A sodium salt promoted nano Co3O4 composite MgO bifunctional material and a preparation method thereof

Abstract

The application discloses a sodium salt promoted nano Co3O4 composite MgO bifunctional material and a preparation method thereof, and comprises the following steps: heating sodium salt to obtain a molten sodium salt; adding magnesium salt and cobalt salt into an aqueous ammonia solution, uniformly stirring, and then drying to obtain a solid product; grinding the solid product into a powder, adding the powder into the molten sodium salt, uniformly stirring under heating, cooling and grinding to obtain a mixed powder; and calcining the mixed powder to obtain the sodium salt promoted nano Co3O4 composite MgO bifunctional material. The synthesized sodium salt promoted nano Co3O4 composite MgO bifunctional material can realize CO2 adsorption and methanation under a medium-temperature condition, realizes efficient CO2 adsorption and conversion, and improves the CO2 adsorption performance of MgO.

Description

TECHNICAL FIELD

[0001] The application relates to a sodium salt promoted nano-Co3O4 composite MgO bifunctional material and a preparation method thereof, and belongs to the technical field of CO2 adsorption and conversion. BACKGROUND

[0002] The increase of artificial CO2 emission is the main reason for the rise of global average surface temperature. The rise of global temperature leads to the reduction of glacier area, the rise of sea level, the frequent occurrence of extreme weather and the breaking of ecological balance, so it is urgent to control artificial CO2 emission. Energy substitution (such as nuclear energy, natural gas, hydrogen fuel cell and renewable energy), the improvement of energy efficiency and carbon capture, utilization and storage are important methods for controlling CO2 emission at present. Carbon capture, utilization and storage (CCUS) is one of the most effective technologies for controlling CO2 emission at present, which includes four links of CO2 capture, transportation, utilization and storage. However, CCUS has the problems of high cost and CO2 leakage. The proposal of integrated CO2 capture and conversion (ICCC) avoids the process of CO2 transportation and storage in CCUS, and reduces the cost of CO2 emission reduction. ICCC includes CO2 capture and CO2 conversion. At present, the methods of CO2 capture have been studied, including absorption method and adsorption method. The absorption method is mature, and mainly uses amine-based solvent as the absorbent, but the amine-based solvent can cause harm to the environment; the adsorption method includes physical adsorption method and chemical adsorption method. The physical adsorption method uses carbonaceous materials, zeolites, molecular sieves and metal organic frameworks as adsorbents; the chemical adsorbents usually use metal oxides, layered hydroxides and amine-based adsorbents. The commonly used catalysts for CO2 conversion are ruthenium, rhodium, gold, nickel, cobalt, iron and platinum, and the commonly used catalyst carriers are aluminum oxide, cerium oxide, magnesium oxide and calcium oxide.

[0003] Dual functional materials (DFMs) are the key to realize ICCC, which are composed of adsorbents and catalysts. Metal oxides have the advantages of low cost, large theoretical adsorption capacity and abundant sources, and are one of the ideal CO2 adsorbents. Transition metals have the advantages of low cost and high conversion efficiency, and can be used as CO2 conversion catalysts. The dual functional materials studied so far include Ni / CaO, Ni-CaO-CeO2, Ru-CaO / Al2O3, Ru-Na2CO3 / Al2O3, Ru / CeO2-MgO, Ru-Na2O / Al2O3, Ni-Na2CO3 / Al2O3, Ni-CaO / Al2O3 and NaNO3-Ni / MgO. However, there are problems such as high CO2 adsorption and conversion temperature, complex preparation method, low adsorption and conversion capacity, poor stability, high pollutant emission, etc. Therefore, the research and preparation of dual functional materials with simple, clean preparation method, high CO2 adsorption and conversion capacity, good stability and low temperature adsorption and conversion is the key direction of ICCC. SUMMARY

[0004] In order to overcome the problems of high CO2 adsorption and conversion temperature, complex preparation method, low adsorption and conversion capacity, poor stability and high pollutant emission in the prior art, the purpose of the present application is to provide a sodium salt promoted nano Co3O4 composite MgO dual functional material and a preparation method thereof. The method is simple and clean to operate, and the prepared sample has high CO2 adsorption and conversion performance and stability.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of a sodium salt promoted nano Co3O4 composite MgO dual functional material, comprising the following steps:

[0007] Heat the sodium salt to melting to obtain a molten sodium salt;

[0008] Add the magnesium salt and the cobalt salt to the aqueous ammonia solution, stir uniformly, and then dry to obtain a solid product;

[0009] Grind the solid product into a powder, add it to the molten sodium salt, stir uniformly under heating, cool and grind to obtain a mixed powder;

[0010] Calcine the mixed powder to obtain a sodium salt promoted nano Co3O4 composite MgO dual functional material.

[0011] Further, the sodium salt is one or both of sodium nitrite and sodium nitrate.

[0012] Further, the heating temperature for melting is 320-400℃.

[0013] Further, the cobalt salt is cobalt nitrate hexahydrate, cobalt chloride hexahydrate or cobalt acetylacetonate.

[0014] Further, the magnesium salt is magnesium carbonate, magnesium nitrate or magnesium acetate.

[0015] Further, the mass ratio of the cobalt salt to the magnesium salt is 1:2-1:9.

[0016] Further, the volume concentration of ammonia in the ammonia water solution is 25-28%, and the volume ratio of the ammonia water solution to the magnesium salt is 1 mL-10 mL: 1 g.

[0017] Further, the molar ratio of the sodium salt to the magnesium salt is 1:3-1:20.

[0018] Further, the drying temperature is 70-100 DEG C, and the time is 8-10 h.

[0019] Further, the calcination atmosphere is one or more mixed gases of H2, N2 and air; the calcination temperature is 300-500 DEG C, and the time is 4-6 h; the temperature is raised from room temperature to 300-500 DEG C at a temperature raising rate of 5-20 DEG C / min.

[0020] A sodium salt promoted nano Co3O4 composite MgO bifunctional material prepared according to the preparation method.

[0021] Compared with the prior art, the present application has the beneficial effects that:

[0022] In the present application, first, sodium salt is used as the molten salt, and the sodium salt can be used as a growth directing agent for the cobalt salt, so that the cobalt salt is grown in a directional manner, the growth process of Co3O4 can be effectively controlled, the obtained Co3O4 has an ultra-thin flaky structure, which is conducive to the maximum exposure of the active sites and the improvement of the conversion efficiency. Meanwhile, the sodium salt can be used as an auxiliary agent for CO2 capture, which can effectively improve the CO2 capture amount of MgO. Since the sodium salt does not need to be separated from the product, no waste is generated, and therefore the preparation process does not cause environmental pollution. The sodium salt promoted Co3O4 composite MgO bifunctional material synthesized in the present application can realize CO2 adsorption and methanation between 300 DEG C and 400 DEG C, realize efficient CO2 adsorption and conversion, and improve the CO2 adsorption performance of MgO. Through multiple CO2 adsorption and conversion, the methane selectivity of the material is still high (about 90%), and the material has good cycle stability. Compared with other bifunctional materials, the preparation method of the present application is simple, the synthesis raw materials are abundant, and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the application flowchart of the sodium salt promoted nano Co3O4 composite MgO bifunctional material in the present application;

[0024] Figure 2 X-ray diffraction (XRD) pattern of the bifunctional material prepared in Example 1 of the present application, denoted as NaNO2-Co3O4-MgO molten salt;

[0025] Figure 3 Scanning electron microscope (SEM) photograph of the bifunctional material prepared in Example 1 of the present application, denoted as NaNO2-Co3O4-MgO molten salt;

[0026] Figure 4 Scanning electron microscope (SEM) photograph of the bifunctional material prepared in Comparative Example 1 of the present application, denoted as Co3O4-MgO;

[0027] Figure 5 Scanning electron microscope (SEM) photograph of the bifunctional material prepared in Comparative Example 1 of the present application, denoted as NaNO2-Co3O4-MgO mechanical mixture;

[0028] Figure 6 Comparison chart of CO2 adsorption capacity of MgO, Co3O4, Co3O4-MgO, NaNO2-Co3O4-MgO mechanical mixture and NaNO2-Co3O4-MgO molten salt;

[0029] Figure 7 Comparison chart of CO2 methanation capacity of MgO, Co3O4, Co3O4-MgO, NaNO2-Co3O4-MgO mechanical mixture and NaNO2-Co3O4-MgO molten salt. DETAILED DESCRIPTION

[0030] For the purpose of promoting the understanding of the present application, the present application will be more fully described by reference to the accompanying drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The present application is capable of many modifications in various obvious aspects, all without departing from the scope of the present application.

[0031] The present application is a preparation method of a sodium salt promoted nano-Co3O4 composite MgO bifunctional material, comprising the following steps:

[0032] Step 1: heating a sodium salt to a molten state and keeping it, to obtain a molten sodium salt;

[0033] wherein the sodium salt is one or both of sodium nitrite and sodium nitrate; the heating temperature of the sodium salt is 320-400℃;

[0034] Step 2: adding magnesium salt and cobalt salt to an aqueous ammonia solution, stirring for 2-4h, and then drying at 70-100℃ for 8-10h to obtain a solid product;

[0035] The cobalt salt is cobalt nitrate hexahydrate, cobalt chloride hexahydrate or cobalt acetylacetonate, the magnesium salt is magnesium carbonate, magnesium nitrate or magnesium acetate, the mass ratio of the cobalt salt to the magnesium salt is 1:2-1:9, the volume concentration of ammonia in the ammonia solution is 25-28%, and the volume ratio of the ammonia solution to the magnesium salt is 1 mL-10 mL: 1 g.

[0036] Step 3: The solid product is ground into powder, added to the molten sodium salt, stirred under heating for 8-12 h, cooled and ground to obtain a mixed powder; the molar ratio of the sodium salt to the magnesium salt is 1:3-1:20;

[0037] Step 4: The mixed powder is heated from room temperature to 300-500°C at a heating rate of 5-20°C / min, calcined for 4-6 h to obtain a nano Co3O4 composite MgO bifunctional material;

[0038] The calcination atmosphere is one or a mixture of several of H2, N2 and air.

[0039] The following are specific examples.

[0040] Example 1

[0041] (1) 0.69 g of sodium nitrite is heated to a molten state at 320°C and kept, to obtain a molten sodium salt;

[0042] (2) 4.22 g of magnesium carbonate and 1.48 g of cobalt nitrate hexahydrate are added to 24 mL of an ammonia solution (volume ratio of ammonia to deionized water = 1:5 mL), stirred for 3 h, and then dried at 70°C for 9 h to obtain a solid product;

[0043] (3) The solid product is ground into powder, added to the molten sodium salt, stirred under heating for 8 h, cooled and ground to obtain a mixed powder;

[0044] (4) The mixed powder is calcined in an air atmosphere at a rate of 10°C / min from room temperature to 300°C for 4 h to obtain a sodium nitrite promoted Co3O4 composite MgO bifunctional material, denoted as NaNO2-Co3O4-MgO molten salt.

[0045] The NaNO2-Co3O4-MgO molten salt bifunctional material is characterized by XRD and SEM, and the results are shown in Figure 2 and Figure 3 From the XRD pattern of Figure 2 , it can be seen that Co3O4, MgO and NaNO3 exist in the NaNO2-Co3O4-MgO molten salt, and NaNO3 is formed by NaNO2-like oxidation. Figure 3SEM images show that the micro-morphology of the NaNO2-Co3O4-MgO molten salt is ultra-thin nanosheets.

[0046] Example 2

[0047] (1) 0.69 g of sodium nitrite was heated to a molten state at 325 °C and maintained, to obtain a molten sodium salt;

[0048] (2) 4.22 g of magnesium carbonate and 1.21 g of cobalt chloride hexahydrate were added to 24 mL of an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 2 h, and then dried at 80 °C for 9 h to obtain a solid product;

[0049] (3) The solid product was ground into a powder, added to the molten sodium salt, and stirred for 10 h while maintaining the heating state, cooled, and ground, to obtain a mixed powder.

[0050] (4) The mixed powder was calcined under an N2 atmosphere, heated at a rate of 15 °C / min from room temperature to 450 °C, and burned for 6 h, to obtain a sodium nitrite-promoted Co3O4 composite MgO bifunctional material.

[0051] Example 3

[0052] (1) 0.69 g of sodium nitrite was heated to a molten state at 317 °C and maintained, to obtain a molten sodium salt;

[0053] (2) 4.22 g of magnesium carbonate and 1.81 g of cobalt acetylacetonate were added to 24 mL of an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 4 h, and then dried at 90 °C for 10 h, to obtain a solid product;

[0054] (3) The solid product was ground into a powder, added to the molten sodium salt, and stirred for 11 h while maintaining the heating state, cooled, and ground, to obtain a mixed powder.

[0055] (4) The mixed powder was calcined under an H2 / N2 (volume percentage of H2 is 5%) atmosphere, heated at a rate of 5 °C / min from room temperature to 500 °C, and burned for 5 h, to obtain a sodium nitrite-promoted Co3O4 composite MgO bifunctional material.

[0056] Example 4

[0057] (1) 0.86 g of sodium nitrate was heated to a molten state at 330 °C and maintained, to obtain a molten sodium salt;

[0058] (2) 4.22 g of magnesium carbonate and 1.48 g of cobalt nitrate hexahydrate were added to 24 mL of an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 3 h, and then dried at 100 °C for 8 h, to obtain a solid product;

[0059] (3) The solid product was ground to a powder, added to the molten sodium salt and stirred under heating for 12 h, cooled and ground to obtain a mixed powder;

[0060] (4) The mixed powder was calcined under air atmosphere at a rate of 20 °C / min from room temperature to 350 °C for 4 h to obtain a sodium nitrate-promoted Co304 composite MgO bifunctional material.

[0061] Example 5

[0062] (1) 0.86 g of sodium nitrate was heated to a molten state at 380 °C and maintained to obtain a molten sodium salt;

[0063] (2) 4.22 g of magnesium carbonate and 1.21 g of cobalt chloride hexahydrate were added to 24 mL of an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 2 h, and then dried at 85 °C for 9 h to obtain a solid product;

[0064] (3) The solid product was ground to a powder, added to the molten sodium salt and stirred under heating for 10 h, cooled and ground to obtain a mixed powder;

[0065] (4) The mixed powder was calcined under N2 atmosphere at a rate of 5 °C / min from room temperature to 450 °C for 4 h to obtain a sodium nitrate-promoted Co304 composite MgO bifunctional material.

[0066] Example 6

[0067] (1) 0.86 g of sodium nitrate was heated to a molten state at 350 °C and maintained to obtain a molten sodium salt;

[0068] (2) 4.22 g of magnesium carbonate and 1.81 g of cobalt acetylacetonate were added to 24 mL of an aqueous ammonia solution (ammonia water: deionized water = 1:5 mL), stirred for 2 h, and then dried at 70 °C for 8 h to obtain a solid product;

[0069] (3) The solid product was ground to a powder, added to the molten sodium salt and stirred under heating for 8 h, cooled and ground to obtain a mixed powder;

[0070] (4) The mixed powder was calcined under air atmosphere at a rate of 10 °C / min from room temperature to 450 °C for 6 h to obtain a sodium nitrate-promoted Co304 composite MgO bifunctional material.

[0071] Example 7

[0072] (1) 0.69 g of sodium nitrite was heated to a molten state at 310 °C and maintained to obtain a molten sodium salt;

[0073] (2) The magnesium nitrate and cobalt nitrate hexahydrate were added into the ammonia water solution (volume ratio of ammonia water: deionized water = 1:5 mL) and stirred for 2 h, and then dried at 70 °C for 8 h to obtain a solid product; the mass ratio of cobalt nitrate hexahydrate to magnesium nitrate was 1:6; the volume ratio of ammonia water solution to magnesium nitrate was 1 mL: 1 g; the molar ratio of sodium nitrite to magnesium nitrate was 1:3;

[0074] (3) The solid product was ground into powder and added into the molten sodium salt while stirring under heating for 9 h, cooled and ground to obtain a mixed powder;

[0075] (4) The mixed powder was calcined in an air atmosphere at a rate of 10 °C / min from room temperature to 450 °C for 5 h to obtain the sodium nitrite promoted Co304 composite MgO bifunctional material.

[0076] Example 8

[0077] (1) 0.69 g of sodium nitrite was heated to a molten state at 315 °C and maintained to obtain a molten sodium salt;

[0078] (2) The magnesium nitrate and cobalt nitrate hexahydrate were added into the ammonia water solution (volume ratio of ammonia water: deionized water = 1:5 mL) and stirred for 2 h, and then dried at 70 °C for 8 h to obtain a solid product; the mass ratio of cobalt nitrate hexahydrate to magnesium nitrate was 1:6; the volume ratio of ammonia water solution to magnesium nitrate was 1 mL: 1 g; the molar ratio of sodium nitrite to magnesium nitrate was 1:3;

[0079] (3) The solid product was ground into powder and added into the molten sodium salt while stirring under heating for 9 h, cooled and ground to obtain a mixed powder;

[0080] (4) The mixed powder was calcined in an air atmosphere at a rate of 10 °C / min from room temperature to 450 °C for 5 h to obtain the sodium nitrite promoted Co304 composite MgO bifunctional material.

[0081] Example 9

[0082] (1) 0.86 g of sodium nitrate was heated to a molten state at 400 °C and maintained to obtain a molten sodium salt;

[0083] (2) The magnesium nitrate and cobalt nitrate hexahydrate were added into the ammonia water solution (volume ratio of ammonia water: deionized water = 1:5 mL) and stirred for 2 h, and then dried at 70 °C for 8 h to obtain a solid product; the mass ratio of cobalt nitrate hexahydrate to magnesium nitrate was 1:6; the volume ratio of ammonia water solution to magnesium nitrate was 1 mL: 1 g; the molar ratio of sodium nitrite to magnesium nitrate was 1:3;

[0084] (3) The solid product was ground into powder, added to the molten sodium salt and stirred under heating for 11 h, cooled and ground to obtain a mixed powder;

[0085] (4) The mixed powder was calcined under H2 / N2 (5% H2 by volume) atmosphere at a rate of 8°C / min from room temperature to 470°C for 6 h to obtain a sodium nitrate promoted Co304 composite MgO bifunctional material.

[0086] Example 10

[0087] (1) Sodium nitrate and sodium nitrite were mixed in a molar ratio of 1:1, heated to a molten state at 315°C and kept, to obtain a molten sodium salt;

[0088] (2) Magnesium carbonate and cobalt nitrate hexahydrate were added to an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 3 h, and then dried at 75°C for 9 h to obtain a solid product; the mass ratio of cobalt nitrate hexahydrate to magnesium carbonate was 1:2; the volume ratio of the aqueous ammonia solution to the mass of magnesium carbonate was 7 mL: 1 g; the molar ratio of the total amount of substance of sodium nitrate and sodium nitrite to magnesium carbonate was 1:15;

[0089] (3) The solid product was ground into powder, added to the molten sodium salt and stirred under heating for 10 h, cooled and ground to obtain a mixed powder;

[0090] (4) The mixed powder was calcined under air atmosphere at a rate of 12°C / min from room temperature to 490°C for 6 h to obtain a sodium nitrate and sodium nitrite co-promoted Co304 composite MgO bifunctional material.

[0091] Comparative Example 1

[0092] (1) 4.22 g of magnesium carbonate and 1.48 g of cobalt nitrate hexahydrate were added to 24 mL of an aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 3 h, and then dried at 70°C for 9 h to obtain a solid product;

[0093] (2) The solid product was ground into powder, cooled and ground to obtain a mixed powder;

[0094] (3) The mixed powder was calcined under air atmosphere at a rate of 10°C / min to 300°C for 4 h to obtain a Co304 composite MgO bifunctional material, denoted as Co304-MgO.

[0095] SEM characterization was performed on the Co304-MgO, and the results are shown in Figure 4 The SEM image shows that the micro-morphology of the Co304-MgO is nanoparticles.

[0096] Comparative Example 2

[0097] (1) 4.22 g of magnesium carbonate and 1.48 g of cobalt nitrate hexahydrate were added into 24 mL of aqueous ammonia solution (volume ratio of aqueous ammonia: deionized water = 1:5 mL), stirred for 3 h, and then dried at 70°C for 9 h to obtain a solid product;

[0098] (2) The solid product was ground into powder, cooled and ground to obtain a mixed powder;

[0099] (3) 0.69 g of sodium nitrite was mechanically mixed with the mixed powder;

[0100] (4) The mixed powder was calcined at 300°C for 4 h at a rate of 10°C / min under an air atmosphere to obtain a sodium nitrite-promoted Co3O4 composite MgO bifunctional material, denoted as NaNO2-Co3O4-MgO mechanical mixture.

[0101] The NaNO2-Co3O4-MgO mechanical mixture sample was characterized by SEM, and the results are shown in Figure 5 The SEM image shows that the micro-morphology of the NaNO2-Co3O4-MgO mechanical mixture is nanoparticles.

[0102] Referring to Figure 1 , the application method of the NaNO2-Co3O4-MgO bifunctional material is as follows: 5%-20% (by volume) CO2 flue gas is subjected to CO2 adsorption by the NaNO2-Co3O4-MgO prepared by the present application, and then hydrogen is added to the NaNO2-Co3O4-MgO prepared by the present application to convert CO2 into methane, carbon monoxide and water. The NaNO2-Co3O4-MgO bifunctional material can realize the reduction of CO2 concentration in flue gas and the resource utilization of CO2.

[0103] Figure 6 and Figure 7 The CO2 adsorption and methanation capacity of MgO, Co3O4, Co3O4-MgO, NaNO2-Co3O4-MgO mechanical mixture and NaNO2-Co3O4-MgO molten salt were compared, and it can be seen from Figure 6 that Co3O4 has poor CO2 adsorption performance, and after adding MgO and NaNO2, the CO2 adsorption capacity is significantly increased. From Figure 7It can be seen that MgO does not have CO2 methanation performance, after adding Co3O4, the material has CO2 adsorption and conversion capacity, but the adsorption capacity is reduced. After adding NaNO2, the bifunctional material has high CO2 adsorption performance and methanation capacity. More importantly, by comparing NaNO2-Co3O4-MgO mechanical mixing and NaNO2-Co3O4-MgO molten salt samples, it can be found that the sample obtained by simply mechanically mixing NaNO2 with the catalyst without molten salt treatment step still has poor methanation capacity. It can be seen that the molten salt strategy of the present application plays an important role in improving the performance of the catalyst.

[0104] The sodium salt synthesized in the embodiment of the present application promotes the Co3O4 composite MgO bifunctional material to realize CO2 adsorption at 300 DEG C and CO2 conversion at 300-400 DEG C. Compared with other bifunctional materials, the preparation method is simple, the source of the synthesized precursor is abundant, and the cost is low.

[0105] The above only describes the best embodiment of the present application, but cannot be understood as limiting the claims. The present application is not limited to the above embodiment, and the specific structure allows changes. Any changes made within the protection scope of the independent claims of the present application are within the protection scope of the present application.

[0106] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

Claims

1. Application of sodium salt promoted nanometer Co304 composite MgO bifunctional material in adsorption of CO2 and methanation, characterized in that, The preparation method of the material comprises the following steps: The sodium salt is heated to be molten to obtain a molten sodium salt; The magnesium salt and the cobalt salt are added into an ammonia water solution, stirred uniformly, and then dried to obtain a solid product; The solid product is ground into powder, added into the molten sodium salt, stirred uniformly under heating, cooled and ground to obtain a mixed powder; The mixed powder is calcined to obtain a sodium salt promoted nano Co3O4 composite MgO bifunctional material; The sodium salt is one or both of sodium nitrite and sodium nitrate.

2. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The heating temperature for being heated to be molten is 320-400℃.

3. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The cobalt salt is cobalt nitrate hexahydrate, cobalt chloride hexahydrate or cobalt acetylacetonate.

4. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The magnesium salt is magnesium carbonate, magnesium nitrate or magnesium acetate.

5. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The mass ratio of the cobalt salt to the magnesium salt is 1:2-1:

9.

6. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The volume concentration of ammonia water in the ammonia water solution is 25-28%, and the volume ratio of the ammonia water solution to the magnesium salt is 1 mL-10 mL:1 g.

7. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material in the adsorption of CO2 and methanation according to claim 1, characterized in that, The molar ratio of the sodium salt to the magnesium salt is 1:3-1:

20.

8. Use of the sodium salt promoted nanosized Co304 composite MgO bifunctional material according to claim 1 in the adsorption of CO2 and methanation, characterized in that, The atmosphere for calcination is one or several mixed gases of H2, N2 and air; the temperature for calcination is 300-500℃, and the time is 4-6h; the temperature is raised from room temperature to 300-500℃ at a temperature rising rate of 5-20℃ / min.

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