Selective hydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention provides a selective hydrogenation catalyst as well as a preparation method and application thereof, and belongs to the technical field of hydrogenation catalysts. The selective hydrogenation catalyst comprises a nitrogen-doped modified activated carbon carrier, a metal A and a metal B, the metal A is Pt, and the metal B is one or more of transition metals Fe, Co, Ni, Cu and Zn. The selective hydrogenation catalyst provided by the invention takes nitrogen-doped modified activated carbon as a carrier, and metal A and metal B are efficiently and synergistically catalyzed on the nitrogen-doped modified carrier containing abundant anchoring sites. The selective hydrogenation catalyst is simple in preparation method and high in yield; when the catalyst is used for catalyzing a reaction for synthesizing parachloroaniline through selective hydrogenation of parachloronitrobenzene, the production cycle is short, the conditions are mild, the strong interaction of metal-carrier (SMSI) generated by induction of the nitrogen-doped modified carrier is beneficial to dispersion and anchoring of active metal, the activity and stability of the catalyst are improved, and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogenation catalysts, and in particular to a selective hydrogenation catalyst and a preparation method and application thereof. Background Art

[0002] p-Chloroaniline is an important fine chemical product and organic intermediate, widely used in the synthesis of fine chemicals such as medicines, dyes, pesticides, etc. p-Chloroaniline is usually prepared by reducing p-chloronitrobenzene, and the reduction methods mainly include chemical reduction, electrochemical reduction, catalytic hydrogenation reduction, etc. Since the catalytic hydrogenation reduction method can solve the high pollution problem of the chemical reduction method and the high energy consumption problem of the electrolytic reduction method, and has the advantages of less three wastes, high product yield, good product quality, simple operation process and low energy consumption, the catalytic hydrogenation reduction method has attracted more and more attention.

[0003] The selective catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline is a complex reaction process. During the catalytic hydrogenation process, dechlorination byproducts such as aniline and azo compounds are easily generated, which makes it difficult to separate and purify the products. Among them, the hydrodechlorination reaction is the most serious side reaction. At present, the methods for inhibiting the dechlorination reaction can be roughly divided into two categories: one is to add dechlorination inhibitors to the reaction. This method not only inhibits the dechlorination side reaction but also greatly reduces the activity of the catalyst and increases the difficulty of product purification; the other is to optimize the properties of the catalyst, such as forming alloys with precious metals, changing the particle size of the catalyst or selecting an appropriate carrier to improve the reaction selectivity.

[0004] In the process of liquid-phase catalytic hydrogenation of nitrochlorobenzene, conversion rate and selectivity are equally important factors, which are related to the quality of the production process. An ideal hydrogenation catalyst should not only ensure that the conversion rate of the reactants after the reaction is completed is high, but also suppress the occurrence of side reactions such as dechlorination on the benzene ring, and maintain high selectivity of the target product. The patent with the publication number of "CN106732568A" and the invention name of "a preparation method and application of a catalyst for selective hydrogenation of p-chloronitrobenzene to p-chloroaniline" discloses a catalyst, which uses TiO2 as a carrier, loads metal A on the carrier TiO2 by photodeposition method, and then loads metal B (B is Rh, Pt, Au or Pd) in the same way to obtain catalyst AB / TiO2. Although the catalyst is used in the reaction of p-chloronitrobenzene hydrogenation to p-chloroaniline, the conversion rate of p-chloronitrobenzene reaches 100%, and the selectivity of p-chloroaniline reaches more than 99%, but due to the narrow absorption range of ultraviolet light, the low utilization rate of light energy and the problem of transmittance cause the catalyst yield prepared by the method to be low. Summary of the invention

[0005] The object of the present invention is to provide a selective hydrogenation catalyst and a preparation method and application thereof. The catalyst not only has a higher yield, but also can improve the conversion rate of p-chloronitrobenzene and the selectivity of p-chloroaniline.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a selective hydrogenation catalyst, comprising a nitrogen-doped modified activated carbon carrier, a metal A and a metal B; the metal A is Pt, and the metal B is one or more of Fe, Co, Ni, Cu and Zn.

[0008] Preferably, the ratio of carbon to nitrogen atoms in the nitrogen-doped modified activated carbon carrier is 1:0.1 to 1:0.4.

[0009] Preferably, the mass fraction of the metal A in the catalyst is 0.1% to 0.5%, and the molar ratio of the metal A to the metal B is 1:0.5 to 1:3.

[0010] Preferably, the specific surface area of ​​the nitrogen-doped modified activated carbon carrier is 816 to 968 m 2 / g, pore volume is 1.5~1.7cm 3 / g, pore size is 0.45~0.7nm.

[0011] The present invention also provides a method for preparing the selective hydrogenation catalyst, comprising the following steps:

[0012] S1. pyrolyzing and carbonizing a carbon source under a nitrogen atmosphere to obtain an activated carbon precursor;

[0013] S2. calcining the activated carbon precursor with a nitrogen source and an activator under a nitrogen atmosphere to obtain nitrogen-doped modified activated carbon; the nitrogen source is one or more of urea, melamine, ammonium nitrate, and dicyandiamide, and the activator is one or more of KOH, K2CO3, and ZnCl2;

[0014] S3. mixing the nitrogen-doped modified activated carbon with a water-soluble compound of metal A, a water-soluble compound of metal B and water to obtain a selective hydrogenation catalyst precursor;

[0015] S4. Performing a reduction reaction on the catalyst precursor under a hydrogen atmosphere to obtain the selective hydrogenation catalyst.

[0016] Preferably, the pyrolysis carbonization temperature is 400-700° C., the pyrolysis carbonization heating rate is 2-5° C. / min; and the pyrolysis carbonization time is 2-4 h.

[0017] Preferably, the mass ratio of the activated carbon precursor to the activator is 1:0.5 to 1:2; the calcination temperature is 500 to 900°C; the calcination heating rate is 2 to 5°C / min; and the calcination time is 2 to 4 hours.

[0018] Preferably, the temperature of the reduction reaction is 250° C. to 500° C., and the time of the reduction reaction is 2 to 6 hours.

[0019] The present invention also provides application of the selective hydrogenation catalyst in catalyzing the reaction of synthesizing p-chloroaniline by selective hydrogenation of p-chloronitrobenzene.

[0020] Preferably, the reaction temperature is 40-90° C., the reaction pressure is 0.5-2 MPa, the reaction time is 60-180 min, and the molar ratio of the selective hydrogenation catalyst to p-chloronitrobenzene is 1:1500-4000.

[0021] By adopting the above technical scheme, the present invention has the following beneficial effects: the selective hydrogenation catalyst of the present invention comprises a nitrogen-doped modified activated carbon carrier, a metal A and a metal B, wherein the metal A is Pt, and the metal B is one or more of transition metals Fe, Co, Ni, Cu, and Zn. The selective hydrogenation catalyst of the present invention uses nitrogen-doped modified activated carbon as a carrier, and metal A and metal B efficiently synergistically catalyze on the nitrogen-doped modified carrier containing abundant anchoring sites. The preparation method of the selective hydrogenation catalyst of the present invention is simple and has a high yield; when catalyzing the selective hydrogenation of p-chloronitrobenzene to synthesize p-chloroaniline, the production cycle is short and the conditions are mild, and the strong metal-carrier interaction (SMSI) induced by the nitrogen-doped modified carrier is helpful for the dispersion and anchoring of the active metal, thereby improving the activity and stability of the catalyst and extending the service life of the catalyst. Since the catalyst is prepared using only a simple impregnation method, the yield is 100% without loss, and the preparation process is simple and controllable, and the preparation process / results have high repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the HAADF-STEM-EDS mapping diagram of N, Pt and Cu elements in Example 1.

[0023] Figure 2 This is the HAADF-STEM-EDS mapping diagram of N, Pt and Zn elements in Example 2. DETAILED DESCRIPTION

[0024] The present invention provides a selective hydrogenation catalyst, comprising a nitrogen-doped modified activated carbon carrier, a metal A and a metal B; the metal A is Pt, and the metal B is one or more of Fe, Co, Ni, Cu and Zn. The ratio of carbon to nitrogen atoms in the nitrogen-doped modified activated carbon carrier is 1:0.1 to 1:0.4, more preferably 1:0.15 to 1:0.3, and more preferably 1:0.2; the mass fraction of the metal A in the catalyst is 0.1% to 0.5%, more preferably 0.2% to 0.4%, and more preferably 0.3%; the molar ratio of the metal A to the metal B is 1:0.5 to 1:3, more preferably 1:1 to 1:2, and more preferably 1:1.5. The specific surface area of ​​the nitrogen-doped modified activated carbon carrier is 816 to 968 m 2 / g, more preferably 850 to 950 m 2 / g, more preferably 900m 2 / g; pore volume is 1.5~1.7cm 3 / g, more preferably 1.55 to 1.65 cm 3 / g, more preferably 1.60cm 3 / g; the pore diameter is 0.45 to 0.7 nm, more preferably 0.5 to 0.6 nm, and more preferably 0.55 nm.

[0025] The present invention also provides a method for preparing the selective hydrogenation catalyst, comprising the following steps:

[0026] S1. pyrolyzing and carbonizing a carbon source under a nitrogen atmosphere to obtain an activated carbon precursor;

[0027] S2. calcining the activated carbon precursor with a nitrogen source and an activator under a nitrogen atmosphere to obtain nitrogen-doped modified activated carbon; the nitrogen source is one or more of urea, melamine, ammonium nitrate, and dicyandiamide, and the activator is one or more of KOH, K2CO3, and ZnCl2;

[0028] S3. mixing the nitrogen-doped modified activated carbon with a water-soluble compound of metal A, a water-soluble compound of metal B and water to obtain a selective hydrogenation catalyst precursor;

[0029] S4. Performing a reduction reaction on the catalyst precursor under a hydrogen atmosphere to obtain the selective hydrogenation catalyst.

[0030] In the present invention, firstly, a carbon source is pyrolyzed and carbonized under a nitrogen atmosphere to obtain an activated carbon precursor, wherein the carbon source is one or more of corn stalks, wood chips, bamboo, and coconut shells, and the temperature of the pyrolysis and carbonization is 400-700°C, more preferably 500-600°C, and more preferably 550°C; the pyrolysis and carbonization heating rate is 2-5°C / min, more preferably 3-4°C / min, and more preferably 3.5°C / min; the pyrolysis and carbonization time is 2-4h, more preferably 2.5-3.5h, and more preferably 3h.

[0031] The present invention bakes the activated carbon precursor, a nitrogen source and an activator under a nitrogen atmosphere to obtain nitrogen-doped modified activated carbon; preferably, the nitrogen source is first transferred to the activated carbon precursor, that is, the activated carbon precursor and the nitrogen source are first physically mixed (impregnated) and then baked with the activator; the impregnation is preferably an equal volume impregnation, and the water absorption rate of the activated carbon precursor needs to be measured before the impregnation, and the equal volume impregnation is performed according to the water absorption rate. The nitrogen source is one or more of urea, melamine, ammonium nitrate, and dicyandiamide; the activator is one or more of KOH, K2CO3, and ZnCl2; the mass ratio of the activated carbon precursor to the activator is 1:0.5 to 1:2, more preferably 1:1 to 1:1.5, and more preferably 1:1.3; the calcination temperature is 500 to 900°C, more preferably 600 to 800°C, and more preferably 700°C; the calcination heating rate is 2 to 5°C / min, more preferably 3 to 4°C / min, and more preferably 3.5°C / min, and nitrogen-doped modified activated carbon is obtained after the calcination is completed.

[0032] The present invention configures a water-soluble compound of metal A and a water-soluble compound of metal B into solutions respectively, mixes the two solutions with deionized water and performs equal volume impregnation on nitrogen-doped modified activated carbon; the equal volume impregnation refers to slowly and evenly dropping the impregnation solution onto the surface of the carrier, the water-soluble compound of metal A includes one or more of chloroplatinic acid and potassium chloroplatinate, and the concentration of the water-soluble compound of metal A in the solution is 0.038-0.040 mol / L, more preferably 0.039 mol / L; the water-soluble compound of metal B includes one or more of cobalt acetate, cobalt nitrate, nickel acetate, nickel nitrate, copper nitrate, copper chloride, zinc nitrate and zinc chloride, and the concentration of the water-soluble compound of metal B in the solution is 0.038-0.040 mol / L, more preferably 0.039 mol / L; the time of the equal volume impregnation is 0.1h, and a selective hydrogenation catalyst precursor is obtained.

[0033] The present invention allows the selective hydrogenation catalyst precursor to stand, then vacuum dry, and then perform a reduction reaction under a hydrogen atmosphere to obtain a selective hydrogenation catalyst. The standing time is 6 to 12 hours, more preferably 8 to 10 hours, and more preferably 9 hours; the vacuum drying temperature is 60 to 90°C, more preferably 70 to 80°C, and more preferably 75°C; the vacuum drying time is 3 to 6 hours, more preferably 4 to 5 hours, and more preferably 4.5 hours; the reduction reaction temperature is 250°C to 500°C, more preferably 300 to 400°C, and more preferably 350°C; the reduction reaction time is 2 to 6 hours, more preferably 3 to 5 hours, and more preferably 4 hours.

[0034] The present invention also provides the use of the selective hydrogenation catalyst in the catalytic reaction of selective hydrogenation of p-chloronitrobenzene to synthesize p-chloroaniline. In the catalytic reaction, the reaction temperature is 40-90°C, more preferably 50-80°C, more preferably 60°C; the reaction pressure is 0.5-2MPa, more preferably 1-1.5MPa, more preferably 1.2MPa; the reaction time is 60-180min, more preferably 100-150min, more preferably 120min; the molar ratio of the selective hydrogenation catalyst to p-chloronitrobenzene is 1:1500-4000, more preferably 1:2000-3000, more preferably 1:2500.

[0035] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0036] Example 1

[0037] Preparation of activated carbon precursor: 6 g of dried coconut shell was placed in a tube furnace, and then heated to 400 °C at a pyrolysis carbonization heating rate of 2 °C / min under a nitrogen atmosphere of 40 mL / min and calcined for 3 h to obtain an activated carbon precursor;

[0038] Preparation of nitrogen-doped activated carbon (NC): First, the water absorption rate of the activated carbon precursor was determined to be 100%; 1g of urea was impregnated into 2g of the dried activated carbon precursor in equal volume, and dried at 80°C under vacuum for 4h to obtain a nitrogen-doped activated carbon carrier precursor. 1g of ZnCl2 activator and nitrogen-doped activated carbon carrier precursor were calcined in a nitrogen atmosphere for 4h at a calcination temperature of 700°C and a calcination heating rate of 2°C / min to obtain a nitrogen-doped activated carbon carrier.

[0039] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid and 0.0074 g of solid copper nitrate respectively, prepare the weighed chloroplatinic acid solid and copper nitrate solid into equal volume impregnation solution with deionized water and evenly impregnate them into nitrogen-doped activated carbon support. The equal volume impregnation time is 0.1 h. Let it stand for 8 h, vacuum dry at 80 ° C for 4 h, and then place it in a tubular furnace for reduction at 400 ° C for 4 h under a hydrogen atmosphere to obtain a selective hydrogenation catalyst. The yield of the selective hydrogenation catalyst is 100%.

[0040] Example 2

[0041] The preparation method of the nitrogen-doped activated carbon carrier in Example 2 is consistent with that in Example 1.

[0042] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid and 0.0091 g of solid zinc nitrate respectively, prepare equal volumes of impregnation solution with deionized water and evenly impregnate the nitrogen-doped activated carbon support, let stand for 8 hours, vacuum dry at 80°C for 4 hours, and then place in a tubular furnace for reduction at 400°C for 4 hours in a hydrogen atmosphere to obtain a selective hydrogenation catalyst. The yield of the selective hydrogenation catalyst is 100%.

[0043] Example 3

[0044] The preparation method of the nitrogen-doped activated carbon carrier in Example 3 is consistent with that in Example 1.

[0045] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid and 0.0089 g of solid nickel nitrate respectively, prepare the weighed chloroplatinic acid solid and nickel nitrate solid into equal volumes of impregnation solution with deionized water and evenly impregnate them into nitrogen-doped activated carbon support C, let it stand for 8 hours, vacuum dry at 80°C for 4 hours, and then place it in a tubular furnace and reduce it at 400°C for 4 hours under a hydrogen atmosphere to obtain a selective hydrogenation catalyst. The yield of the selective hydrogenation catalyst is 100%.

[0046] Comparative Example 1

[0047] The preparation method of the nitrogen-doped activated carbon carrier in Comparative Example 1 is consistent with that in Example 1.

[0048] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid, prepare an equal volume of impregnation solution with deionized water and evenly impregnate it into the nitrogen-doped activated carbon support, let it stand for 8 hours, vacuum dry it at 80°C for 4 hours, and then place it in a tubular furnace and reduce it at 400°C for 4 hours under a hydrogen atmosphere to obtain a selective hydrogenation catalyst.

[0049] Note: Different from Example 1, copper nitrate was not added when preparing the catalyst.

[0050] Comparative Example 2

[0051] Preparation of activated carbon precursor: 6 g of dried coconut shell was placed in a tube furnace, and then heated to 400 °C at a pyrolysis carbonization heating rate of 2 °C / min under a nitrogen atmosphere of 40 mL / min and calcined for 3 h to obtain activated carbon precursor A;

[0052] Preparation of activated carbon (C): First, the water absorption rate of activated carbon precursor A was determined to be 100%. 1 g of ZnCl2 activator and activated carbon precursor A were calcined in a nitrogen atmosphere for 4 h at a calcination temperature of 700°C and a calcination heating rate of 2°C / min to obtain an activated carbon carrier.

[0053] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid and 0.0074 g of solid copper nitrate respectively, prepare equal volumes of impregnation solution with deionized water and evenly impregnate the activated carbon carrier, let it stand for 8 hours, vacuum dry at 80°C for 4 hours, and then place it in a tubular furnace for reduction at 400°C for 4 hours in a hydrogen atmosphere to obtain a selective hydrogenation catalyst.

[0054] Note: The difference between Comparative Example 2 and Example 1 is that activated carbon (C) is used instead of nitrogen-doped activated carbon (NC).

[0055] Comparative Example 3

[0056] Preparation of activated carbon precursor: 6 g of dried coconut shell was placed in a tube furnace, and then heated to 400 °C at a pyrolysis carbonization heating rate of 2 °C / min under a nitrogen atmosphere of 40 mL / min and calcined for 3 h to obtain an activated carbon precursor;

[0057] Preparation of activated carbon (C): First, the water absorption rate of activated carbon precursor A was determined to be 100%. 1 g of ZnCl2 activator and activated carbon precursor A were calcined in a nitrogen atmosphere for 4 h at a calcination temperature of 700°C and a calcination heating rate of 2°C / min to obtain an activated carbon carrier.

[0058] Preparation of catalyst: Weigh 0.0159 g of solid chloroplatinic acid, prepare an equal volume of impregnation solution with deionized water and evenly impregnate it into the activated carbon carrier, let it stand for 8 hours, vacuum dry at 80°C for 4 hours, and then place it in a tubular furnace and reduce it at 400°C for 4 hours in a hydrogen atmosphere to obtain a selective hydrogenation catalyst.

[0059] Note: Comparative Example 3 is different from Example 1 in that activated carbon (C) is used instead of nitrogen-doped activated carbon (NC), and nickel nitrate is not added when preparing the catalyst.

[0060] Experimental Example 1 Evaluation of the properties of selective hydrogenation catalysts

[0061] 1. Evaluation of the pore structure properties of selective hydrogenation catalysts

[0062] The selective hydrogenation catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to N2 physical adsorption test using a physical adsorption instrument (Micromeritics ASAP2020 model), and the specific surface area, pore size and pore volume of the selective hydrogenation catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were recorded. The results are shown in Table 1. The selective hydrogenation catalysts prepared in Examples 1 and 2 were subjected to EDS spectrum analysis using a scanning transmission electron microscope. The results are shown in Table 1. Figure 1 , Figure 2 shown.

[0063] Table 1 Pore structure properties of different groups of selective hydrogenation catalysts

[0064]

[0065]

[0066] Comparing the catalysts before and after nitrogen doping modification in Table 1, it is found that the specific surface area of ​​the nitrogen doped modified catalyst is reduced, indicating the effective doping of nitrogen. The selective hydrogenation catalysts prepared by the post-treatment method of the present invention all have high specific surface area and rich microporous structure, which is conducive to the dispersion of active components and the diffusion of reactant molecules.

[0067] 2. Evaluation results of catalytic reaction activity of selective hydrogenation catalyst

[0068] The hydrogenation activity of the selective hydrogenation catalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was evaluated. The activity evaluation experiment of the catalyst was carried out in a 100mL high-pressure hydrogenation reaction device. 0.5g of the selective hydrogenation catalyst prepared in Examples 1 to 3 and Comparative Examples 1 to 3, 3.322g of p-chloronitrobenzene (>99.5%) and 30mL of ethanol were added to a 100mL high-pressure reactor. The reaction was carried out at a pressure of 2MPa, a temperature of 60°C, and a stirring rod speed of 500r / min. The hydrogenation product was qualitatively and quantitatively analyzed using Agilent GC-MS-5977C, and the results are shown in Table 2.

[0069] Table 2 Evaluation results of the reaction activity of different groups of selective hydrogenation catalysts

[0070]

[0071] As can be seen from Table 2, the selective hydrogenation catalyst prepared by the present invention has very high conversion rate and selectivity in the reaction of hydrogenating p-chloronitrobenzene to p-chloroaniline, the p-chloronitrobenzene conversion rate reaches 100%, and the p-chloroaniline selectivity is above 99%. However, the p-chloronitrobenzene conversion rate and p-chloroaniline selectivity of the catalyst using activated carbon (C) instead of nitrogen-doped activated carbon (NC) as the carrier, or without transition metal anchored on the carrier are relatively low.

[0072] 3. Cyclic stability test and evaluation of selective hydrogenation catalysts

[0073] The cyclic stability test experiment of the catalyst is the key to evaluate the performance of the catalyst. The specific operation is: after each reaction is completed, the catalyst is separated from the reaction system, washed with ethanol and deionized water, and then dried under vacuum conditions at 80°C for the next cycle reaction. The reaction conditions are pressure 2MPa, temperature 60°C, stirring rod speed 500r / min, and the hydrogenation product is qualitatively and quantitatively analyzed using Agilent GC-MS-5977C. The results are shown in Table 3.

[0074] Table 3 Evaluation results of cyclic stability test of selective hydrogenation catalyst prepared in Example 1

[0075]

[0076] It can be seen from Table 3 that the selective hydrogenation catalyst prepared by the present invention has the characteristics of good stability and long service life. After 6 cycles of experiments, the catalyst still maintains high catalytic activity and high selectivity.

[0077] As can be seen from the above embodiments, the present invention provides a selective hydrogenation catalyst and a preparation method and application thereof. The selective hydrogenation catalyst of the present invention uses nitrogen-doped modified activated carbon as a carrier, and metal A and metal B efficiently synergistically catalyze on the nitrogen-doped modified carrier containing abundant anchoring sites. The preparation method of the selective hydrogenation catalyst of the present invention is simple and has a high yield.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A selective hydrogenation catalyst, characterized in that The invention comprises a nitrogen-doped modified activated carbon carrier, a metal A and a metal B; the metal A is Pt, and the metal B is one or more of Fe, Co, Ni, Cu and Zn.

2. The selective hydrogenation catalyst according to claim 1, characterized in that The ratio of carbon to nitrogen atoms in the nitrogen-doped modified activated carbon carrier is 1:0.1 to 1:0.

4.

3. The selective hydrogenation catalyst according to claim 2, characterized in that The mass fraction of the metal A in the catalyst is 0.1% to 0.5%, and the molar ratio of the metal A to the metal B is 1:0.5 to 1:

3.

4. The selective hydrogenation catalyst according to claim 3, characterized in that The specific surface area of ​​the nitrogen-doped modified activated carbon carrier is 816 to 968 m 2 / g, pore volume is 1.5~1.7cm 3 / g, pore size is 0.45~0.7nm.

5. The method for preparing the selective hydrogenation catalyst according to any one of claims 1 to 4, characterized in that: The steps include: S1. pyrolyzing and carbonizing a carbon source under a nitrogen atmosphere to obtain an activated carbon precursor; S2. calcining the activated carbon precursor with a nitrogen source and an activator under a nitrogen atmosphere to obtain nitrogen-doped modified activated carbon; The nitrogen source is one or more of urea, melamine, ammonium nitrate and dicyandiamide, and the activator is one or more of KOH, K2CO3 and ZnCl2; S3. mixing the nitrogen-doped modified activated carbon with a water-soluble compound of metal A, a water-soluble compound of metal B and water to obtain a selective hydrogenation catalyst precursor; S4. Performing a reduction reaction on the catalyst precursor under a hydrogen atmosphere to obtain the selective hydrogenation catalyst.

6. The preparation method according to claim 5, characterized in that: The pyrolysis carbonization temperature is 400-700° C., the pyrolysis carbonization heating rate is 2-5° C. / min; and the pyrolysis carbonization time is 2-4h.

7. The preparation method according to claim 6, characterized in that: The mass ratio of the activated carbon precursor to the activator is 1:0.5 to 1:2; the calcination temperature is 500 to 900°C; the calcination heating rate is 2 to 5°C / min; and the calcination time is 2 to 4 hours.

8. The preparation method according to claim 7, characterized in that: The temperature of the reduction reaction is 250° C. to 500° C., and the time of the reduction reaction is 2 to 6 hours.

9. Use of the selective hydrogenation catalyst according to any one of claims 1 to 4 in catalyzing the selective hydrogenation of p-chloronitrobenzene to synthesize p-chloroaniline.

10. The use according to claim 9, characterized in that: The reaction temperature is 40-90° C., the reaction pressure is 0.5-2 MPa, the reaction time is 60-180 min, and the molar ratio of the selective hydrogenation catalyst to p-chloronitrobenzene is 1:1500-4000.

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