CaO-mgo-al2o3 supported nickel catalyst, its preparation method and application in methanation of fischer-tropsch synthesis tail gas

Abstract

The application belongs to the technical field of catalysts, and discloses a CaO-MgO-Al2O3 supported nickel catalyst, a preparation method thereof and application of the catalyst in methanation of Fischer-Tropsch synthesis tail gas. The CaO-MgO-Al2O3 carrier is prepared by using a coprecipitation method, and Ni and an additive M are loaded on the CaO-MgO-Al2O3 composite carrier by using an impregnation method. After reduction, the catalyst composition is Ni-(M) / CaO-MgO-Al2O3. The mass fraction of Ni is 10-30%, the mass fraction of CaO is 1-10%, the mass fraction of MgO is 5-32%, and the mass fraction of Al2O3 is 20-82%. The catalyst is used for methanation of Fischer-Tropsch synthesis tail gas, and has excellent catalytic activity, selectivity and stability. In a wide temperature range, 96% of CO2 and 100% of CO in the Fischer-Tropsch synthesis tail gas can be converted into CH4, and the waste gas can be used as a resource.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, in particular, it relates to a Ni-based methanation catalyst, a preparation method thereof, and an application thereof in the methanation of tail gas of Fischer-Tropsch synthesis. BACKGROUND

[0002] CO2, as the main greenhouse gas, is the main culprit of global warming, sea level rise and other environmental problems. It is necessary to reduce CO2 emissions and recycle CO2. However, many chemical production scenarios inevitably emit CO2 directly or indirectly. The resource utilization of coal is very important and basic industry, and the Fischer-Tropsch synthesis technology is an important method for clean utilization of coal. Using Fischer-Tropsch synthesis technology, high-temperature synthesis gas obtained by coal gasification can be converted into alkanes, alkenes and alcohols and other chemicals, and a large amount of CO2 by-product will be produced in the process [1] .

[0003] After cooling and separation of the Fischer-Tropsch synthesis product, the tail gas contains a large amount of unreacted carbon monoxide, hydrogen, nitrogen and carbon dioxide produced by reaction, as well as a small amount of low-carbon hydrocarbon substances. The traditional Fischer-Tropsch synthesis tail gas treatment method generally first absorbs CO2 in the tail gas and then burns to produce steam. Using this method will inevitably produce CO2 emissions [2] . The current common Fischer-Tropsch tail gas recycling method mainly includes the following processes: first, using membrane separation technology to separate hydrogen, helium, water vapor and other permeable gases in the tail gas; second, through the catalytic reforming reaction of the tail gas, the hydrocarbons in the tail gas are converted into CO and H2O, and then the CO and H2 ratio is adjusted through the water gas shift reaction; third, using N-methyldiethanolamine and other solvents to remove carbon dioxide; fourth, using deep cooling separation method or low temperature oil washing method to remove C 3+ alkane; finally, through pressure swing adsorption gas separation technology, relatively pure hydrogen is obtained [3,4] . The recycling scheme combined with multiple technologies can accurately separate each component to maximize the utilization of each tail gas component, but the process is obviously complicated and the cost is high.

[0004] In recent years, methanation as a CO2 utilization technology has been widely studied due to its potential economic benefits. CH4, as a storage material, has higher combustion heat value and higher safety compared with H2, and is easy to store and transport through long-distance pipelines [5] . In addition, with the increasing decline in the cost of green hydrogen, the cost of utilizing industrial waste gas through catalytic conversion is also becoming lower and lower [6] . If the Fischer-Tropsch synthesis tail gas containing CO2, CO and H2 is completely converted into high-quality synthetic natural gas (SNG) by supplementing an appropriate amount of H2 at low temperature and high space velocity, the methanation of Fischer-Tropsch synthesis tail gas will be a promising Fischer-Tropsch tail gas treatment scheme[7,8] Therefore, it is particularly important to develop a catalyst that can be applied to the methanation of Fischer-Tropsch tail gas. This requires the catalyst to have high activity at low temperatures and high stability at high temperatures - both to fully convert the high space velocity Fischer-Tropsch synthesis tail gas and to prevent sintering, oxidation, and carbon deposition deactivation over a long period of time.

[0005] The most common CO2 methanation catalyst is a Ni-based catalyst. γ-Al2O3 has a high specific surface area and can achieve high dispersion of Ni, so it is often used as a support for industrial catalysts. Mori et al. compared the methanation performance of Ni-based catalysts supported on γ-Al2O3, MgO, SiO2, α-Al2O3, TiO2, etc. The results showed that the catalyst supported on γ-Al2O3 had the best performance [9] However, Ni supported on Al2O3 is prone to sintering, carbon deposition, oxidation, and other problems at high temperatures, which reduces the activity of the catalyst and affects its industrial application. The most common problem with catalysts is deactivation due to sintering. Xu et al. found that Ni / Al2O3 faced continuous deactivation problems due to Ni sintering during stability tests, while the addition of Mg 2+ or Ca 2+ can effectively improve the stability of Ni / Al2O3, as the structural additives play a role in limiting the sintering of Ni [10,11] .

[0006] Unlike CO2 or CO methanation reactions, catalysts in FT synthesis tail gas methanation will face severe coking tests. This is because FT synthesis tail gas contains hydrocarbons such as ethane, ethylene, propane, and propylene, which are prone to deep cracking at high temperatures, further carbon deposition and coking. Coking on the surface of active sites will also inhibit the catalytic activity of active sites

[12] .

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[0013] [7]Li Y ming, Khurshid A, Khan K. Optimization of coal-to-liquid processes;A way forward towards carbon neutrality, high economic returns and effective resource utilization. Evidences from China. Fuel[J], 2023, 344: 128082.

[0014] [8]Wang C, Zhou L. Life Cycle Assessment of Coal-to-Liquid Process. Environment, Development and Sustainability[J], 2021, 23: 14453-14471.

[0015] [9]Mori T, Masuda H, Imai H. Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts. J. Phys. Chem. 1982, 86(14): 2753–2760.

[0016]

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[0017]

[11] Xu L, Wang F, Chen M. Alkaline-promoted Ni based ordered mesoporous catalysts with enhanced low-temperature catalytic activity toward CO2 methanation. Rsc Adv, 2017, 7(30): 18199-18210.

[0018]

[12] Tang X, Song C, Li H. Thermally stable Ni foam-supported inverse CeAlOx / Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane. Nat Commun, 2024, 15(1): 3115.

[0019]

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[0020]

[14] Feng K, Zhang J, Li Z. Spontaneous regeneration of active sites against catalyst deactivation. Applied Catalysis B: Environmental, 2024, 344: 123647. SUMMARY

[0021] The present application aims to provide a CaO-MgO-Al2O3 supported nickel catalyst and its preparation method, and its application in Fischer-Tropsch synthesis tail gas methanation. The catalyst prepared by the present application has excellent catalytic activity, selectivity and stability, and can convert 96% of CO2 and 100% of CO in the Fischer-Tropsch synthesis tail gas into CH4 in a wide temperature range of 200-500℃, realizing the resource utilization of waste gas.

[0022] According to one aspect of the present application, a preparation method of a CaO-MgO-Al2O3 supported nickel catalyst is provided, which uses a coprecipitation method to prepare a CaO-MgO-Al2O3 carrier, and uses an impregnation method to load Ni and an additive M onto the CaO-MgO-Al2O3 composite carrier; the composition of the catalyst after reduction is Ni-(M) / CaO-MgO-Al2O3.

[0023] Taking the Ni-(M) / CaO-MgO-Al2O3 catalyst as a benchmark, the mass fraction of Ni is 10-40%, the mass fraction of CaO is 1%-10%, the mass fraction of MgO is 5%-32%, and the mass fraction of Al2O3 is 20%-82%; the additive M is Co, La2O3 or CeO2, and the addition amount of the metal in the additive M is 0-4% of the molar amount of Ni.

[0024] Further, the process includes the following steps:

[0025] (1) Dissolve Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a macromolecular pore-forming agent in water to obtain a mixed solution; simultaneously slowly drop the mixed solution and a precipitant solution into a reactor for precipitation, and keep stirring during the precipitation process; continue stirring for a certain time after the precipitation is completed; then stand still, wash the generated precipitate with water and dry; calcine the dried precipitate at 450℃-750℃ for 3-12h to obtain a CaO-MgO-Al2O3 carrier;

[0026] (2) dissolving Ni(NO3)2·6H2O and nitrate of assistant M in water to prepare impregnation solution; dropping the impregnation solution to the catalyst carrier prepared in step (1) uniformly, then standing, and drying; finally calcining at 450-750℃ for 3-12h to obtain CaO-MgO-Al2O3 supported nickel catalyst.

[0027] Preferably, the mass ratio of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O and macromolecular pore-forming agent in step (1) is 1:(3-20):(4-82):(76-160).

[0028] Preferably, the macromolecular pore-forming agent in step (1) is selected from at least one of PVP, PEG, P123 and cellulose.

[0029] Preferably, the cation concentration of the mixed solution in step (1) is 0.5-2mol / L.

[0030] Preferably, the precipitant in step (1) is selected from at least one of Na2CO3, NaHCO3 and NaOH.

[0031] Preferably, the temperature of the precipitation process in step (1) is 60-80℃, and the PH is kept at 9-10.

[0032] Preferably, after the precipitation in step (1) is completed, the stirring is continued for 3-7h, and then the standing is continued for 15-30h.

[0033] Preferably, the temperature of the drying in step (1) is 80-150℃, and the time is 15-30h.

[0034] Preferably, the nitrate of assistant M in step (2) includes one of Co(NO3)2·6H2O, Ce(NO3)3·6H2O and La(NO3)3·6H2O.

[0035] Preferably, the standing time in step (2) is 15-30h.

[0036] Preferably, the temperature of the drying in step (2) is 90-130℃, and the time is 15-30h.

[0037] According to another aspect of the present application, there is provided a CaO-MgO-Al2O3 supported nickel catalyst prepared by the above preparation method.

[0038] According to another aspect of the present application, there is provided an application of the CaO-MgO-Al2O3 supported nickel catalyst in the methanation of Fischer-Tropsch synthesis tail gas.

[0039] Further, the catalyst is placed in the reactor before the reaction, and a mixed gas of H2 or CO and inert gas is introduced into the reactor to reduce the catalyst: the volume content of H2 or CO in the mixed gas is 3-20%; the reduction temperature is 500-800 DEG C, and the reduction time is 1-5h.

[0040] Preferably, the inert gas is N2 or Ar.

[0041] Further, the reaction is carried out after the reduction treatment, the reaction temperature is 200-500 DEG C, the pressure is 0.1-3.5 MPa, and the space velocity is 5000-30000 ml / (g cat ·h).

[0042] The present application has the following advantages:

[0043] The present application adopts a simple precipitation method combined with an equal-volume impregnation method to prepare a catalyst suitable for the methanation of Fischer-Tropsch synthesis tail gas. Compared with a sample simply supported on Al2O3, the CaO-MgO-Al2O3 composite carrier has more basic adsorption sites and oxygen vacancies, which can effectively weaken the influence of carbon deposition caused by hydrocarbon thermal decomposition; CaO and MgO can promote the high dispersion of Ni and stabilize Ni clusters, thereby inhibiting sintering; by adding a small amount of Co, La2O3 or CeO2, on the one hand, the carbon deposition resistance can be improved, and on the other hand, the oxidation resistance of Ni can be improved, and the oxidation of Ni by CO2 or H2O can be weakened. Therefore, the prepared Ni-(M) / CaO-MgO-Al2O3 can efficiently and stably convert CO2 and CO in the Fischer-Tropsch synthesis tail gas into methane, and can effectively resist the influences of sintering, carbon deposition and oxidation caused by the F-T tail gas reaction atmosphere. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 Comparison of XRD spectra of the catalyst prepared in Examples 1 and 6 after calcination with the catalyst without Ca addition;

[0045] Figure 2 Comparison of XRD spectra of the catalyst prepared in Examples 1 and 6 after reduction with the catalyst without Ca addition;

[0046] Figure 3 TEM and element distribution images of the catalyst prepared in Example 1 after reduction;

[0047] Figure 4 Catalytic performance of the catalyst prepared in Example 9 in the methanation of Fischer-Tropsch synthesis tail gas versus reaction temperature;

[0048] Figure 5The figure of the test results of the stability of the catalyst prepared in Example 15 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0049] Figure 6 The figure of the test results of the stability of the catalyst prepared in Example 16 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0050] Figure 7 The figure of the comparison of the XRD spectra of the samples before and after the stability test of the catalyst prepared in Example 16 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0051] Figure 8 The TG curve of the sample after the stability test of the catalyst prepared in Example 16 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0052] Figure 9 The figure of the test results of the stability of the catalyst prepared in Example 17 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0053] Figure 10 The figure of the comparison of the XRD spectra of the samples before and after the stability test of the catalyst prepared in Example 17 in the methanation of the tail gas of the Fischer-Tropsch synthesis;

[0054] Figure 11 The TG curve of the sample after the stability test of the catalyst prepared in Example 17 in the methanation of the tail gas of the Fischer-Tropsch synthesis. DETAILED DESCRIPTION

[0055] The present application is designed to increase the number of oxygen vacancies of the catalyst: on the one hand, CeO2, La2O3 and other transition metal oxides rich in oxygen vacancies can be used as additives; on the other hand, the crystal defects in the carrier of the catalyst can be increased by means of ion doping, such as adding a small amount of Ca 2+ MgAl2O4 carrier, increasing the inherent oxygen vacancies of the carrier.

[0056] In order to obtain a high-efficiency and stable catalyst for the methanation of the tail gas of the Fischer-Tropsch synthesis, the present application uses CaO-MgO-Al2O3 composite oxides as the carrier of the catalyst, and adds appropriate amounts of Co, La and Ce elements to the catalyst to make the improved catalyst suitable for the methanation reaction of the tail gas of the Fischer-Tropsch synthesis containing CO2, CO, H2 and a small amount of hydrocarbons. MgO can promote the high dispersion of Ni, and MgO can stabilize the Ni clusters and inhibit sintering in the reaction. Adding an appropriate amount of Ca to the carrier can increase the oxygen vacancies of the MgO-Al2O3 carrier and improve the oxidation resistance of the catalyst. By increasing Co, the CoNi alloy formed after reduction can effectively weaken the oxidation of Ni. By adding appropriate amounts of La and Ce, metal oxides rich in oxygen vacancies are formed, further improving the carbon deposition resistance and oxidation resistance of the catalyst.

[0057] In some preferred embodiments of the present invention, the CaO-MgO-Al2O3 supported nickel catalyst is prepared according to the following method:

[0058] A. Preparation of catalyst support

[0059] Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a macromolecular pore-forming agent were dissolved in water at a mass ratio of 1:(3-20):(4-82):(76-160) to obtain a mixed solution with a cation concentration of 0.5-2 mol / L. This mixed solution and the precipitant solution were simultaneously and slowly added dropwise to a reactor, maintaining a pH of 9-10 and a temperature of 60-80℃. The precipitation process was carried out with stirring, and stirring was continued for 3-7 hours after precipitation. The mixture was then allowed to stand for 15-30 hours, and the resulting precipitate was washed with water to remove nitrate ions, etc. The obtained precipitate was dried at 80-150℃ for 15-30 hours, and the dried precipitate was calcined at 450℃-750℃ for 3-12 hours to obtain a catalyst support.

[0060] The macromolecular pore-forming agent used in step A is selected from one or more of PVP, PEG, P123 and cellulose, and the precipitant used is one or more of Na2CO3, NaHCO3 and NaOH.

[0061] B. Preparation of Ni-based catalysts for methanation of Fischer-Tropsch synthesis tail gas

[0062] Dissolve Ni(NO3)2·6H2O and the corresponding molar amount of nitrate of the auxiliary agent M in water to prepare an impregnation solution; control the amount of Ni(NO3)2·6H2O to ensure that the mass fraction of Ni in the catalyst after reduction is 10%-30%; uniformly add the impregnation solution to the catalyst support obtained in step A, then let it stand for 15-30 h, and then dry it at 90-130℃ for 15-30 h; calcine it at 450-750℃ for 6 h to obtain the catalyst sample.

[0063] The nitrates of the auxiliary agent M used in step B include Co(NO3)2·6H2O, Ce(NO3)3·6H2O, and La(NO3)3·6H2O.

[0064] The catalyst is placed in a fixed-bed reactor, and a mixture of H2 or CO and inert gas N2 or Ar is introduced into the reactor to reduce the catalyst. The volume content of H2 or CO in the mixture with the inert gas is in the range of 3-20%, the reduction temperature is between 500-800℃, and the reduction time is 1-5h. Industrial Fischer-Tropsch synthesis tail gas is introduced into the reactor for performance testing. The test temperature is 200℃-500℃, the pressure is 0.1-3.5MPa, and the space velocity is 5000-30000ml / (gcat·h).

[0065] The composition (volume fraction) of the test industrial Fischer-Tropsch synthesis tail gas is as follows:

[0066] [N2] [H2] CO2 CO [CAT] [C2H6] [C2H4] [C3H8] [C3H6] [C4H 10 ]]> [C4H8] 36.3％ 46％ 8％ 4％ 4％ 0.4％ 0.1％ 0.3％ 0.5％ 0.1％ 0.3％

[0067] In summary, the application proposes a new Fischer-Tropsch synthesis tail gas utilization idea, and a series of high-activity and high-stability catalysts suitable for Fischer-Tropsch synthesis tail gas methanation are synthesized by using a simple "precipitation + isometric impregnation" synthesis method. During the 200h Fischer-Tropsch synthesis tail gas methanation test, the CO2 conversion rate is always maintained above 96%, the CO conversion rate reaches 100%, and the CH4 selectivity reaches 100%, which shows that the catalyst has very good activity. After 200 hours of Fischer-Tropsch synthesis tail gas methanation test, the catalyst does not show obvious deactivation, which shows good stability. The application is very suitable for catalyst large-scale production and specific scene application, and adds a new feasible scheme for industrial Fischer-Tropsch synthesis tail gas treatment.

[0068] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application is further described in detail below in combination with specific examples and drawings.

[0069] Example 1

[0070] A. Preparation of catalyst carrier

[0071] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1mol / L. The mixed solution and the precipitant solution were slowly added to the substrate solution with a pH of 9.5 and a temperature of 70℃ at the same time, and the pH and temperature of the substrate solution were kept constant during the adding process, and the precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5h. Then stop stirring, and the suspension was placed at 70℃ for 24h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120℃ for 24h, and then the dried precipitate was calcined at 450℃ for 6h, and then the calcined precipitate was crushed into a powder less than 60 mesh, which was used as a catalyst carrier.

[0072] B. Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0073] A certain amount of Ni(NO3)2.6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2.6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded under a pressure of 15 MPa. The obtained catalyst was named NMA-1. The XRD spectrum of the catalyst after calcination is shown in Figure 1 Fig. 1. Compared with the catalyst NMA without Ca addition, the diffraction peak attributed to MgAl2O4 spinel of the catalyst NMA-1 with Ca addition shifted to a lower angle, indicating that Ca was successfully doped into the spinel lattice.

[0074] C. Test of the Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0075] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. H2was introduced into the reactor at a flow rate of 30 mL min -1 -1. The reduction temperature was 750°C, and the reduction time was 2.5 h, to obtain NMA-1-r, as shown in Figure 1 Fig. 2. After the temperature dropped to room temperature, industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance test, and the reaction pressure was 3 MPa. The XRD spectrum of the catalyst after reduction is shown in Figure 2 Fig. 3. Compared with the catalyst NMA without Ca addition, the diffraction peak attributed to MgAl2O4 spinel of the catalyst NMA-1 with Ca addition shifted to a lower angle, indicating that Ca was successfully doped into the spinel lattice. The dispersion of each element in the catalyst was evaluated by EDS image, as shown in Figure 3 Fig. 4. The results showed that Ni, Mg, Al and Ca were uniformly dispersed in the catalyst after reduction.

[0076] The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows at a space velocity of 10000 ml / (g cat ·h):

[0077] At 200℃, the CO2 conversion rate was 3.1%, the CO conversion rate was 3.2%, and the CH4 selectivity was 100%; at 250℃, the CO2 conversion rate was 37.2%, the CO conversion rate was 93.2%, and the CH4 selectivity was 100%; at 300℃, the CO2 conversion rate was 95.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350℃, the CO2 conversion rate was 97.6%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400℃, the CO2 conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450℃, the CO2 conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0078] Example 2

[0079] Preparation of catalyst carrier

[0080] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70℃ at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70℃ for 24 h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120℃ for 24 h, and then calcined at 450℃ for 6 h. Subsequently, the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0081] B. Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0082] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 30%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, and then dried at 120℃ for 24 h. The powder catalyst was obtained by calcination at 450℃ for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-2.

[0083] C. Testing of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0084] The catalyst obtained in step B was ground into small particles of 100-140 mesh, and placed in a fixed bed reactor. 30 mL min-1 of H2 and 30 mL min-1 of CO2 were introduced into the reactor, and the temperature was controlled at 450℃. The reaction was carried out for 24 h, and the reaction products were analyzed by gas chromatography. -1H2, the catalyst was reduced at a temperature of 750°C for 2.5h to obtain NMA-2-r. When the temperature dropped to room temperature, the industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance test at a reaction pressure of 3MPa.

[0085] At a space velocity of 10000ml / (g cat The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0086] At 200°C, the CO2 conversion rate was 6.5%, the CO conversion rate was 4.5%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 40.6%, the CO conversion rate was 93.0%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 96.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350°C, the CO2 conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 450°C, the CO2 conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0087] Example 3

[0088] A. Preparation of the catalyst carrier

[0089] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:80:160 to obtain a mixed solution with a cation concentration of 1mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120°C for 24h. The dried precipitate was calcined at 450°C for 3h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as the catalyst carrier.

[0090] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0091] A certain amount of Ni(NO3)2-6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2-6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 10%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded under a pressure of 15 MPa. The obtained catalyst was named NMA-2.

[0092] C. Test of the Ni-based catalyst for methanation of Fischer-Tropsch synthesis

[0093] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. 30 mL min -1 of H2was introduced into the reactor to reduce the catalyst: the reduction temperature was 750°C, and the reduction time was 1 h to obtain NMA-2-r. When the temperature dropped to room temperature, the industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance test, and the reaction pressure was 3 MPa.

[0094] At an airspeed of 10000 ml / (g cat ·h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0095] At 200°C, the CO2conversion rate was 2.4%, the CO conversion rate was 2.5%, and the CH4selectivity was 100%; at 250°C, the CO2conversion rate was 27.8%, the CO conversion rate was 89.0%, and the CH4selectivity was 100%; at 300°C, the CO2conversion rate was 93.2%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 350°C, the CO2conversion rate was 97.0%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 400°C, the CO2conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 450°C, the CO2conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4selectivity was 100%.

[0096]

Example 4

[0097] A. Preparation of catalyst carrier

[0098] A, Preparation of catalyst support for Fischer-Tropsch synthesis

[0099] B, Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0100] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst support obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 3 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-4.

[0101] C, Test of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0102] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. H2was introduced into the reactor at a flow rate of 30 mL min -1 -1, and the catalyst was reduced at a reduction temperature of 750°C for 5 h to obtain NMA-4-r. When the temperature dropped to room temperature, the performance test was carried out by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor. The reaction pressure was 3 MPa.

[0103] The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows at an airspeed of 10000 ml / (g cat ·h):

[0104] At 200°C, the CO2 conversion rate was 1.6%, the CO conversion rate was 2.0%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 10.0%, the CO conversion rate was 62.0%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 82.1%, the CO conversion rate was 100%, and the CH4 selectivity was 90%; at 350°C, the CO2 conversion rate was 87.2%, the CO conversion rate was 95%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 94.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450°C, the CO2 conversion rate was 95.9%, the CO conversion rate was 99%, and the CH4 selectivity was 100%.

[0105] Example 5

[0106] Preparation of a catalyst carrier

[0107] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:82:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, the pH and temperature of the substrate solution were kept constant during the addition process, the precipitation process was kept stirring, and the stirring was continued for 5 h after the precipitation was completed. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24 h. The generated precipitate was washed with water for 6 times, the obtained precipitate was dried at 120°C for 24 h, the dried precipitate was calcined at 450°C for 12 h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0108] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0109] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-5.

[0110] C. Testing of the Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0111] The catalyst obtained in step B was ground into small particles of 100-140 mesh, and placed in a fixed bed reactor. A mixture of H2 and CO2 was introduced into the reactor at a flow rate of 30 mL min-1, and the temperature of the reactor was controlled at 300°C. The conversion rates of CO2 and CO and the selectivity of CH4 were measured. -1H2, the catalyst was reduced at a temperature of 750°C for 2.5h to obtain NMA-5-r. When the temperature dropped to room temperature, the industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance test at a reaction pressure of 3MPa.

[0112] At a space velocity of 10000ml / (g cat The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0113] At 200°C, the CO2 conversion rate was 2.9%, the CO conversion rate was 3.3%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 26.0%, the CO conversion rate was 84.0%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 93.2%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350°C, the CO2 conversion rate was 96.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 98.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 450°C, the CO2 conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0114]

Example 6

[0115] A. Preparation of the catalyst carrier

[0116] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:3:10:76 to obtain a mixed solution with a cation concentration of 1mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120°C for 24h. The dried precipitate was calcined at 450°C for 6h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as the catalyst carrier.

[0117] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0118] A certain amount of Ni(NO3)2.6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2.6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded at 15 MPa. The obtained catalyst was named NMA-6. The XRD spectrum of the catalyst after calcination is shown in Fig. 1. Compared with the catalyst NMA without Ca addition, the diffraction peaks attributed to MgAl2O4 spinel of the catalyst NMA-6 with Ca addition shifted to low angles, indicating that Ca was successfully doped into the spinel lattice. In addition, due to the excessive addition of Ca, part of the Ca was not doped into the spinel lattice, but existed in the form of CaO. Figure 1

[0119] C. Test of the Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0120] The catalyst obtained in step B was ground into 100-140 mesh small particles and placed in a fixed bed reactor. H2was introduced into the reactor at a flow rate of 30 mL min -1 -1, and the catalyst was reduced at a reduction temperature of 750°C for 2.5 h to obtain NMA-6-r. After the temperature dropped to room temperature, the performance test was carried out by introducing the industrial Fischer-Tropsch synthesis tail gas into the reactor. The reaction pressure was 3 MPa. The XRD spectrum of the catalyst after reduction is shown in Fig. 2. Compared with the catalyst NMA without Ca addition, the diffraction peaks attributed to MgAl2O4 spinel of the catalyst NMA-6 with Ca addition shifted to low angles, indicating that Ca was successfully doped into the spinel lattice. Figure 2

[0121] At a space velocity of 10000 ml / (g cat ·h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0122] At 200°C, the CO2conversion rate was 3.2%, the CO conversion rate was 3.8%, and the CH4selectivity was 100%; at 250°C, the CO2conversion rate was 35.8%, the CO conversion rate was 88.3%, and the CH4selectivity was 100%; at 300°C, the CO2conversion rate was 95.2%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 350°C, the CO2conversion rate was 96.6%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 400°C, the CO2conversion rate was 98.2%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 450°C, the CO2conversion rate was 97.9%, the CO conversion rate was 100%, and the CH4selectivity was 100%. ​​

[0123] Example 7

[0124] Preparation of catalyst carrier

[0125] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:8:11:90 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24 h. The generated precipitate was washed with water 6 times, and the obtained precipitate was dried at 120°C for 24 h. The dried precipitate was calcined at 750°C for 6 h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0126] B. Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0127] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, and then dried at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-7.

[0128] C. Testing of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0129] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. H2 was introduced into the reactor at a flow rate of 30 mL / min, and the catalyst was reduced at a temperature of 750°C for 2.5 h to obtain NMA-7-r. When the temperature dropped to room temperature, the performance test was carried out by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor, and the reaction pressure was 3 MPa. -1

[0130] The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows at an airspeed of 10000 ml / (g cat ·h):

[0131] ​At 200℃, the CO2 conversion rate was 5.5%, the CO conversion rate was 6.3%, and the CH4 selectivity was 100%; at 250℃, the CO2 conversion rate was 48.4%, the CO conversion rate was 88.3%, and the CH4 selectivity was 100%; at 300℃, the CO2 conversion rate was 97.2%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350℃, the CO2 conversion rate was 98.2%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400℃, the CO2 conversion rate was 98.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450℃, the CO2 conversion rate was 97.9%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0132] Example 8

[0133] Preparation of catalyst carrier

[0134] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:4:7:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70℃ at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70℃ for 24 h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120℃ for 24 h, and then calcined at 450℃ for 6 h. Subsequently, the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0135] B. Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0136] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 24%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, and then dried at 120℃ for 24 h. The powder catalyst was obtained by calcination at 750℃ for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-8.

[0137] C. Testing of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0138] The catalyst obtained in step B was ground into small particles of 100-140 mesh, and placed in a fixed bed reactor. A mixture of H2 and CO2 was introduced into the reactor at a flow rate of 30 mL min-1, and the temperature of the reactor was controlled at 300℃. The conversion rate of CO2 was 97.2%, the conversion rate of CO was 100%, and the selectivity of CH4 was 100%. -1H2, the catalyst was reduced at a temperature of 800°C for 1 h to obtain NMA-8-r. When the temperature dropped to room temperature, the industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance testing at a reaction pressure of 3 MPa.

[0139] At a space velocity of 10000 ml / (g cat The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0140] At 200°C, the CO2 conversion rate was 2.8%, the CO conversion rate was 3.2%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 34.4%, the CO conversion rate was 78.3%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 93.3%, the CO conversion rate was 96.3%, and the CH4 selectivity was 100%; at 350°C, the CO2 conversion rate was 95.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 97.9%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450°C, the CO2 conversion rate was 97.8%, the CO conversion rate was 99%, and the CH4 selectivity was 100%.

[0141]

Example 9

[0142] A. Preparation of the catalyst carrier

[0143] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24 h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120°C for 24 h. The dried precipitate was calcined at 450°C for 6 h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as the catalyst carrier.

[0144] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0145] A certain amount of Ni(NO3)2-6H2O and La(NO3)3-6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2-6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amount of La(NO3)3-6H2O was controlled to be 4% of the amount of substance of Ni(NO3)2-6H2O. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 750°C for 6 h. Finally, the catalyst powder was extruded under a pressure of 15 MPa. The obtained catalyst was named NMA-9.

[0146] C. Test of the Ni-based catalyst for methanation of Fischer-Tropsch synthesis

[0147] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. 30 mL min-1of H2was introduced into the reactor to reduce the catalyst: the reduction temperature was 750°C, and the reduction time was 2.5 h, to obtain NMA-9-r. When the temperature dropped to room temperature, the performance test was carried out by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor, and the reaction pressure was 3 MPa. -1

[0148] At a space velocity of 10000 ml / (g cat ·h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0149] At 200°C, the CO2conversion rate was 5.1%, the CO conversion rate was 4.5%, and the CH4selectivity was 100%; at 250°C, the CO2conversion rate was 42.7%, the CO conversion rate was 80.6%, and the CH4selectivity was 100%; at 300°C, the CO2conversion rate was 94.0%, the CO conversion rate was 96.0%, and the CH4selectivity was 100%; at 350°C, the CO2conversion rate was 96.8%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 400°C, the CO2conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4selectivity was 100%; at 450°C, the CO2conversion rate was 97.9%, the CO conversion rate was 100%, and the CH4selectivity was 100%, as shown in Figure 4

[0150]

Example 10

[0151] A. Preparation of the catalyst carrier

[0152] ​​A, Preparation of catalyst support for Fischer-Tropsch synthesis

[0153] B, Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0154] A certain amount of Ni(NO3)2·6H2O and Ce(NO3)3·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amount of Ce(NO3)3·6H2O was controlled to be 4% of the amount of substance of Ni(NO3)2·6H2O. The impregnation solution was uniformly added to the catalyst support obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 750°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-10.

[0155] C, Test of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0156] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. 30 mL min-1of H2was introduced into the reactor to reduce the catalyst: the reduction temperature was 500°C, and the reduction time was 5 h, to obtain NMA-10-r. When the temperature dropped to room temperature, industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance testing. The reaction pressure was 3 MPa. -1

[0157] The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows at a space velocity of 10000 ml / (g cat ·h):

[0158] ​At 200℃, the CO2 conversion rate was 5.6%, the CO conversion rate was 5.0%, and the CH4 selectivity was 100%; at 250℃, the CO2 conversion rate was 45.4%, the CO conversion rate was 83.2%, and the CH4 selectivity was 100%; at 300℃, the CO2 conversion rate was 95.9%, the CO conversion rate was 98.2%, and the CH4 selectivity was 100%; at 350℃, the CO2 conversion rate was 97.7%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400℃, the CO2 conversion rate was 98.0%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450℃, the CO2 conversion rate was 97.7%, the CO conversion rate was 99.4%, and the CH4 selectivity was 100%.

[0159] Example 11

[0160] Preparation of a catalyst carrier

[0161] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:40:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70℃ at the same time as the precipitant solution, the pH and temperature of the substrate solution were kept constant during the addition process, the precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70℃ for 24 h. The generated precipitate was washed with water for 6 times, the obtained precipitate was dried at 120℃ for 24 h, the dried precipitate was calcined at 650℃ for 6 h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0162] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0163] A certain amount of Ni(NO3)2·6H2O and Co(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amount of Co(NO3)2·6H2O was controlled to be 4% of the amount of substance of Ni(NO3)2·6H2O. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, and then dried at 120℃ for 24 h. The powder catalyst was obtained by calcination at 750℃ for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-11.

[0164] C. Testing of the Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0165] The catalyst obtained in step B was ground into 100-140 mesh particles and placed in a fixed-bed reactor. 30 mL of the catalyst was then introduced into the reactor. -1 The catalyst was reduced using H2 at a temperature of 500℃ for 5 hours to obtain NMA-11-r. After the temperature cooled to room temperature, industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance testing at a pressure of 3 MPa.

[0166] At 10000 ml / (g cat At a space velocity of h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction is as follows:

[0167] At 200℃, the CO2 conversion rate was 3.0%, the CO conversion rate was 5.8%, and the CH4 selectivity was 100%; at 250℃, the CO2 conversion rate was 39.9%, the CO conversion rate was 86.0%, and the CH4 selectivity was 100%; at 300℃, the CO2 conversion rate was 95.3%, the CO conversion rate was 98.8%, and the CH4 selectivity was 100%; at 350℃, the CO2 conversion rate was 97.4%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400℃, the CO2 conversion rate was 97.9%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 450℃, the CO2 conversion rate was 97.7%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0168]

Example 12

[0169] A. Preparation of catalyst support

[0170] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water at a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. This mixed solution and the precipitant solution were simultaneously and slowly added dropwise to a base solution with a pH of 9.5 and a temperature of 70℃. During the dropwise addition, the pH and temperature of the base solution were kept constant, and the precipitation process was carried out with stirring. After precipitation, stirring was continued for 5 hours. Then, stirring was stopped, and the suspension was allowed to stand at 70℃ for 24 hours. The resulting precipitate was washed with water 6 times, dried at 120℃ for 24 hours, and then calcined at 450℃ for 6 hours. The calcined precipitate was then ground into powder smaller than 60 mesh and used as a catalyst carrier.

[0171] B. Preparation of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0172] A certain amount of Ni(NO3)2-6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2-6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded under a pressure of 15 MPa. The obtained catalyst was named NMA-12.

[0173] C. Test of the Ni-based catalyst for methanation of Fischer-Tropsch synthesis

[0174] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. H2was introduced into the reactor at a flow rate of 30 mL / min to reduce the catalyst: the reduction temperature was 750°C and the reduction time was 5 h to obtain NMA-12-r. When the temperature dropped to room temperature, the performance test was carried out by introducing the tail gas of industrial Fischer-Tropsch synthesis into the reactor. The reaction pressure was 0.1 MPa. -1

[0175] At a space velocity of 10000 ml / (g cat ·h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0176] At 200°C, the CO2conversion rate was 0.6%, the CO conversion rate was 2.0%, and the CH4selectivity was 100%; at 250°C, the CO2conversion rate was 17.2%, the CO conversion rate was 63.7%, and the CH4selectivity was 100%; at 300°C, the CO2conversion rate was 68.9%, the CO conversion rate was 81.5%, and the CH4selectivity was 100%; at 350°C, the CO2conversion rate was 87.2%, the CO conversion rate was 91%, and the CH4selectivity was 100%; at 400°C, the CO2conversion rate was 88.0%, the CO conversion rate was 92.2%, and the CH4selectivity was 100%; at 450°C, the CO2conversion rate was 87.0%, the CO conversion rate was 92.6%, and the CH4selectivity was 100%.

[0177]

Example 13

[0178] A. Preparation of the catalyst carrier

[0179] ​A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water at a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. This mixed solution and the precipitant solution were simultaneously and slowly added dropwise to a base solution with a pH of 9.5 and a temperature of 70℃. During the dropwise addition, the pH and temperature of the base solution were kept constant, and the precipitation process was carried out with stirring. After precipitation, stirring was continued for 5 hours. Then, stirring was stopped, and the suspension was allowed to stand at 70℃ for 24 hours. The resulting precipitate was washed with water 6 times, dried at 120℃ for 24 hours, and then calcined at 450℃ for 6 hours. The calcined precipitate was then ground into powder smaller than 60 mesh and used as a catalyst carrier.

[0180] B. Preparation of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0181] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added dropwise to the catalyst support obtained in step A, and then allowed to stand for 24 hours, followed by drying at 120℃ for 24 hours. The catalyst was then calcined at 450℃ for 6 hours to obtain a powdered catalyst. Finally, the catalyst powder was extruded and molded at 15 MPa. The resulting catalyst was named NMA-13.

[0182] C. Testing of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0183] The catalyst obtained in step B was ground into 100-140 mesh particles and placed in a fixed-bed reactor. 30 mL of the catalyst was then introduced into the reactor. -1 The catalyst was reduced using H2 at a reduction temperature of 750℃ for 5 hours to obtain NMA-13-r. Figure 1 As shown. After the temperature drops to room temperature, industrial Fischer-Tropsch synthesis tail gas is introduced into the reactor for performance testing at a reaction pressure of 1 MPa.

[0184] At 5000ml / (g cat At a space velocity of h), the performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction is as follows:

[0185] At 200°C, the CO2 conversion rate was 14.6%, the CO conversion rate was 22.0%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 70.2%, the CO conversion rate was 93.7%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 96.9%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350°C, the CO2 conversion rate was 98.2%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 98.2%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450°C, the CO2 conversion rate was 98.0%, the CO conversion rate was 99.6%, and the CH4 selectivity was 100%.

[0186] Example 14

[0187] Preparation of a catalyst carrier

[0188] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, the pH and temperature of the substrate solution were kept constant during the addition process, the precipitation process was kept stirring, and the stirring was continued for 5 h after the precipitation was completed. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24 h. The generated precipitate was washed with water for 6 times, the obtained precipitate was dried at 120°C for 24 h, the dried precipitate was calcined at 450°C for 6 h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0189] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0190] A certain amount of Ni(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 450°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-14.

[0191] C. Testing of the Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0192] The catalyst obtained in step B was ground into small particles of 100-140 mesh, and placed in a fixed bed reactor. A mixture of H2 and CO2 was introduced into the reactor at a flow rate of 30 mL min-1, and the temperature of the reactor was controlled at 450°C. The conversion rates of CO2 and CO and the selectivity of CH4 were measured. -1H2, the catalyst was reduced: the reduction temperature was 750°C, and the reduction time was 2.5h, to obtain NMA-14-r, as shown in Figure 1 When the temperature dropped to room temperature, the industrial Fischer-Tropsch synthesis tail gas was introduced into the reactor for performance testing, and the reaction pressure was 3.5 MPa.

[0193] At a space velocity of 30000 ml / (g cat The performance of the catalytic Fischer-Tropsch synthesis tail gas methanation reaction was as follows:

[0194] At 200°C, the CO2 conversion rate was 2.1%, the CO conversion rate was 3.7%, and the CH4 selectivity was 100%; at 250°C, the CO2 conversion rate was 50.2%, the CO conversion rate was 93.0%, and the CH4 selectivity was 100%; at 300°C, the CO2 conversion rate was 94.1%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 350°C, the CO2 conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; at 400°C, the CO2 conversion rate was 97.8%, the CO conversion rate was 100%, and the CH4 selectivity was 100%; and at 450°C, the CO2 conversion rate was 97.7%, the CO conversion rate was 100%, and the CH4 selectivity was 100%.

[0195]

Example 15

[0196] A. Preparation of the catalyst carrier

[0197] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of a macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120°C for 24h. The dried precipitate was calcined at 450°C for 6h, and then the calcined precipitate was ground into a powder of less than 60 mesh, which was used as the catalyst carrier.

[0198] B. Preparation of a Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0199] A certain amount of Ni(NO3)2.6H2O and La(NO3)3.6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2.6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amount of La(NO3)3.6H2O was controlled to be 4% of the amount of substance of Ni(NO3)2.6H2O. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 750°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-15.

[0200] C, Test of the Ni-based catalyst for methanation of Fischer-Tropsch synthesis

[0201] The catalyst obtained in step B was ground into small particles of 100-140 mesh and placed in a fixed bed reactor. H2was introduced into the reactor at a flow rate of 30 mL / min to reduce the catalyst: the reduction temperature was 750°C, and the reduction time was 2.5 h, to obtain NMA-15-r. The stability test was performed by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor: the reaction temperature was 313°C, the reaction pressure was 3 MPa, the space velocity was 10000 ml / (g -1 ·h), and the test time was 500 h. cat

[0202] Under the conditions of a reaction temperature of 313°C, a reaction pressure of 3.5 MPa, and a space velocity of 10000 ml / (g cat ·h), the stability of NMA-15-r in the methanation reaction of Fischer-Tropsch synthesis tail gas was as follows: Figure 5 : the CO2conversion rate was maintained at 94.9%-95.4%, the CO conversion rate was maintained at 98.4%-100%, and the CH4selectivity was maintained at 100%.

[0203]

Example 16

[0204] A, Preparation of a catalyst carrier

[0205] ​A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water at a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. This mixed solution and the precipitant solution were simultaneously and slowly added dropwise to a base solution with a pH of 9.5 and a temperature of 70℃. During the dropwise addition, the pH and temperature of the base solution were kept constant, and the precipitation process was carried out with stirring. After precipitation, stirring was continued for 5 hours. Then, stirring was stopped, and the suspension was allowed to stand at 70℃ for 24 hours. The resulting precipitate was washed with water 6 times, dried at 120℃ for 24 hours, and then calcined at 450℃ for 6 hours. The calcined precipitate was then ground into powder smaller than 60 mesh and used as a catalyst carrier.

[0206] B. Preparation of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0207] A certain amount of Ni(NO3)2·6H2O and La(NO3)3·6H2O were dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amount of La(NO3)3·6H2O was controlled to be 4% of the molar amount of Ni(NO3)2·6H2O. The impregnation solution was uniformly added dropwise to the catalyst support obtained in step A, and then allowed to stand for 24 hours, followed by drying at 120℃ for 24 hours. Calcination at 750℃ for 6 hours yielded a powdered catalyst. Finally, the catalyst powder was extruded and molded at 15 MPa. The obtained catalyst was named NMA-16.

[0208] C. Testing of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0209] The catalyst obtained in step B was ground into 100-140 mesh particles and placed in a fixed-bed reactor. 30 mL of the catalyst was then introduced into the reactor. -1 The catalyst was reduced using H2 at a reduction temperature of 750℃ for 2.5 h to obtain NMA-16-r. Stability tests were then conducted by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor at a reaction temperature of 313℃, a reaction pressure of 3 MPa, and a space velocity of 10000 ml / (g⁻¹). cat ·h), test time 500h.

[0210] The reaction was carried out at a temperature of 413℃, a pressure of 3MPa, and a space velocity of 10000 ml / (g). cat Under the conditions of ·h), the stability of the NMA-16-r catalytic Fischer-Tropsch synthesis tail gas methanation reaction is as follows: Figure 6The CO2 conversion rate was maintained at 97.4%-98.1%, the CO conversion rate was maintained at 99.2%-100%, and the CH4 selectivity was maintained at 100%.

[0211] The XRD pattern of the catalyst after the stability test is shown in FIG. 2, and no obvious growth of Ni particles was observed in the catalyst after the stability test, indicating that the catalyst has excellent sintering resistance. In addition, no diffraction peak of NiO was observed, indicating that the catalyst has excellent oxidation resistance. Figure 7 The TG curve of the catalyst after the stability test is shown in FIG. 3, and the weight loss of the catalyst caused by carbon deposition combustion was only 8% of the mass of the catalyst after 500 h of high-temperature stability test, indicating that the catalyst has excellent carbon deposition resistance. Figure 8

[0212]

Example 17

[0213] A. Preparation of catalyst carrier

[0214] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water in a mass ratio of 1:5:20:76 to obtain a mixed solution with a cation concentration of 1 mol / L. The mixed solution was slowly added to a substrate solution with a pH of 9.5 and a temperature of 70°C at the same time as the precipitant solution, and the pH and temperature of the substrate solution were kept constant during the addition process. The precipitation process was kept stirring, and after the precipitation was completed, the stirring was continued for 5 h. Then the stirring was stopped, and the suspension was left to stand at 70°C for 24 h. The generated precipitate was washed with water for 6 times, and the obtained precipitate was dried at 120°C for 24 h. The dried precipitate was calcined at 450°C for 6 h, and then the calcined precipitate was crushed into a powder of less than 60 mesh, which was used as a catalyst carrier.

[0215] B. Preparation of Ni-based catalyst for Fischer-Tropsch synthesis methanation

[0216] A certain amount of Ni(NO3)2·6H2O, La(NO3)3·6H2O, and Co(NO3)2·6H2O was dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 25%. The amounts of La(NO3)3·6H2O and Co(NO3)2·6H2O were controlled to be 4% of the amount of substance of Ni(NO3)2·6H2O, respectively. The impregnation solution was uniformly added to the catalyst carrier obtained in step A, and then left to stand for 24 h, followed by drying at 120°C for 24 h. The powder catalyst was obtained by calcination at 750°C for 6 h. Finally, the catalyst powder was extruded into a shape under a pressure of 15 MPa. The obtained catalyst was named NMA-17.

[0217] ​C. Testing of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0218] The catalyst obtained in step B was ground into 100-140 mesh particles and placed in a fixed-bed reactor. 30 mL of the catalyst was then introduced into the reactor. -1 The catalyst was reduced using H2 at a reduction temperature of 750℃ for 2.5 h to obtain NMA-17-r. Stability tests were then conducted by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor at a reaction temperature of 313℃, a reaction pressure of 3 MPa, and a space velocity of 10000 ml / (g⁻¹). cat ·h), test time 500h.

[0219] The reaction was carried out at a temperature of 413℃, a pressure of 3MPa, and a space velocity of 10000 ml / (g). cat Under the conditions of ·h), the stability of the NMA-17-r catalytic Fischer-Tropsch synthesis tail gas methanation reaction is as follows: Figure 9 CO2 conversion rate remained at 97.5%-98.0%, CO conversion rate remained at 99.6%-100%, and CH4 selectivity remained at 100%.

[0220] The XRD pattern of the catalyst after stability testing is as follows: Figure 10 As shown, after the stability test, no significant Ni particle growth was observed in the catalyst, indicating excellent anti-sintering ability. Furthermore, no NiO diffraction peaks were observed, indicating excellent oxidation resistance. The thermogravimetric curve of the catalyst after the stability test is shown below. Figure 11 As shown, after 500 hours of high-temperature stability testing, the weight loss of the catalyst caused by carbon deposition combustion accounted for only 9% of the catalyst mass, indicating that the catalyst has excellent resistance to carbon deposition.

[0221]

Example 18

[0222] A. Preparation of catalyst support

[0223] A certain amount of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a certain amount of macromolecular pore-forming agent were dissolved in water at a mass ratio of 1:5.5:4:76 to obtain a mixed solution with a cation concentration of 1 mol / L. This mixed solution and the precipitant solution were simultaneously and slowly added dropwise to a base solution with a pH of 9.5 and a temperature of 70℃. During the dropwise addition, the pH and temperature of the base solution were kept constant, and the precipitation process was carried out with stirring. After precipitation, stirring was continued for 5 hours. Then, stirring was stopped, and the suspension was allowed to stand at 70℃ for 24 hours. The resulting precipitate was washed with water 6 times, dried at 120℃ for 24 hours, and then calcined at 450℃ for 6 hours. The calcined precipitate was then ground into powder smaller than 60 mesh and used as a catalyst carrier.

[0224] B. Preparation of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0225] A certain amount of Ni(NO3)2·6H2O, La(NO3)3·6H2O, and Co(NO3)2·6H2O were dissolved in water to prepare an impregnation solution. The amount of Ni(NO3)2·6H2O was controlled to ensure that the mass fraction of Ni in the catalyst after reduction was 40%. The amounts of La(NO3)3·6H2O and Co(NO3)2·6H2O were controlled to be 2% of the molar amount of Ni(NO3)2·6H2O. The impregnation solution was uniformly added dropwise to the catalyst support obtained in step A, and then allowed to stand for 24 hours, followed by drying at 120℃ for 24 hours. Calcination at 650℃ for 6 hours yielded a powdered catalyst. Finally, the catalyst powder was extruded and molded at 15 MPa. The obtained catalyst was named NMA-18-r.

[0226] C. Testing of Ni-based catalysts for methanation in Fischer-Tropsch synthesis

[0227] The catalyst obtained in step B was ground into 100-140 mesh particles and placed in a fixed-bed reactor. 30 mL of the catalyst was then introduced into the reactor. -1 The catalyst was reduced using H2 at a reduction temperature of 750℃ for 3.5 h to obtain NMA-17-r. Stability tests were then conducted by introducing industrial Fischer-Tropsch synthesis tail gas into the reactor at a reaction temperature of 313℃, a reaction pressure of 0.1 MPa, and a space velocity of 15000 ml / (g⁻¹). cat ·h), test time 500h.

[0228] The reaction was carried out at a temperature of 500℃, a pressure of 0.1 MPa, and a space velocity of 15000 ml / (g). cat Under the conditions of ·h), the stability of the tail gas methanation reaction of NMA-18-r catalytic Fischer-Tropsch synthesis was as follows: CO2 conversion remained at 97.1%-97.8%, CO conversion remained at 99.0%-99.8%, and CH4 selectivity remained at 99.2%-100%.

[0229] All embodiments described in this invention exhibit excellent catalytic activity and extremely high selectivity in the methanation reaction of Fischer-Tropsch synthesis tail gas. Furthermore, after prolonged stability testing at various temperatures, the conversion rates of CO2 and CO remained stable without significant deactivation, demonstrating excellent stability. Characterization results indicate that the Ni particles in the catalyst are well dispersed and possess high levels of resistance to sintering, oxidation, and carbon deposition. In conclusion, this catalyst shows promise for application in the methanation treatment of industrial Fischer-Tropsch synthesis tail gas.

[0230] The technical solutions disclosed and presented in the present application can be implemented by referring to the content of the present application, changing the conditions and routes, etc. Although the method and preparation technology of the present application have been described by means of preferred embodiments, the related technical personnel can obviously make changes or recombine the method and technical route described in the present application without departing from the content, spirit and scope of the present application, to realize the final preparation technology. It is particularly pointed out that all similar substitutions and changes are obvious to the technical personnel in the art, and they are considered to be included in the spirit, scope and content of the present application.

Claims

1. Use of a CaO-MgO-Al2O3 supported nickel catalyst in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, The reaction is carried out at a temperature of 200-500°C, a pressure of 0.1-3.5 MPa, and a space velocity of 5000-30000 ml / (g catalyst cat h); The preparation method of the CaO-MgO-Al2O3 supported nickel catalyst is as follows: The CaO-MgO-Al2O3 carrier is prepared by a coprecipitation method, and Ni and the additive M are loaded on the CaO-MgO-Al2O3 composite carrier by an impregnation method; and the composition of the catalyst after reduction is Ni-(M) / CaO-MgO-Al2O3; Taking the Ni-M / CaO-MgO-Al2O3 catalyst as a benchmark, the mass fraction of Ni is 10-40%, the mass fraction of CaO is 1-10%, the mass fraction of MgO is 5-32%, and the mass fraction of Al2O3 is 20-82%; the additive M is Co, La2O3 or CeO2, and the addition amount of the metal in the additive M is 0-4% of the molar amount of Ni.

2. The use of a CaO-MgO-Al203-supported nickel catalyst in the methanation of Fischer-Tropsch synthesis tail gas according to claim 1, characterized in that, The preparation method of the CaO-MgO-Al2O3 supported nickel catalyst comprises the following processes: (1) Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and a macromolecular pore-forming agent are dissolved in water to obtain a mixed solution; the mixed solution and a precipitant solution are simultaneously and slowly added to a reactor for precipitation, the precipitation process is kept stirring, and after the precipitation is completed, the stirring is continued for a certain time; then, standing, the generated precipitate is washed with water and dried; the dried precipitate is calcined at 450-750°C for 3-12h to obtain a CaO-MgO-Al2O3 carrier; (2) Ni(NO3)2·6H2O and a nitrate salt of the additive M are dissolved in water to prepare an impregnation solution; the impregnation solution is uniformly added to the catalyst carrier obtained in step (1), then standing, and then drying; finally, calcining at 450-750°C for 3-12h to obtain a CaO-MgO-Al2O3 supported nickel catalyst.

3. Use of a CaO-MgO-Al203 supported nickel catalyst according to claim 2 in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, In step (1), the macromolecular pore-forming agent is selected from at least one of PVP, PEG, and cellulose; the mass ratio of Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O to the macromolecular pore-forming agent is 1: (3-20): (4-82): (76-160); and the cation concentration of the mixed solution is 0.5-2 mol / L.

4. The use of a CaO-MgO-Al203-supported nickel catalyst in the methanation of Fischer-Tropsch synthesis tail gas according to claim 2, characterized in that, In step (1), the precipitant is selected from at least one of Na2CO3, NaHCO3, and NaOH; the temperature of the precipitation process is 60-80°C, and the PH is kept at 9-10; after the precipitation is completed, the stirring is continued for 3-7h, and then standing for 15-30h.

5. The use of a CaO-MgO-Al203 supported nickel catalyst according to claim 2 in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, In step (1), the drying temperature is 80-150°C, and the time is 15-30h.

6. The use of a CaO-MgO-Al203 supported nickel catalyst according to claim 2 in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, In step (2), the nitrate salt of the additive M includes one of Co(NO3)2·6H2O, Ce(NO3)3·6H2O, and La(NO3)3·6H2O.

7. The use of a CaO-MgO-Al203 supported nickel catalyst according to claim 2 in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, In step (2), the standing time is 15-30h; the drying temperature is 90-130°C, and the time is 15-30h.

8. Use of the CaO-MgO-Al203 supported nickel catalyst according to claim 1 in the methanation of Fischer-Tropsch synthesis tail gas, characterized in that, Before the reaction, the catalyst is put into the reactor, and a mixed gas of H2 or CO and inert gas is introduced into the reactor to reduce the catalyst: the volume content of H2 or CO in the mixed gas is 3-20%; the reduction temperature is 500-800℃, and the reduction time is 1-5h.

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