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 64.7%, and the CH4 selectivity was 99.6%. At 550℃, the CO2 conversion rate was 53.3%, and the CH4 selectivity was 82.4%.

[0048] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 5000 mL / (g) under normal pressure and a temperature of 450-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0049] At 450℃, the CO2 conversion rate was 63.8% and the CO selectivity was 4.3%. At 700℃, the CO2 conversion rate was 62.9% and the CO selectivity was 81.4%. At 750℃, the CO2 conversion rate was 67.7% and the CO selectivity was 90.3%.

[0050] 8) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 120,000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0051] At 250℃, the CO2 conversion rate was 10.3%, and the CH4 selectivity was 95.8%. At 300℃, the CO2 conversion rate was 45.6%, and the CH4 selectivity was 92.0%. At 550℃, the CO2 conversion rate was 47.8%, and the CH4 selectivity was 71.3%.

[0052] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at atmospheric pressure and a temperature of 450-750 °C at a volume hourly space velocity (VHSV) of 120,000 mL / (g). cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0053] At 450℃, the CO2 conversion rate was 55.8%, and the CO selectivity was 11.4%. At 700℃, the CO2 conversion rate was 51.5%, and the CO selectivity was 84.9%. At 750℃, the CO2 conversion rate was 54.2%, and the CO selectivity was 94.8%.

[0054] 9) At 550℃, the volumetric hourly space velocity is 40000 mL / (g). cat Under the test conditions (h), a 200-hour stability test was conducted, and the test results are attached. Figure 4As shown, the activity and stability remained stable within 200 hours, without any decreasing trend.

[0055] Example 2

[0056] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:1:6;

[0057] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0058] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0059] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0060] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2°C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as Ni1Mg1. (Appendix) Figure 3 The XRD pattern of the reduced sample shows that metallic Ni was formed in Ni1Mg1 after reduction.

[0061] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0062] At 250℃, the CO2 conversion rate was 10.3%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.8%, and the CH4 selectivity was 99.6%. At 550℃, the CO2 conversion rate was 54.2%, and the CH4 selectivity was 73.9%.

[0063] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0064] At 550℃, the CO2 conversion rate was 54.2%, and the CO selectivity was 26.1%. At 700℃, the CO2 conversion rate was 62.9%, and the CO selectivity was 88.7%. At 750℃, the CO2 conversion rate was 65.8%, and the CO selectivity was 93.7%.

[0065] Example 3

[0066] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:2:9;

[0067] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 150°C for 48 hours.

[0068] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0069] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 3h, with a heating rate of 1℃ / min.

[0070] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as Ni1Mg2. (Appendix) Figure 3 The XRD pattern of the reduced sample shows that metallic Ni was formed in Ni1Mg2 after reduction.

[0071] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0072] At 250℃, the CO2 conversion rate was 12.8%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.0%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 53.5%, and the CH4 selectivity was 74.2%.

[0073] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cath) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0074] At 550℃, the CO2 conversion rate was 53.5%, and the CO selectivity was 25.8%. At 700℃, the CO2 conversion rate was 60.3%, and the CO selectivity was 89.5%. At 750℃, the CO2 conversion rate was 64.6%, and the CO selectivity was 95.1%.

[0075] Example 4

[0076] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:4:15;

[0077] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 150°C for 48 hours.

[0078] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0079] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0080] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as Ni1Mg4. Figure 3 The XRD pattern of the reduced sample shows that metallic Ni was formed in Ni1Mg4 after reduction.

[0081] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0082] At 250℃, the CO2 conversion rate was 8.3%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.1%, and the CH4 selectivity was 99.6%. At 550℃, the CO2 conversion rate was 55.8%, and the CH4 selectivity was 75.2%.

[0083] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0084] At 550℃, the CO2 conversion rate was 55.8%, and the CO selectivity was 26.8%. At 700℃, the CO2 conversion rate was 64.6%, and the CO selectivity was 88.8%. At 750℃, the CO2 conversion rate was 68.2%, and the CO selectivity was 94.7%.

[0085] Example 5

[0086] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0087] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 2 hours. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.3. Then, put the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0088] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in an 80°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0089] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0090] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as NiMgAl. 0.3 .

[0091] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0092] At 250℃, the CO2 conversion rate was 12.2%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 52.3%, and the CH4 selectivity was 98.8%. At 550℃, the CO2 conversion rate was 50.6%, and the CH4 selectivity was 71.2%.

[0093] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0094] At 550℃, the CO2 conversion rate was 50.6% and the CO selectivity was 28.8%. At 700℃, the CO2 conversion rate was 48.3% and the CO selectivity was 90.2%. At 750℃, the CO2 conversion rate was 52.4% and the CO selectivity was 96.2%.

[0095] Example 6

[0096] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0097] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 2 hours. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:1. Then, put the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0098] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in an 80°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0099] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0100] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as NiMgAl. 1.0 .

[0101] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0102] At 250℃, the CO2 conversion rate was 4.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 57.4%, and the CH4 selectivity was 99.6%. At 550℃, the CO2 conversion rate was 49.8%, and the CH4 selectivity was 84.2%.

[0103] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0104] At 550℃, the CO2 conversion rate was 49.8%, and the CO selectivity was 25.8%. At 700℃, the CO2 conversion rate was 56.3%, and the CO selectivity was 76.5%. At 750℃, the CO2 conversion rate was 60.3%, and the CO selectivity was 87.2%.

[0105] Example 7

[0106] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0107] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 2 hours. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:1.2. Then, put the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0108] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in an 80°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0109] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0110] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as NiMgAl. 1.2 .

[0111] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0112] At 250℃, the CO2 conversion rate was 4.2%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 57.0%, and the CH4 selectivity was 99.5%. At 550℃, the CO2 conversion rate was 49.6%, and the CH4 selectivity was 73.1%.

[0113] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0114] At 550℃, the CO2 conversion rate was 49.6% and the CO selectivity was 26.9%. At 700℃, the CO2 conversion rate was 60.5% and the CO selectivity was 90.6%. At 750℃, the CO2 conversion rate was 64.8% and the CO selectivity was 95.8%.

[0115] Example 8

[0116] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0117] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:2. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0118] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0119] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0120] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3, labeled as NiMgAl2.

[0121] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0122] At 250℃, the CO2 conversion rate was 3.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 53.2%, and the CH4 selectivity was 97.2%. At 550℃, the CO2 conversion rate was 50.5%, and the CH4 selectivity was 73.8%.

[0123] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0124] At 550℃, the CO2 conversion rate was 50.5%, and the CO selectivity was 26.2%. At 700℃, the CO2 conversion rate was 61.8%, and the CO selectivity was 81.2%. At 750℃, the CO2 conversion rate was 65.9%, and the CO selectivity was 92.3%.

[0125] Example 9

[0126] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0127] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0128] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0129] 4) Calcine NiMgAl-LDH / Al2O3 at 500℃ for 4h, with a heating rate of 1℃ / min.

[0130] 5) The calcined product obtained in step 4) was reduced in 5% H2 / Ar at a flow rate of 30 mL / min at 650 °C for 4 h at a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-500C.

[0131] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0132] At 250℃, the CO2 conversion rate was 12.4%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.4%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 51.7%, and the CH4 selectivity was 74.5%.

[0133] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0134] At 550℃, the CO2 conversion rate was 51.7% and the CO selectivity was 25.5%. At 700℃, the CO2 conversion rate was 61.0% and the CO selectivity was 90.0%. At 750℃, the CO2 conversion rate was 65.5% and the CO selectivity was 95.1%.

[0135] Example 10

[0136] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0137] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0138] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0139] 4) Calcine NiMgAl-LDH / Al2O3 at 600℃ for 4h, with a heating rate of 1℃ / min.

[0140] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-600C.

[0141] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0142] At 250℃, the CO2 conversion rate was 9.4%, and the CH4 selectivity was 99.8%. At 350℃, the CO2 conversion rate was 62.0%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 50.8%, and the CH4 selectivity was 73.6%.

[0143] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0144] At 550℃, the CO2 conversion rate was 50.8% and the CO selectivity was 26.4%. At 700℃, the CO2 conversion rate was 59.9% and the CO selectivity was 90.2%. At 750℃, the CO2 conversion rate was 64.7% and the CO selectivity was 95.8%.

[0145] Example 11

[0146] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0147] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0148] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0149] 4) Calcine NiMgAl-LDH / Al2O3 at 700℃ for 4h, with a heating rate of 1℃ / min.

[0150] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-700C.

[0151] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0152] At 250℃, the CO2 conversion rate was 6.8%, and the CH4 selectivity was 99.1%. At 350℃, the CO2 conversion rate was 58.7%, and the CH4 selectivity was 98.9%. At 550℃, the CO2 conversion rate was 49.9%, and the CH4 selectivity was 67.2%.

[0153] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0154] At 550℃, the CO2 conversion rate was 50.1% and the CO selectivity was 32.8%. At 700℃, the CO2 conversion rate was 59.5% and the CO selectivity was 90.1%. At 750℃, the CO2 conversion rate was 64.7% and the CO selectivity was 96.2%.

[0155] Example 12

[0156] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0157] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0158] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0159] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0160] 5) The calcined product obtained in step 4) was reduced in 5% H2 / Ar at a flow rate of 30 mL / min at 550 °C for 4 h at a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-550R.

[0161] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0162] At 250℃, the CO2 conversion rate was 7.8%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.7%, and the CH4 selectivity was 99.5%. At 550℃, the CO2 conversion rate was 55.7%, and the CH4 selectivity was 73.6%.

[0163] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0164] At 550℃, the CO2 conversion rate was 55.7% and the CO selectivity was 26.4%. At 700℃, the CO2 conversion rate was 61.7% and the CO selectivity was 89.8%. At 750℃, the CO2 conversion rate was 66.2% and the CO selectivity was 95.1%.

[0165] Example 13

[0166] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0167] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0168] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0169] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0170] 5) The calcined product obtained in step 4) was reduced at 600℃ for 4h in 5% H2 / Ar at a flow rate of 30mL / min and a heating rate of 2℃ / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-600R.

[0171] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0172] At 250℃, the CO2 conversion rate was 13.8%, and the CH4 selectivity was 99.4%. At 350℃, the CO2 conversion rate was 64.4%, and the CH4 selectivity was 99.1%. At 550℃, the CO2 conversion rate was 52.3%, and the CH4 selectivity was 74.1%.

[0173] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0174] At 550℃, the CO2 conversion rate was 52.3%, and the CO selectivity was 25.9%. At 700℃, the CO2 conversion rate was 61.6%, and the CO selectivity was 90.6%. At 750℃, the CO2 conversion rate was 66.8%, and the CO selectivity was 95.9%.

[0175] Example 14

[0176] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:12;

[0177] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 120°C for 24 hours.

[0178] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0179] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0180] 5) The calcined product obtained in step 4) was reduced at 700°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3-700R.

[0181] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0182] At 250℃, the CO2 conversion rate was 7.1%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 63.5%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 52.6%, and the CH4 selectivity was 73.6%.

[0183] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0184] At 550℃, the CO2 conversion rate was 52.6% and the CO selectivity was 26.4%. At 700℃, the CO2 conversion rate was 62.0% and the CO selectivity was 90.8%. At 750℃, the CO2 conversion rate was 67.4% and the CO selectivity was 96.2%.

[0185] Example 15

[0186] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:8;

[0187] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 0.5 h. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 100°C for 12 h.

[0188] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in an 80°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0189] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 2h, with a heating rate of 2℃ / min.

[0190] 5) The calcined product obtained in step 4) was reduced in CO at a flow rate of 10 mL / min at 650 °C for 1 h at a heating rate of 1 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3.

[0191] 6) Add 60 mg of catalyst to the reactor and, under conditions of 3 MPa and a temperature of 250-350 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 1:1.

[0192] At 250℃, the CO2 conversion rate was 10.7%, and the CH4 selectivity was 100%. At 300℃, the CO2 conversion rate was 58.3%, and the CH4 selectivity was 99.7%. At 350℃, the CO2 conversion rate was 61.7%, and the CH4 selectivity was 99.6%.

[0193] 60 mg of catalyst was added to the reactor, and the reactor was subjected to a volume hourly space velocity (VHSV) of 40,000 mL / (g) at a pressure of 3 MPa and a temperature of 550-700 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 1:1 to conduct a reverse water-gas conversion activity test.

[0194] At 550℃, the CO2 conversion rate was 62.3% and the CO selectivity was 28.5%. At 700℃, the CO2 conversion rate was 60.3% and the CO selectivity was 90.8%. At 750℃, the CO2 conversion rate was 67.4% and the CO selectivity was 96.2%.

[0195] Example 16

[0196] 1) Prepare a solution of magnesium nitrate, nickel nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: urea = 1:3:20;

[0197] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 2 hours. The molar ratio is (magnesium nitrate + nickel nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reactor and seal it. Place the hydrothermal reactor into an oven and hydrothermally heat it at 150°C for 48 hours.

[0198] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 100°C oven. NiMgAl-LDH / Al2O3 was obtained.

[0199] 4) Calcine NiMgAl-LDH / Al2O3 at 400℃ for 6 hours, with a heating rate of 10℃ / min.

[0200] 5) The calcined product obtained in step 4) was reduced in H2 at a flow rate of 20 mL / min at 650 °C for 3 h at a heating rate of 10 °C / min to obtain the nickel-based catalyst Ni-MgO / Al2O3.

[0201] 6) Add 60 mg of catalyst to the reactor and, under conditions of 5 MPa and a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 15000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 1:2.

[0202] At 250℃, the CO2 conversion rate was 40.2%, and the CH4 selectivity was 100%. At 300℃, the CO2 conversion rate was 81.3%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 89.5%, and the CH4 selectivity was 100%.

[0203] 60 mg of catalyst was added to the reactor, and the reactor was subjected to a volume hourly space velocity (VHSV) of 40,000 mL / (g) at a pressure of 5 MPa and a temperature of 550-700 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 1:5 to conduct a reverse water-gas conversion activity test.

[0204] At 550℃, the CO2 conversion rate was 78.3% and the CO selectivity was 3.2%. At 700℃, the CO2 conversion rate was 64.2% and the CO selectivity was 81.2%. At 750℃, the CO2 conversion rate was 65.4% and the CO selectivity was 84.2%.

[0205] Example 17

[0206] 1) Prepare a solution of magnesium nitrate, nickel nitrate, cobalt nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: cobalt nitrate: urea = 1:3:0.33:12.6;

[0207] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + cobalt nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0208] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgCoAl-LDH / Al2O3 was obtained.

[0209] 4) Calcine NiMgCoAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0210] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst NiCo-MgO / Al2O3.

[0211] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0212] At 250℃, the CO2 conversion rate was 16.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 64.4%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 52.2%, and the CH4 selectivity was 77.1%.

[0213] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0214] At 550℃, the CO2 conversion rate was 52.2%, and the CO selectivity was 22.9%. At 700℃, the CO2 conversion rate was 62.4%, and the CO selectivity was 86.9%. At 750℃, the CO2 conversion rate was 65.4%, and the CO selectivity was 92.5%.

[0215] Example 18

[0216] 1) Prepare a solution of magnesium nitrate, nickel nitrate, ferric nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: ferric nitrate: urea = 1:3:0.33:12.6;

[0217] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + ferric nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0218] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgFeAl-LDH / Al2O3 was obtained.

[0219] 4) Calcine NiMgFeAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0220] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst NiFe-MgO / Al2O3.

[0221] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0222] At 250℃, the CO2 conversion rate was 13.7%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 61.9%, and the CH4 selectivity was 99.6%. At 550℃, the CO2 conversion rate was 52.8%, and the CH4 selectivity was 78.3%.

[0223] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0224] At 550℃, the CO2 conversion rate was 52.8%, and the CO selectivity was 21.7%. At 700℃, the CO2 conversion rate was 58.7%, and the CO selectivity was 82.1%. At 750℃, the CO2 conversion rate was 65.8%, and the CO selectivity was 89.7%.

[0225] Example 19

[0226] 1) Prepare a solution of magnesium nitrate, nickel nitrate, zinc nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: zinc nitrate: urea = 1:3:0.33:12.6;

[0227] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + zinc nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0228] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgZnAl-LDH / Al2O3 was obtained.

[0229] 4) Calcine NiMgZnAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0230] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO-ZnO / Al2O3.

[0231] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0232] At 250℃, the CO2 conversion rate was 4.1%, and the CH4 selectivity was 70.9%. At 350℃, the CO2 conversion rate was 52.1%, and the CH4 selectivity was 96.9%. At 550℃, the CO2 conversion rate was 52.9%, and the CH4 selectivity was 76.7%.

[0233] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0234] At 550℃, the CO2 conversion rate was 52.9% and the CO selectivity was 23.3%. At 700℃, the CO2 conversion rate was 61.5% and the CO selectivity was 87.9%. At 750℃, the CO2 conversion rate was 66.4% and the CO selectivity was 93.8%.

[0235] Example 20

[0236] 1) Prepare a solution of magnesium nitrate, nickel nitrate, ammonium molybdate and urea in a molar ratio of nickel nitrate: magnesium nitrate: ammonium molybdate: urea = 1:3:0.2:12.6;

[0237] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + ammonium molybdate: alumina = 1:0.5). Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0238] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgMoAl-LDH / Al2O3 was obtained.

[0239] 4) Calcine NiMgMoAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0240] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO-MoO3 / Al2O3.

[0241] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0242] At 250℃, the CO2 conversion rate was 14.2%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 61.7%, and the CH4 selectivity was 99.5%. At 550℃, the CO2 conversion rate was 53.4%, and the CH4 selectivity was 70.6%.

[0243] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0244] At 550℃, the CO2 conversion rate was 53.4%, and the CO selectivity was 29.4%. At 700℃, the CO2 conversion rate was 62.2%, and the CO selectivity was 90.2%. At 750℃, the CO2 conversion rate was 65.8%, and the CO selectivity was 95.3%.

[0245] Example 21

[0246] 1) Prepare a solution of magnesium nitrate, nickel nitrate, cerium nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: cerium nitrate: urea = 1:3:0.33:12.6;

[0247] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + cerium nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0248] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgCeAl-LDH / Al2O3 was obtained.

[0249] 4) Calcine NiMgCeAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0250] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO-CeO2 / Al2O3.

[0251] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0252] At 250℃, the CO2 conversion rate was 18.8%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 68.5%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 57.4%, and the CH4 selectivity was 73.5%.

[0253] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0254] At 550℃, the CO2 conversion rate was 57.4%, and the CO selectivity was 26.5%. At 700℃, the CO2 conversion rate was 61.8%, and the CO selectivity was 88.4%. At 750℃, the CO2 conversion rate was 66.2%, and the CO selectivity was 94.2%.

[0255] Example 22

[0256] 1) Prepare a solution of magnesium nitrate, nickel nitrate, cerium nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: cerium nitrate: urea = 1:3:0.1:12.3;

[0257] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + cerium nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0258] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgCeAl-LDH / Al2O3 was obtained.

[0259] 4) Calcine NiMgCeAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0260] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO-CeO2 / Al2O3.

[0261] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0262] At 250℃, the CO2 conversion rate was 16.2%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 64.3%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 55.9%, and the CH4 selectivity was 72.6%.

[0263] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0264] At 550℃, the CO2 conversion rate was 55.9%, and the CO selectivity was 27.4%. At 700℃, the CO2 conversion rate was 60.3%, and the CO selectivity was 89.2%. At 750℃, the CO2 conversion rate was 65.0%, and the CO selectivity was 95.1%.

[0265] Example 23

[0266] 1) Prepare a solution of magnesium nitrate, nickel nitrate, cerium nitrate and urea in a molar ratio of nickel nitrate: magnesium nitrate: cerium nitrate: urea = 1:3:1:15;

[0267] 2) Place the macroporous alumina carrier in the solution and impregnate it under vacuum for 1 hour. The molar ratio is (magnesium nitrate + nickel nitrate + cerium nitrate): alumina = 1:0.5. Then, put the impregnated macroporous alumina and the remaining solution into the reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 120°C for 24 hours.

[0268] 3) After the reactor cooled to room temperature, the macroporous alumina was removed, ultrasonically washed several times, and then dried overnight in a 60°C oven. NiMgCeAl-LDH / Al2O3 was obtained.

[0269] 4) Calcine NiMgCeAl-LDH / Al2O3 at 400℃ for 4h, with a heating rate of 1℃ / min.

[0270] 5) The calcined product obtained in step 4) was reduced at 650°C for 4 h in 5% H2 / Ar at a flow rate of 30 mL / min and a heating rate of 2 °C / min to obtain the nickel-based catalyst Ni-MgO-CeO2 / Al2O3.

[0271] 6) Add 60 mg of catalyst to the reactor and, under normal pressure and at a temperature of 250-550 °C, introduce it into the reactor at a volume hourly space velocity (VHSV) of 40000 mL / (g). cat h) A CO2 methanation test was conducted by introducing carbon dioxide and hydrogen in a molar ratio of 3:1.

[0272] At 250℃, the CO2 conversion rate was 11.8%, and the CH4 selectivity was 100%. At 350℃, the CO2 conversion rate was 59.7%, and the CH4 selectivity was 99.7%. At 550℃, the CO2 conversion rate was 52.4%, and the CH4 selectivity was 73.9%.

[0273] 60 mg of catalyst was added to the reactor, and the mixture was introduced into the reactor at a volume hourly space velocity (VHSV) of 40,000 mL / (g) under normal pressure and a temperature of 550-750 °C. cat h) Introduce carbon dioxide and hydrogen in a molar ratio of 3:1 to conduct a reverse water-gas conversion activity test.

[0274] At 550℃, the CO2 conversion rate was 52.4%, and the CO selectivity was 26.1%. At 700℃, the CO2 conversion rate was 57.2%, and the CO selectivity was 90.1%. At 750℃, the CO2 conversion rate was 63.8%, and the CO selectivity was 95.8%.

[0275] All embodiments involved in this invention exhibit good catalytic performance in CO2 methanation reaction, and after long-term stability testing, the selectivity of the product remains stable without significant deactivation, demonstrating excellent stability. By adjusting the reaction conditions, the embodiments exhibit excellent catalytic performance in reverse water-gas shift reaction, maintaining a high CO2 conversion rate at high temperature with a CO selectivity >90%, which has high application value.

[0276] 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 nickel-based catalyst grown in situ on the surface of macroporous alumina for use in CO2 methanation or reverse water-gas shift reaction, characterized in that, The macroporous alumina has a crystal form of γ-Al₂O₃ and a specific surface area of ​​150–450 m². 2 / g, with an average macropore diameter of 1–40 μm; the catalyst has the structural formula NiMgMAl-LDH / Al2O3; where M is an added auxiliary agent, including Co, Fe, Zn, Ce, or Mo; the catalyst has a molar ratio of Ni:Mg:M = 1:(1–4):(0–1), where M is not 0; (Ni+Mg):Al = 1:(0.6–4); NiMgMAl-LDH has a hydrotalcite-like structure, which is reduced to obtain a supported nickel-based catalyst; in the catalyst, Ni nanoparticles are uniformly dispersed and supported on MgO nanosheets, and the MgO nanosheets are uniformly grown on the support; the catalyst preparation method includes the following steps: 1) Prepare a solution by mixing magnesium nitrate, nickel nitrate, the corresponding metal salt of the auxiliary agent, and urea, with the molar ratio of nickel nitrate: magnesium nitrate: the corresponding metal salt of the auxiliary agent = 1: (1~4): (0~1), and the molar ratio of the corresponding metal salt of the auxiliary agent is not 0; (magnesium nitrate + nickel nitrate + the corresponding metal salt of the auxiliary agent): urea = 1: (2~5); 2) Place the macroporous alumina support in the solution and impregnate it under vacuum for 0.5–2 h, according to the molar ratio (magnesium nitrate + nickel nitrate): alumina = 1: (0.3–2). Then, put the impregnated macroporous alumina and the remaining solution into a reaction vessel and seal it. Place the hydrothermal reaction vessel into an oven and hydrothermally heat it at 100–150 °C for 12–48 h. 3) After the reactor cools to room temperature, the macroporous alumina is removed, ultrasonically washed several times, and then dried in an oven at 60-100℃ overnight to obtain the catalyst precursor; 4) Calcine the catalyst precursor obtained in step 3) at 400–700 °C; 5) The calcined product obtained in step 4) is reduced at 550–700 °C to obtain a nickel-based catalyst.

2. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 1, applied to CO2 methanation reaction or reverse water-gas shift reaction, is characterized in that: Step 1) The metal salt corresponding to the auxiliary agent is one of cobalt nitrate, ferric nitrate, zinc nitrate, cerium nitrate, or ammonium molybdate.

3. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 1, applied to CO2 methanation reaction or reverse water-gas shift reaction, is characterized in that: Step 4) The calcination conditions are 400-700℃ for 2-6 hours, and the heating rate is 1-10℃ / min.

4. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 1, applied to CO2 methanation reaction or reverse water-gas shift reaction, characterized in that: Step 5) The reduction conditions are as follows: the reducing gas flow rate is 10-30 mL / min, the reduction time is 1-3 h, the reduction temperature is 550-700 ℃, and the heating rate is 1-10 ℃ / min.

5. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 4, applied to CO2 methanation reaction or reverse water-gas shift reaction, characterized in that: Step 5) 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% to 99%.

6. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 1, applied to the CO2 methanation reaction, is characterized in that... The catalyst was added to a fixed-bed reactor at a temperature of 250–550 °C and a pressure of 0.1–5 MPa, with a volume hourly space velocity (VHSV) of 5000–120000 mL / (g). cat h) Carbon dioxide and hydrogen are introduced, wherein the molar ratio of carbon dioxide to hydrogen is 1:(1-5), to obtain the target product methane.

7. The in-situ grown nickel-based catalyst on the macroporous alumina surface as described in claim 1 is applied to the reverse water-gas shift reaction, characterized in that... The catalyst was added to a fixed-bed reactor at a temperature of 450–750 °C and a pressure of 0.1–5 MPa, with a volume hourly space velocity (VHSV) of 5000–120000 mL / (g). cat h) Carbon dioxide and hydrogen are introduced, wherein the molar ratio of carbon dioxide to hydrogen is 1:(1-5), to obtain the target product carbon monoxide.

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