Flaky carbon supported gold-based catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of catalyst preparation technology and application, and relates to a flaky carbon-loaded gold-based catalyst as well as a preparation method and application thereof. The catalyst comprises a carrier and an active component on the carrier, the active component is Au; the carrier is an acid, alkali, salt and / or organic matter modified activated carbon carrier. The modified carrier can improve the dispersity of metal and further enhance the reduction resistance of gold, so that active sites in the catalyst are increased, and the activity and stability of the catalyst are improved. The catalyst has good catalytic activity and vinyl chloride selectivity in an acetylene hydrochlorination system.

Description

Technical Field

[0001] The invention belongs to the field of catalyst preparation technology and application, and in particular relates to a flaky carbon-supported gold-based catalyst and a preparation method and application thereof. Background Art

[0002] Polyvinyl chloride is synthesized from vinyl chloride under the action of an inducing agent. It is the third largest polymer material in the world and is widely used in building materials, packaging, clothing and other fields. The demand for polyvinyl chloride as a basic chemical raw material is increasing day by day. At present, 70% of vinyl chloride production in my country adopts the acetylene method, using calcium carbide and acetylene as production raw materials. At present, mercury catalyst is the catalyst for large-scale industrial application of vinyl chloride production. However, mercury is highly toxic and easily sublimates during the reaction process, causing adverse effects on human health and the environment. Therefore, the research and development of green mercury-free catalysts is the general trend.

[0003] Currently, researchers are committed to studying mercury-free catalysts. Precious metal catalysts including Au, Ru, Pt and Pd show higher activity in acetylene hydrochlorination, but the high price of precious metals limits their further application. Non-precious metal catalysts have poor reaction activity. When organic additives and reduced metal components come into contact with air, redox reactions are likely to occur, which releases heat and triggers the catalyst to naturally oxidize, causing not only equipment damage but also a threat to personnel health. Therefore, it is particularly important to develop a catalyst preparation method with certain mechanical strength, highly dispersed metal active components, simple process and relatively low production cost.

[0004] Patent CN202410110278.8 discloses a method for preparing and regenerating a precious metal catalyst for synthesizing vinyl chloride by hydrochlorination of acetylene, using platinum, palladium and ruthenium as active components. At 140-240°C, the acetylene volume space velocity is 30-2000h -1 , a catalyst with better performance was obtained under the condition of a feed volume ratio of hydrogen chloride to acetylene of 0.8-1.5:1. However, the selectivity during the reaction is unknown.

[0005] Patent CN202110858268.9 discloses a preparation method for synthesizing a copper molybdate catalyst. The active component of the catalyst is copper molybdate, the auxiliary agent is one of barium, nickel, cobalt, cerium, and tin, and the carrier is activated carbon.

[0006] Patent CN202410048678.0 discloses a method for preparing a copper-based mercury-free catalyst for VCM synthesis, which uses carbon nanotubes, hexadecyltrimethylammonium bromide, ethyl orthosilicate, ethanol, sodium hydroxide and water to obtain an original carrier, and then mixes the original carrier with urea, acetic acid, hydrogen peroxide and pure water and calcines to obtain a carrier.

[0007] Li J. et al. Appl. Organomet. Chem. 2021, e63180. et al. used divinylbenzene and 4-vinylpyridine to synthesize a metal-free pure pyridine-based polymer catalyst at a temperature of 220°C and an acetylene space velocity of 30 h -1 , molar HCl / C 2 H 2 =1.2, the acetylene conversion rate is as high as 88%, and the selectivity is over 99%. However, its preparation process is currently complex and difficult to achieve industrial application. Summary of the invention

[0008] In order to solve the above technical problems, the purpose of the present invention is to provide a flaky carbon-supported gold-based catalyst and a preparation method and application thereof, which can be used as a catalyst for synthesizing vinyl chloride by the acetylene process.

[0009] Specifically, the catalyst includes a carrier and an active component, wherein the carrier is a sheet-like activated carbon carrier modified by acid, alkali, salt and / or organic matter, the active component is Au, and the mass percentage of the active component Au in the catalyst is: 0.05% to 0.1%, and the mass percentage of the raw materials used for the modification is 0% to 20% of the activated carbon carrier.

[0010] Specifically, industrially produced coconut shell flake activated carbon uses activated carbon modified by acid, alkali, salt and / or organic matter as a carrier, which effectively improves the dispersibility of active components on the carrier surface, enhances the interaction between active components and functional groups on the carrier surface, and improves the catalyst activity and selectivity to a certain extent.

[0011] The present invention also provides a variety of preparation methods for the catalyst, wherein in scheme 1, a flaky carbon-supported gold-based catalyst and its preparation method and application are characterized by comprising the following steps: (1) stirring and dissolving a certain amount of acid substance in deionized water at 25-40° C. to obtain an impregnation solution for modification, then impregnating the impregnation solution into the flaky activated carbon by an excessive impregnation method, and after standing at room temperature for 6 hours, placing the sample in a blast oven at 60-120° C. to completely dry it to obtain a precursor; wherein the acid is one of boric acid, oxalic acid, and hydrochloric acid; and the mass ratio of the acid substance: deionized water is 0.05-0.20:1.0;

[0012] (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. / min in an inert atmosphere, keeping the temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon;

[0013] (3) At 25-40° C., dilute the chloroauric acid solution to obtain an impregnation solution, then use an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, let it stand at room temperature overnight, and then completely dry it in a 60-80° C. forced air oven to obtain a catalyst, wherein the gold content is 0.05-0.1%.

[0014] In one embodiment, a flaky carbon-supported gold-based catalyst and a preparation method and application thereof are characterized by comprising the following steps:

[0015] (1) At 25-40°C, a certain amount of concentrated hydrochloric acid and hydrogen peroxide are mixed and stirred to obtain an impregnation solution for modification, and then the impregnation solution is impregnated into the sheet activated carbon by an excessive impregnation method. After standing at room temperature for 6 hours, the sample is placed in a blast oven at 60-80°C and completely dried to obtain a precursor, wherein the mass ratio of hydrochloric acid: hydrogen peroxide is 1.0-3.0:1.0;

[0016] (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. / min in an inert atmosphere, keeping the temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon;

[0017] (3) At 25-40° C., dilute the chloroauric acid solution to obtain an impregnation solution, then use an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, let it stand at room temperature overnight, and then completely dry it in a 60-80° C. forced air oven to obtain a catalyst, wherein the gold content is 0.05-0.1%.

[0018] In scheme 3, a flaky carbon-supported gold-based catalyst and a preparation method and application thereof are characterized by comprising the following steps:

[0019] (1) Under the condition of 25-40°C, a certain amount of alkaline substance is dissolved in deionized water and stirred evenly to obtain an impregnation solution for modification, and then the impregnation solution is impregnated into the sheet activated carbon by an excessive impregnation method. After standing at room temperature for 6 hours, the sample is placed in a blast oven at 60-80°C and completely dried to obtain a precursor, wherein the mass ratio of alkaline substance to deionized water is 0.05-0.20:1.0;

[0020] (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. / min in an inert atmosphere, keeping the temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon;

[0021] (3) At 25-40° C., dilute the chloroauric acid solution to obtain an impregnation solution, then use an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, let it stand at room temperature overnight, and then completely dry it in a 60-80° C. forced air oven to obtain a catalyst, wherein the gold content is 0.05-0.1%.

[0022] In scheme 4, a flaky carbon-supported gold-based catalyst and a preparation method and application thereof are characterized by comprising the following steps:

[0023] (1) At 25-40°C, a certain amount of salt / organic matter is dissolved in deionized water or anhydrous ethanol and stirred to obtain an impregnation solution for modification, and then the impregnation solution is impregnated into the sheet activated carbon by an excess impregnation method. After standing at room temperature for 6 hours, the sample is placed in a forced air oven at 60-80°C and completely dried to obtain a precursor, wherein the mass ratio of salt substance / organic matter: deionized water / ethanol is 0.05-0.20:1.0;

[0024] (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. / min in an inert atmosphere, keeping the temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon;

[0025] (3) At 25-40° C., dilute the chloroauric acid solution to obtain an impregnation solution, then use an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, let it stand at room temperature overnight, and then completely dry it in a 60-80° C. forced air oven to obtain a catalyst, wherein the gold content is 0.05-0.1%.

[0026] Beneficial effects of the present invention

[0027] (1) Compared with the background, the active component of the present invention uses gold as the active component, and reaction intermediates are produced during the acetylene hydrochlorination reaction. The gold-based catalyst can better stabilize these intermediates, reduce the activation energy required for the reaction, and promote the reaction to proceed in the direction of vinyl chloride;

[0028] (2) The modified activated carbon carrier obtained by the carrier modification method of the present invention has a large specific surface area, which is beneficial to increase the loading amount of the active component, improve the dispersion of the active component, and has good anti-carbon deposition and anti-poisoning properties to a certain extent, and can maintain the catalytic activity and stability for a long time; the present invention prepares the catalyst by the impregnation method, the preparation process is simple, and it is easy to industrialize production;

[0029] (3) The catalyst of the present invention is used for synthesizing vinyl chloride by the acetylene process. The reaction conditions are mild. When the reaction temperature is 180°C-220°C, the acetylene conversion rate is 50-90%, and the selectivity of vinyl chloride is 99.50%-99.99%. While improving the acetylene conversion rate, the selectivity of vinyl chloride is also improved.

[0030] (4) The catalyst of the present invention is a mercury-free catalyst, which is green and environmentally friendly, and the preparation method is simple and easy to repeat. DETAILED DESCRIPTION

[0031] For a better understanding of the present invention, the present invention is illustrated by the following examples. It should be clear to those skilled in the art that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0032] Example 1

[0033] (1) Weigh 6.18 g of boric acid and dissolve it in 1 L of deionized water to prepare a 0.1 mol / L boric acid solution;

[0034] (2) Weigh 20.00 g of activated carbon flakes into a beaker, add 28 mL of boric acid solution, soak for 6 h, and then dry in an oven at 110 °C for 12 h. Then place the activated carbon flakes in a tubular furnace, calcine at 600 °C for 2 h in a nitrogen atmosphere, with a program heating rate of 5 °C / min, and then cool to room temperature;

[0035] (3) Measure the chloroauric acid solution to prepare 30 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the modified activated carbon flakes, soak for 12 hours, and then dry in an oven at 120° C. for 12 hours to obtain a supported catalyst with a gold content of 0.1%, recorded as Cat-1.

[0036] Example 2

[0037] The preparation steps of Example 2 are similar to those of Example 1, except that 6.18 g of boric acid in (1) is replaced by 9.00 g of oxalic acid. The prepared catalyst is designated as Cat-2.

[0038] Example 3

[0039] The preparation steps of Example 3 are similar to those of Example 1, except that the boric acid in (1) is replaced with a hydrochloric acid solution and mixed with hydrogen peroxide in a ratio of 3:1. The prepared catalyst is denoted as Cat-3;

[0040] Example 4

[0041] (1) Weigh 0.80 g of sodium hydroxide and dissolve it in 100 ml of deionized water to prepare a 0.2 mol / L sodium hydroxide solution;

[0042] (2) Weigh 20.00 g of activated carbon flakes into a beaker, add 28 mL of sodium hydroxide solution, soak for 6 h, and then dry in an oven at 120 °C for 12 h. Then place the activated carbon flakes in a tubular furnace, calcine at 800 °C for 2 h in a nitrogen atmosphere, with a program heating rate of 5 °C / min, and then cool to room temperature;

[0043] (3) Measure the chloroauric acid solution to prepare 30 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the modified activated carbon flakes, soak for 12 hours, and then dry in an oven at 120° C. for 12 hours to obtain a supported catalyst with a gold content of 0.1%, recorded as Cat-4.

[0044] Example 5

[0045] The preparation steps of Example 5 are similar to those of Example 4, except that 0.80 g of sodium hydroxide in (1) is replaced with 1.12 g of potassium hydroxide. The prepared catalyst is designated as Cat-5.

[0046] Example 6

[0047] (1) Weigh 0.60 g of sodium hydroxide and dissolve it in 100 ml of deionized water to prepare a 0.1 mol / L urea solution;

[0048] (2) Weigh 20.00 g of activated carbon flakes into a beaker, add 28 mL of urea solution, soak for 6 h, and then dry in an oven at 120 °C for 12 h. Then place the activated carbon flakes in a tubular furnace, calcine at 700 °C for 2 h in a nitrogen atmosphere, with a program heating rate of 5 °C / min, and then cool to room temperature;

[0049] (3) Measure the chloroauric acid solution to prepare 30 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the modified activated carbon flakes, soak for 12 hours, and then dry in an oven at 120° C. for 12 hours to obtain a supported catalyst with a gold content of 0.1%, recorded as Cat-6.

[0050] Example 7

[0051] (1) Weigh 3.0 g of triphenylphosphonium chloride and dissolve it in 20 ml of anhydrous ethanol to prepare a triphenylphosphonium chloride alcohol solution;

[0052] (2) Weigh 10.00 g of activated carbon flakes into a beaker, add 14 mL of triphenylphosphonium chloride alcohol solution, soak for 6 hours, and then dry in an oven at 60°C for 12 hours. Then place the activated carbon flakes in a tubular furnace, calcine at 700°C for 2 hours in a nitrogen atmosphere, with a program heating rate of 5°C / min, and then cool to room temperature;

[0053] (3) Measure the chloroauric acid solution to prepare 15 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the modified activated carbon flakes, soak for 12 hours, and then dry in an oven at 110° C. for 12 hours to obtain a supported catalyst with a gold content of 0.1%, recorded as Cat-7.

[0054] Example 8

[0055] The preparation steps of Example 8 are similar to those of Example 7, except that the triphenylphosphonium chloride in (1) is replaced with tetraphenylphosphonium bromide. The prepared catalyst is denoted as Cat-8.

[0056] Comparative Example 1

[0057] (1) Weigh 10.0 g of activated carbon flakes, soak them in deionized water for 2 h, wash them 3-4 times, and then dry them in an oven at 120 °C for 12 h. Then place the activated carbon flakes in a tubular furnace, calcine them at 700 °C for 2 h in a nitrogen atmosphere, with a program heating rate of 5 °C / min, and then cool them to room temperature;

[0058] (2) Measure the chloroauric acid solution to prepare 15 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the flaky activated carbon, soak for 12 hours, and then dry in an oven at 110° C. for 12 hours to obtain a supported catalyst with a gold content of 0.1%, which is recorded as Cat-9.

[0059] Comparative Example 2

[0060] (1) Weigh 10.0 g of activated carbon flakes, place the activated carbon flakes in a tubular furnace, calcine at 700 °C for 2 h in a nitrogen atmosphere at a program heating rate of 5 °C / min, and then cool to room temperature;

[0061] (2) Measure the chloroauric acid solution to prepare 15 mL of chloroauric acid aqueous solution, then evenly add the chloroauric acid aqueous solution to the flaky activated carbon, soak for 12 h, and then dry in an oven at 110° C. for 12 h to obtain a supported catalyst with a gold content of 0.1%, which is recorded as Cat-10.

[0062] The catalyst evaluation conditions are:

[0063] (1) 5 mL of the above catalyst was placed in a fixed bed reactor, heated to 180°C in a nitrogen atmosphere, and maintained at this temperature for half an hour, with a nitrogen volume space velocity of 80 h / min. -1 ;

[0064] (2) Switch nitrogen to hydrogen chloride gas and maintain the temperature for 2 hours, with the volumetric space velocity of hydrogen chloride being 80 h -1 ;

[0065] (3) Adjust the volumetric space velocity of hydrogen chloride to 240h -1 Then, acetylene gas was introduced, and the volumetric space velocity of acetylene gas was 240h -1 ;

[0066] The reaction product gas was sampled every 20 minutes using gas chromatography for online qualitative and quantitative analysis.

[0067] Table 1 Performance test results of catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 2

[0068]

[0069]

[0070] It can be seen from the data in Table 1 that the conversion rate of the flaky carbon-gold-based catalysts prepared in Examples 1-8 of the present application is significantly better than that of Comparative Examples 9-10, and the selectivity is almost the same; the reason may be that the modified substances can increase the oxygen-containing and nitrogen-containing functional groups on the surface of the activated carbon, improve the adsorption capacity of hydrogen chloride, increase the number and size of activated carbon pores, and improve the adsorption efficiency. At the same time, the modified activated carbon can better load the metal active components to form a synergistic effect and improve the catalytic performance.

[0071] The applicant declares that the present invention illustrates the detailed process conditions and process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process conditions and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process conditions and process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., as well as equivalent replacement and specific selection of process conditions and process equipment of the present invention, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A flaky carbon-supported gold-based catalyst, characterized in that the catalyst is prepared according to the following steps: (1) A modified impregnation solution is obtained by stirring an acid, an alkali, a salt and / or an organic matter and dissolving it in deionized water. The impregnation solution is then impregnated into a sheet of activated carbon by an excess impregnation method. After standing at room temperature for 6 hours, the sample is placed in a forced air oven and completely dried at 80° C. to obtain a precursor; wherein: The acid is selected from one or more of boric acid, oxalic acid, and hydrochloric acid; the base is selected from one or more of sodium hydroxide and potassium hydroxide; the salt is selected from urea; the organic matter is selected from one or more of triphenylphosphonium chloride and tetraphenylphosphonium bromide; (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. in an inert atmosphere, keeping it at that temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon; (3) diluting the chloroauric acid solution to obtain an impregnation solution, then using an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, leaving it to stand overnight at room temperature, and then completely drying it in a 60-120° C. forced air oven to obtain a catalyst.

2. A flaky carbon-supported gold-based catalyst, characterized in that the catalyst is prepared according to the following steps: (1) A modified impregnation solution is obtained by stirring and dissolving an acid, a base, a salt and / or an organic matter in deionized water or ethanol at 25-40° C., and an auxiliary agent may be added as needed in the above operation. Then, the impregnation solution is impregnated into the sheet-shaped activated carbon by an excessive impregnation method. After standing at room temperature for 6 hours, the sample is placed in a blast oven at 60-80° C. and completely dried to obtain a precursor; wherein, The acid is selected from one or more of boric acid, oxalic acid and hydrochloric acid; the base is selected from one or more of sodium hydroxide and potassium hydroxide; the salt is selected from urea; the organic matter is selected from one or more of triphenylphosphonium chloride and tetraphenylphosphonium bromide; the auxiliary agent is selected from hydrogen peroxide; (2) placing the precursor in a tube furnace, heating it to 500-800° C. at a heating rate of 5° C. in an inert atmosphere, keeping it at that temperature for 2 hours, and then cooling it to room temperature to obtain a modified carrier activated carbon; (3) At 25-40° C., dilute the chloroauric acid solution to obtain an impregnation solution, then use an excess impregnation method to impregnate the impregnation solution onto the modified carrier activated carbon, let it stand at room temperature overnight, and then completely dry it in a 60-120° C. forced air oven to obtain a catalyst.

3. The catalyst according to claim 1 or 2, characterized in that The mass ratio of the acid, alkali, salt and / or organic matter to deionized water in step (1) is 0.05-0.20:1.0; and stirring is required for 30-60 minutes after the immersion in step (1).

4. The catalyst according to claim 1 or 2, characterized in that The inert gas in the inert atmosphere of step (2) is selected from nitrogen, argon and helium; the volume space velocity of the inert gas in the inert atmosphere of step (2) is 200-300h -1 .

5. The catalyst according to claim 1, characterized in that After the immersion in step (3), mechanical stirring is performed for 30 minutes.

6. The catalyst according to claim 2, characterized in that The solvent of the organic triphenylphosphonium chloride and tetraphenylphosphonium bromide in step (1) is ethanol.

7. Use of the catalyst according to claim 1 or 2, characterized in that: It is used as a catalyst for the synthesis of vinyl chloride from acetylene.

8. The method for evaluating a catalyst according to claim 1 or 2, characterized in that: The evaluation method includes the following steps: (1) A certain volume of catalyst is loaded into a fixed bed reactor and the temperature is raised to 160-220° C. in a nitrogen atmosphere. The nitrogen volume space velocity is 80h -1 ; (2) Turn off nitrogen and switch to hydrogen chloride gas, maintain the temperature for 1-2 hours, and the volume space velocity of hydrogen chloride is 40-80h -1 ; (3) Then, acetylene gas is introduced, and the acetylene volume space velocity is 80-200h -1 , and adjusting the molar ratio of hydrogen chloride to acetylene to 1.05-1.2:1; (4) Use gas chromatography to conduct qualitative and quantitative analysis of the product gas.

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