M-sb intermetallic compound catalyst, its preparation method and application

Abstract

The application belongs to the technical field of catalyst preparation, and discloses an M-Sb intermetallic compound catalyst, a preparation method and application thereof, a carrier of the M-Sb intermetallic compound catalyst is a magnesium-aluminum metal mixed oxide, M-Sb alloy nanoparticles are loaded on the carrier, the loading amount of metal M is 3.0wt%-10.0wt%, and the metal M is selected from one of Pd, Pt, Rh or Ir; in the M-Sb intermetallic compound catalyst, Sb modifies the active metal M with high electronegativity to form an electron-deficient Sb isolated electron-rich M M2Sb2 site structure, and the molar ratio of the loading amount of metal M to Sb is 1:1. The M-Sb intermetallic compound catalyst provided in the application has excellent performance in the selective hydrogenation reaction of dinitrobenzene, can realize nearly complete conversion of dinitrobenzene under low-temperature conditions, and has excellent phenylenediamine selectivity and catalytic stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to an M-Sb intermetallic compound catalyst, its preparation method, and its application. Background Technology

[0002] The hydrogenation reactions of ortho-, meta-, and p-dinitrobenzene (o-DNB, m-DNB, p-DNB) play a crucial role in the fine chemical and pharmaceutical industries. Among these, m-phenylenediamine (MPD) and p-phenylenediamine (PPD), prepared from the hydrogenation of m- and p-dinitrobenzene, are important raw materials for the production of meta- and para-aramid fibers. Aramid fibers, due to their excellent high-temperature resistance, corrosion resistance, high strength, and insulation properties, are widely used in aerospace, defense, electronics and communications, automotive manufacturing, and environmental protection, and are core members of modern high-performance materials. For example, meta-aramid fibers, due to their excellent flame retardancy and high-temperature resistance, are widely used in protective clothing and filter materials; para-aramid fibers, known for their ultra-high strength and modulus, are key materials for bulletproof vests, aerospace structural components, and high-strength ropes. Furthermore, ortho-dinitrobenzene (o-DNB) is also a basic raw material for the production of dyes, pesticides, and other fine chemicals. O-phenylenediamine (OPD) is widely used in dyes, pharmaceuticals, polymer materials, rubber, and pesticides, playing a vital role as a key intermediate or auxiliary agent.

[0003] For the hydrogenation of ortho, meta, and para-dinitrobenzenes to the corresponding phenylenediamines, conventional noble metal catalysts (such as Pd and Pt) are commonly used in existing technologies. Although these catalysts exhibit high catalytic activity, their high noble metal content leads to excessively high catalyst costs, and the high temperatures and pressures required for the hydrogenation reaction limit their industrial application. For example, the paper "Tian Xianfeng, Liu Feng, Liu Guangqin, Research on the Application of m-phenylenediamine in Synthesis Process [A], Process Technology, 2021, 10, 188-189" describes the use of a conventional skeletal nickel catalyst with a reaction temperature of 120–130℃ and a pressure of 4.0–4.5 MPa, ultimately achieving a yield of 96%. Therefore, developing novel catalysts with high conversion, high selectivity, high stability, and mild reaction conditions is an important research topic.

[0004] To address this issue, the modification of Pd-based catalysts typically involves introducing guest metals to modulate the spatial and electronic structures of Pd active sites, thereby altering the substrate's adsorption behavior and improving catalytic performance. Layered bimetallic hydroxides (LDHs), due to their tunable host layer composition and readily exchangeable intercalated anions, are widely used as precursors for preparing various intermetallic compound catalysts and represent an effective approach for modifying Pd-based catalysts. However, existing M-Sb (metal-antimony) intermetallic compound catalyst preparation processes are generally complex and costly, and they are prone to uneven distribution of active sites during catalysis, limiting their large-scale industrial application. Summary of the Invention

[0005] To address the aforementioned issues, an M-Sb intermetallic compound catalyst and its preparation method are provided. The M-Sb intermetallic compound catalyst exhibits excellent catalytic activity and selectivity when applied to the selective hydrogenation of dinitrobenzene to prepare the corresponding phenylenediamine, and the hydrogenation reaction conditions are mild.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] An M-Sb intermetallic compound catalyst is disclosed, wherein the catalyst is supported on a magnesium-aluminum metal mixed oxide, and M-Sb alloy nanoparticles are loaded on the support, with the loading amount of metal M being 3.0 wt% to 10.0 wt%; wherein metal M is an active metal selected from Pd, Pt, Rh, or Ir; in the M-Sb intermetallic compound catalyst, Sb modifies the highly electronegative active metal M to form an electron-deficient Sb isolated electron-rich M2Sb2 site structure, and the molar ratio of metal M to Sb loading is 1:1.

[0008] This invention provides a method for preparing an M-Sb intermetallic compound catalyst, comprising the following steps:

[0009] (1) Using magnesium and aluminum nitrates as carrier precursors, magnesium aluminum nitrate solution was prepared, and Mg / Al layered hydroxide was prepared by co-precipitation method.

[0010] (2) Add M precursor solution to the Mg / Al layered hydroxide suspension prepared in step (1) for ion exchange, and after filtration, washing and drying, obtain M / Mg / Al ternary layered hydroxide J;

[0011] (3) Grind and mix M / Mg / Al ternary layered hydroxide J with inert metal Sb powder to obtain M / Sb / Mg / Al quaternary layered hydroxide JY;

[0012] (4) The M / Sb / Mg / Al quaternary layered hydroxide JY was thermally reduced to obtain the M-Sb intermetallic compound catalyst.

[0013] Among them, metal M is selected from Pd, Pt, Rh or Ir.

[0014] The present invention is further configured such that, in step (1), the molar ratio of Mg to Al ions in the magnesium aluminum nitrate solution in step (1) is (2-4):1; preferably, the molar ratio of Mg to Al ions is (2.5-3.5):1.

[0015] The present invention is further configured such that, in step (2), the concentration of metal M ions in the M precursor solution is 0.032 to 0.040 mol / L.

[0016] The present invention is further configured such that steps (1) and (2) are carried out continuously in the same reaction site, and the temperature of the reaction system is controlled at 55-75°C, including the following process:

[0017] Under stirring conditions, magnesium aluminum nitrate solution and M precursor solution were added sequentially to the precipitant, with the addition rate of the two metal salt solutions controlled at 0.8–1.2 mL / min, and the pH of the reaction system was controlled at 10 ± 1 by a pH adjuster. After the addition was completed, the reaction was stirred for 10–20 hours. Finally, the mixture was filtered, washed, and dried to obtain the M / Mg / Al ternary layered hydroxide J.

[0018] The present invention is further configured such that, in step (1), the magnesium and aluminum nitrates are Mg(NO3)2·6H2O and Al(NO3)3·9H2O, respectively; the Pd precursor is selected from PdCl2 and H2PdCl4; the Pt precursor is selected from H2PtCl6·6H2O and Pt(NO3)2; the Rh precursor is selected from K3RhCl6·6H2O and RhCl3·3H2O; and the Ir precursor is selected from H2IrCl6·6H2O and IrCl3·3H2O.

[0019] The present invention is further configured such that the precipitant is selected from one of Na2CO3 solution, NaHCO3 solution or K2CO3 solution; and the molar concentration of the precipitant is 0.3 to 0.5 mol / L.

[0020] The present invention is further configured such that the pH adjuster is selected from either NaOH solution or KOH solution. The molar concentration of the pH adjuster is 0.8–1.2 mol / L.

[0021] The present invention is further configured such that the drying conditions in step (2) are: temperature 80-150°C, drying time 12-20 hours; preferably, the drying temperature is 100-120°C.

[0022] The present invention is further configured such that, in step (3), the M / Mg / Al ternary layered hydroxide J is mixed with inert metal Sb powder at a molar ratio of M to Sb of 1:(0.9 to 1.2).

[0023] The present invention is further configured such that the thermal reduction treatment in step (4) is performed at 800-1000°C for 3-5 hours in an H2 / Ar atmosphere.

[0024] The present invention is further configured such that the loading of metal M in the M-Sb intermetallic compound catalyst prepared by the above preparation method is 3.0 wt% to 10.0 wt%, for example 3.0 wt%, 4.0 wt%, 5.0 wt%, 6.0 wt%, 7.0 wt%, 8.0 wt%, or 9.0 wt%.

[0025] The present invention also provides an application of the above-mentioned M-Sb intermetallic compound catalyst or the M-Sb intermetallic compound catalyst prepared by the above preparation method, wherein the M-Sb intermetallic catalyst is used for the selective hydrogenation reaction of dinitrobenzene to prepare phenylenediamine, wherein the dinitrobenzene includes o-dinitrobenzene, m-dinitrobenzene or p-dinitrobenzene.

[0026] The M-Sb intermetallic compound catalyst of this invention forms an M2Sb2 site structure of electron-deficient Sb and isolated electron-rich M through the strong hybridization of the d orbital of the active metal M and the p orbital of the inert metal Sb at the Fermi level. This structure can simultaneously promote the adsorption and activation of electrophilic nitro groups in dinitrobenzene at the M site and the timely desorption of nucleophilic amino groups in phenylenediamine from the M site, thereby achieving complete conversion of nitro groups at low temperatures and exhibiting excellent amino selectivity and catalytic stability.

[0027] The present invention further specifies that the conditions for the hydrogenation reaction are: temperature 30-60°C and pressure 1.0-2.0 MPa.

[0028] The present invention is further configured such that the hydrogenation reaction includes o-DNB selective hydrogenation to o-phenylenediamine (OPD), m-DNB selective hydrogenation to m-phenylenediamine (MPD), and p-DNB selective hydrogenation to p-phenylenediamine (PPD); the hydrogenation reaction conditions are: the feed concentration is 4-16 mg (dinitrobenzene) / mL (solvent), the reaction temperature is 40±10℃, the reaction pressure is 1.0-1.5 MPaH2, and the mass ratio of the M-Sb intermetallic compound catalyst to the feed dinitrobenzene is 1:(20-200).

[0029] Compared with existing technologies, the present invention has the following beneficial effects: Compared with traditional M-based catalysts, the M-Sb intermetallic compound catalyst prepared by the present invention changes the electronic and spatial structures of the M active sites due to the introduction of the inert metal Sb. After high-temperature thermal reduction treatment, the M sites are isolated by Sb atoms, which significantly improves the atomic utilization rate of the active component M and effectively regulates the adsorption behavior between H2, o-DNB, m-DNB, p-DNB and M-Sb intermetallic catalysts. The M-Sb intermetallic compound catalyst exhibits extremely excellent o-DNB, m-DNB, and p-DNB conversion rates and OPD, MPD, and PPD selectivity. Moreover, the reaction conditions are mild, and it can be recycled multiple times, showing ideal prospects for industrial applications. Attached Figure Description

[0030] Figure 1 The image shows the XRD pattern of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention.

[0031] Figure 2 This is a transmission electron microscope (TEM) image of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention.

[0032] Figure 3 The image shows a high-angle annular dark-field scanning transmission electron microscope image and corresponding particle size distribution of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention.

[0033] Figure 4 The images shown are high-angle annular dark-field scanning transmission electron microscope images and corresponding line scan elemental distribution maps of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention.

[0034] Figure 5 The images shown are high-angle annular dark-field scanning transmission electron microscope images and corresponding surface scan elemental distribution maps of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention.

[0035] Figure 6 Figure a is a high-angle annular dark-field scanning transmission microscope image of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention with spherical aberration correction. Figure b is an atomic image intensity distribution map along the arrow in Figure a. Figure c is a Fourier transform diagram of the catalyst. Figure d is an enlarged view of the matrix-marked area in Figure a and a crystal model projected onto the zone axis.

[0036] Figure 7 This is a two-dimensional differential charge density diagram of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention.

[0037] Figure 8 The adsorption configuration of m-dinitrobenzene and m-phenylenediamine on the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention is shown. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. It should be understood that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of the present invention.

[0039] Example 1

[0040] Preparation of Pd-Sb intermetallic compound catalysts

[0041] Specifically, the steps include the following:

[0042] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse by ultrasonication, and record as magnesium aluminum nitrate solution; dissolve 0.1496g PdCl2 and 0.141mL concentrated hydrochloric acid in 25mL of ultrapure water and disperse by ultrasonication, and record as chloropalladium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and record as precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and record as pH adjuster.

[0043] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. The magnesium aluminum nitrate solution and the chloropalladium acid solution were then added dropwise to the flask sequentially at a speed of 120 rpm, with a constant flow pump controlling the addition rate at 1.0 mL / min. Simultaneously, the pH adjuster was added using a constant flow pump to maintain the pH of the reaction system in the three-necked flask at 10.5. After the addition was complete, the mixture was continuously stirred at 65 °C for 12 hours, followed by vacuum filtration and washing multiple times until the pH was neutral, yielding a dark brown, blocky solid.

[0044] (2) The dark brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pd / Mg / Al ternary LDH material, labeled J1.

[0045] (3) Take the Pd / Mg / Al ternary LDH material J1 obtained in step (2) and mix it with 0.103g of inert metal Sb powder and grind it thoroughly so that the molar ratio of Pd to Sb is 1:1, and obtain the Pd / Sb / Mg / Al quaternary LDH material, which is marked as J1Y1.

[0046] (4) The quaternary layered hydroxide J1Y1 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pd-Sb intermetallic compound catalyst with a Pd loading of about 9%, labeled as J1Y1-900.

[0047] Example 2

[0048] Preparation of Pd-Sb intermetallic compound catalysts

[0049] Specifically, the steps include the following:

[0050] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse by ultrasonication, and record as magnesium aluminum nitrate solution; dissolve 0.0756g PdCl2 and 0.141mL concentrated hydrochloric acid in 25mL of ultrapure water and disperse by ultrasonication, and record as chloropalladium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and record as precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and record as pH adjuster.

[0051] The desired precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 h. Then, magnesium aluminum nitrate solution and chloropalladium acid solution were added dropwise to the flask sequentially at 120 rpm, with a constant flow rate of 1.0 mL / min controlled by a constant flow pump. Simultaneously, a pH adjuster was added using a constant flow pump to maintain the pH of the reaction system at 10.5. After the addition was complete, the reaction was continued at 65 °C for 12 hours, followed by vacuum filtration and washing multiple times until the pH was neutral, yielding a dark brown, blocky solid.

[0052] (2) The dark brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pd / Mg / Al ternary LDH material, labeled as J2.

[0053] (3) Take the Pd / Mg / Al ternary LDH material J2 obtained in step (1) and mix it with 0.0519g of inert metal Sb powder. Grind it thoroughly so that the molar ratio of Pd to Sb is 1:1, and obtain the Pd / Sb / Mg / Al quaternary LDH material, which is labeled as J2Y2.

[0054] (4) The quaternary layered hydroxide J2Y2 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pd-Sb intermetallic compound catalyst with a Pd loading of about 5%, labeled as J2Y2-900.

[0055] Comparative Example 1

[0056] Preparation of Pd single-metal catalysts

[0057] Specifically, the steps include the following:

[0058] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.1336g PdCl2 and 0.141mL concentrated hydrochloric acid in 25mL of ultrapure water and disperse them by ultrasonication to prepare a chloropalladium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the pH adjuster.

[0059] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloropalladium acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added using a constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a dark brown, blocky solid.

[0060] (2) The dark brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pd / Mg / Al ternary LDH material, labeled as J3.

[0061] (3) The Pd / Mg / Al ternary LDH material J3 obtained in step (2) was reduced at 900℃ in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pd monometallic catalyst with a Pd loading of about 9%, labeled as J3-900.

[0062] Example 3

[0063] Preparation of Pt-Sb intermetallic compound catalysts

[0064] Specifically, the steps include the following:

[0065] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse by ultrasonication to prepare a magnesium aluminum nitrate solution. Dissolve 0.437g H2PtCl6·6H2O in 25mL of ultrapure water and disperse by ultrasonication to prepare a chloroplatinic acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and this is designated as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and this is designated as the pH adjuster.

[0066] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroplatinic acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added using a constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, blocky solid.

[0067] (2) The brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pt / Mg / Al ternary LDH material, labeled as J4.

[0068] (3) Take the Pt / Mg / Al ternary LDH material J4 obtained in step (2) and mix it with 0.103g of inert metal Sb powder and grind it thoroughly so that the molar ratio of Pt to Sb is 1:1, and obtain the Pt / Sb / Mg / Al quaternary LDH material, which is labeled as J4Y4.

[0069] (4) The quaternary layered hydroxide J4Y4 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pt-Sb intermetallic compound catalyst with a Pt loading of about 9%, labeled as J4Y4-900.

[0070] Example 4

[0071] Preparation of Pt-Sb intermetallic compound catalysts

[0072] Specifically, the steps include the following:

[0073] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.0441g H2PtCl6·6H2O in 25mL of ultrapure water and disperse by ultrasonication to prepare a chloroplatinic acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and this is recorded as the pH adjuster.

[0074] The required precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroplatinic acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, lumpy solid.

[0075] (2) The brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pt / Mg / Al ternary LDH material, labeled as J5.

[0076] (3) The brownish-gray blocky solid J5 obtained in step (1) is mixed with 0.0275g of inert metal Sb powder and ground thoroughly so that the molar ratio of Pt to Sb is 1:1, and the Pt / Sb / Mg / Al quaternary LDH material is obtained and labeled as J5Y5.

[0077] (4) The quaternary layered hydroxide J5Y5 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pt-Sb intermetallic compound catalyst with a Pt loading of about 5%, labeled as J5Y5-900.

[0078] Comparative Example 2

[0079] Preparation of Pt single metal catalysts

[0080] Specifically, the steps include the following:

[0081] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.2129g H2PtCl6·6H2O in 25mL of ultrapure water and disperse by ultrasonication to prepare a chloroplatinic acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and this is recorded as the pH adjuster.

[0082] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroplatinic acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added using a constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, blocky solid.

[0083] (2) The brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Pt / Mg / Al ternary LDH material, labeled as J6.

[0084] (3) The Pt / Mg / Al ternary LDH material J6 obtained in step (2) was reduced at 900℃ in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Pt monometallic catalyst with a Pt loading of about 9%, labeled as J6-900.

[0085] Example 5

[0086] Preparation of Rh-Sb intermetallic compound catalysts

[0087] Specifically, the steps include the following:

[0088] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.365g K3RhCl6 in 25mL of ultrapure water and disperse it by ultrasonication to prepare a potassium chlororhodium solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and record it as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and record it as the pH adjuster.

[0089] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and potassium rhodium chloride solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a dark brown, blocky solid.

[0090] (2) The dark brown solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Rh / Mg / Al ternary LDH material, labeled as J7.

[0091] (3) The Rh / Mg / Al ternary LDH material J7 obtained in step (2) is mixed with 0.103g of inert metal Sb powder and ground thoroughly so that the molar ratio of Rh to Sb is 1:1, and the Rh / Sb / Mg / Al quaternary LDH material is obtained and labeled as J7Y7.

[0092] (4) The quaternary layered hydroxide J7Y7 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Rh-Sb intermetallic compound catalyst with an Rh loading of about 9%, labeled as J7Y7-900.

[0093] Example 6

[0094] Preparation of Rh-Sb intermetallic compound catalysts

[0095] Specifically, the steps include the following:

[0096] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution. Dissolve 0.1913g K3RhCl6 in 25mL of ultrapure water and disperse it by ultrasonication to prepare a potassium chlororhodium solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the pH adjuster.

[0097] The required precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and potassium rhodium chloride solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a dark brown lumpy solid.

[0098] (2) The dark brown solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Rh / Mg / Al ternary LDH material, labeled as J8.

[0099] (3) The dark brown blocky solid J8 obtained in step (1) is mixed with 0.0538g of inert metal Sb powder and ground thoroughly so that the molar ratio of Rh to Sb is 1:1, and the Rh / Sb / Mg / Al quaternary LDH material is obtained and labeled as J8Y8.

[0100] (4) The quaternary layered hydroxide J8Y8 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Rh-Sb intermetallic compound catalyst with an Rh loading of about 5%, labeled as J8Y8-900.

[0101] Comparative Example 3

[0102] Preparation of Rh single metal catalysts

[0103] Specifically, the steps include the following:

[0104] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.3373g K3RhCl6 in 25mL of ultrapure water and disperse it by ultrasonication to prepare a potassium chlororhodium solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and record it as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and record it as the pH adjuster.

[0105] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and potassium rhodium chloride solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a dark brown, blocky solid.

[0106] (2) The dark brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Rh / Mg / Al ternary LDH material, labeled as J9.

[0107] (3) The ternary layered hydroxide J9 obtained in step (2) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Rh single metal catalyst with an Rh loading of about 9%, labeled as J9-900.

[0108] Example 7

[0109] Preparation of Ir-Sb intermetallic compound catalysts

[0110] Specifically, the steps include the following:

[0111] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.435g H2IrCl6·6H2O in 25mL of ultrapure water and disperse them by ultrasonication to prepare a chloroiridium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and this is recorded as the pH adjuster.

[0112] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroiridium acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, blocky solid.

[0113] (2) The brownish-gray blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Ir / Mg / Al ternary LDH material, labeled as J10.

[0114] (3) The Ir / Mg / Al ternary LDH material J10 obtained in step (2) is mixed with 0.103g of inert metal Sb powder and ground thoroughly so that the molar ratio of Ir to Sb is 1:1, and the Ir / Sb / Mg / Al quaternary LDH material is obtained and labeled as J10Y10.

[0115] (4) The quaternary layered hydroxide J10Y10 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Ir-Sb intermetallic compound catalyst with an Ir loading of about 9%, labeled as J10Y10-900.

[0116] Example 8

[0117] Preparation of Ir-Sb intermetallic compound catalysts

[0118] Specifically, the steps include the following:

[0119] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse evenly by ultrasonication to prepare a magnesium aluminum nitrate solution. Dissolve 0.0441g H2IrCl6·6H2O in 25mL of ultrapure water and disperse by ultrasonication to prepare a chloroiridium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse by ultrasonication, and this is recorded as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse by ultrasonication, and this is recorded as the pH adjuster.

[0120] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroiridium acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, blocky solid.

[0121] (2) The brownish-gray blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Ir / Mg / Al ternary LDH material, labeled as J11.

[0122] (3) The brownish-gray blocky solid J11 obtained in step (1) is mixed with 0.028g of inert metal Sb powder and ground thoroughly so that the molar ratio of Ir to Sb is 1:1, and the Ir / Sb / Mg / Al quaternary LDH material is obtained and labeled as J11Y11.

[0123] (4) The quaternary layered hydroxide J11Y11 obtained in step (3) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Ir-Sb intermetallic compound catalyst with an Ir loading of about 5%, labeled as J11Y11-900.

[0124] Comparative Example 4

[0125] Preparation of Ir single metal catalysts

[0126] Specifically, the steps include the following:

[0127] (1) Dissolve 7.69g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O in 50mL of ultrapure water and disperse them evenly by ultrasonication to prepare a magnesium aluminum nitrate solution; dissolve 0.2148g H2IrCl6·6H2O in 25mL of ultrapure water and disperse them by ultrasonication to prepare a chloroiridium acid solution; dissolve 2.12g Na2CO3 powder in 50mL of ultrapure water and disperse it by ultrasonication, and record it as the precipitant; dissolve 6.00g NaOH powder in 150mL of ultrapure water and disperse it by ultrasonication, and record it as the pH adjuster.

[0128] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 °C for 1 hour. Magnesium aluminum nitrate solution and chloroiridium acid solution were added dropwise to the flask sequentially with a stirring speed of 120 rpm, using a constant flow pump to control the feeding rate at 1.0 mL / min. Simultaneously, a pH adjuster was added via the constant flow pump to ensure the pH of the reaction system remained constant at 10.5. After the addition was complete, stirring continued at 65 °C for 12 hours. After the reaction was complete, the mixture was vacuum filtered, and the reaction product was washed multiple times until the pH was neutral, finally yielding a brown, blocky solid.

[0129] (2) The brown blocky solid obtained in step (1) is dried at 110°C for 12 hours and then subjected to thorough mechanical grinding to obtain Ir / Mg / Al ternary LDH material, labeled as J12.

[0130] (3) The ternary layered hydroxide J12 obtained in step (2) was reduced at 900°C in an H2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Ir single metal catalyst with an Ir loading of about 9%, labeled as J12-900.

[0131] control group

[0132] The catalyst is a Pd-Sn intermetallic compound provided by patent CN118059957A, with a Pd loading of 9%.

[0133] Characterization of M-Sb intermetallic compound catalysts

[0134] The M-Sb intermetallic compound catalysts prepared in the above embodiments were characterized, such as... Figure 1 As shown, the XRD pattern of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 shows that the intermetallic compound synthesized in this invention has an obvious crystal structure, and the (102) crystal plane has the highest diffraction intensity, indicating that this crystal plane has the largest distribution on the surface of the medium-entropy alloy particles. Figure 2 The Pd-Sb intermetallic compound catalyst J1Y1-900 exhibits clear lattice fringes, which also verifies... Figure 1 The XRD results show that the catalyst has a distinct crystal structure. Figure 3 The particle size distribution results show that the synthesized Pd-Sb intermetallic compound catalyst has a uniform particle size with an average particle size of about 10 nm. Figure 4 The results showed that Pd and Sb elements were evenly distributed. Figure 5 The high-angle annular dark-field scanning transmission electron microscope (TEM) image and corresponding surface scan elemental distribution map of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 show that Pd, Sb, Mg, and Al elements are uniformly distributed, and... Figure 4 The results are consistent with the analysis results in the previous analysis.

[0135] The catalyst was further characterized by aberration-corrected electron microscopy, and the results are as follows: Figure 6 As shown, in (a) the lattice spacing along the arrow direction is 0.240 nm, corresponding to the (102) crystal plane of the Pd-Sb intermetallic compound. Figure 6 Figure (d) further illustrates the atomic arrangement of the catalyst particles, showing a high degree of agreement with the density functional theory simulation results of Pd-Sb. The sites of the two metal elements are arranged in an orderly manner, forming a Pd1Sb1 intermetallic compound structure of isolated Sb and Pd. Figure 7 The charge analysis results of the catalyst J1Y1-900 shown indicate that the charge is mainly distributed at the Pd sites, indicating that electron transfer has occurred from the guest metal Sb to the active metal Pd, forming a Pd2Sb2 quadruple site structure of electron-deficient Sb and isolated electron-rich Pd.

[0136] Figure 8 This is a schematic diagram of the catalytic hydrogenation of m-dinitrobenzene using the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of this invention. The PdSb catalyst forms a unique Pd2Sb2 site structure with isolated electron-deficient Sb and electron-rich Pd, which promotes the adsorption and activation of electrophilic nitro groups in m-dinitrobenzene at the Pd sites and the timely desorption of nucleophilic amino groups in m-phenylenediamine from the Pd sites. This results in the complete conversion of nitro groups at low temperatures, exhibiting excellent amino selectivity and catalytic stability.

[0137] Test Example 1

[0138] Evaluation of the catalytic hydrogenation performance of M-Sb intermetallic compound catalysts for o-DNB

[0139] The catalytic hydrogenation activity of o-DNB was evaluated using the M-Sb intermetallic compound catalysts prepared in Examples 1-8 and the M single-metal catalysts prepared in Comparative Examples 1-4. The performance evaluation of the o-DNB hydrogenation reaction was conducted in a high-pressure hydrogenation reactor at Iwasei Instruments. Methanol was used as the solvent, with a concentration of 16 mg (o-DNB) / mL (methanol), a reaction temperature of 40°C, a reaction pressure of 1.15 MPa H2, a stirring speed of 1000 rpm, and a reaction time of 2 hours.

[0140] The specific steps are as follows: Add 25 mL of o-DNB solution to the inner liner of a 100 mL reaction vessel. Before the reaction begins, continuously purge with argon gas and observe whether the pressure remains constant to ensure good airtightness of the equipment. Then, under an inert atmosphere, raise the temperature to the required reaction temperature. After the temperature stabilizes, switch the inert gas to 1.15 MPa hydrogen gas and start stirring; the reaction begins at this point. Maintain constant temperature and pressure, and proceed with the reaction for 2 hours. After the reaction is complete, take approximately 1.5 mL of sample from the sampling port. The components of the reactants and products are analyzed using an Agilent GC8860 gas chromatograph.

[0141] The o-DNB conversion rate C of the above-mentioned M single-metal catalyst and M-Sb intermetallic compound catalyst was tested. o-DNB intermediate o-NA (o-nitroaniline) selective S o-NA And product OPD selectivity S OPD The catalytic performance of the catalyst prepared in this invention for the selective hydrogenation of o-DNB to OPD is evaluated using the following formula:

[0142]

[0143] The catalytic performance evaluation results of the catalysts prepared in each embodiment and comparative example are shown in Table 1 below:

[0144] Table 1. Catalytic performance evaluation results of the catalyst

[0145] serial number catalyst Reaction temperature / ℃ <![CDATA[C o-DNB / %]]> <![CDATA[S o-NA / %]]> <![CDATA[S OPD / %]]> Example 1 J1Y1-900 40 100 0.9 99.1 Example 2 J2Y2-900 40 100 1.1 98.8 Comparative Example 1 J3-900 40 100 78.3 21.5 Example 3 J4Y4-900 40 99.0 5.1 93.8 Example 4 J5Y5-900 40 98.9 5.4 93.5 Comparative Example 2 J6-900 40 98.7 69.1 29.6 Example 5 J7Y7-900 40 99.9 3.5 96.2 Example 6 J8Y8-900 40 99.9 4.2 95.5 Comparative Example 3 J9-900 40 99.3 73.8 25.2 Example 7 J10Y10-900 40 99.6 4.9 94.8 Example 8 J11Y11-900 40 99.5 5.3 94.0 Comparative Example 4 J12-900 40 99.0 70.9 28.1 control group Pd-Sn 40 99.8 10.3 89.5

[0146] As shown in Table 1, the Pd monometallic catalyst prepared in Comparative Example 1 exhibits extremely high activity in the o-DNB conversion, but its OPD selectivity is only 21.5%, with most products remaining on the monoamine intermediate o-NA. However, when an appropriate amount of Sb is introduced, the Pd-Sb intermetallic compound catalyst prepared in Example 1 shows a significant improvement in OPD selectivity; in particular, the Pd-Sb catalyst can achieve an OPD selectivity of 99.1% even with complete o-DNB conversion. In Example 2, the Pd-Sb intermetallic catalyst with a Pd loading of 5% also achieves an OPD selectivity of 98.8% for catalytic hydrogenation. Those skilled in the art will readily understand that the Pd-Sb intermetallic compound catalyst prepared in this invention effectively optimizes the surface structure of the Pd-Sb sites through pd orbital hybridization between Sb and Pd, enabling the Pd-based catalyst to possess higher OPD selectivity under low-temperature conditions.

[0147] Further research revealed that by introducing the inert component Sb into Pt, Rh, and Ir catalysts, the corresponding M-Sb intermetallic compound catalysts prepared could also form similar M-Sb site structures, as shown in Examples 3-8. These catalysts also exhibited excellent low-temperature selective hydrogenation performance. A comparative analysis of these eight M-Sb intermetallic compound catalysts showed that the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 exhibited the best performance, achieving an OPD selectivity of up to 99.1% under conditions of complete o-DNB conversion, indicating that the synergistic catalytic effect between Pd sites isolated by Sb sites was the most effective. In summary, the M-Sb intermetallic compound catalysts prepared in this invention demonstrate excellent low-temperature hydrogenation activity and OPD selectivity, providing an effective pathway for the industrial application of intermetallic compound catalysts.

[0148] Test Example 2

[0149] Stability evaluation of o-DNB catalytic hydrogenation of M-Sb intermetallic compound catalysts

[0150] The stability of the Pd-Sb intermetallic compound catalyst prepared in Example 1 for o-DNB selective hydrogenation was evaluated. Following the catalyst performance evaluation method of Example 1, the catalyst and product after the reaction were separated by centrifugation, and the catalyst was repeatedly added to the next batch of reaction under the same conditions for five cycles. The results are shown in Table 2.

[0151] Table 2 Stability Evaluation of J1Y1-900 Catalytic Hydrogenation

[0152] Loop count <![CDATA[C o-DNB / %]]> <![CDATA[S OPD / %]]> 1 100 99.1 2 100 98.7 3 100 97.6 4 100 96.9 5 100 95.9

[0153] As can be seen from the data in Table 2, the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 maintained a 100% conversion rate of o-DNB after 5 cycles, and the selectivity of OPD was also stable at over 95.9%, which indicates that the catalyst J1Y1-900 has excellent catalytic stability.

[0154] Test Example 3

[0155] The catalytic hydrogenation activity of m-DNB was evaluated using the M-Sb intermetallic compound catalysts and M single-metal catalysts prepared in Examples 1-8 and Comparative Examples 1-4. The performance evaluation of the m-DNB hydrogenation reaction was conducted in a high-pressure hydrogenation reactor at Iwasaki Instruments. Ethanol was used as the solvent, with a reaction concentration of 16 mg (m-DNB) / mL (ethanol), a reaction temperature of 40°C, a reaction pressure of 1.15 MPa H2, a stirring speed of 1000 rpm, and a reaction time of 2 hours.

[0156] The specific steps are the same as in Test Example 1, except that the reaction raw material is an m-DNB solution.

[0157] The m-DNB conversion rate C of the above-mentioned M single-metal catalyst and M-Sb intermetallic compound catalyst was tested. m-DNB intermediate m-NA selectivity m-NA and product MPD selectivity S MPD The catalytic performance of the catalyst prepared in this invention for the selective hydrogenation of m-DNB to MPD was evaluated. The catalytic performance evaluation results of the catalysts prepared in each example and comparative example are shown in Table 3 below:

[0158] Table 3. Catalytic performance evaluation results of the catalysts

[0159] serial number catalyst Reaction temperature / °C <![CDATA[C m-DNB / %]]> <![CDATA[S m-NA / %]]> <![CDATA[S MPD / %]]> Example 1 J1Y1-900 40 100 0.1 99.8 Example 2 J2Y2-900 40 100 0.7 99.2 Comparative Example 1 J3-900 40 100 80.2 19.5 Example 3 J4Y4-900 40 99.5 3.2 96.1 Example 4 J5Y5-900 40 99.0 4.1 94.8 Comparative Example 2 J6-900 40 99.3 90.1 9.5 Example 5 J7Y7-900 40 99.7 1.8 98.1 Example 6 J8Y8-900 40 99.5 2.3 97.2 Comparative Example 3 J9-900 40 99.2 79.2 19.9 Example 7 J10Y10-900 40 99.8 2.2 97.6 Example 8 J11Y11-900 40 99.6 2.6 96.8 Comparative Example 4 J12-900 40 99.4 85.6 13.7 control group Pd-Sn 40 99.5 8.7 90.7

[0160] As shown in Table 1, the Pd monometallic catalyst prepared in Comparative Example 1 exhibits extremely high activity in the m-DNB conversion, but its MPD selectivity is only 19.5%, with most products remaining on the monoamine intermediate m-NA. However, when an appropriate amount of Sb is introduced, the Pd-Sb intermetallic compound catalyst prepared in Example 1 shows a significant improvement in MPD selectivity; in particular, the Pd-Sb catalyst can achieve an MPD selectivity of 99.8% even with complete m-DNB conversion; the Pd-Sb intermetallic compound catalyst prepared in Example 2, with a Pd loading of 5%, also achieves an MPD selectivity of 99.2% for the catalytic hydrogenation reaction. Those skilled in the art will readily understand that the Pd-Sb intermetallic compound catalyst prepared in this invention effectively optimizes the surface structure of the Pd-Sb sites through pd orbital hybridization between Sb and Pd, enabling the Pd-based catalyst to possess higher MPD selectivity under low-temperature conditions.

[0161] Similarly, by introducing the inert component Sb into Pt, Rh, and Ir catalysts, the corresponding M-Sb intermetallic compound catalysts prepared can also form similar M-Sb site structures, as shown in Examples 3 to 8. These catalysts also exhibit excellent low-temperature selective hydrogenation performance.

[0162] Test Example 4

[0163] Stability evaluation of m-DNB catalytic hydrogenation

[0164] The stability of the Pd-Sb intermetallic compound catalyst prepared in Example 1 for m-DNB selective hydrogenation was evaluated. Following the catalyst performance evaluation method of Example 1, the catalyst and product after the reaction were separated by centrifugation, and the catalyst was repeatedly added to the next batch of reaction under the same conditions for five cycles. The results are shown in Table 4.

[0165] Table 4. Stability Evaluation of J1Y1-900 Catalytic Hydrogenation

[0166] Loop count <![CDATA[C m-DNB / %]]> <![CDATA[S MPD / %]]> 1 100 99.3 2 100 98.9 3 100 98.0 4 100 97.3 5 100 95.1

[0167] As can be seen from the data in Table 4, the conversion rate of m-DNB of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 remained at 100% after 5 cycles, and the selectivity of MPD was also stable at over 95.1%, which indicates that the catalyst J1Y1-900 has excellent catalytic stability.

[0168] Test Example 5

[0169] The catalytic hydrogenation activity of p-DNB was evaluated using the M-Sb intermetallic compound catalysts and M single-metal catalysts prepared in Examples 1-8 and Comparative Examples 1-4. The performance evaluation of the p-DNB hydrogenation reaction was conducted in a high-pressure hydrogenation reactor at Iwasaki Instruments. Ethanol was used as the solvent, the reaction concentration was 16 mg (p-DNB) / mL (tetrahydrofuran), the reaction temperature was 40 °C, the reaction pressure was 1.15 MPa H2, the stirring speed was 1000 rpm, and the reaction time was 2 hours.

[0170] The specific steps are the same as in Test Example 1, except that the reaction raw material is a p-DNB solution.

[0171] The p-DNB conversion rate C of the above-mentioned M single-metal catalyst and M-Sb intermetallic compound catalyst was tested. p-DNB intermediate p-NA selectivity p-NA and product PPD selectivity S PPD The catalytic performance of the catalyst prepared in this invention for the selective hydrogenation of p-DNB to PPD was evaluated. The catalytic performance evaluation results of the catalysts prepared in each example and comparative example are shown in Table 5 below:

[0172] Table 5. Catalytic performance evaluation results of the catalysts

[0173]

[0174]

[0175] As shown in Table 5, the Pd monometallic catalyst prepared in Comparative Example 1 exhibits extremely high activity in the p-DNB conversion, but its PPD selectivity is only 20.8%, with most products remaining on the monoamine intermediate p-NA. However, when an appropriate amount of Sb is introduced, the Pd-Sb intermetallic compound catalyst prepared in Example 1 shows a significant improvement in PPD selectivity; in particular, the Pd-Sb catalyst can achieve a PPD selectivity of 99.7% even with complete p-DNB conversion; the Pd-Sb intermetallic compound catalyst prepared in Example 2, with a Pd loading of 5%, also achieves a PPD selectivity of 99.2% for the catalytic hydrogenation reaction. Those skilled in the art will readily understand that the Pd-Sb intermetallic compound catalyst prepared in this invention effectively optimizes the surface structure of the Pd-Sb sites through the pd orbital hybridization between Sb and Pd, enabling the Pd-based catalyst to possess higher PPD selectivity under low-temperature conditions.

[0176] Similarly, by introducing the inert component Sb into Pt, Rh, and Ir catalysts, the corresponding M-Sb intermetallic compound catalysts prepared can also form similar M-Sb site structures, as shown in Examples 3 to 8. These catalysts also exhibit excellent low-temperature selective hydrogenation performance.

[0177] Test Example 6

[0178] Stability evaluation of p-DNB catalytic hydrogenation

[0179] The stability of the Pd-Sb intermetallic compound catalyst prepared in Example 1 for p-DNB selective hydrogenation was evaluated. Following the catalyst performance evaluation method of Example 1, the catalyst and product after the reaction were separated by centrifugation, and the catalyst was repeatedly added to the next batch of reaction under the same conditions for five cycles. The results are shown in Table 6.

[0180] Table 6. Stability Evaluation of J1Y1-900 Catalytic Hydrogenation

[0181] Loop count <![CDATA[C p-DNB / %]]> <![CDATA[S PPD / %]]> 1 100 99.7 2 100 98.7 3 100 97.8 4 100 97.0 5 100 95.9

[0182] As can be seen from the data in Table 6, the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 maintained a p-DNB conversion rate of 100% after 5 cycles, while the PPD selectivity was also stable at over 95.9%, indicating that the catalyst J1Y1-900 has excellent catalytic stability.

[0183] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An M-Sb intermetallic compound catalyst, characterized in that, The support for the M-Sb intermetallic compound catalyst is a magnesium-aluminum metal mixed oxide, and M-Sb alloy nanoparticles are loaded on the support. The loading amount of metal M is 3.0 wt% to 10.0 wt%. Among them, metal M is an active metal, and M is selected from Pd, Pt, Rh or Ir. In the M-Sb intermetallic compound catalyst, Sb modifies the highly electronegative active metal M to form an electron-deficient Sb isolated electron-rich M2Sb2 site structure, and the molar ratio of metal M to Sb loading is 1:

1.

2. A method for preparing an M-Sb intermetallic compound catalyst, characterized in that, Includes the following steps: (1) Using magnesium and aluminum nitrates as carrier precursors, magnesium aluminum nitrate solution was prepared, and Mg / Al layered hydroxide was prepared by co-precipitation method. (2) Add M precursor solution to the Mg / Al layered hydroxide suspension prepared in step (1) for ion exchange, and after filtration, washing and drying, obtain M / Mg / Al ternary layered hydroxide J; (3) Grind and mix M / Mg / Al ternary layered hydroxide J with inert metal Sb powder to obtain M / Sb / Mg / Al quaternary layered hydroxide JY; (4) The M / Sb / Mg / Al quaternary layered hydroxide JY was thermally reduced to obtain the M-Sb intermetallic compound catalyst. Among them, metal M is selected from Pd, Pt, Rh or Ir.

3. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, In the magnesium aluminum nitrate solution described in step (1), the molar ratio of Mg to Al ions is (2-4):

1.

4. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, Steps (1) and (2) are carried out continuously in the same reaction site, and the temperature of the reaction system is controlled at 55-75℃. The process includes the following steps: under stirring conditions, magnesium aluminum nitrate solution and M precursor solution are added to the precipitant in sequence, and the addition rate of the two metal salt solutions is controlled at 0.8-1.2 mL / min. The pH value of the reaction system is controlled at 10±1 by pH adjuster. After the addition is completed, the reaction is stirred for 10-20 hours. Finally, the reaction is filtered, washed and dried to obtain the M / Mg / Al ternary layered hydroxide J.

5. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, The drying conditions in step (2) are: temperature 80-150℃, drying time 12-20 hours.

6. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, In step (3), the M / Mg / Al ternary layered hydroxide J is mixed with inert metal Sb powder at a molar ratio of M to Sb of 1:(0.9 to 1.2).

7. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, The conditions for thermal reduction treatment in step (4) are reduction at 800-1000℃ for 3-5 hours in an H2 / Ar atmosphere.

8. The method for preparing an M-Sb intermetallic compound catalyst according to claim 2, characterized in that, The loading of metal M in the prepared M-Sb intermetallic compound catalyst was 3.0 wt% to 10.0 wt%.

9. The application of an M-Sb intermetallic compound catalyst as described in claim 1 or an M-Sb intermetallic compound catalyst prepared according to any one of claims 2 to 8, characterized in that, The M-Sb intermetallic catalyst is used for the selective hydrogenation reaction of dinitrobenzene to prepare phenylenediamine, wherein the dinitrobenzene includes o-dinitrobenzene, m-dinitrobenzene, or p-dinitrobenzene.

10. The application according to claim 9, characterized in that, The conditions for hydrogenation reaction are: temperature 30–60℃ and pressure 1.0–2.0 MPa.

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