A catalyst for preparing aniline and dibenzylamine by hydrogenation of benzonitrile and a preparation method thereof

Abstract

The application provides a catalyst for preparing aniline and dibenzylamine by hydrogenation of benzonitrile and a preparation method of the catalyst, and the catalyst is a bimetallic transition metal phosphide catalyst with a chemical formula of Ni7M1P4, wherein M is Mo, Cu, Co, W or Fe. The bimetallic transition metal phosphide catalyst of the application can significantly reduce the reaction pressure and energy consumption of the preparation of aniline and dibenzylamine by hydrogenation of benzonitrile, has the advantages of high stability, high catalytic activity and high selectivity, and the selectivity of aniline and dibenzylamine in the product reaches 51.89% and 11.06% respectively. Meanwhile, the bimetallic transition metal phosphide catalyst of the application is a bulk catalyst, can replace a supported catalyst, and solves the problem of difficult separation and recovery of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the hydrogenation of benzonitrile (BN) to prepare aniline (BA) and dibenzylamine (DBA) and its preparation method. Background Technology

[0002] Among nitrogen-containing compounds, amines are an important class of substances widely found in various bioactive molecules, and also serve as crucial intermediates in the industrial synthesis of polymers, dyes, pharmaceuticals, agrochemicals, and fine chemicals. Compared to other functional compounds, the synthesis of amines has received considerable attention in organic chemistry.

[0003] In traditional nitrile hydrogenation processes, abundant metal catalysts, such as nickel-based and cobalt-based metal sponges, are mainly used. However, these metal catalysts suffer from fatal air instability (spontaneous combustion), making them difficult to handle and complicating chemical processes. Furthermore, these catalysts exhibit low activity, require harsh reaction conditions (such as high-pressure hydrogen), have limited substrate applicability, and are prone to deactivation during storage. Transition metal phosphides (TMPs) possess unique metal-like properties and air stability. Their structure consists of highly dispersed metal nanoclusters chemically embedded in a phosphorus lattice, forming a class of solid materials with ideal atomic and crystal structures. Although metal phosphides have shown great potential in electrocatalysis and photocatalysis of hydrogen evolution reactions and in petroleum hydrotreating in recent years, their catalytic applications in organic synthesis remain largely unexplored. Therefore, metal phosphides, significantly different from traditional modified metal nanoparticles, metal sponges, and metal complex catalysts, can be classified as a novel class of nitrile hydrogenation catalysts.

[0004] However, existing metal phosphide catalysts are mostly supported catalysts, which are relatively lightweight, have low settling rates, and are difficult to settle, leading to challenges in catalyst separation and recovery. Furthermore, single metal phosphide catalysts exhibit low catalytic activity and stability. Current technologies propose introducing a second synergistic metal into the single-metal phosphide structure to construct low-cost bimetallic nanocatalysts with unique catalytic reaction performance and optimized electronic structure.

[0005] Therefore, this invention introduces a second metal (M = Fe, Co, Mo, Cu and W) into a single metal phosphide (nickel phosphide) to prepare a bulk bimetallic transition metal phosphide catalyst, thereby obtaining high catalytic activity while maintaining air stability. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a catalyst for the conversion of benzonitrile and hydrogen into aniline and dibenzylamine. Compared with the prior art, the catalyst of this invention can significantly reduce reaction pressure and energy consumption, and improve the selectivity of the conversion of benzonitrile and hydrogen into aniline and dibenzylamine.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a catalyst for the hydrogenation of benzonitrile to prepare aniline and dibenzylamine, wherein the catalyst is a bimetallic transition metal phosphide catalyst with the chemical formula Ni7M1P4, wherein M is Mo, Cu, Co, W or Fe, the molar ratio of Ni to M is 7, and the molar ratio of (Ni+M) to P is 2.

[0008] The preparation method of the bimetallic transition metal phosphide catalyst includes the following steps: S1. The metal salts of Ni and M and diammonium hydrogen phosphate are added sequentially to an aqueous solution of citric acid. After stirring at room temperature, the solution is first evaporated by rotary evaporation until it reaches a viscous state, then dried. The dried solid is then ground into powder and calcined to obtain the precursor. S2. The precursor obtained in S1 is placed in a tube furnace and reduced under H2 atmosphere. After the reduction reaction is completed, the temperature is lowered to room temperature and passivated under 1% O2 / N2 atmosphere to obtain the bimetallic transition metal phosphide catalyst Ni7M1P4.

[0009] Preferably, the metal salt of Ni in S1 is nickel nitrate; the molar ratio of citric acid to (Ni+M+P) is 2.

[0010] Preferably, the stirring time at room temperature in S1 is 12 hours.

[0011] Preferably, drying in S1 is first performed in... Dry for 12 hours, then heat to Continue drying until the sample is completely dry, then place it in a muffle furnace. The heating rate increased to And keep it for 1 hour.

[0012] Preferably, the calcination described in S1 is carried out in an air atmosphere. The heating rate increased to Roast for 3 hours.

[0013] Preferably, the flow rate of H2 in S2 is 100 mL / min, and the temperature control program for the reduction reaction is as follows: The heating rate is increased to And keep it for 3 hours.

[0014] Preferably, the passivation time at room temperature in S2 is 1 hour.

[0015] The bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to prepare aniline and dibenzylamine of the present invention can be activated by reduction with hydrogen before use. The activation conditions are: 10% H2 / Ar mixed gas, and the reduction temperature is... The restoration time is 1 hour.

[0016] Compared with the prior art, the present invention has the following significant technical effects: 1. This invention provides a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to prepare aniline and dibenzylamine. This catalyst is a bulk catalyst, characterized by large particle size, rapid sedimentation, and high density. Using a bulk catalyst instead of a supported catalyst can significantly shorten the catalyst separation cycle, and even achieve in-situ sedimentation separation within the reactor, eliminating the need for complex external filtration or centrifugation equipment. This solves the key engineering problem of catalyst separation and recovery in the reaction system. Simultaneously, it can reduce catalyst consumption and replenishment frequency, resulting in high product purity, strong economic efficiency and operational reliability, and has significant engineering value for the industrial scale-up of hydrogenation processes.

[0017] 2. The bimetallic transition metal phosphide catalyst of the present invention can significantly reduce the reaction pressure and energy consumption of benzonitrile hydrogenation to prepare aniline and dibenzylamine. It has the advantages of high stability, high catalytic activity and high selectivity. The conversion rate of benzonitrile can reach 100%, and the selectivity of aniline and dibenzylamine in the product reaches 51.89% and 11.06%, respectively.

[0018] The present invention will be further described in detail below with reference to the embodiments. Detailed Implementation

[0019] Example 1

[0020] This embodiment describes a method for preparing a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to aniline and dibenzylamine. The method employs a temperature-programmed reduction approach and includes the following steps: (1) Under stirring conditions at room temperature, first weigh 11.2245 g of citric acid (C6H8O7, 0.0584 mol) to prepare a 0.4 mol / L citric acid aqueous solution, then add 4.955 g of nickel nitrate (Ni(NO3)2·6H2O, 0.0170 mol) and 0.4297 g of ammonium molybdate ((NH4)6Mo7O) 24 ·4H2O (0.000348 mol) and 1.28579 g diammonium hydrogen phosphate ((NH4)2HPO4 (0.00974 mol)) were added sequentially to the above solution (n (柠檬酸) / n (Ni+Mo+P) =2), and continue stirring the reaction for 12 hours. Then, dry the above solution on a rotary evaporator until a viscous solution forms, transfer it to a desiccator, and first... Dry for 12 hours, then raise the temperature to Until dry; then place the sample in a muffle furnace to... The heating rate increased to And keep it for 1 hour. Then, grind the resulting solid into powder and again expose it to air. The heating rate increased to The precursor was obtained by calcination for 3 hours. (2) The precursor was placed in a tube furnace for reduction reaction under a H2 gas flow of 100 mL / min. The heating rate is increased to The mixture was kept at this temperature for 3 hours. Then, it was cooled to room temperature in a flowing hydrogen atmosphere, and then switched to 1% O2 / N2 passivation gas and passivated at room temperature for 1 hour to obtain the bimetallic transition metal phosphide catalyst Ni7Mo1P4-550, in which the molar ratio of active components nickel and molybdenum was 7, and it was designated as Cat-1.

[0021] Example 2

[0022] This embodiment describes a method for preparing a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to aniline and dibenzylamine. The method employs a temperature-programmed reduction approach and includes the following steps: (1) Under stirring conditions at room temperature, first weigh 11.2245g of citric acid (C6H8O7, 0.0584mol) to prepare a 0.4mol / L citric acid aqueous solution, then add 4.955g of nickel nitrate and 0.59966g of ammonium metatungstate ((NH4)6H2W) 12 O 40 ·xH2O, 0.2028 mmol) and 1.285787 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (Ni+W+P) =2), and continue stirring the reaction for 12 hours. Then, dry the above solution on a rotary evaporator until a viscous solution forms, transfer it to a desiccator, and first... Dry for 12 hours, then raise the temperature to Until dry; then place the sample in a muffle furnace to... The heating rate increased to And keep it for 1 hour. Then, grind the resulting solid into powder and again expose it to air. The heating rate increased to The precursor was obtained by calcination for 3 hours. (2) The precursor was placed in a tube furnace for reduction reaction under a H2 gas flow of 100 mL / min. The heating rate is increased to The mixture was kept at this temperature for 3 hours. Then, it was cooled to room temperature in a flowing hydrogen atmosphere, and then switched to 1% O2 / N2 passivation gas and passivated at room temperature for 1 hour to obtain the bimetallic transition metal phosphide catalyst Ni7W1P4-550, in which the molar ratio of active components nickel and tungsten was 7, and it was designated as Cat-2.

[0023] Example 3

[0024] This embodiment describes a method for preparing a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to aniline and dibenzylamine. The method employs a temperature-programmed reduction approach and includes the following steps: (1) Under stirring conditions at room temperature, first weigh 11.2245 g of citric acid (C6H8O7, 0.0584 mol) to prepare a 0.4 mol / L citric acid aqueous solution, then add 4.955 g of nickel nitrate, 0.58807 g of copper nitrate (Cu(NO3)2·3H2O, 0.002434 mol) and 1.285787 g of diammonium hydrogen phosphate to the above solution in sequence (n (柠檬酸) / n (Ni+Cu+P) =2), and continue stirring the reaction for 12 hours. Then, dry the above solution on a rotary evaporator until a viscous solution forms, transfer it to a desiccator, and first... Dry for 12 hours, then raise the temperature to Until dry; then place the sample in a muffle furnace to... The heating rate increased to And keep it for 1 hour. Then, grind the resulting solid into powder and again expose it to air. The heating rate increased to The precursor was obtained by calcination for 3 hours. (2) The precursor was placed in a tube furnace for reduction reaction under a H2 gas flow of 100 mL / min. The heating rate is increased to The mixture was kept at this temperature for 3 hours. Then, it was cooled to room temperature in a flowing hydrogen atmosphere, and then switched to 1% O2 / N2 passivation gas and passivated at room temperature for 1 hour to obtain the bimetallic transition metal phosphide catalyst Ni7Cu1P4-550, in which the molar ratio of active components nickel and copper was 7, and it was designated Cat-3.

[0025] Example 4

[0026] This embodiment describes a method for preparing a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to aniline and dibenzylamine. The method employs a temperature-programmed reduction approach and includes the following steps: (1) Under stirring conditions at room temperature, first weigh 11.2245 g of citric acid (C6H8O7, 0.0584 mol) to prepare a 0.4 mol / L citric acid aqueous solution. Then, add 4.955 g of nickel nitrate, 0.983375 g of ferric nitrate (Fe(NO3)3·9H2O, 0.002434 mol) and 1.285787 g of diammonium hydrogen phosphate to the above solution in sequence (n (柠檬酸) / n (Ni+Fe+P) =2), and continue stirring the reaction for 12 hours. Then, dry the above solution on a rotary evaporator until a viscous solution forms, transfer it to a desiccator, and first... Dry for 12 hours, then heat to Until dry; then place the sample in a muffle furnace to... The heating rate increased to And keep it for 1 hour. Then, grind the resulting solid into powder and again expose it to air. The heating rate increased to The precursor was obtained by calcination for 3 hours. (2) The precursor was placed in a tube furnace for reduction reaction under a H2 gas flow of 100 mL / min. The temperature was increased to 550 °C and held for 3 h at a heating rate; then cooled to room temperature in a flowing hydrogen atmosphere, and then switched to 1% O2 / N2 passivation gas and passivated at room temperature for 1 h to obtain the bimetallic transition metal phosphide catalyst Ni7Fe1P4-550, in which the molar ratio of active components nickel and iron is 7, and it is numbered Cat-4.

[0027] Example 5

[0028] This embodiment describes a method for preparing a bimetallic transition metal phosphide catalyst for the hydrogenation of benzonitrile to aniline and dibenzylamine. The method employs a temperature-programmed reduction approach and includes the following steps: (1) Under stirring conditions at room temperature, first weigh 11.2245 g of citric acid (C6H8O7, 0.0584 mol) to prepare a 0.4 mol / L citric acid aqueous solution, then add 4.955 g of nickel nitrate, 0.7083952 g of cobalt nitrate (Co(NO3)2·6H2O, 0.002434 mol) and 1.285787 g of diammonium hydrogen phosphate to the above solution in sequence (n (柠檬酸) / n (Ni+Co+P) =2), and continue stirring the reaction for 12 h. Then, dry the above solution on a rotary evaporator until a viscous solution forms, transfer it to a desiccator, and first... Dry for 12 hours, then raise the temperature to Until dry; then place the sample in a muffle furnace to... The heating rate increased to And keep it for 1 hour. Then, grind the resulting solid into powder and again expose it to air. The heating rate increased to The precursor was obtained by calcination for 3 hours. (2) The precursor was placed in a tube furnace for reduction reaction under a H2 gas flow of 100 mL / min. The heating rate is increased to The mixture was kept at this temperature for 3 hours. Then, it was cooled to room temperature in a flowing hydrogen atmosphere, and then switched to 1% O2 / N2 passivation gas and passivated at room temperature for 1 hour to obtain the bimetallic transition metal phosphide catalyst Ni7Co1P4-550, in which the molar ratio of active components nickel and cobalt was 7, and it was designated Cat-5.

[0029] Example 6

[0030] The preparation method is the same as in Example 1, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Mo1P4-600, designated Cat-6, was prepared using a temperature-programmed reduction method.

[0031] Example 7

[0032] The preparation method is the same as in Example 1, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Mo1P4-650, designated Cat-7, was prepared using a temperature-programmed reduction method.

[0033] Example 8

[0034] The preparation method is the same as in Example 1, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Mo1P4-700, designated Cat-8, was prepared by a temperature-programmed reduction method.

[0035] Example 9

[0036] The preparation method is the same as in Example 2, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7W1P4-600, designated Cat-9, was prepared using a temperature-programmed reduction method.

[0037] Example 10

[0038] The preparation method is the same as in Example 2, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7W1P4-650, designated Cat-10, was prepared by a temperature-programmed reduction method.

[0039] Example 11

[0040] The preparation method is the same as in Example 2, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7W1P4-700, designated Cat-11, was prepared by a temperature-programmed reduction method.

[0041] Example 12

[0042] The preparation method is the same as in Example 3, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Cu1P4-600, designated Cat-12, was prepared using a temperature-programmed reduction method.

[0043] Example 13

[0044] The preparation method is the same as in Example 3, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Cu1P4-650, designated Cat-13, was prepared by a temperature-programmed reduction method.

[0045] Example 14

[0046] The preparation method is the same as in Example 3, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Cu1P4-700, designated Cat-14, was prepared by a temperature-programmed reduction method.

[0047] Example 15

[0048] The preparation method is the same as in Example 4, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Fe1P4-600, designated Cat-15, was prepared using a temperature-programmed reduction method.

[0049] Example 16

[0050] The preparation method is the same as in Example 4, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Fe1P4-650, designated Cat-16, was prepared using a temperature-programmed reduction method.

[0051] Example 17

[0052] The preparation method is the same as in Example 4, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Fe1P4-700, designated Cat-17, was prepared using a temperature-programmed reduction method.

[0053] Example 18

[0054] The preparation method is the same as in Example 5, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Co1P4-600, designated Cat-18, was prepared using a temperature-programmed reduction method.

[0055] Example 19

[0056] The preparation method is the same as in Example 5, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Co1P4-650, designated Cat-19, was prepared using a temperature-programmed reduction method.

[0057] Example 20

[0058] The preparation method is the same as in Example 5, except that the reduction temperature is: The bimetallic transition metal phosphide catalyst Ni7Co1P4-700, designated Cat-20, was prepared by a temperature-programmed reduction method.

[0059] Comparative Example 1 Ni₂P-550 was prepared using a temperature-programmed reduction method, containing only Ni as the metallic component. The preparation method was the same as in Example 1, except that: 9.8214 g of citric acid (C₆H₈O₇, 0.0511 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 4.955 g of nickel nitrate and 1.125 g of diammonium hydrogen phosphate were sequentially added to the above solution (n...). (柠檬酸) / n (Ni+P) =2), reduction temperature is The catalyst Ni2P-550, designated Cat-21, was prepared.

[0060] Comparative Example 2 Ni₂P-600 was prepared using a temperature-programmed reduction method, containing only Ni as the metallic component. The preparation method was the same as in Example 1, except that: 9.8214 g of citric acid (C₆H₈O₇, 0.0511 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 4.955 g of nickel nitrate and 1.125 g of diammonium hydrogen phosphate were added sequentially to the above solution (n...). (柠檬酸) / n (Ni+P) =2), reduction temperature is The catalyst Ni2P-600, designated Cat-22, was prepared.

[0061] Comparative Example 3 Ni₂P-650 was prepared using a temperature-programmed reduction method, containing only Ni as the metallic component. The preparation method was the same as in Example 1, except that: first, 9.8214 g of citric acid (C₆H₈O₇, 0.0511 mol) was weighed to prepare a 0.4 mol / L citric acid aqueous solution; then, 4.955 g of nickel nitrate and 1.125 g of diammonium hydrogen phosphate were added sequentially to the above solution (n...). (柠檬酸) / n (Ni+P) =2), reduction temperature is The catalyst Ni2P-650, designated Cat-23, was prepared.

[0062] Comparative Example 4 Ni₂P-700 was prepared using a temperature-programmed reduction method, containing only Ni as the metallic component. The preparation method was the same as in Example 1, except that: 9.8214 g of citric acid (C₆H₈O₇, 0.0511 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 4.955 g of nickel nitrate and 1.125 g of diammonium hydrogen phosphate were added sequentially to the above solution (n...). (柠檬酸) / n (Ni+P) =2), reduction temperature is The catalyst Ni2P-700, designated Cat-24, was prepared.

[0063] Comparative Example 5 The metal component contained only Mo, and Mo1P1-700 was prepared by a temperature-programmed reduction method. The preparation method was the same as in Example 1, except that: 7.6856 g of citric acid (C6H8O7, 0.04 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 1.7655 g of ammonium molybdate and 1.3206 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (Mo+P) =2), reduction temperature is Catalyst Mo1P1-700, designated Cat-25, was prepared.

[0064] Comparative Example 6 The metal component contains only W, and W1P1-700 was prepared using a temperature-programmed reduction method. The preparation method is the same as in Example 2, except that: first, 7.6856 g of citric acid (C6H8O7, 0.04 mol) was weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 2.46358 g of ammonium metatungstate and 1.3206 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (W+P) =2), reduction temperature is Catalyst W1P1-700, designated Cat-26, was prepared.

[0065] Comparative Example 7 The metal component contains only Cu, and Cu1P1-700 was prepared using a temperature-programmed reduction method. The preparation method is the same as in Example 3, except that: first, 7.6856 g of citric acid (C6H8O7, 0.04 mol) was weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 2.416 g of copper nitrate and 1.3206 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (Cu+P) =2), reduction temperature is Catalyst Cu1P1-700, designated Cat-27, was prepared.

[0066] Comparative Example 8 The metal component contained only Fe, and Fe1P1-700 was prepared by a temperature-programmed reduction method. The preparation method was the same as in Example 4, except that: 7.6856 g of citric acid (C6H8O7, 0.04 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 4.04 g of ferric nitrate and 1.3206 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (Fe+P) =2), reduction temperature is Catalyst Fe1P1-700, designated Cat-28, was prepared.

[0067] Comparative Example 9 The metal component contained only Co, and Co1P1-700 was prepared by a temperature-programmed reduction method. The preparation method was the same as in Example 5, except that: 7.6856 g of citric acid (C6H8O7, 0.04 mol) was first weighed to prepare a 0.4 mol / L citric acid aqueous solution, and then 2.9103 g of cobalt nitrate and 1.3206 g of diammonium hydrogen phosphate were added sequentially to the above solution (n (柠檬酸) / n (Co+P) =2), reduction temperature is Catalyst Co1P1-700, designated Cat-29, was prepared.

[0068] Catalysts Cat-1 to Cat-29 prepared in Examples 1-20 and Comparative Examples 1-9 were used for the hydrogenation of benzonitrile (BN) to produce aniline (BA) and dibenzylamine (DBA). Before use, the catalysts were activated by hydrogen treatment under the following conditions: an H2 / Ar (10% H2) mixture. Reduction for 1 hour. The activated catalyst is then placed in a 100 mL batch reactor and reacted at a temperature of [temperature missing]. The hydrogenation reaction was carried out at a reaction pressure of 6.0 MPa, with 9.7 mmol of benzonitrile (BN) and 30 mL of ethanol as the reaction solvent, for a reaction time of 4 h. Hexadecane was used as an internal standard. Samples were taken for analysis, and the conversion rate (%) of benzonitrile (BN) and the selectivity (%) of aniline (BA) and dibenzylamine (DBA) in the product were calculated. Detection conditions were: HP-5 capillary column, FID detector, and area normalization.

[0069] The activity evaluation results of catalysts Cat-1 to Cat-29 are summarized in Table 1.

[0070] Table 1. Catalyst activity evaluation results As shown in Table 1, compared with Ni2P and nickel-free phosphide catalysts, the bimetallic transition metal phosphide catalysts exhibit significantly increased activity for the hydrogenation of benzonitrile. Furthermore, except for the W-modified catalysts, the bimetallic transition metal phosphide catalysts modified with other metals (Mo, Cu, Fe, Co) show increased activity with increasing reduction temperature during preparation. As the reduction temperature increases, the hydrogenation activity of benzonitrile gradually decreases. However, for W-modified bimetallic transition metal phosphide catalysts, the catalytic hydrogenation activity first increases and then decreases with increasing reduction temperature, and aniline is the predominant product. The reduced bimetallic transition metal phosphide catalyst (Ni7W1P4-600) exhibited maximum catalytic hydrogenation activity for benzonitrile (BN) (benzonitrile conversion reached 100%, and selectivity for aniline and dibenzylamine was 51.89% and 11.06%, respectively). This bimetallic transition metal phosphide catalyst significantly reduces reaction pressure and energy consumption, enabling the hydrogenation of benzonitrile to aniline and dibenzylamine, and possesses advantages such as high stability, high catalytic activity, and high selectivity. Furthermore, the bimetallic transition metal phosphide catalyst of this invention is a bulk catalyst with characteristics such as large particle size, fast sedimentation, and high density. It can replace supported catalysts, significantly shorten the catalyst separation cycle, and even achieve in-situ sedimentation separation within the reactor, eliminating the need for complex external filtration or centrifugation equipment. This solves the key engineering problem of catalyst separation and recovery in reaction systems (including the hydrogenation of benzonitrile to prepare aniline and dibenzylamine using bimetallic transition metal phosphide catalysts). At the same time, it can also reduce catalyst consumption and replenishment frequency, produce high product purity, and has strong economic efficiency and operational reliability, making it of significant engineering value for the industrial scale-up of hydrogenation processes.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A catalyst for the hydrogenation of benzonitrile to prepare aniline and dibenzylamine, characterized in that, The catalyst is a bimetallic transition metal phosphide catalyst with the chemical formula Ni7M1P4, where M is Mo, Cu, Co, W or Fe, the molar ratio of Ni to M is 7, and the molar ratio of (Ni+M) to P is 2.

2. A method for preparing the catalyst according to claim 1, characterized in that, Includes the following steps: S1. The metal salts of Ni and M and diammonium hydrogen phosphate are added sequentially to an aqueous solution of citric acid. After stirring at room temperature, the solution is first evaporated by rotary evaporation until it reaches a viscous state, then dried. The dried solid is then ground into powder and calcined to obtain the precursor. S2. The precursor obtained in S1 is placed in a tube furnace and reduced under H2 atmosphere. After the reduction reaction is completed, the temperature is lowered to room temperature and passivated under 1% O2 / N2 atmosphere to obtain the bimetallic transition metal phosphide catalyst Ni7M1P4.

3. The method according to claim 2, characterized in that, The metal salt of Ni mentioned in S1 is nickel nitrate; the molar ratio of citric acid to (Ni+M+P) is 2.

4. The method according to claim 2, characterized in that, The stirring time at room temperature as described in S1 is 12 hours.

5. The method according to claim 2, characterized in that, In S1, drying is first done in... Dry for 12 hours, then heat to Continue drying until the sample is completely dry, then place it in a muffle furnace. The heating rate increased to And keep it for 1 hour.

6. The method according to claim 2, characterized in that, The roasting described in S1 is carried out in an air atmosphere. The heating rate increased to Roast for 3 hours.

7. The method according to claim 2, characterized in that, The flow rate of H2 in S2 is 100 mL / min, and the temperature control program for the reduction reaction is as follows: The heating rate is increased to And keep it on for 3 hours.

8. The method according to claim 2, characterized in that, The passivation time at room temperature described in S2 is 1 hour.

9. The catalyst according to claim 1, characterized in that, The catalyst can be activated by reduction with hydrogen before use. The activation conditions are: 10% H2 / Ar mixture, and the reduction temperature is [temperature missing]. The restoration time is 1 hour.

Images