Preparation method and use method of silver catalyst

Abstract

The invention discloses a preparation method of a silver catalyst, which comprises the following steps: cleaning rice husks, drying to obtain dried rice husks, and refluxing the dried rice husks in a hydrochloric acid solution for 18-25 hours; the method comprises the following steps: taking out rice hulls in a hydrochloric acid solution, washing the rice hulls with distilled water until the rice hulls are neutral, drying the neutral rice hulls, feeding the dried neutral rice hulls into ethanol according to a ratio of clean rice hulls to silver nitrate of 8: (0.8-1.2), stirring at normal temperature, and distilling the ethanol after the silver nitrate is in full contact with the clean rice hulls to obtain a solid. The invention also comprises a use method of the silver catalyst. Cheap and easily available rice husks are matched with silver, a series of treatments are carried out to form a porous carrier, the added value of the rice husks is increased, the production cost of the catalyst is greatly reduced, the performance is stable, the safety is high, and as a hydrogenation catalyst, the reaction risk of catalytic hydrogenation is greatly reduced; and the reaction safety is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogenation catalytic reaction, and in particular to a preparation method of a silver catalyst and a use method thereof. Background Art

[0002] A hydrogenation catalyst is a catalyst that can accelerate the reaction between hydrogen and compounds. It is widely used in chemical, petroleum, organic synthesis, fuel and other fields. In the field of organic synthesis, hydrogenation catalysts can be used for various reactions, such as the hydrogenation of olefins, alkynes, aldehydes, ketones, etc., and the reduction of nitrobenzene.

[0003] Currently, commonly used catalysts include Pd / C catalysts and Raney tweezers catalysts. Not only are they expensive, but they will also spontaneously combust during use, requiring great caution during chemical operations. Improper operations can easily lead to safety hazards. To this end, we proposed a preparation method for a silver catalyst and a method for using it to solve the above problems. Summary of the invention

[0004] The present application provides a method for preparing a silver catalyst and a method for using the same, which solves the problems of high cost, easy spontaneous combustion and potential safety hazards of traditional hydrogenation catalysts.

[0005] The present application provides a method for preparing a silver catalyst, which is characterized by comprising the following steps:

[0006] S1, cleaning and drying the rice husk to obtain dry rice husk, and placing the dry rice husk in a hydrochloric acid solution and refluxing for 18-25 hours;

[0007] S2, taking out the rice husk from the hydrochloric acid solution, washing it with distilled water until it becomes neutral, and obtaining neutral rice husk;

[0008] S3, drying the neutral rice husk to obtain clean rice husk;

[0009] S4, adding the clean rice husk to silver nitrate in a ratio of 8: (0.8-1.2) to ethanol, stirring at room temperature, and after the silver nitrate is fully in contact with the clean rice husk, distilling the ethanol to obtain a solid;

[0010] S5, calcining the solid at a temperature of 400-800° C. for 5-6 hours to obtain a catalyst body.

[0011] Preferably, in S1, the dried rice husk is placed in a hydrochloric acid solution with a mass ratio of five times and refluxed for 24 hours.

[0012] Preferably, the concentration of the hydrochloric acid solution is 10%.

[0013] Preferably, in S3, the neutral rice husk is dried at 70°C for 24 hours.

[0014] Preferably, the clean rice husks and the silver nitrate are stirred at room temperature for 24 hours.

[0015] Preferably, the fixed body is calcined at 400, 500, 600, 700, 800° C. for one hour respectively.

[0016] Preferably, in S1, the rice husk is washed 2-3 times with deionized water or distilled water under stirring.

[0017] The present application also includes a method for using a silver catalyst, which is characterized by comprising the following steps:

[0018] Add the nitro compound, 1.4 mol% of the silver catalyst and 180-140 ml / mol (the amount of the nitro compound substance) of acetonitrile into the hydrogenation kettle;

[0019] After sealing the hydrogenation kettle, the air in the hydrogenation kettle was evacuated, and then hydrogen was introduced until the pressure of the hydrogenation kettle reached 10 kg;

[0020] The hydrogenation kettle was heated to 120°C until it stopped absorbing hydrogen and kept warm for 2 hours.

[0021] Preferably, the method for exhausting the air after the hydrogen kettle is to first introduce nitrogen into the hydrogenation kettle for replacement three times, and then introduce hydrogen into the hydrogenation kettle for replacement twice.

[0022] Preferably, the nitro compound is one of nitrobenzene, 4-nitrochlorobenzene, 4-fluoronitrobenzene, 4-nitroiodobenzene, 4-nitrophenyl isocyanide, nitrocyclopentane or nitropropane.

[0023] It can be seen from the above technical scheme that the present application provides a method for preparing a silver catalyst. In the specific operation of the present application, the rice husk is first cleaned, and then refluxed through a hydrochloric acid solution to remove a small amount of metal and dirt in the rice husk, and then washed with distilled water to neutrality, and the neutral rice husk is sent to low-temperature drying, and then the dried rice husk is sent to an ethanol solution, and silver nitrate is added at the same time. After stirring for a specified time, the alcohol is evaporated, and the remaining solid is calcined to obtain the silver catalyst of the present application.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In this application, rice husk is a cheap and readily available raw material, and the cost of silver is also lower than that of other precious metals. Therefore, the combination of the two can obtain a low-cost catalyst, increase the added value of rice husk, and reduce production costs;

[0026] 2. In this application, a porous carrier is formed by using rice husk to improve the catalytic efficiency, and the preparation method is simple, safe, and can be mass-produced;

[0027] 3. The present invention has stable properties and is not prone to spontaneous combustion. As a hydrogenation catalyst, it greatly reduces the reaction risk of catalytic hydrogenation and greatly improves the safety of the reaction.

[0028] In summary, the present application adopts cheap and readily available rice husks in combination with silver, and after a series of treatments, it becomes a porous carrier, which not only increases the added value of the rice husks, but also greatly reduces the production cost of the catalyst, thereby reducing the production cost of catalytic hydrogenation, and has stable performance and high safety. As a hydrogenation catalyst, it greatly reduces the reaction risk of catalytic hydrogenation and greatly improves the safety of the reaction. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application are clearly and completely described.

[0030] A method for preparing a silver catalyst comprises the following steps:

[0031] S1, clean the rice husk and dry it, mainly to remove dust and other impurities in the rice husk. Specifically, the rice husk can be washed with deionized water or distilled water under stirring, washed 2-3 times to obtain dry rice husk. The rice husk washed with water alone still has some residual metal and dirt, so the dry rice husk needs to be placed in a hydrochloric acid solution and refluxed for 18-25 hours, which can easily wash away the residual metal and other impurities in the rice husk. In the specific cleaning process, the dry rice husk can be placed in a hydrochloric acid solution with a mass ratio of five times, wherein the concentration of the hydrochloric acid solution is 10%, and refluxed for 24 hours to further improve the purity of the rice husk;

[0032] S2, taking out the rice husks from the hydrochloric acid solution, washing them with distilled water until they are neutral, obtaining neutral rice husks, washing away the hydrochloric acid components, and ensuring the cleanliness of the rice husks;

[0033] S3, drying the neutral rice husk. In order to ensure the state of the rice husk, it needs to be dried at a low temperature, and the temperature should not be too high. Therefore, the neutral rice husk is dried at 70° C. for 24 hours to obtain clean rice husk;

[0034] S4, adding the clean rice husk to silver nitrate in a ratio of 8: (0.8-1.2) to ethanol and stirring at room temperature. Specifically, the clean rice husk and silver nitrate are stirred at room temperature for 24 hours. After the silver nitrate and the clean rice husk are fully in contact, the ethanol is distilled clean to obtain a solid, and the ethanol and condensate are reused;

[0035] S5, calcining the solid at a temperature of 400-800°C for 5-6 hours to obtain the catalyst body. During the specific calcination, the fixed body is calcined at 400, 500, 600, 700, and 800°C for one hour respectively. In the present application, the rice husk is processed to become a porous carrier, and after combining with Ag, it is used as a hydrogenation catalyst. The storage safety factor is high, which greatly reduces the reaction risk of catalytic hydrogenation, and the safety of the reaction is greatly improved. In addition, the rice husk used in the present application is not only cheap and easy to obtain, but also has the advantages of large surface area and high filling efficiency. Compared with other precious metals, silver is also lower in cost than other precious metals used as catalysts, thereby further reducing the catalyst cost during the reaction process.

[0036] The present application also includes a method for using a silver catalyst, comprising the following steps:

[0037] Add nitro compound, 1.4 mol% of silver catalyst and 180-140 ml / mol (amount of nitro compound substance) of acetonitrile into a hydrogenation kettle;

[0038] After sealing the hydrogenation kettle, the air in the hydrogenation kettle is evacuated to improve the reaction efficiency. Specifically, the method of evacuating the air after the hydrogenation kettle is to first introduce nitrogen into the hydrogenation kettle for replacement three times, then introduce hydrogen into the hydrogenation kettle for replacement twice, and then introduce hydrogen until the pressure of the hydrogenation kettle reaches 10kg;

[0039] The hydrogenation kettle was heated to 120°C until it stopped absorbing hydrogen and kept warm for 2 hours to complete the hydrogenation reaction.

[0040] The following will be combined with specific implementation methods, as follows:

[0041] Example 1

[0042] 100g of washed and dried rice husks were refluxed in 500ml of 10% hydrochloric acid for 24 hours to remove a small amount of metal and dirt in the rice husks, cooled to room temperature and filtered, and the filtered rice husks were washed with distilled water until neutral, and then the rice husks were placed in a drying oven at 70℃ and dried for 24 hours to obtain 80g of dried and clean rice husks. 80g of rice husks were added with 10.4g of silver nitrate and 500ml of ethanol and stirred at room temperature for 24 hours to make the silver nitrate and rice husks fully contact, and then the ethanol was distilled clean to obtain 90.4g of solid. 90.4g of solid was placed in a muffle furnace and dried at 400, 500, 600, 700, and 800℃ for one hour each to obtain a white solid (with a little yellowish surface).

[0043] Example 2

[0044] In a 1L hydrogenation kettle, add 0.1mol of nitro compound, 1.4mol% of silver catalyst and 200ml of acetonitrile. After sealing the hydrogenation kettle, replace the air with nitrogen three times to expel the air in the reactor, then replace it with hydrogen twice, and then pass hydrogen to make the pressure reach 10kg, raise the temperature to 120℃, until it stops absorbing hydrogen, and then keep warm for 2 hours.

[0045]

[0046] It can be seen from the above technical scheme that the present application can reach more than 97% in the hydrogenation reaction of nitrobenzene, 4-nitrochlorobenzene, 4-fluoronitrobenzene, 4-nitroiodobenzene, 4-nitrophenyl isonitrile, nitrocyclopentane and nitropropane, and some can reach 99%, with good catalytic effect. The catalytic effect of the present application in the present application can achieve the same catalytic performance as traditional Pd / C and Raney nickel. The current market price of Pd / C catalyst is 24,000 yuan / kg, and the market price of Raney tweezers is also around 1,000 yuan / kg, while the present catalyst is only a few hundred yuan per kilogram. In addition, the preparation process of the silver catalyst of the present application is simple, and it is safe and efficient during storage and application. Therefore, the present application has obvious advantages in terms of economy and safety, and the advantages are very obvious, with high application value.

[0047] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope of the present application is indicated by the claims.

[0048] It should be understood that the present application is not limited to the specific implementations described above, and various modifications and changes can be made without departing from the scope thereof. The implementations of the present application described above do not constitute a limitation on the scope of protection of the present application.

Claims

1. A method for preparing a silver catalyst, characterized in that: The following steps are involved: S1, cleaning and drying the rice husk to obtain dry rice husk, and placing the dry rice husk in a hydrochloric acid solution and refluxing for 18-25 hours; S2, taking out the rice husk from the hydrochloric acid solution, washing it with distilled water until it becomes neutral, and obtaining neutral rice husk; S3, drying the neutral rice husk to obtain clean rice husk; S4, adding the clean rice husk to silver nitrate in a ratio of 8: (0.8-1.2) to ethanol, stirring at room temperature, and after the silver nitrate is fully in contact with the clean rice husk, distilling the ethanol to obtain a solid; S5, calcining the solid at a temperature of 400-800° C. for 5-6 hours to obtain a catalyst body.

2. The method for preparing a silver catalyst according to claim 1, characterized in that: In S1, the dried rice husk is placed in a hydrochloric acid solution with a mass ratio of five times, and refluxed for 24 hours.

3. The method for preparing a silver catalyst according to claim 2, characterized in that: The concentration of the hydrochloric acid solution is 10%.

4. The method for preparing a silver catalyst according to claim 1, characterized in that: In S3, the neutral rice husk is dried at 70°C for 24 hours.

5. The method for preparing a silver catalyst according to claim 1, characterized in that: The clean rice husk and the silver nitrate are stirred at room temperature for 24 hours.

6. The method for preparing a silver catalyst according to claim 1, characterized in that: The fixed body was calcined at 400, 500, 600, 700 and 800° C. for one hour respectively.

7. The method for preparing a silver catalyst according to claim 1, characterized in that: In S1, the rice husk is washed 2-3 times with deionized water or distilled water under stirring.

8. A method for using a silver catalyst, characterized in that: The following steps are involved: Add the nitro compound, 1.4 mol% of the silver catalyst and 180-140 ml / mol (the amount of the nitro compound substance) of acetonitrile into the hydrogenation kettle; After sealing the hydrogenation kettle, the air in the hydrogenation kettle was evacuated, and then hydrogen was introduced until the pressure of the hydrogenation kettle reached 10 kg; The hydrogenation kettle was heated to 120°C until it stopped absorbing hydrogen and kept warm for 2 hours.

9. The method for using a silver catalyst according to claim 8, characterized in that: The method for exhausting the air behind the hydrogen kettle is to first introduce nitrogen into the hydrogenation kettle for replacement three times, and then introduce hydrogen into the hydrogenation kettle for replacement twice.

10. The method for using a silver catalyst according to claim 8, characterized in that: The nitro compound is one of nitrobenzene, 4-nitrochlorobenzene, 4-fluoronitrobenzene, 4-nitroiodobenzene, 4-nitrophenyl isonitrile, nitrocyclopentane or nitropropane.

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