Diamond-based catalyst for synthesizing methanol through carbon dioxide hydrogenation, preparation method of diamond-based catalyst and method for synthesizing methanol through carbon dioxide hydrogenation

Abstract

The invention provides a preparation method of a diamond-based catalyst for synthesizing methanol through hydrogenation of carbon dioxide, which comprises the following steps: preparing the catalyst: providing nano conductive diamond, adding nano conductive diamond particles into a metal salt solution, mixing for 24 hours, and roasting to obtain the diamond-based catalyst; the metal of the metal salt solution comprises at least one of copper, zinc, chromium, palladium and indium.

Description

Technical Field

[0001] The present invention relates to the field of materials for hydrogen production by electrolyzing water, and particularly to catalyst materials for hydrogen production by electrolysis in an alkaline environment. Background Art

[0002] Methanol is an important chemical raw material, chemical product, and clean fuel. The green development of its synthesis technology is crucial for reducing carbon emissions and promoting the utilization of sustainable energy. Carbon capture and carbon dioxide reduction have become important topics in the green industrial development of society in recent years. Currently, based on the background of the development of carbon capture technology, there are already a variety of heterogeneous thermal catalytic processes in its downstream that can realize the catalytic synthesis of various carbon-containing fuels and chemical raw materials by adding green hydrogen to carbon dioxide. In particular, the process for synthesizing green methanol has developed most rapidly.

[0003] Since the methanol synthesis reaction involves high-temperature and high-pressure conditions, common copper-based catalysts may sinter and agglomerate at high temperatures, resulting in a reduction in surface area. Moreover, at high temperatures, CO2 and hydrocarbons (such as CH4) crack to form carbon deposits, covering the active sites, leading to a decrease in the methanol yield. Current research on catalysts focuses on improving catalytic activity, stability, and renewability to solve the problems of easy deactivation of current catalysts, reduction in stability due to catalyst agglomeration, and non-renewability, in order to meet the requirements of green methanol synthesis. Summary of the Invention

[0004] Based on the above-mentioned problems, it is necessary to provide a diamond-based catalyst for hydrogenation of carbon dioxide to methanol, a preparation method of the catalyst, and a method for hydrogenation of carbon dioxide to methanol using the catalyst. Conductive diamond, as a corrosion-resistant material, is very suitable as a catalyst support due to its strong mechanical and chemical stability, no chemical characteristic adsorption, and extremely large specific surface area after nanosizing. Using nanosized diamond as a support to carry the catalyst has the functions of resisting structural corrosion and increasing the active specific surface area, and can effectively solve the above problems.

[0005] A preparation method of a diamond-based catalyst for hydrogenation of carbon dioxide to methanol includes a catalyst preparation step:

[0006] Provide nanosized conductive diamond, add the nanosized conductive diamond particles to a metal salt solution, mix for 24 h, and then perform a calcination treatment to obtain a diamond-based catalyst;

[0007] The metal in the metal salt solution includes at least one of copper, zinc, chromium, palladium, and indium.

[0008] In one embodiment, it further includes a pretreatment step before the catalyst preparation step: provide nanosized conductive diamond particles, put the nanosized conductive diamond particles into a mixed aqueous solution of citric acid and hydrogen peroxide, and treat at 35 - 60 °C for 3 - 6 h.

[0009] In one embodiment, in the mixed aqueous solution, the concentration of citric acid is 0.01 - 4 M, and the concentration of hydrogen peroxide is 3% - 10%.

[0010] In one embodiment, the conditions for the calcination treatment are: treating in a hydrogen - argon mixed gas with 5% hydrogen at 180 - 300 °C for 2 - 3 h, and then treating in an air atmosphere at 200 - 500 °C for 2 - 5 h.

[0011] In one embodiment, the metal content of the metal salt solution is 20 - 50 mg / mL.

[0012] In one embodiment, the solvent of the metal salt solution is a mixed solution of ethanol, glycerol and water with a volume ratio of 85:12:3.

[0013] In one embodiment, the metal salt solution further includes an additive, and the additive is disodium ethylenediaminetetraacetate or disodium nitrilotriacetate at 2 - 5% of the solvent mass.

[0014] A diamond - based catalyst for hydrogenation of carbon dioxide to methanol is prepared by the preparation method of the diamond - based catalyst for hydrogenation of carbon dioxide to methanol described in any one of the above.

[0015] A method for hydrogenation of carbon dioxide to methanol uses the diamond - based catalyst for hydrogenation of carbon dioxide to methanol described in any one of the above.

[0016] In one embodiment, it includes a methanol synthesis step: placing the diamond - based catalyst in a reactor, introducing a carbon dioxide gas source and a hydrogen gas source for reaction to produce methanol.

[0017] In one embodiment, the carbon dioxide source is carbon dioxide or a carbon dioxide mixed gas containing 0.1 - 5% carbon monoxide by mass fraction.

[0018] In one embodiment, the hydrogen gas source is hydrogen with a mass fraction ratio of 2 - 10%.

[0019] In one embodiment, the reaction conditions of the method are: pressure 2.5 - 10 MPa, temperature 150 - 280 °C, time 0.5 - 8 h, the volume ratio of reaction gases is H2 / CO2 = 1.5 - 4:1, and the mass space velocity is 0.2 - 3 h-1.

[0020] In one embodiment, it further includes a recycling and regeneration step: taking out the catalyst that has worked for a long time from the reactor, putting it into the metal salt solution, mechanically mixing and then performing a calcination treatment.

[0021] In one embodiment, in the recycling step, the mass ratio of metal in the metal salt solution to the catalyst metal is 1:50. In one embodiment, in the recycling step, the calcination treatment conditions are as follows: treating in a hydrogen-argon mixed gas containing 1-5% hydrogen at 105-150°C for 0.5-3 h, and then treating in an air atmosphere at 200-250°C for 1-3 h.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. Due to the strong mechanical and chemical stability, no chemical characteristic adsorption, and extremely large specific surface area after nanosizing of nanodiamond, using nanosized diamond as a carrier to support a catalyst has the function of resisting structural corrosion and increasing the active specific surface area.

[0024] 2. Nano-conductive diamond provides excellent local conductivity for the catalyst carrier, improves the electron transfer efficiency of the catalytic reaction, and at the same time nano-disperses the active metal phase to improve the catalyst utilization rate.

[0025] 3. The diamond phase structure can provide high structural stability for the catalyst, and its high thermal conductivity is beneficial to improving the heat dissipation performance of the catalyst, avoiding sintering or activity reduction of the catalyst caused by local overheating.

[0026] 4. Nanodiamond has an extremely low carbon adsorption energy, and can more effectively inhibit catalyst carbon deposition compared with metal oxide carriers. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a flow chart of the preparation method of the diamond-based catalyst for hydrogenation of carbon dioxide to methanol according to an embodiment of the present invention.

[0029] Figure 2 It is an electron microscope image of the diamond-based catalyst according to an embodiment of the present invention.

[0030] Figure 3 It is a comparison chart of the activity decay rates of the embodiments and comparative examples of the present invention after 10 catalyst regeneration cycles. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The present invention provides a diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide. Using nano-conductive diamond as a carrier to support the active material, the nano-sized conductive diamond has a huge specific surface area. After nano-sizing the diamond and using it as a carrier to support the catalyst, it has the functions of anti-structural corrosion and improving the active specific surface area.

[0033] This application provides a preparation method for the above-mentioned diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide. Specifically, as Figure 1 shown, it includes the catalyst preparation step S1:

[0034] Provide nano-conductive diamond, add the nano-conductive diamond particles to the metal salt solution, mix for 8-24 h and then perform calcination treatment to obtain the diamond-based catalyst;

[0035] The metal in the metal salt solution includes at least one of copper, zinc, chromium, palladium, and indium.

[0036] Among them, in this embodiment, the metal salt solution is an inorganic metal salt, for example, at least one of metal sulfate, metal nitrate, and metal chloride.

[0037] Among them, in a preferred embodiment, the conditions for the calcination treatment are: treat in a hydrogen-argon mixture with 5% hydrogen at 180-300 °C for 2-3 h, and then treat in an air atmosphere at 200-500 °C for 2-5 h.

[0038] Among them, in a preferred embodiment, the metal content in the metal salt solution is 20-50 mg / mL. In this embodiment, the metal content in the metal salt solution is the total metal content. For example, the metal salt solution contains multiple metals among copper, zinc, chromium, palladium, and indium, and the total content of multiple metals is 40 mg / mL.

[0039] Among them, in a preferred embodiment, the solvent of the metal salt solution is a mixed solution of ethanol, glycerol, and water with a volume ratio of 85:12:3.

[0040] Among them, in a preferred embodiment, the metal salt solution further includes an additive, and the additive is disodium ethylenediaminetetraacetate or disodium nitrilotriacetate at 2-5% of the solvent mass.

[0041] In this embodiment, a catalyst with metal supported on nano-conductive diamond as a carrier is obtained by mixing and calcining nano-conductive diamond with a metal salt solution.

[0042] The beneficial effects of this application are as follows:

[0043] 1. Due to the strong mechanical and chemical stability, no chemical characteristic adsorption of nano-diamond, and the huge specific surface area after nano-sizing, using nano-sized diamond as a carrier to support the catalyst has the function of resisting structural corrosion and improving the active specific surface area.

[0044] 2. Nano-conductive diamond provides excellent local conductivity of the catalyst carrier, improves the electron transfer efficiency of the catalytic reaction, and at the same time nano-disperses the active metal phase to improve the catalyst utilization rate.

[0045] 3. The diamond phase structure can provide high structural stability of the catalyst, and its high thermal conductivity is beneficial to improving the heat dissipation performance of the catalyst, avoiding sintering or activity reduction of the catalyst caused by local overheating.

[0046] 4. Nano-diamond has an extremely low carbon adsorption energy, and can inhibit catalyst carbon deposition more effectively than metal oxide carriers.

[0047] In one embodiment, as Figure 1 shown, the preparation method of the diamond-based catalyst further includes a pretreatment step S0 before the catalyst preparation step S1: providing nano-conductive diamond particles, putting the nano-conductive diamond particles into a mixed aqueous solution of citric acid and hydrogen peroxide, and treating at 35 - 60 °C for 3 - 6 h. In a preferred embodiment, in the mixed aqueous solution, the concentration of citric acid is 0.01 - 4 M, and the concentration of hydrogen peroxide is 3% - 10%. In this embodiment, through the treatment with citric acid and hydrogen peroxide, the surface functional groups of the nano-conductive diamond particles are modified, which is beneficial to the uniform adsorption of the metal precursor on the surface of the nano-diamond.

[0048] Among them, the nano-conductive diamond particles can be obtained commercially or prepared by oneself. For example, non-conductive diamond particles can be obtained by the explosion method, and then, for example, conductive diamond can be obtained by chemical vapor deposition. In one embodiment, conductive diamond particles are obtained by the hot filament chemical vapor deposition method. Specifically, the parameters of the hot filament chemical vapor deposition method are: substrate temperature 500 - 800 °C, hot filament temperature 180 - 2400 °C, gas pressure 1 - 5 kPa, hydrogen is introduced at 100 - 1000 sccm, methane at 1 - 20 sccm, borane at 1 - 20 sccm, and the growth time is more than 10 min. For example, in another embodiment, conductive diamond particles are obtained by the microwave plasma chemical vapor deposition method. Specifically, the parameters of the microwave plasma chemical vapor deposition method are: microwave power 500 - 3000 watts, hydrogen is introduced at 100 - 1000 sccm, methane at 1 - 20 sccm, borane at 1 - 10 sccm, substrate temperature 500 - 700 °C, gas pressure 4 - 6 kPa, and the growth time is 3 - 10 h.

[0049] The present application provides a diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide, which is prepared by the preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide described in any of the above embodiments. Among them, the catalyst is nano-conductive diamond as a carrier to support the active material metal.

[0050] The present application also provides a method for synthesizing methanol by hydrogenating carbon dioxide, using the diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide described in any of the above embodiments.

[0051] The present application provides a method for synthesizing methanol by hydrogenating carbon dioxide. In a preferred embodiment, it includes a methanol synthesis step: placing the diamond-based catalyst in a reactor, introducing a carbon dioxide gas source and a hydrogen gas source to react to produce methanol.

[0052] Among them, in a preferred embodiment, the carbon dioxide carbon source is carbon dioxide or a carbon dioxide mixed gas containing 0.1 - 5% carbon monoxide by mass fraction.

[0053] Among them, in a preferred embodiment, the hydrogen gas source is hydrogen with a mass fraction ratio of 2 - 10%.

[0054] Among them, in a preferred embodiment, the reaction conditions of the method for synthesizing methanol by hydrogenating carbon dioxide are: pressure 2.5 - 10 MPa, temperature 150 - 280 °C, time 0.5 - 8 h, the volume ratio of the reaction gas is H2 / CO2 = 1.5 - 4:1, and the mass space velocity is 0.2 - 3 h -1 .

[0055] The present application provides a preferred embodiment. The method for synthesizing methanol by hydrogenating carbon dioxide further includes a recycling and regeneration step: taking out the diamond-based catalyst that has worked for a long time from the reactor, putting it into a metal salt solution, mechanically mixing it, and then performing a calcination treatment.

[0056] For example, the working time of the diamond-based catalyst selected in the recycling and regeneration step exceeds 500 hours.

[0057] Among them, in the preferred embodiment, in the recycling and regeneration step, the mass ratio of metal in the metal salt solution to the metal of the catalyst is 1:50.

[0058] Among them, in the preferred embodiment, in the recycling and regeneration step, the conditions for the calcination treatment are: treating in a hydrogen-argon mixed gas with 1-5% hydrogen at 105-150 °C for 0.5-3 h, and then treating in an air atmosphere at 200-250 °C for 1-3 h.

[0059] The beneficial effect of this embodiment is:

[0060] By simply chemical treatment, the metal phase of the catalyst can be washed out and the unaffected nanodiamond nanostructure can be retained for repeated use of the supported added metal in synthesis, and the process has outstanding renewable performance.

[0061] The following provides specific embodiments:

[0062] Preparation method of a diamond-based catalyst for synthesizing methanol by hydrogenating carbon dioxide: providing nano-conductive diamond, adding nano-conductive diamond particles into a metal salt solution, mixing for 24 h, and then performing a calcination treatment to obtain a diamond-based catalyst.

[0063] The metal salt solution is at least one of metal sulfate, metal nitrate, and metal chloride.

[0064] The conditions for the calcination treatment are: treating in a hydrogen-argon mixed gas with 5% hydrogen at 180-300 °C for 2-3 h, and then treating in an air atmosphere at 200-500 °C for 2-5 h.

[0065] The metal content of the metal salt solution is 40 mg / mL.

[0066] Example 1:

[0067] The metal salt solution contains Cu, Zn, Pd, and Mo.

[0068] The mass fraction ratio of metals in the metal salt solution is 68% (Cu): 11% (Zn): 5% (Pd): 16% (Mo).

[0069] Example 2:

[0070] The metal salt solution contains Cu, Zn, and In.

[0071] The mass fraction ratio of metals in the metal salt solution is 78% (Cu): 11% (Zn): 11% (In).

[0072] Example 3:

[0073] The metal salt solution contains Cu, Zn, In, and Zr.

[0074] The mass fraction ratio of metals in the metal salt solution is 80% (Cu): 11% (Zn): 1% (In): 8% (Zr).

[0075] Comparative Example

[0076] A commercially available Cu-Zn / Al2O3 catalyst, i.e., a catalyst supported by metal oxides.

[0077] The catalysts of the above Example 1, Example 2, Example 3, and Comparative Example were placed in a reactor, and a carbon dioxide gas source and a hydrogen gas source were introduced for methanol synthesis reaction.

[0078] As Figure 2 shown, it is the activity decay rate graph of Example 1, Example 2, Example 3, and Comparative Example after 10 catalyst regeneration cycles (each experiment time is 300 h). It can be seen from the figure that for the catalysts of this patent with different metal active components, the TOF (catalyst conversion efficiency) still maintains a higher value than that of the Comparative Example after 10 regeneration cycles.

[0079] The catalysts of the above examples were applied to the method of synthesizing methanol by hydrogenation of carbon dioxide: the diamond-based catalyst was placed in a reactor, and a carbon dioxide gas source and a hydrogen gas source were introduced for reaction to produce methanol. Keeping the reaction conditions of each example the same, the reaction conditions were: pressure 4.5 MPa, reaction time 2.5 h at a temperature of 236 °C, the volume ratio of reaction gases H2 / CO2 = 1.5 - 4, and the mass space velocity 0.6 h -1 , and experiments were carried out using a 5% hydrogen / argon mixed gas, and the following table results were obtained:

[0080] Example Methanol selectivity % Carbon monoxide selectivity % Carbon dioxide conversion ability % Comparative example 66％ 34％ 16％ Example 1 96.00％ 4％ 27％ Example 2 86％ 14％ 20％ Example 3 91％ 9％ 22％

[0081] Table 1

[0082] It can be seen from Table 1 that the nanodiamond-based catalysts of the examples of this application have higher methanol selectivity and carbon dioxide conversion ability compared with the common commercially available copper-zinc-aluminum type catalysts under the same reaction conditions, and at the same time, less carbon monoxide is produced as a by-product. Therefore, the nanodiamond support catalyst proposed in this application has superiority as a catalyst for the hydrogenation of carbon dioxide to synthesize methanol.

[0083] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0084] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. 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 be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a diamond-based catalyst for hydrogenating carbon dioxide to synthesize methanol, characterized in that, It includes a catalyst preparation step: Provide nano-conductive diamond, add the nano-conductive diamond particles into a metal salt solution, mix for 8 - 24 h and then carry out a calcination treatment to obtain a diamond-based catalyst; The metal in the metal salt solution includes at least one of copper, zinc, chromium, palladium, and indium.

2. The preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that, It also includes a pretreatment step, which is before the catalyst preparation step: Provide nano-conductive diamond particles, put the nano-conductive diamond particles into a mixed aqueous solution of citric acid and hydrogen peroxide, and treat at 35 - 60 °C for 3 - 6 h.

3. The preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that, In the mixed aqueous solution, the concentration of citric acid is 0.01 - 4 M, and the concentration of hydrogen peroxide is 3% - 10%.

4. The preparation method of the diamond-based catalyst for hydrogenating carbon dioxide to synthesize methanol according to claim 2, characterized in that, The conditions of the calcination treatment are: Treat in a hydrogen-argon mixed gas with 5% hydrogen at 180 - 300 °C for 2 - 3 h, and then treat in an air atmosphere at 200 - 500 °C for 2 - 5 h.

5. The preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that, The metal content of the metal salt solution is 20 - 50 mg / mL.

6. The preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that, The solvent of the metal salt solution is a mixed solution of ethanol, glycerol, and water with a volume ratio of 85:12:

3.

7. The preparation method of the diamond-based catalyst for synthesizing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that, The metal salt solution also includes an additive, and the additive is disodium ethylenediaminetetraacetate or disodium nitrilotriacetate at 2 - 5% of the solvent mass.

8. A diamond-based catalyst for the synthesis of methanol by hydrogenation of carbon dioxide, characterized in that, It is prepared by the preparation method of the diamond-based catalyst for hydrogenation of carbon dioxide to methanol according to any one of claims 1 - 7.

9. A method for synthesizing methanol by hydrogenating carbon dioxide, characterized in that, Use the diamond-based catalyst for hydrogenation of carbon dioxide to methanol according to any one of claims 1 - 7.

10. The method for synthesizing methanol by hydrogenating carbon dioxide according to claim 9, wherein It includes a methanol synthesis step: Place the diamond-based catalyst in a reactor, introduce a carbon dioxide gas source and a hydrogen gas source to react to produce methanol.

11. The method for synthesizing methanol by hydrogenation of carbon dioxide according to claim 10, characterized in that, The carbon dioxide source is carbon dioxide or a carbon dioxide mixed gas containing 0.1 - 5% carbon monoxide by mass fraction.

12. The method for synthesizing methanol by hydrogenating carbon dioxide according to claim 10, wherein The hydrogen gas source is hydrogen with a mass fraction ratio of 2 - 10%.

13. The method for synthesizing methanol by hydrogenating carbon dioxide according to claim 10, characterized in that, The reaction conditions of the said method are: pressure 2.5 - 10 MPa, temperature 150 - 280 °C, time 0.5 - 8 h, the volume ratio of the reaction gases is H2 / CO2 = 1.5 - 4:1, and the mass space velocity is 0.2 - 3 h -1 .

14. The method for synthesizing methanol by hydrogenating carbon dioxide according to claim 9, characterized in that, It also includes a recycling and regeneration step: Take out the catalyst that has worked for a long time from the reactor, put it into a metal salt solution, mechanically mix and then carry out a calcination treatment.

15. The method for synthesizing methanol by hydrogenation of carbon dioxide according to claim 14, wherein, In the recycling and regeneration step, the mass ratio of metal in the metal salt solution to metal in the catalyst is 1:

50.

16. The method for synthesizing methanol by hydrogenating carbon dioxide according to claim 14, wherein In the recycling and regeneration step, the conditions of the calcination treatment are: Treat in a hydrogen-argon mixed gas with 1 - 5% hydrogen at 105 - 150 °C for 0.5 - 3 h, and then treat in an air atmosphere at 200 - 250 °C for 1 - 3 h.

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