Cerium oxide supported nickel catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and relates to a cerium oxide supported nickel catalyst and a preparation method and application thereof, and the catalyst is composed of a metal nickel active component and a cerium oxide carrier. The cerium oxide prepared by adopting a reversed-phase microemulsion method is dispersed in a nano-scale manner, has a large specific surface area and abundant oxygen vacancies on the surface, can realize high dispersion of metal nickel after loading nickel on the cerium oxide, has relatively high stability, and is beneficial to realizing efficient methanation of carbon dioxide hydrogenation. By changing the preparation conditions of the reversed-phase microemulsion, the number of oxygen vacancies on the surface of the catalyst can be effectively adjusted, and the CO2 hydrogenation reaction performance of the catalyst is regulated and controlled. The cerium oxide supported nickel catalyst prepared by the invention has the CO2 conversion rate of 83% and the CH4 selectivity of 97%, and shows excellent CO2 conversion rate and methane selectivity, which indicates that the cerium oxide-containing catalyst provided by the invention has excellent CO2 hydrogenation performance, shows excellent catalytic activity, product selectivity and stability, and can be used for preparing a catalyst for hydrogenation of CO2. And large-scale industrial application can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a cerium oxide supported nickel catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Since the Industrial Revolution, the accumulation of carbon dioxide in the atmosphere has reached a critical level. The excessive emission and accumulation of carbon dioxide have caused a series of environmental problems. With the vigorous development of carbon capture technology and the electrolysis of water industry, the resource utilization technology of carbon dioxide hydrogenation to methane has received extensive attention. The CO2 molecular structure is stable, and there are still great challenges in the activation of CO2 and the dissociation of the C-O bond.

[0003] At present, the main catalysts used in the CO2 hydrogenation to methane reaction are supported metal catalysts, mainly using Group VIII metals (Ni, Ru, Co, Pt, etc.) as active components and oxides (such as CeO2, Al2O3, TiO2, ZrO2, etc.) as carriers. Among them, noble metal Ru-based catalysts have high reaction activity and stability, but due to their high cost, it is difficult to carry out large-scale applications. Non-noble metal Ni shows excellent reaction performance in the CO2 hydrogenation to methane reaction and has received extensive attention from researchers. It has been found that when Ni / CeO2 and Ni / Al2O3 are used for CO2 hydrogenation to methane, Ni / CeO2 shows more excellent reaction performance. CeO2 can provide more oxygen vacancies, which is beneficial to the activation of CO2 molecules (Appl. Catal., B, 2020, 265, 118538). Therefore, realizing the controllable preparation of the CeO2 carrier and constructing rich oxygen vacancies on its surface are beneficial to the efficient progress of the CO2 hydrogenation to methane reaction.

[0004] Ni / CeO2 has attracted much attention in carbon dioxide hydrogenation catalysts due to its high catalytic activity and low price. The specific surface area and the number of surface oxygen vacancies of cerium oxide play an important role in stabilizing Ni particles, improving the low-temperature activity and high-temperature stability of CO2 methanation. Usually, the cerium oxide prepared by the traditional precipitation method has a wide particle size distribution, the product purity is affected by the precipitant, and the number of surface oxygen vacancies of cerium oxide is low. The cerium oxide prepared by the reverse microemulsion method has a large specific surface area and a high oxygen vacancy content; after loading the non-noble metal Ni, the formed Ni particles are small in size and uniformly dispersed, and are not prone to problems such as sintering and agglomeration during the reaction process, showing excellent low-temperature activity and high-temperature stability. In the prior art, Ni / CeO2 catalysts usually have problems such as uneven dispersion of Ni particles and easy high-temperature agglomeration, resulting in disadvantages such as poor low-temperature activity and poor high-temperature stability when the Ni / CeO2 catalyst is used for CO2 hydrogenation to methane. Summary of the Invention

[0005] One of the technical problems to be solved by the present invention is to solve the problems of low low-temperature activity, low selectivity of methane products, and poor high-temperature stability of the catalyst used in the carbon dioxide hydrogenation methanation reaction, and to provide a cerium oxide-supported nickel catalyst. In this catalyst, cerium oxide is dispersed at the nanoscale, has a large specific surface area, and a high oxygen vacancy content. In the formed Ni / CeO2 catalyst, the metal Ni particles are small in size and highly dispersed, and the particle size distribution is uniform. The present invention also provides a preparation method of a supported catalyst, which has the characteristics of simple operation, strong repeatability, and high universality.

[0006] The purpose of the present invention is to provide an application of a cerium oxide-supported nickel catalyst. By providing a preparation method of nano-ceria with simple operation, controllable morphology and particle size, uniform particle size distribution and narrow distribution range, when it is loaded with metal Ni and used in the carbon dioxide hydrogenation methanation reaction, it has the characteristics of high activity, high selectivity of methane products, and high stability.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a preparation method of a cerium oxide-supported nickel catalyst, and this preparation method includes the following steps:

[0009] (1) Mix an oil phase, a surfactant and a co-surfactant in a certain proportion to form a uniform oil phase solution, and distribute the obtained oil phase solution into two systems A and B;

[0010] (2) Add a cerium salt precursor and a precipitant to the aqueous phase respectively, and add the obtained solution containing the cerium precursor and the solution containing the precipitant to the oil phase solutions of the above-prepared systems A and B respectively. Mix the solutions of the two systems and stir evenly to form a mixture;

[0011] (3) Centrifuge, wash and dry the above-obtained mixture to obtain a solid powder;

[0012] (4) Grind the solid powder evenly and calcine it at 200-400 °C for 2-12 h to obtain cerium oxide powder;

[0013] (5) Prepare a cerium oxide-supported nickel catalyst from the cerium oxide powder and a nickel salt precursor by an impregnation method.

[0014] Further, in step (1), the oil phase is one or two of cyclohexane and n-octane;

[0015] The surfactant is one or more of polyethylene glycol octyl phenyl ether (Triton), cetyl trimethyl ammonium bromide (CTAB), and sodium dodecyl sulfate (SDS); the co-surfactant is one or two of isopropyl alcohol and n-butanol; the cerium salt precursor includes one or more of Ce(NO3)3·6H2O, CeCl3·7H2O, and Ce(Ac)3·xH2O; the precipitant is one or more of ammonia water, dilute sodium hydroxide solution, and dilute potassium hydroxide solution.

[0016] Further, in step (1), the volume ratio of the aqueous phase: surfactant: co-surfactant: oil phase is 1:1:4 - 6:3 - 5; in step (2), the molar ratio of the cerium salt precursor to the precipitant is 1:1 - 1:3.

[0017] Further, in step (2), when the two system solutions are mixed, the solution containing the cerium precursor needs to be slowly dropped into the solution containing the precipitant, and continuously stirred. After the dropping is completed, stir for at least 30 min.

[0018] Further, in step (3), the drying condition is to dry in an oven at 60 - 100 °C for 6 - 24 h. Further, in step (4), the roasting operation condition is to grind the solid powder evenly, transfer it into a muffle furnace, and heat it to 200 - 400 °C at a heating rate of 1 - 10 °C min -1 and roast for 2 - 12 h.

[0019] Further, in step (5), the nickel salt precursor includes one or more of Ni(NO3)2·6H2O, NiCl2·6H2O, NiSO4·6H2O, and Ni(Ac)2·4H2O.

[0020] In the technical solution of the present invention, the impregnation method can be prepared by the equal-volume impregnation method or the excess impregnation method. After impregnation, roasting is carried out. The roasting condition is to heat to 300 - 500 °C at a heating rate of 1 - 10 °C min -1 and keep for 2 - 6 h.

[0021] The second aspect of the present invention provides a cerium oxide supported nickel catalyst prepared by the above preparation method. The catalyst includes a metallic nickel active component and cerium oxide as a carrier; wherein, the content of the metallic nickel active component is 1 wt% - 40 wt%, and the content of CeO2 is 60 wt% - 99 wt%.

[0022] Further, the content of the active metallic nickel is 3 wt% - 25 wt%.

[0023] The third aspect of the present invention provides the application of the cerium oxide supported nickel catalyst in the carbon dioxide hydrogenation to methane reaction, including the following steps:

[0024] (1) Prior to the reaction, the supported catalyst is subjected to in-situ reduction treatment at a reduction temperature of 300 - 600 °C, and the reduction atmosphere is high-purity H2 or one or more of the inert gases N2, Ar, and He mixed with H2;

[0025] (2) In an atmospheric fixed-bed reactor, the reaction temperature is controlled at 200 - 400 °C, the molar ratio of H2 to CO2 in the feed gas is 0.5 - 6, and the gas hourly space velocity is 6000 - 120000 mL h -1 g cat -1 -1.

[0026] Furthermore, in step (1), the temperature of the in-situ reduction pretreatment is 400 - 500 °C, and the reduction atmosphere is pure hydrogen; in step (2), the molar ratio of H2 to CO2 in the feed gas is 2 - 4, and the gas hourly space velocity is 12000 - 90000 mL h -1 g cat -1 -1.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1) The ceria-supported nickel catalyst prepared by the present invention is composed of a metallic nickel active component and a ceria support. The ceria support with abundant oxygen vacancies is prepared by the reverse microemulsion method. By regulating the concentration and type of the precipitating agent, the ceria support shows nanoscale dispersion, with uniform particle size and narrow distribution range. The size and morphology of ceria can be controllably adjusted, and the adjustable range of the metal loading amount is large. Moreover, the preparation operation is simple and the method is reliable, which is conducive to large-scale production and use.

[0029] 2) By impregnation method, metallic nickel is loaded onto ceria, and the Ni particles in the obtained catalyst are small in size and highly dispersed. The catalyst has abundant oxygen vacancies, which can serve as the adsorption sites for CO2, promoting the activation of CO2 and the cleavage of C - O bonds, and facilitating the efficient conversion of carbon dioxide hydrogenation.

[0030] 3) The ceria-supported nickel catalyst prepared by the present invention is used for the carbon dioxide hydrogenation methanation reaction, with high reaction activity, high selectivity for methane products, and excellent high-temperature stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a graph showing the evaluation of the carbon dioxide reaction performance of the catalysts of Examples 1 - 3 and Comparative Examples 1 - 3 of the present invention (reaction conditions: atmospheric pressure, 200 - 400 °C, GHSV = 60000 mL h -1 g cat -1 -1).

[0032] Figure 2 This is the X-ray diffraction (XRD) pattern of the catalysts of Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0033] Figure 3 This is the transmission electron microscope (TEM) image of the catalysts of Examples 1 and 2 and Comparative Example 1 of the present invention. Detailed implementation manners

[0034] The present invention will be described in detail below in conjunction with the specific implementation manners.

[0035] Example 1

[0036] 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether were successively added to beakers A and B and stirred evenly. 3.78 g of Ce(NO3)3·6H2O solid was weighed and dissolved in 30 mL of deionized water, and then added to beaker A. 30 mL of ammonia water was measured and added to beaker B. The reverse microemulsions in beakers A and B were stirred evenly. The solution in beaker A was slowly added dropwise to beaker B under stirring. After the addition, stirring was continued for more than 30 min. The obtained precipitate was centrifuged, washed with deionized water until neutral, placed in an oven at 60 °C for drying. The obtained solid was ground and then added to a tubular furnace and calcined at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, 0.25 g of Ni(NO3)2·6H2O and an appropriate amount of deionized water were mixed evenly, and then 0.95 g of CeO2 powder was added. After mixing evenly, it was placed in an oven at 60 °C for drying. The obtained solid powder was ground and then placed in a muffle furnace and heated to 400 °C at a heating rate of 5 °C / min -1 and calcined for 3 h. After cooling to room temperature, a 5% Ni / CeO2-RM catalyst was obtained.

[0037] Example 2

[0038] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir well. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it into beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly, and add them into beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid, add it into a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.25 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water. Then add 0.95 g of CeO2 powder, mix them evenly, and place them in an oven at 60 °C for drying. Grind the obtained solid powder, place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 5% Ni / CeO2-RM-1:1 catalyst after calcining for 3 h and cooling to room temperature.

[0039] Example 3

[0040] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir well. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it into beaker A. Measure 10 mL of ammonia water and 20 mL of deionized water, mix them evenly, and add them into beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid, add it into a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.25 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water. Then add 0.95 g of CeO2 powder, mix them evenly, and place them in an oven at 60 °C for drying. Grind the obtained solid powder, place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 5% Ni / CeO2-RM-1:2 catalyst after calcining for 3 h and cooling to room temperature.

[0041] Example 4

[0042] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it into beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly and add them into beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it into a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.15 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water, then add 0.97 g of CeO2 powder. After mixing evenly, place it in an oven at 60 °C for drying. Grind the obtained solid powder and place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 3% Ni / CeO2-RM-1:1 catalyst after calcining for 3 h and cooling to room temperature.

[0043] Example 5

[0044] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it into beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly and add them into beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it into a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.51 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water, then add 0.90 g of CeO2 powder. After mixing evenly, place it in an oven at 60 °C for drying. Grind the obtained solid powder and place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 10% Ni / CeO2-RM-1:1 catalyst after calcining for 3 h and cooling to room temperature.

[0045] Example 6

[0046] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it to beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly, and add them to beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it to a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.76 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water, then add 0.85 g of CeO2 powder. After mixing evenly, place it in an oven at 60 °C for drying. Grind the obtained solid powder and place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 15% Ni / CeO2-RM-1:1 catalyst after calcining for 3 h and cooling to room temperature.

[0047] Comparative Example 1

[0048] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it to beaker A. Weigh 16.31 g of NaOH solid, dissolve it in 30 mL of deionized water (concentrated NaOH solution), mix them evenly, and add them to beaker B. Stir the reverse microemulsions in beakers A and B evenly. Slowly drip the solution in beaker A into beaker B under stirring. After dripping, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it to a tubular furnace, and calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. According to the loading amount and water absorption, weigh 0.25 g of Ni(NO3)2·6H2O and mix it evenly with an appropriate amount of deionized water, then add 0.95 g of CeO2 powder. After mixing evenly, place it in an oven at 60 °C for drying. Grind the obtained solid powder and place it in a muffle furnace, and heat it up to 400 °C at a heating rate of 5 °C min -1 to obtain a 5% Ni / CeO2-RM-NaOH catalyst after calcining for 3 h and cooling to room temperature.

[0049] Comparative Example 2

[0050] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it to beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly and add them to beaker B. Stir the reverse microemulsion in beakers A and B evenly. Slowly add the solution in beaker A dropwise to beaker B under stirring. After the addition, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it to a tubular furnace, calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. Weigh 3.33 g of nitrosyl ruthenium nitrate solution (1.5 wt% Ru) and place it in a beaker, add 10 mL of deionized water, stir evenly, then add 0.95 g of CeO2-RM-1:1 powder. After stirring vigorously for 30 min, place it in a water bath at 60 °C and stir and evaporate until it becomes viscous. Place the obtained sample in an oven at 60 °C for drying. After complete drying, take it out and grind it, and place it in a muffle furnace and heat it to 400 °C at a heating rate of 5 °C min -1 to obtain a 5% Ru / CeO2-RM-1:1 catalyst by calcining for 3 h.

[0051] Comparative Example 3

[0052] Add 135 mL of isopropanol, 105 mL of cyclohexane, and 30 mL of polyethylene glycol octyl phenyl ether into beakers A and B respectively, and stir evenly. Weigh 3.78 g of Ce(NO3)3·6H2O solid, dissolve it in 30 mL of deionized water, and add it to beaker A. Measure 15 mL of ammonia water and 15 mL of deionized water, mix them evenly and add them to beaker B. Stir the reverse microemulsion in beakers A and B evenly. Slowly add the solution in beaker A dropwise to beaker B under stirring. After the addition, stir for more than 30 min. Centrifuge the obtained precipitate, wash it with deionized water until neutral, place it in an oven at 60 °C for drying. Grind the obtained solid and add it to a tubular furnace, calcine it at 275 °C for 4 h to obtain pale yellow cerium oxide powder. Weigh 0.25 g of Co(NO3)2·6H2O solid and place it in a beaker, add 10 mL of deionized water, dissolve and stir evenly, then add 0.95 g of CeO2-RM-1:1 solid. After stirring vigorously for 30 min, place it in a water bath at 60 °C and stir and evaporate until it becomes viscous. Place the obtained sample in an oven at 60 °C for drying. After complete drying, take it out and grind it, and place it in a muffle furnace and heat it to 400 °C at a heating rate of 5 °C min -1 to obtain a 5% Co / CeO2-RM-1:1 catalyst by calcining for 3 h.

[0053] I. Performance evaluation of carbon dioxide hydrogenation reaction

[0054] The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were evaluated for their performance in the hydrogenation of carbon dioxide. 0.1 g of the catalyst was weighed and loaded into a quartz reaction tube of a fixed-bed reactor. First, the above catalyst was subjected to H2 reduction treatment, with in-situ reduction at 500 °C for 2 h. After the reduction was completed, it was cooled to below the reaction temperature, and the feed gas was introduced for reaction. The reaction conditions for the hydrogenation of carbon dioxide were as follows: atmospheric pressure, a reaction temperature of 200-400 °C, a molar ratio of H2 to CO2 in the feed gas of 4, and a feed gas space velocity of 60,000 mL / h -1 g cat -1 . The feed gas and reaction products were analyzed online using an Agilent 8860 gas chromatograph equipped with a TDX-01 packed column and a TCD detector.

[0055] It can be seen that Figure 1 in the temperature range of 200-400 °C, the CO2 conversion rate and methane selectivity of Examples 1-3 were significantly higher than those of Comparative Examples 1-3. Among them, when the reaction temperature was 400 °C, the CO2 conversion rate of the 5% Ni / CeO2-RM-1:1 catalyst was 83%, and the selectivity of CH4 was 97%. This shows that the Ni / CeO2-RM catalyst formed by loading Ni on CeO2 prepared by the reverse microemulsion method has excellent performance in the methanation of carbon dioxide by hydrogenation.

[0056] It can be seen from Figure 2 the XRD results that among the XRD patterns of Examples 1-3 and Comparative Examples 1-3, only the corresponding metal peaks appeared in two catalysts, 5% Ni / CeO2-RM-NaOH (Comparative Example 1) and 5% Co / CeO2-RM-1:1. This shows that the metals in the examples were highly dispersed and the metal utilization rate was high; metal agglomeration occurred in the comparative examples.

[0057] It can be seen from Figure 3 the TEM results that the cerium oxide carriers of 5% Ni / CeO2-RM (Example 1) and 5% Ni / CeO2-RM-1:1 (Example 2) were evenly distributed; the cerium oxide carriers of 5% Ni / CeO2-RM-NaOH (Comparative Example 1) were of different sizes and showed aggregation.

[0058] In summary, the present invention uses the reverse microemulsion method to prepare a cerium oxide support, and prepares a nickel-loaded cerium oxide catalyst by the impregnation method. The cerium oxide support prepared by the reverse microemulsion method in the present invention has a large specific surface area and a high oxygen vacancy content; the active metal Ni particles in the formed catalyst are small in size and uniformly dispersed, and remain stable at high temperatures. The supported catalyst provided in the present invention is used for the CO2 hydrogenation methanation reaction, has high reaction activity, high product selectivity, and the catalyst has good stability. The present invention provides an effective implementation scheme for the resource utilization of CO2. The preparation method of the catalyst in the present invention is simple to operate, has good repeatability, and is conducive to large-scale industrial use.

[0059] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A preparation method of a cerium oxide supported nickel catalyst, characterized in that, The preparation method comprises the following steps: (1) Mix an oil phase, a surfactant and a co-surfactant in a certain proportion to form a homogeneous oil phase solution, and distribute the obtained oil phase solution into two systems, A and B; (2) Add a cerium salt precursor and a precipitant to an aqueous phase respectively. Add the obtained solution containing the cerium precursor and the solution containing the precipitant into the oil phase solutions of the above-prepared systems A and B respectively, mix the solutions of the two systems, and stir evenly to form a mixture; (3) Centrifuge, wash and dry the mixture obtained above to obtain a solid powder; (4) Grind the solid powder evenly, and calcine it at 200-400 °C for 2-12 h to obtain cerium oxide powder; (5) Prepare a cerium oxide supported nickel catalyst by an impregnation method using the cerium oxide powder and a nickel salt precursor.

2. The preparation method of the cerium oxide supported nickel catalyst according to claim 1, characterized in that, In step (1), the oil phase is one or both of cyclohexane and n-octane; The surfactant is one or several of polyethylene glycol octyl phenyl ether (Triton), cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS); the co-surfactant is one or both of isopropyl alcohol and n-butanol; the cerium salt precursor includes one or several of Ce(NO3)3·6H2O, CeCl3·7H2O, Ce(Ac)3·xH2O; the precipitant is one or several of ammonia water, dilute sodium hydroxide solution, dilute potassium hydroxide solution; In step (5), the nickel salt precursor includes one or several of Ni(NO3)2·6H2O, NiCl2·6H2O, NiSO4·6H2O, Ni(Ac)2·4H2O.

3. The preparation method of the cerium oxide supported nickel catalyst according to claim 1, characterized in that, In step (1), the volume ratio of the aqueous phase: surfactant: co-surfactant: oil phase is 1:1:4-6:3-5; in step (2), the molar ratio of the cerium salt precursor to the precipitant is 1:1-1:

3.

4. The preparation method of the cerium oxide supported nickel catalyst according to claim 1, characterized in that, In step (2), when mixing the solutions of the two systems, the solution containing the cerium precursor needs to be slowly dropped into the solution containing the precipitant, and stirred continuously. After the dropping is completed, stir for at least 30 min.

5. The preparation method of the ceria-supported nickel catalyst according to claim 1, characterized in that, In step (3), the drying condition is drying in an oven at 60-100 °C for 6-24 h; in step (4), the roasting operation condition is grinding the solid powder evenly, transferring it into a muffle furnace, and heating it to 200-400 °C at a heating rate of 1-10 °C / min -1 and roasting for 2-12 h.

6. The preparation method of the cerium oxide supported nickel catalyst according to claim 1, characterized in that, The impregnation method can be prepared by the equal-volume impregnation method or the excess impregnation method. After impregnation, calcination is carried out. The conditions for calcination are heating to 300-500 °C at a heating rate of 1-10 °C / min -1 and maintaining for 2-6 h.

7. A cerium oxide supported nickel catalyst, characterized in that, Prepared by the preparation method according to any one of claims 1-6, characterized in that the catalyst comprises a metallic nickel active component and cerium oxide as a carrier; wherein, the content of the metallic nickel active component is 1 wt% - 40 wt%, and the content of CeO2 is 60 wt% - 99 wt%; preferably, the content of the active metallic nickel is 3 wt% - 25 wt%.

8. Use of the cerium oxide supported nickel catalyst according to claim 7 in the carbon dioxide hydrogenation methanation reaction, characterized in that, Comprises the following steps: (1) Perform in-situ reduction treatment on the supported catalyst before the reaction, the reduction temperature is 300-600 °C, and the reduction atmosphere is high-purity H2 or one or more of inert gases such as H2 and N2, Ar, He; (2) In an atmospheric pressure fixed bed reactor, control the reaction temperature at 200 - 400 °C, the molar ratio of H2 to CO2 in the raw material gas is 0.5 - 6, and the gas hourly space velocity is 6000 - 120000 mL h -1 g cat -1 .

9. Use of the cerium oxide supported nickel catalyst according to claim 8 in the carbon dioxide hydrogenation methanation reaction, characterized in that, The carbon dioxide conversion rate of the catalyst ≥ 83% 10. Use of the cerium oxide-supported nickel catalyst according to claim 8 in the carbon dioxide hydrogenation methanation reaction, characterized in that, In step (1), the temperature of the in-situ reduction pretreatment is 400 - 500 °C, and the reduction atmosphere is pure hydrogen; in step (2), the molar ratio of H2 to CO2 in the feed gas is 2 - 4, and the gas hourly space velocity is 12000 - 90000 mLh -1 g cat -1 .

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