High-entropy alloy catalyst with super-large specific surface area as well as preparation method and CO2 hydrogenation application of high-entropy alloy catalyst

Abstract

The invention discloses a high-entropy alloy catalyst with an ultra-large specific surface area and a preparation method and CO2 hydrogenation application thereof. The high-entropy alloy material comprises active metal elements and structure-stable metal elements, the active metal elements are selected from any three of copper, cobalt, nickel, indium, chromium, gold, silver, palladium and platinum; the metal elements with stable structures are selected from any two of zinc, aluminum, zirconium, cerium, silicon and calcium; the molar ratio of the active metal element to the metal element with the stable structure is 6: 4; the crystallinity of the high-entropy alloy material is 56 to 83 percent; the particle size of the high-entropy alloy material is 5-10 nm, and the specific surface area is 150-220 m < 2 > / g. The high-entropy alloy material disclosed by the invention is small in particle size and large in specific surface area, can expose abundant active sites, and shows excellent catalytic performance and stability in a CO2 hydrogenation reaction.

Description

Technical Field

[0001] The present invention relates to a high entropy alloy catalyst with ultra-large specific surface area and a preparation method thereof. 2 The application of hydrogenation belongs to the field of preparation and application of inorganic metal materials. Background Art

[0002] With the rapid development of human industrial activities, the increasing consumption of fossil fuels has brought about many environmental problems, including air pollutants and greenhouse gas carbon dioxide (CO 2 ) emissions have caused obvious environmental problems. In particular, CO 2 The emission of carbon dioxide has not only caused global warming, but also brought serious consequences such as acid rain and glacier melting. To this end, the global political community has formulated relevant policies to cope with the above challenges. Countries around the world have begun to implement carbon reduction plans and set the goal of achieving carbon neutrality. However, the achievement of the above goals still requires the academic community to carry out relevant research in the field of scientific research.

[0003] CO emissions from industry 2 The current capture and storage technology only converts the emitted CO 2 Temporary control cannot fundamentally solve the problem. 2 Converted to CO, CH 4 and methanol, etc., which not only has important scientific significance, but also can realize their high-value utilization, fundamentally solving the problem of CO 2 Environmental pollution caused by emissions. 2 The catalysts reported in catalytic conversion applications mainly include Cu-based oxides, Mo-based carbides / sulfides, and noble metal-based catalysts. Among them, CuZnAl catalysts are the most popular catalysts in CO 2 It shows great application potential in hydrogenation reaction and has been applied in industry. However, the instability and easy deactivation of traditional Cu-based catalysts under complex working conditions limit their application in industrial CO 2 Further developments in the field of transformation.

[0004] Therefore, the development of efficient Cu-based alloy CO 2 Hydrogenation catalysts have become particularly urgent. Among the many Cu-based alloy catalysts, high entropy alloys (HEAs) have become the most popular materials for Cu-based alloys CO due to their fixed crystal form, high thermal stability, rich physical and chemical properties, and adjustable element types and proportions. 2Catalyst design provides more possibilities. In particular, HEAs exhibit excellent catalytic performance due to their multi-component characteristics. These alloys are usually composed of five or more metal elements in equimolar or nearly equimolar proportions. However, in the preparation process of high entropy alloy catalysts, due to the high processing temperature and single crystal characteristics, the high entropy alloy materials prepared by traditional methods often have large particles and extremely small specific surface area, which is not conducive to the dispersion of active sites and the transmission of gas molecules. This is also the reason for its poor performance in CO 2 The key factor to be improved in the catalytic efficiency in the field of hydroconversion.

[0005] In summary, high entropy alloy materials in CO 2 Application in hydrogenation catalyst design, especially the influence of high specific surface area and small particle size on catalytic performance, can improve CO 2 The conversion rate, promoting the synthesis of hydrocarbons, and providing technical support for achieving the goal of carbon neutrality are worthy of further research and exploration. Therefore, the development of new preparation methods to overcome the above challenges is crucial to realize the application of high entropy materials in the field of catalysis. Summary of the invention

[0006] The present invention aims to provide a high entropy alloy catalyst with ultra-large specific surface area and a preparation method thereof and a CO 2 In hydrogenation applications, the high entropy alloy material has a small particle size and a large specific surface area, which can expose abundant active sites. 2 It exhibits excellent catalytic performance and stability in hydrogenation reactions.

[0007] In a first aspect, the present invention provides a high entropy alloy material, comprising an active metal element and a structurally stable metal element;

[0008] The active metal elements are selected from any three of copper, cobalt, nickel, indium, chromium, gold, silver, palladium and platinum;

[0009] The structural stabilizing metal elements are selected from any two of zinc, aluminum, zirconium, cerium, silicon, and calcium;

[0010] The molar ratio of the active metal element to the structure-stabilizing metal element is 6:4;

[0011] The crystallinity of the high entropy alloy material is 56-83%;

[0012] The particle size of the high entropy alloy material is 5 to 10 nm, and the specific surface area is 150 to 220 m 2 / g.

[0013] In one embodiment of the present invention, the high entropy alloy material presents a particle stacking morphology, and the morphology formed by the particle stacking presents a spherical shape;

[0014] The pore volume of the high entropy alloy material is 0.150 to 0.460 cm 3 g -1 , the average pore size is 33.20~10.80nm.

[0015] In one embodiment of the present invention, the molar ratio of any three active metal elements is 1:1:1;

[0016] The molar ratio of any two structure-stabilizing metal elements is 1:1.

[0017] In a second aspect, the present invention provides a method for preparing the high entropy alloy material as described in any one of the above, comprising the following steps:

[0018] S1, impregnating a mixed solution of inorganic salts containing active metal elements and structurally stable metal elements into a silica carrier, and drying the carrier after impregnation;

[0019] S2, reducing the product obtained in step S1 to obtain a supported high entropy material;

[0020] S3, etching the supported high entropy material obtained in step S2 to obtain the high entropy alloy material.

[0021] In one embodiment of the present invention, the silica carrier has a spherical shape and a particle size between 30 and 500 nm;

[0022] The total mass of the active metal elements and the structurally stable metal elements accounts for 6-48% of the mass of the silicon dioxide carrier.

[0023] In one embodiment of the present invention, the total molar concentration of the inorganic salt mixed solution containing active metal elements and structurally stable metal elements is 40 to 120 mmol / L;

[0024] The active metal element inorganic salt and the structure-stabilizing metal element inorganic salt are selected from at least one of nitrates, sulfates and chlorides of the corresponding metal elements;

[0025] The immersion is carried out under stirring conditions for 1 to 3 hours;

[0026] The drying treatment is to dry the suspension containing the metal mixed solution and the silica carrier at 60-80° C. for 6 hours, and then transfer it to a vacuum drying oven and dry it at 100-120° C. for 12-16 hours.

[0027] In one embodiment of the present invention, the reduction treatment is to use hydrogen at 300-500° C. for 2-6 hours, with a heating rate of 3° C. / min-15° C. / min.

[0028] In one embodiment of the present invention, the etching treatment is to use a 3-5 mol / L sodium hydroxide solution at 30-60° C. for 2-4 hours, wherein the molar amount of sodium hydroxide is 3 times the molar amount of silicon dioxide;

[0029] After the etching process is completed, the method further comprises: washing the product after the etching process by centrifugation until it becomes neutral, and then drying it at 120° C. for 6 hours.

[0030] In a third aspect, the present invention provides a method for hydrogenating carbon dioxide, comprising the following steps:

[0031] The high entropy alloy material described in any one of the above or the high entropy alloy material prepared by any one of the preparation methods described in the above is used as a catalyst, and a mixed gas containing carbon dioxide and hydrogen is contacted with the catalyst to react.

[0032] In one embodiment of the present invention, in the mixed gas, the volume ratio of carbon dioxide to hydrogen is 1:(3-4);

[0033] The flow rate of the mixed gas corresponding to each 50 mg of the catalyst is 50 mL / min to 100 mL / min;

[0034] The reaction temperature is 200-550°C;

[0035] The mixed gas uses nitrogen as the balance gas, CO 2 The volume fraction is 4%, H 2 The volume fraction is 12% to 16%.

[0036] The present invention has the following beneficial effects:

[0037] 1) The ultra-large high entropy alloy catalyst prepared by the present invention is prepared at a relatively low reaction temperature, with a simple process and high yield, which is conducive to large-scale preparation.

[0038] 2) The present invention can adjust and improve the physicochemical properties of the high entropy alloy catalyst by simply changing the mass ratio of the alloy metal elements to the carrier, the type of alloy metal elements and the carrier particle size.

[0039] 3) The high entropy alloy catalyst prepared by the present invention has a small particle size and a large specific surface area. 2 It has excellent catalytic activity and stability in the field of hydrogenation catalytic conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 XRD spectra of ultra-large specific surface area high entropy oxides prepared in Examples 1, 2, and 3 of the present invention;

[0042] Figure 2 a is a SEM image of the high entropy oxide prepared in Comparative Example 1 of the present invention, Figure 2 b and c are SEM images of high entropy oxides prepared in Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0043] In the description of this specification, the description with reference to the terms "one implementation", "an embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0044] As described in the background technology, high entropy alloy materials prepared by traditional methods often have large particles and extremely small specific surface area, which leads to their 2 The catalytic efficiency in the field of hydroconversion needs to be improved.

[0045] In order to obtain increased CO 2 Conversion rate, the present invention provides a high entropy alloy material, including active metal elements and structural stabilizing metal elements; the active metal elements are selected from any three of copper, cobalt, nickel, indium, chromium, gold, silver, palladium, and platinum; the structural stabilizing metal elements are selected from any two of zinc, aluminum, zirconium, cerium, silicon, and calcium; the molar ratio of the active metal element to the structural stabilizing metal element is 6:4 (that is, based on the total metal elements, the molar contents of the active metal element and the structural stabilizing metal element are 60% and 40%, respectively); the crystallinity of the high entropy alloy material is 56% to 83%; the particle size of the high entropy alloy material is 5 to 10 nm, and the specific surface area is 150 to 220 m 2 / g. This high entropy alloy material can expose abundant active sites and show excellent physical and chemical properties. 2 The invention provides a new idea for the preparation and modification of high entropy alloy materials under low energy consumption conditions, and has important application value and broad market prospects. By optimizing the structural composition of the catalyst, CO 2 conversion rate, promote the synthesis of hydrocarbons, and provide technical support for achieving the goal of carbon neutrality.

[0046] The selection and combination of the active metal elements and the structural stabilizing elements described above can further 2 Adsorption and activation are carried out, which is beneficial to CO 2 Hydrogenation catalytic reaction. Optionally, the high entropy alloy material is any one of the following: 1) the active metal elements are copper, cobalt, and nickel, and the structurally stable metal elements are zinc and aluminum; 2) the active metal elements are copper, platinum, and nickel, and the structurally stable metal elements are calcium and aluminum; 3) the active metal elements are copper, cobalt, and indium, and the structurally stable metal elements are zinc and calcium; 4) the active metal elements are copper, indium, and nickel, and the structurally stable metal elements are calcium and aluminum; 5) the active metal elements are copper, platinum, and indium, and the structurally stable metal elements are zinc and calcium.

[0047] According to one embodiment of the present invention, the high entropy alloy material presents a particle stacking morphology, and the morphology formed by the particle stacking presents a spherical shape; the pore volume of the high entropy alloy material is 0.150-0.460cm 3 g -1 The average pore size is 33.20-10.80 nm. Specifically, the pore volume of the high entropy alloy material is 0.178-0.396 cm 3 g -1 , the average pore size is 3.39~9.79nm.

[0048] According to one embodiment of the present invention, the crystal form of the high entropy alloy material is a rock salt type. The molar ratio of any three active metal elements is 1:1:1; the molar ratio of any two structural stabilizing metal elements is 1:1. By controlling the above molar ratio, it is possible to further 2 Adsorption and activation are carried out, which is more conducive to CO 2 Hydrogenation catalytic reaction.

[0049] In order to obtain the Cu-based high entropy alloy material with a smaller particle size and a larger specific surface area as described above. The present invention further provides a method for preparing the high entropy alloy material described in any one of the above, comprising the following steps: S1, impregnating a mixed solution of an inorganic salt containing an active metal element and a structurally stable metal element into a silica carrier, and drying the silica carrier after the impregnation; S2, reducing the product obtained in step S1 to obtain a supported high entropy material; S3, etching the supported high entropy material obtained in step S2 to obtain the high entropy alloy material.

[0050] Based on the above technical scheme, the present invention obtains a Cu-based high-entropy alloy material with a small particle size and a large specific surface area by impregnating a metal element inorganic salt solution into a silica carrier, and then undergoing a series of drying treatments, reduction treatments and alkaline solution etching treatments. The main idea is as follows: using a silica carrier, the high entropy is uniformly loaded on the silica by impregnation loading, and the specific surface area of ​​the original high entropy is greatly increased by adding a silica carrier and then etching. The method is simple and easy, short in time, low in energy consumption, and high in yield.

[0051] According to one embodiment of the present invention, the morphology of the silica carrier is spherical, and the particle size is between 30 and 500 nm. If the particle size of the silica carrier is too large, the high entropy alloy particles formed will be far apart, the interaction will be weak, and a spherical high entropy alloy cannot be formed. If the particle size is too small, the high entropy alloy particles formed will be densely packed and have a small specific surface area. Optionally, the carrier particle size is 30nm, 500nm; the total mass of the active metal elements and the structurally stable metal elements accounts for 6-48% of the mass ratio of the silica carrier. If the mass percentage of the active metal elements and the structurally stable metal elements is too large, some metal elements will not be able to form a high entropy alloy during the reduction process. If the mass percentage is too small, the high entropy alloy particles formed will be far apart, the interaction will be weak, and a spherical high entropy alloy cannot be formed. Optionally, the high entropy loading is 6%, 24%, and 48%.

[0052] According to one embodiment of the present invention, the inorganic salt mixed solution containing active metal elements and structurally stable metal elements is an aqueous solution thereof, and the total molar concentration is 40-120 mmol / L, such as 60-80 mmol / L, including but not limited to 120 mM, 80 mM, 60 mM; the inorganic salt of active metal elements and the inorganic salt of structurally stable metal elements are selected from at least one of nitrates, sulfates, and chlorides of the corresponding metal elements; for example, copper nitrate, cobalt chloride, nickel nitrate, zinc nitrate, indium nitrate, aluminum nitrate, platinum nitrate, calcium nitrate, etc., thereby enabling the decomposition of anionic species during the reduction and heating process. The impregnation is carried out under stirring conditions for 1-3 hours, including but not limited to 3 hours; the drying treatment is to dry the suspension containing the metal mixed solution and the silica carrier at 60-80°C for 6 hours, and then transfer it to a vacuum drying oven to dry it at 100-120°C for 12-16 hours, such as evaporating excess liquid in a water bath at 80°C, and then transfer it to a vacuum drying oven to dry it overnight at 110°C.

[0053] According to one embodiment of the present invention, the reduction treatment is to treat with hydrogen at 300-500°C for 2-6 hours, with a heating rate of 3°C / min-15°C / min. Optionally, the reduction temperature is 300°C, 400°C, or 500°C, such as using hydrogen for reduction treatment in a 400°C tubular furnace for 2 hours, with a heating rate of 5°C / min. The reduction treatment does not require high-temperature calcination and has low energy consumption.

[0054] According to one embodiment of the present invention, the etching treatment is to use a 3-5 mol / L sodium hydroxide solution at 30-60°C for 2-4 hours, wherein the molar amount of sodium hydroxide is 3 times the molar amount of silicon dioxide. In the etching treatment step, the concentration of the sodium hydroxide solution, the etching temperature and time, and the molar amount of sodium hydroxide are reasonably adjusted within the above range so that the silicon dioxide can be fully etched, thereby obtaining a high entropy alloy material with the required specific surface area and particle size. Optionally, the alkali solution concentration is 3 mol / L, 4 mol / L, 5 mol / L, such as using a 3 mol / L sodium hydroxide solution at 60°C for 4 hours. After the etching treatment is completed, the method also includes: centrifuging and washing the product after the etching treatment to neutrality, and then drying it at 120°C for 6 hours.

[0055] In order to realize the application of the high entropy alloy material, the present invention also provides a method for hydrogenating carbon dioxide, comprising the following steps: using the high entropy alloy material described in any one of the above or the high entropy alloy material prepared by the preparation method described in any one of the above as a catalyst, and contacting a mixed gas containing carbon dioxide and hydrogen with the catalyst for reaction.

[0056] According to one embodiment of the present invention, in order to improve the conversion rate of carbon dioxide, the volume ratio of carbon dioxide to hydrogen in the mixed gas is 1: (3-4); optionally, the volume ratio of carbon dioxide to hydrogen in the mixed gas is 1: 4 or 1: 3; the flow rate of the mixed gas corresponding to each 50 mg of the catalyst is 50 mL / min-100 mL / min; optionally, the flow rate of the mixed gas corresponding to each 50 mg of the catalyst is 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min. The temperature of the reaction is 200-550°C, preferably 250-550°C, more preferably 300-550°C, and further preferably 350-550°C. Optionally, the heating rate is 3°C / min. Optionally, the reaction temperature can be independently selected from 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C. The mixed gas uses nitrogen as the balance gas, CO 2 The volume fraction is 4%, H 2 The volume fraction is 12% or 16%. Optionally, CO 2 The volume fraction is 4%, H 2 The volume fraction is 16%.

[0057] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0058] The methods used in the following examples, unless otherwise specified, are conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources. The features and properties of the present invention are further described in detail below in conjunction with the examples.

[0059] Example 1

[0060] Weigh 0.4832 g of copper nitrate hexahydrate, 0.4758 g of cobalt chloride hexahydrate, 0.5816 g of nickel nitrate hexahydrate, 0.5950 g of zinc nitrate hexahydrate, and 0.7464 g of aluminum nitrate nonahydrate, and transfer them to 25 mL of deionized water to prepare a 120 mM mixed solution, which is recorded as solution 1. Weigh 4 g of SiO 2-30nm carrier was poured into the above mixture, stirred for 3h, then evaporated the excess liquid in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2 hours (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and dried in a drying oven at 120℃ for 6h to finally obtain high entropy alloy catalyst A.

[0061] Example 2

[0062] Weigh 0.3221 g of copper nitrate hexahydrate, 0.5106 g of platinum nitrate monohydrate, 0.3877 g of nickel nitrate hexahydrate, 0.3778 g of calcium nitrate tetrahydrate, and 0.4976 g of aluminum nitrate nonahydrate, and transfer them to 25 mL of deionized water to prepare a mixed solution of 80 mM, which is recorded as solution 3. Weigh 4 g of SiO 2 -30nm carrier was poured into the above mixture, stirred for 3h, then the excess liquid was evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2h (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and dried in a vacuum drying oven at 120℃ for 6h to finally obtain high entropy alloy catalyst C.

[0063] Example 3

[0064] Weigh 0.2416 g of copper nitrate hexahydrate, 0.2364 g of cobalt chloride hexahydrate, 0.4822 g of indium nitrate tetrahydrate, 0.2975 g of zinc nitrate hexahydrate, and 0.2834 g of calcium nitrate tetrahydrate, and transfer them into 25 mL of deionized water to prepare a 60 mM mixed solution, which is recorded as solution 2. Weigh 4 g of SiO 2-30nm carrier was poured into the above mixture, stirred for 3h, then the excess liquid was evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2 hours (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and then treated in a drying oven at 120℃ for 6h to finally obtain high entropy alloy catalyst B.

[0065] Example 4

[0066] Weigh 0.4832 g of copper nitrate hexahydrate, 0.4822 g of indium nitrate tetrahydrate, 0.5816 g of nickel nitrate hexahydrate, 0.2834 g of calcium nitrate tetrahydrate, and 0.7464 g of aluminum nitrate nonahydrate, and transfer them to 25 mL of deionized water to prepare a 120 mM mixed solution, which is recorded as solution 4. Weigh 4 g of SiO 2 -500nm carrier was poured into the above mixture, stirred for 3h, then the excess liquid was evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2 hours (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and dried in a vacuum drying oven at 120℃ for 6h to finally obtain high entropy alloy catalyst D.

[0067] Example 5

[0068] Weigh 0.3221 g of copper nitrate hexahydrate, 0.5106 g of platinum nitrate monohydrate, 0.6429 g of indium nitrate tetrahydrate, 0.3967 g of zinc nitrate hexahydrate, and 0.3778 g of calcium nitrate tetrahydrate respectively, and then transfer them into 25 mL of deionized water to prepare a mixed solution of 80 mM, which is recorded as solution 6. Weigh 4 g of SiO 2-500nm carrier was poured into the above mixture, stirred for 3h, then the excess liquid was evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2 hours (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and dried in a vacuum drying oven at 120℃ for 6h to finally obtain high entropy alloy catalyst E.

[0069] Example 6

[0070] Weigh 0.2416 g of copper nitrate hexahydrate, 0.2364 g of cobalt chloride hexahydrate, 0.2908 g of nickel nitrate hexahydrate, 0.2975 g of zinc nitrate hexahydrate, and 0.3732 g of aluminum nitrate nonahydrate, and transfer them to 25 mL of deionized water to prepare a 60 mM mixed solution, which is recorded as solution 5. Weigh 4 g of SiO 2 -30nm carrier was poured into the above mixture, stirred for 3h, then the excess liquid was evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a 400℃ tube furnace for 2 hours (heating rate of 5℃ / min) was a supported high entropy catalyst. Then the above supported high entropy catalyst was stirred and treated with 3mol / L sodium hydroxide solution at 60℃ for 4h (the molar amount of sodium hydroxide was 3 times the molar amount of silica), and the final product was centrifuged and washed to neutrality and then treated in a drying oven at 120℃ for 6h to finally obtain a high entropy alloy catalyst F.

[0071] Comparative Example 1

[0072] Weigh 0.58 g of copper nitrate trihydrate, 0.7 g of cobalt nitrate hexahydrate, 0.7 g of nickel nitrate hexahydrate, 0.714 g of zinc nitrate hexahydrate, and 0.9 g of aluminum nitrate nonahydrate (all 2.4 mmol), grind them into powder in a mortar, and then reduce them at 400° C. for 1 h to obtain a black powder, which is recorded as comparison sample G.

[0073] Comparative Example 2

[0074] 0.58 g of copper nitrate trihydrate, 0.7 g of cobalt nitrate hexahydrate, 0.7 g of nickel nitrate hexahydrate, 0.714 g of zinc nitrate hexahydrate, and 0.9 g of aluminum nitrate nonahydrate (all 2.4 mmol) were weighed respectively, ground into powder in a mortar, and then treated at 900°C for 2 h to obtain a powder. The powder was then transferred to a tube furnace and reduced at 400°C for 1 h to obtain a black powder, which was recorded as comparison sample H.

[0075] Comparative Example 3

[0076] Weigh 0.4832 g of copper nitrate hexahydrate, 0.4758 g of cobalt chloride hexahydrate, 0.5816 g of nickel nitrate hexahydrate, 0.5950 g of zinc nitrate hexahydrate, and 0.7464 g of aluminum nitrate nonahydrate, and transfer them to 25 mL of deionized water to prepare a 120 mM mixed solution, which is recorded as solution 1. Weigh 4 g of SiO 2 -30nm carrier was poured into the above mixture, stirred for 3h, then evaporated in a water bath at 80℃, and then transferred to a vacuum drying oven and dried overnight at 110℃. The black product obtained after further reduction treatment with hydrogen in a tube furnace at 400℃ for 2h (heating rate of 5℃ / min) was a supported high entropy catalyst. It was recorded as comparative sample I.

[0077] Analysis and test cases

[0078] Figure 1 The XRD spectra of the ultra-large specific surface area high entropy alloy materials prepared in Experimental Examples 1, 2 and 3 show that both samples have sharp diffraction peaks, indicating that they have high crystallinity. After further attribution, it was found that the prepared high entropy alloy material has a rock salt crystal structure, indicating that the high entropy alloy material was successfully synthesized. In addition, the change of the loading amount and the change of the carrier particle size will not affect the crystal structure of the prepared high entropy alloy material, indicating the universality of this method.

[0079] Figure 2 The scanning electron microscope images of the Cu-based high entropy alloy materials prepared in Comparative Example 1 and Experimental Examples 1 and 2 are shown in FIG. Figure 2 It can be seen from a that the high entropy alloy material prepared by the traditional method presents an uneven, solid large particle shape, with a maximum particle size of 3-5μm. The high entropy alloy materials prepared in Experimental Examples 1 and 2 present a smaller particle accumulation morphology, and the morphology formed by the particle accumulation is spherical, and the size of the sphere is affected by the carrier particle size. Figure 2 b and Figure 2 c It can be seen that the particle size of the high entropy alloy material is 5 to 10 nm.

[0080] The specific surface area, pore volume and average pore size of the high entropy alloy material were tested by low-temperature nitrogen adsorption-desorption curve and BJH method. The results are shown in Table 1.

[0081] Table 1 Structural parameters of high entropy alloy materials prepared in Examples 1-3 of the present invention and Comparative Example 1

[0082] catalyst <![CDATA[Specific surface area (m 2 g -1 )]]> <![CDATA[Pore volume (cm 3 g -1 )]]> Average pore size (nm) Catalyst A 212 0.178 3.39 Catalyst B 161 0.367 9.11 Catalyst D 153 0.396 9.79 Comparison sample G 3.2 0.003 25.6

[0083] It can be seen from Table 1 that among the high entropy alloy catalysts prepared in Examples 1-3, Catalyst A has the largest specific surface area, which can reach 212 m 2 g -1In addition, the catalysts B and C obtained by changing the parameters according to the strategy proposed by the present invention still maintain a large specific surface area, both in the range of 150 to 212 m 2 g -1 The average pore size is between 9 and 10 nm. In contrast, the specific surface area of ​​the comparative sample G obtained by the traditional method is only 3.2 m 2 g -1 , which is far lower than the catalyst prepared by the present invention.

[0084] Carbon dioxide hydrogenation test case

[0085] The catalysts of Examples 1-6 and Comparative Examples 1-3 were applied to CO 2 Hydrogenation activity test, the activity and stability results of the catalyst are based on CO 2 The conversion rate indicates that CO 2 Conversion rate (%) = (CO 2 Inlet-CO 2 Export) / CO 2 Inlet × 100%, CO 2 The concentration was tested using online chromatography, and the results are shown in Table 2 below.

[0086] CO 2 The conditions for the hydrogenation activity test were: catalyst loading of 50 mg, reaction temperature of 200°C-550°C (heating rate of 3°C / min), CO 2 / H 2 (v / v=1:4) The mixed gas flow rate is 100 mL / min, of which CO 2 The volume fraction is 4%, and the balance gas is nitrogen.

[0087] Table 2. CO 2 Conversion rate

[0088]

[0089] The high entropy alloy catalysts prepared in Examples 1-6, wherein Catalyst F has excellent CO 2 Conversion rate. Although in the low temperature stage (200-300℃) CO 2 The conversion rate is low, but higher than that of the catalysts prepared in other examples, especially the comparative catalyst. 2 The conversion rate has been significantly improved, reaching 31.78% at 400°C, and as the temperature increases further, the CO 2The conversion rate can reach 49.57%. Although the overall performance of the catalysts prepared in Examples 1-5 is slightly lower than that of Catalyst F, they still have better catalytic performance. The catalysts prepared by the traditional method not only have poor low-temperature performance, but also have no improvement in high-temperature performance, which may be related to the fact that the active sites are not fully exposed due to the large particle size and small surface area. Among them, the CO 2 Although the conversion rate is better than that of Comparative Examples 1-2, it can be seen from the comparison results of Example 1 and Comparative Example 3 that the catalyst A has a high CO conversion rate at 200°C or above. 2 The conversion rate of is significantly higher than that of catalyst I. This is because the etching step greatly increases the original high-entropy specific surface area, thereby exposing abundant active sites and significantly improving the catalytic activity.

[0090] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A high entropy alloy material, characterized in that: Includes active metal elements and structurally stable metal elements; The active metal elements are selected from any three of copper, cobalt, nickel, indium, chromium, gold, silver, palladium and platinum; The structural stabilizing metal elements are selected from any two of zinc, aluminum, zirconium, cerium, silicon, and calcium; The molar ratio of the active metal element to the structure-stabilizing metal element is 6:4; The crystallinity of the high entropy alloy material is 56% to 83%; The particle size of the high entropy alloy material is 5 to 10 nm, and the specific surface area is 150 to 220 m 2 / g.

2. The high entropy alloy material according to claim 1, characterized in that: The high entropy alloy material presents a particle stacking morphology, and the morphology formed by the particle stacking presents a spherical shape; The pore volume of the high entropy alloy material is 0.150 to 0.460 cm 3 g -1 , the average pore size is 33.20~10.80nm.

3. The high entropy alloy material according to any one of claims 1-2, characterized in that: The molar ratio of any three active metal elements is 1:1:1; The molar ratio of any two structure-stabilizing metal elements is 1:

1.

4. The method for preparing the high entropy alloy material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, impregnating a mixed solution of inorganic salts containing active metal elements and structurally stable metal elements into a silica carrier, and drying the carrier after impregnation; S2, reducing the product obtained in step S1 to obtain a supported high entropy material; S3, etching the supported high entropy material obtained in step S2 to obtain the high entropy alloy material.

5. The method for preparing a high entropy alloy material according to claim 4, characterized in that: The silica carrier has a spherical shape and a particle size between 30 and 500 nm; The total mass of the active metal elements and the structurally stable metal elements accounts for 6-48% of the mass of the silicon dioxide carrier.

6. The method for preparing a high entropy alloy material according to any one of claims 4-5, characterized in that: The total molar concentration of the inorganic salt mixed solution containing active metal elements and structurally stable metal elements is 40 to 120 mmol / L; The active metal element inorganic salt and the structure-stabilizing metal element inorganic salt are selected from at least one of nitrates, sulfates and chlorides of the corresponding metal elements; The immersion is carried out under stirring conditions for 1 to 3 hours; The drying treatment is to dry the suspension containing the metal mixed solution and the silica carrier at 60-80° C. for 6 hours, and then transfer it to a vacuum drying oven and dry it at 100-120° C. for 12-16 hours.

7. The method for preparing a high entropy alloy material according to any one of claims 4 to 6, characterized in that: The reduction treatment is to use hydrogen at 300-500° C. for 2-6 hours, with a heating rate of 3° C. / min-15° C. / min.

8. The method for preparing a high entropy alloy material according to any one of claims 4 to 7, characterized in that: The etching treatment is carried out by treating with a 3-5 mol / L sodium hydroxide solution at 30-60° C. for 2-4 hours, wherein the molar amount of sodium hydroxide is 3 times the molar amount of silicon dioxide; After the etching process is completed, the method further comprises: washing the product after the etching process by centrifugation until it becomes neutral, and then drying it at 120° C. for 6 hours.

9. A method for hydrogenating carbon dioxide, characterized in that: The following steps are involved: The high entropy alloy material according to any one of claims 1 to 3 or the high entropy alloy material prepared by the preparation method according to any one of claims 4 to 8 is used as a catalyst, and a mixed gas containing carbon dioxide and hydrogen is contacted with the catalyst for reaction.

10. The method for hydrogenating carbon dioxide according to claim 9, characterized in that: In the mixed gas, the volume ratio of carbon dioxide to hydrogen is 1:(3-4); The flow rate of the mixed gas corresponding to each 50 mg of the catalyst is 50 mL / min to 100 mL / min; The reaction temperature is 200-550°C; The mixed gas uses nitrogen as the balance gas, the volume fraction of CO2 is 4%, and the volume fraction of H2 is 12% to 16%.

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