A vacant site-rich molybdenum disulfide catalyst, its preparation method and use

Abstract

The application discloses a kind of rich vacancy molybdenum disulfide catalyst and preparation method and purposes, and preparation method is as follows:1) according to the proportion of 1-5mg / mL, molybdenum disulfide powder is mixed with deionized water, and molybdenum disulfide water dispersion is obtained;2) molybdenum disulfide water dispersion obtained in step 1) is loaded into the hydrothermal kettle with polytetrafluoroethylene lining, and sealed;Hydrothermal reaction is carried out at 140-190 DEG C for 4-20h;Drop to room temperature, centrifugal, dry, and obtain rich vacancy molybdenum disulfide catalyst.The method of the application is simple, efficient, green and pollution-free, and easy to scale up.The rich vacancy molybdenum disulfide catalyst prepared by the application has rich active sites, and the catalytic activity in the field of substituted nitrobenzene hydrogenation can be significantly improved due to the increase of active site sulfur vacancy, which is used for the hydrogenation catalysis of p-chloronitrobenzene, and the conversion rate of p-chloronitrobenzene is 100%, and the selectivity of p-chloroaniline is 100%.The performance of the catalyst exceeds that of raw material molybdenum disulfide.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthesis of molybdenum disulfide-based catalysts, and particularly relates to a vacancy-rich molybdenum disulfide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Molybdenum disulfide is a kind of widely used catalytic hydrogenation catalyst. The active site of molybdenum disulfide is usually determined as an edge coordination unsaturated site, that is, a sulfur vacancy, and the basal plane is usually inert. Therefore, in order to increase the active site of the molybdenum disulfide catalyst and improve its reaction activity, more vacancies need to be introduced.

[0003] p-Chloroaniline is a key raw material and intermediate of dyes, medicines, pesticides and other fine chemical products, and the selective hydrogenation of p-chloronitrobenzene by catalysis is an effective way to synthesize p-chloroaniline.

[0004] Chinese patent CN 109455675 B discloses a synthesis method for oxidizing molybdenum disulfide with a weak oxidizing aqueous solution to increase sulfur vacancies; Chinese patent CN 108671942 B discloses a synthesis method for treating molybdenum disulfide with high-temperature water vapor at 200-1000℃ to increase sulfur vacancies. The former involves strong corrosive chemicals such as oxidizing agents, and the latter involves harsh conditions of high temperature, small processing capacity and insufficient gas-solid phase reaction. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a vacancy-rich molybdenum disulfide catalyst.

[0006] The second purpose of the present application is to provide a preparation method of the vacancy-rich molybdenum disulfide catalyst.

[0007] The third purpose of the present application is to provide a use of the vacancy-rich molybdenum disulfide catalyst for catalyzing p-chloronitrobenzene to p-chloroaniline.

[0008] The technical solution of the present application is summarized as follows:

[0009] A preparation method of a vacancy-rich molybdenum disulfide catalyst, comprising the following steps:

[0010] 1) Molybdenum disulfide powder is mixed with deionized water at a ratio of 1-5 mg / mL to obtain a molybdenum disulfide water dispersion;

[0011] 2) The molybdenum disulfide water dispersion obtained in step 1) is loaded into a hydrothermal kettle with a polytetrafluoroethylene liner and sealed; hydrothermal reaction is carried out at 140-190℃ for 4-20h; cooled to room temperature, centrifuged, dried to obtain a vacancy-rich molybdenum disulfide catalyst.

[0012] Preferably, the molybdenum disulfide powder is a natural molybdenum disulfide powder, a hydrothermal synthesis molybdenum disulfide powder or a solvothermal synthesis molybdenum disulfide powder.

[0013] Preferably, the ratio of the molybdenum disulfide powder to deionized water in step 1) is 3 mg / mL.

[0014] Preferably, the temperature in step 2) is 180℃ and the hydrothermal reaction is 8 h.

[0015] A kind of vacancy-rich molybdenum disulfide catalyst prepared by the above preparation method.

[0016] The use of the above-mentioned vacancy-rich molybdenum disulfide catalyst for catalyzing p-chloronitrobenzene to p-chloroaniline.

[0017] The beneficial effects of the present application are:

[0018] The method of the present application is simple, efficient, green and pollution-free, and easy to scale up. The vacancy-rich molybdenum disulfide catalyst prepared by the present application has abundant active sites. Due to the increase of sulfur vacancies in the active sites, the catalytic activity in the field of hydrogenation of substituted nitrobenzene can be significantly improved. The conversion rate of p-chloronitrobenzene is 100% and the selectivity of p-chloroaniline is 100% when the catalyst is used for the hydrogenation of p-chloronitrobenzene. The performance exceeds that of the raw material molybdenum disulfide catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is an electron paramagnetic resonance spectrum of a vacancy-rich molybdenum disulfide catalyst prepared in Example 1 and a raw material molybdenum disulfide powder.

[0020] Figure 2 FIG. 2 is a scanning electron microscope image of a raw material molybdenum disulfide powder.

[0021] Figure 3 FIG. 3 is a scanning electron microscope image of a vacancy-rich molybdenum disulfide catalyst prepared in Example 1. DETAILED DESCRIPTION

[0022] The present application will be further described below through specific examples.

[0023] Example 1

[0024] A method for preparing a vacancy-rich molybdenum disulfide catalyst, comprising the following steps:

[0025] 1) Mix a hydrothermal synthesis molybdenum disulfide powder with deionized water at a ratio of 3 mg / mL, and stir to obtain a molybdenum disulfide water dispersion;

[0026] 2) 30 mL of the aqueous dispersion of molybdenum disulfide obtained in step 1) was loaded into a 50 mL hydrothermal kettle with a polytetrafluoroethylene liner, sealed; and placed in an oven for hydrothermal reaction at 180°C for 8 h; cooled to room temperature, centrifuged, dried, to obtain a vacancy-rich molybdenum disulfide catalyst. See Figure 1 、 Figure 2 and Figure 3 .

[0027] As can be seen from Figure 1 , the vacancy-rich molybdenum disulfide catalyst has a stronger sulfur vacancy signal than the raw material hydrothermally synthesized molybdenum disulfide powder.

[0028] As can be seen from Figure 2 and Figure 3 , the reaction of the present application does not change the morphology of molybdenum disulfide.

[0029] Example 2

[0030] A method for preparing a vacancy-rich molybdenum disulfide catalyst, comprising the following steps:

[0031] 1) A hydrothermally synthesized molybdenum disulfide powder was mixed with deionized water at a ratio of 1 mg / mL, and stirred to obtain an aqueous dispersion of molybdenum disulfide;

[0032] 2) 30 mL of the aqueous dispersion of molybdenum disulfide obtained in step 1) was loaded into a 50 mL hydrothermal kettle with a polytetrafluoroethylene liner, sealed; and placed in an oven for hydrothermal reaction at 140°C for 20 h; cooled to room temperature, centrifuged, dried, to obtain a vacancy-rich molybdenum disulfide catalyst.

[0033] Example 3

[0034] A method for preparing a vacancy-rich molybdenum disulfide catalyst, comprising the following steps:

[0035] 1) A natural molybdenum disulfide powder was mixed with deionized water at a ratio of 5 mg / mL, and ultrasonicated to obtain an aqueous dispersion of molybdenum disulfide;

[0036] 2) 30 mL of the aqueous dispersion of molybdenum disulfide obtained in step 1) was loaded into a 50 mL hydrothermal kettle with a polytetrafluoroethylene liner, sealed; and placed in an oven for high-temperature hydrothermal reaction at 190°C for 4 h; cooled to room temperature, centrifuged, dried, to obtain a vacancy-rich molybdenum disulfide catalyst.

[0037] Experiments show that the electron paramagnetic resonance spectrum of a vacancy-rich molybdenum disulfide catalyst prepared by example 2 and example 3 is similar to the electron paramagnetic resonance spectrum of a vacancy-rich molybdenum disulfide catalyst prepared by example 1.

[0038] The scanning electron micrographs of the vacancy-rich molybdenum disulfide catalysts prepared in Examples 2 and 3 are similar to the scanning electron micrograph of the vacancy-rich molybdenum disulfide catalyst prepared in Example 1.

[0039] Example 4

[0040] The vacancy-rich molybdenum disulfide catalyst is used to catalyze the conversion of p-chloronitrobenzene to p-chloroaniline, and the steps are as follows:

[0041] The vacancy-rich molybdenum disulfide catalyst prepared in Example 1 and p-chloronitrobenzene were added to 30 mL of isopropanol at a mass ratio of 1:4.2, and ultrasonicated for 15 minutes. The hydrogenation reaction was carried out in a batch reactor at a hydrogen pressure of 1.6 MPa, 150° C., and a stirring speed of 500 rpm for 1 hour.

[0042] After the reaction was completed, the liquid product was analyzed by gas chromatography, and the conversion rate of p-chloronitrobenzene was 100%, and the selectivity of p-chloroaniline was 100%.

[0043] The vacancy-rich molybdenum disulfide catalyst prepared in Example 2 and Example 3 were used to replace the vacancy-rich molybdenum disulfide catalyst (prepared in Example 1) in Example 4, respectively. Other aspects were the same as in Example 4. After the reaction, the liquid product was analyzed by gas chromatography. The conversion rates of p-chloronitrobenzene were 90% and 75%, respectively, and the selectivities of p-chloroaniline were 100% and 100%, respectively.

[0044] Comparative Example

[0045] The vacancy-rich molybdenum disulfide catalyst in Example 4 was replaced by molybdenum disulfide powder synthesized by the hydrothermal method. Other reactions were the same as in Example 4. After the reaction, the liquid product was analyzed by gas chromatography. The conversion of p-chloronitrobenzene was 24%, and the selectivity of p-chloroaniline was 100%.

[0046] It can be seen from Example 4 and the comparative example that the vacancy-rich molybdenum disulfide catalyst of the present invention has better catalytic performance for the hydrogenation of p-chloronitrobenzene than the raw material molybdenum disulfide powder.

Claims

1. A method for preparing a vacancy-rich molybdenum disulfide catalyst, characterized in that The steps include: 1) mixing molybdenum disulfide powder with deionized water at a ratio of 1 to 5 mg / mL to obtain a molybdenum disulfide aqueous dispersion; 2) placing the molybdenum disulfide aqueous dispersion obtained in step 1) into a hydrothermal kettle lined with polytetrafluoroethylene and sealing the kettle; The hydrothermal reaction is carried out at 140-190° C. for 4-20 hours; the reaction is cooled to room temperature, centrifuged, and dried to obtain a vacancy-rich molybdenum disulfide catalyst.

2. The preparation method according to claim 1, wherein The molybdenum disulfide powder is natural molybdenum disulfide powder, molybdenum disulfide powder synthesized by a hydrothermal method or molybdenum disulfide powder synthesized by a solvent thermal method.

3. The preparation method according to claim 1 or 2, wherein the step 1) The ratio of molybdenum disulfide powder to deionized water is 3 mg / mL.

4. The preparation method according to claim 1, characterized in that In step 2), the temperature is 180° C. and the hydrothermal reaction is carried out for 8 hours.

Images