Methanation catalyst suitable for high carbon dioxide concentration, method of preparation and use

Abstract

The application discloses a methane catalyst suitable for high-concentration carbon dioxide, which comprises the following components in percentage by mass: a carrier 12-85%, a carrier modifier 1-75wt%, an active component NiO 10-50wt%, and an auxiliary agent 1-5wt%, and the sum of the mass percentages of the above components is 100%. The application further provides a preparation method and application of the methane catalyst suitable for high-concentration carbon dioxide. The application provides a method suitable for high-concentration carbon dioxide methane, a series of carbon dioxide methane catalysts and a catalyst loading method with simple structure, high reaction efficiency, slow bed layer temperature rise, low hotspot temperature and avoidance of local high-temperature zones, so as to solve the problems of catalyst sintering deactivation, low hydrothermal stability, short catalyst service life and poor device operation safety.

Description

Technical Field

[0001] This invention belongs to the field of chemical waste gas resource utilization technology, and relates to methanation catalysts suitable for high concentrations of carbon dioxide, as well as the preparation method and application of the above-mentioned methanation catalysts suitable for high concentrations of carbon dioxide. Background Technology With the increasing depletion of non-renewable energy sources and rising concentrations of greenhouse gases in the atmosphere, converting carbon dioxide into high-value-added chemical products has become a research hotspot both domestically and internationally. Among these methods, the synthesis of methane via carbon dioxide hydrogenation can not only reduce atmospheric carbon dioxide concentration but also produce methane that can be used as fuel, thus alleviating energy problems to some extent. Therefore, developing an efficient carbon dioxide methanation technology has significant practical implications. The reaction formula is as follows: CO2(g)+4H2(g)→CH4(g)+2H2O(g) △Hθ 298K=-165kJ / mol, △Gθ 298K=-113kJ / mol Most common methanation catalysts use transition metals such as nickel, ruthenium, rhodium, and palladium as active components, supported on oxide supports such as alumina, zirconium oxide, and silicon oxide. Among these, catalysts made from noble metals like ruthenium, rhodium, and palladium exhibit strong catalytic activity, but their high cost limits their large-scale industrial application. In contrast, catalysts with nickel as the active phase show better application prospects. Ni / Al₂O₃ is the most commonly used catalyst for carbon dioxide methanation, offering advantages such as high activity and low cost. However, due to the water produced during carbon dioxide methanation, nickel-based catalysts are prone to sintering during the reaction, easily forming carbon deposits at high temperatures, exhibiting poor hydrothermal stability, and unable to operate stably for extended periods. Furthermore, their poor low-temperature reactivity leads to high energy consumption.

[0002] Furthermore, methanation is a strongly exothermic reaction, and the thermal conductivity of the catalyst affects the heat transfer efficiency of the entire system, especially when using a heat-transfer reactor. Besides considering the reaction process, the catalyst's structural design and material selection significantly impact the system's heat transfer efficiency. To reduce equipment investment, heat-transfer reactors generally operate at temperatures lower than adiabatic reactors. Therefore, developing low-temperature, highly active methanation catalysts is of great significance.

[0003] Meanwhile, in multi-stage or multi-stage methanation processes, as the methanation reaction continues, the high levels of CH4 and CO2 as products in the final 1-2 stages inhibit the methanation reaction to some extent. Simultaneously, side reactions such as reverse water-gas shift reaction occur, further limiting the conversion of H2 and CO into CH4 and CO2. Therefore, the catalyst used in these final 1-2 stages of methanation requires high methanation catalytic activity, low reverse water-gas shift reaction activity, and high catalytic activity stability. However, most existing methanation catalysts do not meet these requirements.

[0004] From a thermodynamic perspective, lowering the methanation operating temperature favors the forward equilibrium of the reaction. Theoretical calculations show that when the inlet CO+CO2 content is below 20%, the CO / CO2 equilibrium conversion rate is ≥99% within the operating temperature range of ≤320℃ and operating pressure of 2.5-4.5MPa. Therefore, by employing an effective temperature-controlled reactor to keep the bed outlet temperature below 320℃, only a single reactor is needed to achieve efficient CO / CO2 conversion, reducing equipment investment and operating energy consumption.

[0005] In response, Chinese invention patent CN110237778A, filed on May 28, 2019, entitled "An Isothermal Reactor with Convenient Catalyst Replacement and its Process Method," discloses an isothermal reactor with convenient catalyst replacement and its process method. Its characteristic is that the reactor adopts a concentric circle design, the catalyst is filled in an annular screen, the entire screen is filled into the concentric circle reactor, and the catalyst is disassembled as a whole. The patent focuses on the structural features of the reactor. Another Chinese invention patent, filed on June 22, 2021, with publication number CN110237778A, discloses an isothermal reactor with convenient catalyst replacement and its process method. Chinese invention patent 113289663A, entitled "Methanation Catalyst Preparation Method for Isothermal Fixed Bed", discloses a method for preparing a methanation catalyst for isothermal fixed bed, which uses silicon nitride and alumina to prepare a mesoporous support. Chinese invention patent CN204247177U, entitled "An Adiabatic-Isothermal Methanation Reactor", with an application date of 2014-11-24, discloses an adiabatic-isothermal methanation reactor, which is provided with an adiabatic section and an isothermal section, and the isothermal section is a tubular structure.

[0006] The starting point for the catalysts developed in the above patents is to improve the activity of the catalyst. However, the intrinsic rate of CO2 methanation reaction is very fast. In industrial adiabatic fixed-bed reactors, hot spots appear at 1 / 5 to 1 / 8 of the bed position. After the hot spots, the temperature of the catalyst bed decreases, making it easy for local high-temperature zones to appear in the methanation catalyst bed. The catalyst is prone to sintering, and the reaction performance of the catalyst on the back side is not reflected.

[0007] In actual operation, improper temperature control within the methanation reactor can easily lead to bed overheating, burning through reactor components, and catalyst deactivation due to high-temperature sintering. Therefore, to ensure the methanation reaction proceeds smoothly within the reactor and the generated heat is effectively removed to achieve uniform bed temperature control, it is necessary to study the use and loading methods of the methanation catalyst from a kinetic perspective. Summary of the Invention

[0008] The first objective of this invention is to provide a methanation catalyst suitable for high concentrations of carbon dioxide, and to provide a series of carbon dioxide methanation catalysts and their loading methods, which have the characteristics of simple structure, high reaction efficiency, mild bed heating and low hot spot temperature, thereby avoiding the generation of local high temperature and solving problems such as catalyst sintering deactivation, low hydrothermal stability, short catalyst life and poor equipment operation safety.

[0009] A second objective of this invention is to provide a method for preparing the above-mentioned methanation catalyst suitable for high concentrations of carbon dioxide.

[0010] A third objective of this invention is to provide the application of the above-mentioned methanation catalyst suitable for high concentrations of carbon dioxide.

[0011] The first technical solution adopted in this invention is a methanation catalyst suitable for high concentrations of carbon dioxide, comprising the following components by mass percentage: 12%~85% support, 1~75wt% support modifier, 10~50wt% active component NiO, and 1~5wt% additive, with the sum of the mass percentages of the above components being 100%.

[0012] The invention is further characterized in that, The support consists of Al2O3 and ZrO2, with a mass ratio of Al2O3 to ZrO2 of 0.67-35:1; The carrier modifiers are nitrogen-doped mesoporous carbon and silicon carbide, with a mass ratio of 1:0.3-3. The nitrogen content in the nitrogen-doped mesoporous carbon is 1.5-12%, and the specific surface area is 800-1200 m². 2 / g, with an average pore size of 4~8.1nm; The additives include CeO2, MnO2 and MgO, with the mass ratio of CeO2 to MnO2 being 1 to 5:1 and the mass ratio of MnO2 to MgO being 1:1 to 1.05.

[0013] The second technical solution adopted in this invention is a method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps of which are as follows: S1. The carrier modifier is stirred at 600 rpm and ultrasonically dispersed in the salt solution to form a suspension, and the suspension is heated to 50~80℃. S2. Dissolve the weighed Al, Zr, Ce, Ni, and Mn salts in deionized water to form a first precursor salt solution. Heat the first precursor salt solution and the precipitant solution to 50-80°C and add them dropwise to the heated suspension for the first precipitation. Maintain the pH of the solution at 7-8 and continue stirring to form a mixed solution. S3. Continue to add the second precursor salt solution (magnesium nitrate solution) to the mixture, add precipitant, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 1-2 hours to obtain the precipitate. S4. After precipitation, the entire solution is hydrothermally aged at 110~150℃ for 2~3 hours, and then the precipitate is filtered out. S5. After hydrothermal aging, the precipitate is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 50~500μS / cm. Then, it is dried and calcined at 300~600℃ for 4~12h in a nitrogen atmosphere to obtain a methanation catalyst suitable for high concentrations of carbon dioxide. By mass percentage, it includes the following components: support 12%~85%, support modifier 1~75wt%, active component NiO 10~50wt%, and auxiliary agent 1~5wt%. The sum of the mass percentages of the above components is 100%.

[0014] The invention is further characterized in that, The ultrasonic frequency in S1 is 40~80kHz and the power is 200~800kW. The salt solution is a nitrate solution or a sulfate solution; the mass concentration of the salt solution is 0.5-5%, and the solid-liquid weight ratio of the suspension is 1:20-50.

[0015] The molar ratio of the first precursor salt solution to the precipitant in S2 is 0.1~1.1:1. The precursor salt solution is composed of nickel nitrate, manganese nitrate, cerium nitrate, aluminum nitrate, and zirconium nitrate. The precipitant solution is any one of sodium carbonate, potassium carbonate, sodium bicarbonate, or potassium bicarbonate.

[0016] The third technical solution adopted in this invention is a methanation catalyst suitable for high-concentration carbon dioxide. The loading method of the methanation catalyst includes a catalyst active layer disposed in the reactor and inert packing layers located at both ends of the catalyst active layer. The catalyst active layer is composed of catalyst A, catalyst B and catalyst C. The catalyst active layer is arranged in three layers along the air flow direction. The first catalyst layer along the air flow direction is catalyst A and catalyst B, the second catalyst layer is catalyst A, catalyst B and catalyst C, and the third catalyst layer is catalyst A and catalyst C.

[0017] The invention is further characterized in that, Each layer of catalyst A, catalyst B, and catalyst C can be divided into several smaller layers of varying thicknesses. In the first active catalyst layer, the mixing weight ratio of catalyst A to catalyst B is 3:0 to 2, and the weight ratio of catalyst B increases layer by layer along the gas flow direction. In the second active catalyst layer, the mixing weight ratio of catalyst A to catalyst B is 1 to 2:3, and the mixing weight ratio of catalyst B to catalyst C is 3:0 to 1, and the weight ratio of catalyst C increases layer by layer along the gas flow direction. In the third active catalyst layer, the mixing weight ratio of catalyst A to catalyst C is 3:0 to 1, and the weight ratio of catalyst C increases layer by layer along the gas flow direction.

[0018] In catalyst A, by mass percentage, the content of Al2O3 is 10~30wt%, the content of ZrO2 is 2~5wt%, the content of support modifier is 40~75wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3~3, the content of active component NiO is 10~15wt%, and the content of auxiliary agent is 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05; In catalyst B, by mass percentage, the content of Al2O3 is 20~50wt%, the content of ZrO2 is 2~10wt%, the content of support modifier is 15~30wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3~3, the content of active component NiO is 20~40wt%, and the content of auxiliary agent is 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05; In catalyst C, by mass percentage, the content of Al2O3 is 40~60wt%, the content of ZrO2 is 2~10wt%, the content of support modifier is 1~10wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3~3, the content of active component NiO is 25~50wt%, and the content of auxiliary agent is 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05.

[0019] The inert packing layer is filled in cylindrical or Raschig ring form, and the composition of the inert packing layer is one or more of ceramic balls, corundum, silicon carbide, boron nitride or magnesium oxide in any proportion. Catalysts A, B, and C are cylindrical, spherical, four-hole wheel-shaped, or five-hole wheel-shaped. Catalysts in the same active layer have the same shape, while catalysts in different active layers have different shapes.

[0020] The entire reaction process takes place in a reactor. During the entire reaction, the process conditions are as follows: the bed temperature is controlled at 240-290℃, the hot spot temperature is controlled at 330-500℃, and the reactor gas outlet temperature is less than or equal to 300℃.

[0021] The beneficial effects of this invention are: (1) The preparation method of the carbon dioxide methanation catalyst of the present invention uses a series of catalysts. The catalysts have good thermal stability and hydrothermal stability, and their performance shows a gradient distribution. The packing method of the present invention can effectively reduce the hot spot temperature of the bed, reduce the concentration gradient of the catalyst along the axis, slow down the intensity of the methanation reaction, achieve a gentle temperature rise in the bed, effectively avoid the risk of local high temperature zone and catalyst sintering deactivation, and extend the service life of the catalyst and reactor. (2) The carbon dioxide methanation catalyst of the present invention adopts the packing structure of the present invention. It does not need to change the reactor structure. When the CO2 content at the reaction gas inlet is within 20%, a single reactor can achieve efficient CO2 conversion. The bed temperature rise is small and the safety is high. There is no need to introduce circulating gas or steam dilution, which saves energy and reduces consumption, and also effectively reduces equipment investment and operating costs. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments.

[0023] The methanation catalyst suitable for high concentrations of carbon dioxide comprises, by mass percentage, the following components: 12%~85% support, 1~75wt% support modifier, 10~50wt% active component NiO, and 1~5wt% additives, with the sum of the mass percentages of the above components being 100%. Furthermore, the support includes Al2O3 and ZrO2, with a mass ratio of Al2O3 to ZrO2 of 0.67-35:1; The carrier modifier is nitrogen-doped mesoporous carbon and silicon carbide, with a ratio of 1:0.3~3. The nitrogen-doped mesoporous carbon contains 1.5~12% nitrogen and has a specific surface area of ​​800~1200 m². 2 / g, with an average pore size of 4~8.1nm; The additives include CeO2, MnO2 and MgO, with the mass ratio of CeO2 to MnO2 being 1 to 5:1 and the mass ratio of MnO2 to MgO being 1:1 to 1.05.

[0024] The preparation method of methanation catalyst suitable for high concentrations of carbon dioxide includes the following specific steps: S1. The carrier modifier is stirred at 600 rpm and ultrasonically dispersed in the salt solution to form a suspension, and the suspension is heated to 50~80℃. Among them, the ultrasonic frequency is 40~80kHz and the power is 200~800kW; The salt solution is a nitrate solution or a sulfate solution; the mass concentration of the salt solution is 0.5-5%, and the solid-liquid weight ratio of the suspension is 1:20-50.

[0025] S2. Dissolve the weighed Al, Zr, Ce, Ni, and Mn salts in deionized water to form a first precursor salt solution. Heat the first precursor salt solution and the precipitant solution to 50-80°C and add them dropwise to the heated suspension for the first precipitation. Maintain the pH of the solution at 7-8 and continue stirring to form a mixed solution. The precursor salt solution is composed of nickel nitrate, manganese nitrate, cerium nitrate, aluminum nitrate, and zirconium nitrate; the precipitant solution is any one of sodium carbonate, potassium carbonate, sodium bicarbonate, or potassium bicarbonate.

[0026] The molar ratio of the first precursor salt solution to the precipitant is 0.1~1.1:1.

[0027] S3. Continue to add the second precursor salt solution (magnesium nitrate solution) to the mixture, add precipitant, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 1-2 hours to obtain the precipitate. S4. After precipitation, the entire solution is hydrothermally aged at 110~150℃ for 2~3 hours, and then the precipitate is filtered out. S5. After hydrothermal aging, the precipitate is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 50~500 μS / cm. After drying, it is calcined at 300~600℃ for 4~12h in a nitrogen atmosphere to obtain a methanation catalyst suitable for high concentrations of carbon dioxide. By mass percentage, it includes the following components: support 12%~85%, support modifier 1~75wt%, active component NiO 10~50wt%, and auxiliary agent 1~5wt%, with the sum of the mass percentages of the above components being 100%. The application of methanation catalysts suitable for high-concentration carbon dioxide involves a loading method for the methanation catalyst, which includes an active catalyst layer disposed within the reactor and inert packing layers located at both ends of the active catalyst layer. The active catalyst layer consists of catalyst A, catalyst B, and catalyst C, arranged in three layers sequentially along the gas flow direction. The first layer of catalyst along the gas flow direction consists of catalyst A and catalyst B, the second layer consists of catalyst A, catalyst B, and catalyst C, and the third layer consists of catalyst A and catalyst C.

[0028] Furthermore, each layer of catalyst A, catalyst B, and catalyst C can be divided into several smaller layers of varying thicknesses. In the first active catalyst layer, the mixing weight ratio of catalyst A to catalyst B is 3:0 to 2, and the weight (i.e., thickness) of catalyst B increases layer by layer along the airflow direction. In the second active catalyst layer, the mixing weight ratio of catalyst A to catalyst B is 1 to 2:3, and the mixing weight ratio of catalyst B to catalyst C is 3:0 to 1, with the weight ratio of catalyst C increasing layer by layer along the airflow direction. In the third active catalyst layer, the mixing weight ratio of catalyst A to catalyst C is 3:0 to 1, with the weight ratio of catalyst C increasing layer by layer along the airflow direction. The reactor is a tubular temperature-controlled reactor, with the catalyst packed in the shell layer, and water supplying and removing heat through the tube layers.

[0029] In catalyst A, by mass percentage, the content of Al2O3 is 10~30wt%, the content of ZrO2 is 2~5wt%, the content of support modifier is 40~75wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3~3, the content of active component NiO is 10~15wt%, the content of auxiliary agent is 1~5wt%, the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05.

[0030] In catalyst B, by mass percentage, the content of Al2O3 is 20-50 wt%, the content of ZrO2 is 2-10 wt%, the content of support modifier is 15-30 wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3-3, the content of active component NiO is 20-40 wt%, and the content of auxiliary agent is 1-5 wt%, wherein the mass ratio of CeO2 to MnO2 is 1-5:1, and the mass ratio of MnO2 to MgO is 1:1-1.05.

[0031] In catalyst C, by mass percentage, the content of Al2O3 is 40-60 wt%, the content of ZrO2 is 2-10 wt%, the content of support modifier is 1-10 wt%, the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3-3, the content of active component NiO is 25-50 wt%, and the content of auxiliary agent is 1-5 wt%, wherein the mass ratio of CeO2 to MnO2 is 1-5:1. The mass ratio of MnO2 to MgO is 1:1~1.05.

[0032] The inert packing layer is filled in cylindrical or Raschig ring form, and the composition of the inert packing layer is one or more of ceramic balls, corundum, silicon carbide, boron nitride or magnesium oxide in any proportion. Catalysts A, B, and C are cylindrical, spherical, four-hole wheel-shaped, or five-hole wheel-shaped. Catalysts in the same active layer have the same shape, while those in different active layers have different shapes. This ensures uniform mixing of the catalysts in each bed and facilitates segmented loading, making it suitable for industrial-scale application.

[0033] The entire reaction process is carried out in a reactor. During the entire reaction, the process conditions are as follows: the bed temperature is controlled at 240-290℃, the hot spot temperature is controlled at 330-500℃, and the reactor gas outlet temperature is less than or equal to 300℃.

[0034] The principle of this invention is as follows: Mesoporous carbon has a well-developed mesoporous structure, which is conducive to the molecular diffusion of reactants and products, and also facilitates the transfer of reaction heat. Nitrogen doping in mesoporous carbon promotes electron transfer and improves the reducing power of the catalyst. Nitrogen doping is beneficial to the loading and dispersion of Ni, promotes Ni reduction, and helps to improve the low-temperature activity and high-temperature stability of the catalyst.

[0035] The catalyst of this invention uses ZrO2-Al2O3 and nitrogen-doped mesoporous carbon or SiC as a composite support. The addition of ZrO2 improves the electron transfer capacity and acidity of the Al2O3 support. The nitrogen-doped material surface can adsorb a large amount of hydrogen, which is transferred to the active sites on the catalyst surface, thereby increasing the hydrogenation reaction rate. MgO modification is beneficial to improving the adsorption activity of CO2, which is beneficial to improving the catalyst activity in the low-temperature methanation reaction of CO2. It also has excellent thermal conductivity and electron transfer performance, and improves the low-temperature activity and high-temperature resistance of the catalyst. The hydrophobicity of the nitrogen-doped mesoporous carbon material is beneficial to the desorption of water generated after carbon dioxide methanation, which improves the carbon dioxide methanation performance at low temperature. The introduction of nitrogen-doped mesoporous carbon and the interaction of Ni active components promote the effective dispersion of the active component Ni in the shaped catalyst. The Ni grains after calcination are small, the reaction activation temperature is low, and it has good low-temperature reaction activity. It is particularly suitable for methanation heat transfer reactors, which can effectively reduce reactor equipment investment and operating costs. Meanwhile, the introduction of nitrogen-doped mesoporous carbon into the catalyst forms carbon sites on the catalyst surface. The mesoporous channels facilitate heat and mass transfer, and nitrogen doping promotes the electron mobility of the surface. The formed carbon sites inhibit the formation and further expansion of carbon deposits, thus improving the catalyst's resistance to carbon deposition. The in-situ introduction of SiC into the catalyst further enhances its thermal conductivity and hydrothermal stability. High-temperature hydrothermal treatment of the catalyst precursor enhances the interaction between the active component, promoters, and support, further improving catalytic performance while also improving high-temperature resistance and hydrothermal stability. The introduction of Ce and Mn promoters further improves the catalyst's activity and stability.

[0036] Because methanation reactions are rapid and exothermic, the heat transfer effect is limited when using temperature-controlled methanation processes relying solely on physical methods. Therefore, using a single catalyst system is insufficient for effective temperature control. This patent innovatively uses the same preparation method but modifies the active component and support composition to prepare a series of catalysts with different effects. Here, three catalysts are creatively mixed to achieve reasonable control of the catalyst bed reaction temperature, avoiding runaway reactions or localized hot spots, extending catalyst lifespan, and thus exerting a synergistic catalytic effect.

[0037] In this invention, three catalyst active layers are sequentially arranged along the airflow direction. In addition to these multiple active layers, the mixing ratio of the two catalysts in each layer is limited. Based on kinetics, it was found that the catalyst hotspot temperature is closely related to the intrinsic activity of the catalyst. Therefore, the amount of catalyst with high methanation activity and high hydrothermal stability is gradually increased layer by layer along the airflow direction, while the amount of catalyst with high thermal conductivity, high hydrothermal stability, and suitable methanation activity is gradually decreased. Catalysts with weaker methanation activity and stronger hydrothermal stability are used. This effectively lengthens the distance between the zero-meter temperature and the hotspot temperature, ensuring a relatively gradual temperature rise in the bed and a step-by-step reaction. The hotspot temperature can then occur at the second or third catalyst active layer without significant displacement, thus reducing the bed hotspot temperature. The final layer uses catalysts with both high and low methanation activity. This progressive layering further completes the methanation reaction while chemically lengthening the reaction gradient. Combined with physical heat transfer methods, this results in a gradual change in bed temperature. Example 1 A method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps for preparing catalyst A are as follows: S1. 25g of nitrogen-doped mesoporous carbon and 30g of SiC are stirred at 600rpm and ultrasonically dispersed in a sodium nitrate solution with a sodium nitrate solution mass concentration of 5% to form a suspension with a solid-liquid weight ratio of 1:20. The suspension is then heated to 50℃. Among them, nitrogen-doped mesoporous carbon has a size >500 mesh and 1100 μm. 2 / g, average pore size 5.5nm, nitrogen content 5%, including pyridine nitrogen 44.51%, pyrrole nitrogen 26.59%, graphitic nitrogen 20.52%, and oxide nitrogen 8.38%; SiC size > 500 mesh; The ultrasonic frequency is 40kHz and the power is 800kW.

[0038] S2. Dissolve 46.6g of nickel nitrate, 183.3g of aluminum nitrate, 12.2g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate in 1000mL of deionized water to prepare the first precursor salt solution. Prepare the precipitant solution with sodium carbonate. The molar ratio of the first precursor salt solution to sodium carbonate is 0.1:1. Heat the first precursor salt solution and the precipitant solution to 80℃ respectively, and add them dropwise to the heated suspension to carry out the first precipitation. The dropwise addition is selected to be completed within 50min. The stirring speed is 600rpm. Maintain the pH of the solution at 7~8 and continue stirring to start precipitation and form a mixed solution.

[0039] S3. Continue to add the second precursor salt solution, magnesium nitrate solution, containing 0.5g of magnesium nitrate, to the mixture. Add precipitant to maintain the pH of the mixture at 7-8. Continue stirring to carry out the second precipitation and maintain for 1 hour to obtain the precipitate. S4. After precipitation, the entire solution is hydrothermally aged at 130℃ for 2 hours, and then the precipitate is filtered out. S5. The precipitate after hydrothermal aging is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 50 μS / cm. After drying, it is calcined at 300℃ for 12 h in a nitrogen atmosphere to obtain the catalyst. Nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide account for 12%, 25%, 3.5%, 1%, 3%, and 0.5% of the catalyst mass, respectively. Nitrogen-doped mesoporous carbon and SiC account for 25% and 30% of the catalyst mass, respectively.

[0040] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 25%, 35%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0041] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 35%, 50%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2.5% and 2.5% of the catalyst mass, respectively.

[0042] The reactor packing structure is as follows: two layers of inert packing material (M layer and N layer) and three layers of catalyst active layer (from top to bottom, the first layer, the second layer, and the third layer). The first layer contains catalysts A and B, shaped like four-hole wheels with an outer diameter of 6 mm. The second layer contains catalysts A, B, and C, shaped like cylinders with an outer diameter of 3 mm. The third layer contains catalysts A and C, both spherical in shape with an outer diameter of 4 mm. In the first catalyst active layer, the weight ratio of A to B is 3:(0-2), with the weight ratio of B increasing layer by layer along the airflow direction. In the second catalyst active layer, the weight ratio of A, B, and C is (1-2):3:(0-1), with the weight ratio of C increasing layer by layer along the airflow direction. In the third catalyst active layer, the weight ratio of A to C is 3:(0-1), with the weight ratio of C increasing layer by layer along the airflow direction.

[0043] Throughout the reaction process, the process conditions were as follows: bed temperature controlled at 270℃, hot spot temperature at 330℃, and reactor gas outlet temperature less than or equal to 300℃.

[0044] Catalyst loading performance test: The reaction pressure was 2.5 MPa, the feed gas composition was 15% CO2 with a hydrogen-to-carbon ratio of 4:1, and the remainder was N2 / CH4 and other components. The gas was preheated to 270℃ before entering the catalyst active layer. The hot spot temperature appeared in the middle of the second layer at 360℃. After passing through the third bed, the gas temperature was 280℃. The CO2 conversion rate was ≥97.5%, the CH4 selectivity was ≥99.5%, and after 1000 hours of continuous operation, the hot spot position did not move significantly, and the catalyst activity remained unchanged.

[0045] Example 2 A method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps for preparing catalyst A are as follows: S1. 32.5g of nitrogen-doped mesoporous carbon (specifications and content as in Example 1) and 30g of SiC (size > 500 mesh) were stirred at 600rpm and ultrasonically dispersed in a sodium nitrate solution with a mass concentration of 0.5% to form a suspension. The solid-liquid weight ratio of the suspension was 1:30. The suspension was heated to 70°C. The ultrasonic frequency was 80kHz and the power was 600kW.

[0046] S2. Dissolve 38.8g of nickel nitrate, 147.1g of aluminum nitrate, 10.5g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate in 1000mL of deionized water to prepare the first precursor salt solution. Prepare the potassium carbonate solution as the precipitant solution. Take the first precursor salt solution and potassium carbonate molar ratio as 1:10. Heat the first precursor salt solution and the precipitant solution to 50℃ respectively, and add them dropwise to the heated suspension to carry out the first precipitation. Maintain the pH of the solution at 7~8 and continue stirring to start precipitation and form a mixed solution.

[0047] S3. Continue to add the second precursor salt solution, magnesium nitrate solution, containing 0.5g of magnesium nitrate, to the mixture, add precipitant, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 2 hours to obtain the precipitate; S4. After precipitation, the entire solution is hydrothermally aged at 150℃ for 2.5 hours, and then the precipitate is filtered out. S5. The precipitate after hydrothermal aging is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 100 μS / cm. After drying, it is calcined at 600℃ for 4 hours in a nitrogen atmosphere to obtain a catalyst. Nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide account for 10%, 20%, 3%, 1%, 3%, and 0.5% of the catalyst mass, respectively. Nitrogen-doped mesoporous carbon and SiC account for 32.5% and 30% of the catalyst mass, respectively.

[0048] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 25%, 35%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0049] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 36%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2.5% and 2.5% of the catalyst mass, respectively.

[0050] The reactor packing structure is the same as in Example 1, except that: the first layer is cylindrical, the second layer is spherical, and the third layer is a five-hole wheel shape; wherein, in the first catalyst active layer, the mixed weight ratio of A and B is 3:(0-1), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixed weight ratio of A, B and C is (1~2):3:(0~0.5), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixed weight ratio of A and C is 3:(0-0.8), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0051] Throughout the reaction process, the process conditions were as follows: bed temperature controlled at 270℃, hot spot temperature at 400℃, and reactor gas outlet temperature less than or equal to 300℃.

[0052] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 356℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥97.2%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0053] Example 3 A method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps for preparing catalyst A are as follows: S1. 30.5g of nitrogen-doped mesoporous carbon (specifications and content as in Example 1) and 30g of SiC (size > 500 mesh) were stirred at 600rpm and ultrasonically dispersed in a sodium sulfate solution with a mass concentration of 3% to form a suspension. The solid-liquid weight ratio of the suspension was 1:50. The suspension was heated to 80°C. The ultrasonic frequency was 60kHz and the power was 200kW.

[0054] S2. Dissolve 46.6g of nickel nitrate, 147.1g of aluminum nitrate, 10.5g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate in 1000mL of deionized water to prepare the first precursor salt solution. Prepare the precipitant solution with sodium bicarbonate. Take the first precursor salt solution and sodium bicarbonate in a molar ratio of 1:5. Heat the first precursor salt solution and the precipitant solution to 70℃ respectively, and add them dropwise to the heated suspension to carry out the first precipitation. Maintain the pH of the solution at 7~8 and continue stirring to start precipitation and form a mixed solution.

[0055] S3. Continue to add the second precursor salt solution, magnesium nitrate solution, containing 0.5g of magnesium nitrate, to the mixture, add precipitant solution, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 1.5h to obtain the precipitate; S4. After precipitation, the entire solution is hydrothermally aged at 110℃ for 3 hours, and then the precipitate is filtered out. S5. The precipitate after hydrothermal aging is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 500 μS / cm. After drying, it is calcined at 400℃ for 8 hours in a nitrogen atmosphere to obtain a catalyst. Nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide account for 12%, 20%, 3%, 1%, 3%, and 0.5% of the catalyst mass, respectively. Nitrogen-doped mesoporous carbon and SiC account for 30.5% and 30% of the catalyst mass, respectively.

[0056] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 22%, 38%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0057] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 36%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2.5% and 2.5% of the catalyst mass, respectively.

[0058] The reactor packing structure is the same as in Example 1, except that: the first layer is spherical, the second layer is four-hole wheel-shaped, and the third layer is cylindrical; wherein, in the first catalyst active layer, the mixed weight ratio of A and B is 3:(0-1), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixed weight ratio of A, B and C is (1-2):3:(0-0.8), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixed weight ratio of A and C is 3:(0-1), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0059] Throughout the reaction process, the process conditions were as follows: bed temperature controlled at 270℃, hot spot temperature at 500℃, and reactor gas outlet temperature less than or equal to 300℃.

[0060] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 355℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥97.1%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0061] Example 4 A method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps for preparing catalyst A are as follows: S1. 27.5g of nitrogen-doped mesoporous carbon (specifications and content as in Example 1) and 30g of SiC (size > 500 mesh) were stirred at 600rpm and ultrasonically dispersed in a sodium nitrate solution with a mass concentration of 5% to form a suspension. The solid-liquid weight ratio of the suspension was 1:20. The suspension was heated to 50°C. The ultrasonic frequency was 40kHz and the power was 800kW.

[0062] S2. Dissolve 38.8g of nickel nitrate, 183.9g of aluminum nitrate, 10.5g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate in 1000mL of deionized water to prepare the first precursor salt solution. Prepare the precipitant solution with potassium bicarbonate. The molar ratio of the first precursor salt solution to potassium bicarbonate is 0.1:1. Heat the first precursor salt solution and the precipitant solution to 80℃ respectively, and add them dropwise to the heated suspension to carry out the first precipitation. The dropwise addition is selected to be completed within 50min. The stirring speed is 600rpm. Maintain the pH of the solution at 7~8 and continue stirring to start precipitation and form a mixed solution.

[0063] S3. Continue to add the second precursor salt solution, magnesium nitrate solution, containing 0.5g of magnesium nitrate, to the mixture, add precipitant solution, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 2h to obtain the precipitate; S4. After precipitation, the entire solution is hydrothermally aged at 130℃ for 2 hours, and then the precipitate is filtered out. S5. The precipitate after hydrothermal aging is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 50 μS / cm. After drying, it is calcined at 400℃ for 8 hours in a nitrogen atmosphere to obtain the catalyst. In this catalyst, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide account for 10%, 25%, 3%, 1%, 3%, and 0.5% of the catalyst mass, respectively. Nitrogen-doped mesoporous carbon and SiC account for 27.5% and 30% of the catalyst mass, respectively.

[0064] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 23%, 37%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0065] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 36%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2.5% and 2.5% of the catalyst mass, respectively.

[0066] The reactor packing structure is the same as in Example 1, except that: the first layer is spherical, the second layer is cylindrical, and the third layer is a five-hole wheel shape; wherein, in the first catalyst active layer, the mixed weight ratio of A and B is 3:(0~1), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixed weight ratio of A, B and C is (1-2):3:(0~1), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixed weight ratio of A and C is 3:(0~0.5), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0067] Throughout the reaction process, the process conditions were as follows: bed temperature controlled at 270℃, hot spot temperature at 380℃, and reactor gas outlet temperature less than or equal to 300℃.

[0068] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 352℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥96.8%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0069] Example 5 A method for preparing a methanation catalyst suitable for high-concentration carbon dioxide, the specific steps for preparing catalyst A are as follows: S1. 27.5g of nitrogen-doped mesoporous carbon (specifications and content as in Example 1) and 30g of SiC (size > 500 mesh) were stirred at 600rpm and ultrasonically dispersed in a sodium nitrate solution with a mass concentration of 5% to form a suspension. The solid-liquid weight ratio of the suspension was 1:20. The suspension was heated to 50°C. The ultrasonic frequency was 40kHz and the power was 800kW.

[0070] S2. Dissolve 42.7g of nickel nitrate, 183.9g of aluminum nitrate, 6.9g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate in 1000mL of deionized water to prepare the first precursor salt solution. Prepare the precipitant solution with sodium carbonate. The molar ratio of the first precursor salt solution to sodium carbonate is 0.1:1. Heat the first precursor salt solution and the precipitant solution to 80℃ respectively, and add them dropwise to the heated suspension to carry out the first precipitation. The dropwise addition is selected to be completed within 50min. The stirring speed is 600rpm. Maintain the pH of the solution at 7~8 and continue stirring to start precipitation and form a mixed solution.

[0071] S3. Continue to add the second precursor salt solution, magnesium nitrate solution, containing 0.5g of magnesium nitrate, to the mixture, add precipitant solution, maintain the pH of the mixture at 7-8, continue stirring to carry out the second precipitation and maintain for 2h to obtain the precipitate; S4. After precipitation, the entire solution is hydrothermally aged at 130℃ for 2 hours, and then the precipitate is filtered out. S5. The precipitate after hydrothermal aging is subjected to multiple cycles of pressure filtration, pulping, and washing until the conductivity of the filtrate is 50 μS / cm. After drying, it is calcined at 400℃ for 8 hours in a nitrogen atmosphere to obtain the catalyst. Nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide account for 11%, 25%, 2%, 1%, 3%, and 0.5% of the catalyst mass, respectively. Nitrogen-doped mesoporous carbon and SiC account for 27.5% and 30% of the catalyst mass, respectively.

[0072] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 23%, 37%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0073] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 37%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2% and 2% of the catalyst mass, respectively.

[0074] The reactor packing structure is the same as in Example 1, except that: in the first catalyst active layer, the mixing weight ratio of A and B is 3:(0-1), showing a trend of increasing weight ratio of catalyst B layer by layer along the airflow direction; in the second catalyst active layer, the mixing weight ratio of A, B and C is 1:3:(0-1), and showing a trend of increasing weight ratio of catalyst C layer by layer along the airflow direction; in the third catalyst active layer, the mixing weight ratio of A and C is 3:(0-1), and showing a trend of increasing weight ratio of catalyst C layer by layer along the airflow direction.

[0075] The entire reaction process is carried out in a reactor. During the entire reaction, the process conditions are as follows: the bed temperature is controlled at 270℃, the hot spot temperature is 450℃, and the reactor gas outlet temperature is less than or equal to 300℃.

[0076] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 350℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥96.7%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0077] Example 6 The preparation method and process of the catalyst are the same as in Example 5, except that the amount used is different, as detailed below: The amount of nitrogen-doped mesoporous carbon is 28g; The first precursor salt solution was prepared by adding 38.8g of nickel nitrate, 183.9g of aluminum nitrate, 6.9g of zirconium nitrate, 4.1g of manganese nitrate, and 7.6g of cerium nitrate; the second precursor salt solution contained 0.9g of magnesium nitrate.

[0078] Catalyst A was obtained, wherein nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide, and magnesium oxide accounted for 10%, 25%, 2%, 1%, 3%, and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC accounted for 28% and 30% of the catalyst mass, respectively.

[0079] The preparation method is the same as that of catalyst A, but the dosage is adjusted to prepare catalyst B and catalyst C respectively. In the prepared catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 23%, 37%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0080] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 37%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2% and 2% of the catalyst mass, respectively.

[0081] The reactor packing structure is the same as in Example 5, except that: in the first catalyst active layer, the mixing weight ratio of A and B is 3:(0-2), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixing weight ratio of A, B and C is 1:3:(0-0.5), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixing weight ratio of A and C is 3:(0-0.8), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0082] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 358℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥96.8%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0083] Example 7 The preparation method and process of catalyst A are the same as in Example 6, except that the amounts are adjusted to prepare catalyst B and catalyst C respectively. In the catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 23%, 37%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 10% and 20% of the catalyst mass, respectively.

[0084] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 37%, 49%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 2% and 2% of the catalyst mass, respectively.

[0085] The reactor packing structure is the same as in Example 6, except that: in the first catalyst active layer, the mixing weight ratio of A and B is 3:(0-2), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixing weight ratio of A, B and C is 1:3:(0-0.8), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixing weight ratio of A and C is 3:(0-0.7), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0086] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 359℃, after passing through the third layer the gas temperature was 280℃, CO2 conversion rate ≥97.0%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0087] Example 8 The preparation method of catalyst A and the obtained catalyst A are the same as in Example 6. The difference from Example 6 is that the amounts of catalyst B and catalyst C are adjusted. In the obtained catalyst B powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 22%, 38%, 4.5%, 1.5%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 15% and 15% of the catalyst mass, respectively.

[0088] In the prepared catalyst C powder, by mass of oxides, nickel oxide, aluminum oxide, zirconium oxide, manganese oxide, cerium oxide and magnesium oxide account for 38%, 50%, 5%, 1%, 3% and 1% of the catalyst mass, respectively, and nitrogen-doped mesoporous carbon and SiC account for 1% and 1% of the catalyst mass, respectively.

[0089] The reactor packing structure is the same as in Example 6, except that: in the first catalyst active layer, the mixing weight ratio of A and B is 3:(0-2), and the weight ratio of catalyst B increases layer by layer along the airflow direction; in the second catalyst active layer, the mixing weight ratio of A, B and C is 1:3:(0-1), and the weight ratio of catalyst C increases layer by layer along the airflow direction; in the third catalyst active layer, the mixing weight ratio of A and C is 3:(0-1), and the weight ratio of catalyst C increases layer by layer along the airflow direction.

[0090] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appeared in the middle of the second layer at 362℃, after passing through the third layer the gas temperature was 282℃, CO2 conversion rate ≥96.7%, CH4 selectivity ≥99.5%, continuous operation for 1000h, hot spot position did not move significantly, catalyst activity remained unchanged.

[0091] Comparative Example 1 The preparation method and the content of each component of the catalyst are the same as in Example 1. The difference between Example 1 and Example 1 is the filling method: a filling method of 2 layers of inert packing layer (M layer and N layer) and 1 layer of catalyst active layer is adopted, and all of them are filled with catalyst A. The catalysts used are all spherical.

[0092] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appears in the middle of the catalyst layer at 285℃, gas temperature after passing through the bed is 220℃, CO2 conversion rate ≥48.5%, CH4 selectivity ≥95.5%, continuous operation for 1000h, hot spot position, temperature and catalyst activity remain unchanged.

[0093] Comparative Example 2 The preparation method and the content of each component of the catalyst are the same as in Example 1. The difference between Example 1 and Example 1 is that the filling method is different: a two-layer inert packing layer (M layer and N layer) and a one-layer catalyst active layer are used. All catalysts are filled with catalyst B and the catalyst shape is cylindrical.

[0094] The reaction pressure was 2.5 MPa, the feed gas composition was 15% CO2 with a hydrogen-to-carbon ratio of 4:1, and the remainder was N2 / CH4 and other components. The gas was preheated to 270°C before entering the catalyst active layer. The hot spot temperature appeared at the front of the catalyst layer at 425°C. After passing through the bed, the gas temperature was 280°C. The CO2 conversion rate was ≥80.5%, and the CH4 selectivity was ≥98.5%. After 1000 hours of continuous operation, the hot spot position shifted downwards, but the hot spot temperature remained unchanged, and the CO2 conversion rate and CH4 selectivity remained unchanged.

[0095] Comparative Example 3 The preparation method of the catalyst and the content of each component are the same as in Example 1. The difference from Example 1 is the filling method: a filling method of 2 layers of inert packing layer (M layer and N layer) and 1 layer of catalyst active layer is adopted, and all the catalysts are filled with catalyst C. The catalysts used are all cylindrical.

[0096] Catalyst loading performance test: reaction pressure 2.5MPa, feed gas composition 15% CO2, hydrogen-to-carbon ratio 4:1, the remainder being N2 / CH4 and other components, preheated to 270℃ before entering the catalyst active layer, hot spot temperature appears at the front of the catalyst layer at 450℃, after passing through the bed the gas temperature is 280℃, CO2 conversion rate ≥97.1%, CH4 selectivity ≥99.6%, after continuous operation for 1000h, the hot spot position shifts downward, the hot spot temperature drops to 441℃, catalyst activity decreases, CO2 conversion rate ≥96.5%, CH4 selectivity ≥99.5%.

[0097] Comparative Example 4 The preparation methods of catalyst A, catalyst B and catalyst C are the same as in Example 1. The difference between them and Example 1 is that this example does not undergo hydrothermal treatment and the filling method is the same as in Example 1.

[0098] Catalyst loading performance test: The reaction pressure was 2.5 MPa, the feed gas composition was 15% CO2 with a hydrogen-to-carbon ratio of 4:1, and the remainder was N2 / CH4 and other components. The gas was preheated to 270℃ before entering the catalyst active layer. The hot spot temperature appeared in the middle of the second layer at 360℃. After passing through the third bed, the gas temperature was 280℃. The CO2 conversion rate was ≥97.2%, and the CH4 selectivity was ≥99.5%. After 1000 hours of continuous operation, the hot spot temperature dropped to 355℃, the hot spot position shifted downward, the catalyst activity decreased, and the CO2 conversion rate was ≥96.5%, and the CH4 selectivity was ≥99.5%.

[0099] Catalyst performance testing: The catalysts prepared in Examples 1-8 and Comparative Example 4 were subjected to reduction at 500℃ for 10 h for carbon dioxide methanation performance evaluation. The reaction evaluation was conducted at a reaction temperature of 270℃, a reaction pressure of 2.5 MPa, and a feed gas composition of 20% CO and 80% H2. The reaction results are shown in Table 1.

[0100] Table 1 Catalyst Evaluation Results

[0101] The above results illustrate the evaluation of the catalyst, demonstrating that different series of catalysts exhibit varying activities. By adjusting the composition of the catalyst's active components, promoters, and support, the catalyst activity can be flexibly adjusted. The 1000-hour evaluation results of the examples and comparative examples show that using the catalyst combination method of the present invention results in a gradual and controllable temperature rise in the catalyst bed, which can improve the overall activity and stability of the packed catalyst. The hydrothermal treatment method promotes catalyst activity while improving its stability in hydrothermal atmospheres.

Claims

1. An application of a methanation catalyst suitable for high-concentration carbon dioxide, characterized in that, The method for loading the methanation catalyst includes a catalyst active layer disposed in the reactor and inert packing layers located at both ends of the catalyst active layer. The catalyst active layer is composed of catalyst A, catalyst B and catalyst C. The catalyst active layer is arranged in three layers along the gas flow direction. The first layer of catalyst along the gas flow direction is catalyst A and catalyst B, the second layer of catalyst is catalyst A, catalyst B and catalyst C, and the third layer of catalyst is catalyst A and catalyst C. Each of the catalysts A, B, and C can be divided into several smaller layers of varying thicknesses. In the first active catalyst layer, the weight ratio of catalyst A to catalyst B is 3:0 to 2, and the weight ratio of catalyst B increases with each layer along the airflow direction. In the second active catalyst layer, the weight ratio of catalyst A to catalyst B is 1 to 2:3, and the weight ratio of catalyst B to catalyst C is 3:0 to 1, and the weight ratio of catalyst C increases with each layer along the airflow direction. In the third active catalyst layer, the weight ratio of catalyst A to catalyst C is 3:0 to 1, and the weight ratio of catalyst C increases with each layer along the airflow direction. In catalyst A, the support comprises Al2O3 and ZrO2 by mass percentage, wherein the mass ratio of Al2O3 to ZrO2 is 0.67-35:1, the content of Al2O3 is 10-30 wt%, and the content of ZrO2 is 2-5 wt%. The support modifier is nitrogen-doped mesoporous carbon and silicon carbide, with a content of 40-75 wt%, wherein the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3-3, the nitrogen content in the nitrogen-doped mesoporous carbon is 1.5-12%, and the specific surface area is 800-1200 m². 2 / g, with an average pore size of 4~8.1nm; the content of the active component NiO is 10~15wt%; the additives include CeO2, MnO2 and MgO, with an additive content of 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05; In catalyst B, the support comprises Al2O3 and ZrO2 by mass percentage, wherein the mass ratio of Al2O3 to ZrO2 is 0.67-35:1, the content of Al2O3 is 20-50 wt%, and the content of ZrO2 is 2-10 wt%. The support modifier is nitrogen-doped mesoporous carbon and silicon carbide, with a content of 15-30 wt%, wherein the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3-3, the nitrogen content in the nitrogen-doped mesoporous carbon is 1.5-12%, and the specific surface area is 800-1200 m². 2 / g, with an average pore size of 4~8.1nm; the active component NiO content is 20~40wt%; the additives include CeO2, MnO2 and MgO, with an additive content of 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05; In the catalyst C, the support comprises Al2O3 and ZrO2 by mass percentage, wherein the mass ratio of Al2O3 to ZrO2 is 0.67-35:1, the content of Al2O3 is 40-60 wt%, and the content of ZrO2 is 2-10 wt%. The support modifier is nitrogen-doped mesoporous carbon and silicon carbide, with a content of 1-10 wt%, wherein the mass ratio of nitrogen-doped mesoporous carbon to silicon carbide is 1:0.3-3, the nitrogen content in the nitrogen-doped mesoporous carbon is 1.5-12%, and the specific surface area is 800-1200 m². 2 / g, with an average pore size of 4~8.1nm; the content of the active component NiO is 25~50wt%; the additives include CeO2, MnO2 and MgO, with an additive content of 1~5wt%, wherein the mass ratio of CeO2 to MnO2 is 1~5:1, and the mass ratio of MnO2 to MgO is 1:1~1.05; The inert filler layer is filled in a cylindrical or Raschig ring shape, and the inert filler layer is composed of one or more of ceramic balls, corundum, silicon carbide, boron nitride or magnesium oxide in any ratio; The catalysts A, B, and C are cylindrical, spherical, four-hole wheel-shaped, or five-hole wheel-shaped. The catalysts in the same active layer have the same shape, while the catalysts in different active layers have different shapes.

2. The application of the methanation catalyst according to claim 1 for high-concentration carbon dioxide, characterized in that, The entire reaction process takes place in a reactor. During the entire reaction, the process conditions are as follows: the bed temperature is controlled at 240-290℃, the hot spot temperature is controlled at 330-500℃, and the reactor gas outlet temperature is less than or equal to 300℃.

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