M-Sb intermetallic compound catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalyst preparation, and discloses an M-Sb intermetallic compound catalyst and 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 the metal M is 3.0 wt%-10.0 wt%, and the metal M is selected from one of Pd, Pt, Rh or Ir; in the M-Sb intermetallic compound catalyst, Sb modifies active metal M with high electronegativity to form an M2Sb2 site structure of electron-deficient Sb isolated electron-rich M, and the loading amount molar ratio of the metal M to the Sb is 1: 1. The M-Sb intermetallic compound catalyst provided by the invention shows excellent performance in selective hydrogenation reaction of dinitrobenzene, can realize almost complete conversion of dinitrobenzene under a low-temperature condition, and has excellent phenylenediamine selectivity and catalytic stability at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and specifically relates to an M-Sb intermetallic compound catalyst and a preparation method and application thereof. Background Art

[0002] The hydrogenation reaction of o-, m- and p-dinitrobenzene (o-DNB, m-DNB, p-DNB) occupies an important position in the fine chemical and pharmaceutical industries. Among them, m-phenylenediamine (MPD) and p-phenylenediamine (PPD) prepared by hydrogenation of m- and p-dinitrobenzene are important raw materials for the production of m- and p-aramid fibers. Aramid fibers are widely used in aerospace, national defense, electronic communications, automobile manufacturing and environmental protection due to their excellent properties such as high temperature resistance, corrosion resistance, high strength and insulation. They are core members of modern high-performance materials. For example, m-aramid fibers are widely used in protective clothing and filter materials due to their excellent flame retardancy and high temperature resistance; p-aramid fibers are known for their ultra-high strength and modulus, and are key materials for bulletproof vests, aviation structural parts and high-strength ropes. In addition, o-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, medicines, polymer materials, rubbers and pesticides, and plays an important role as a key intermediate or auxiliary agent.

[0003] For the hydrogenation of o-, m-, and p-dinitrobenzene to prepare the corresponding phenylenediamines, the conventional precious metal catalysts (such as Pd and Pt) commonly used in the prior art show high catalytic activity, but the catalyst cost is too high due to the high precious metal content, and the temperature and pressure required for the hydrogenation reaction are high, which limits its industrial promotion. For example, "Tian Xianfeng, Liu Feng, Liu Guangqin, Research on the Application of Metaphenylenediamine in Synthesis Process [A], Process Technology, 2021, 10, 188-189" gives the use of conventional skeleton nickel catalysts, with a reaction temperature of 120-130°C and a pressure of 4.0-4.5MPa, and finally achieves a yield of 96%. Therefore, the development of new catalysts with high conversion rate, high selectivity, high stability and mild reaction conditions is an important topic of current research.

[0004] To solve this problem, the modification of Pd-based catalysts is usually carried out by introducing guest metals to regulate the spatial structure and electronic structure of the Pd active sites, thereby changing the adsorption behavior of the substrate to improve the catalytic performance. Layered double hydroxides (LDHs) are widely used as precursors for the preparation of various intermetallic compound catalysts due to their adjustable composition of the main layer plates and the easy exchange of intercalated anions. They are an effective way to modify Pd-based catalysts. However, the existing preparation process of M-Sb (metal-antimony) intermetallic compound catalysts is usually complicated and costly, and the problem of uneven distribution of active sites is prone to occur during the catalytic process, which limits their large-scale industrial application. Summary of the invention

[0005] To solve the above problems, an M-Sb intermetallic compound catalyst and a preparation method thereof are provided. The M-Sb intermetallic compound catalyst is applied to the selective hydrogenation of dinitrobenzene to prepare the corresponding phenylenediamine, has excellent catalytic activity and selectivity, and the hydrogenation reaction conditions are mild.

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

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

[0008] The present 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, preparing a magnesium aluminum nitrate solution, and preparing Mg / Al layered hydroxide by a coprecipitation method;

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

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

[0012] (4) subjecting the M / Sb / Mg / Al quaternary layered hydroxide JY to thermal reduction treatment to obtain an M-Sb intermetallic compound catalyst;

[0013] Wherein, the metal M is selected from one of Pd, Pt, Rh or Ir.

[0014] The present invention is further configured as follows: in step (1), in the magnesium aluminum nitrate solution in step (1), the molar ratio of Mg to Al ions 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 ion concentration of the metal M in the M precursor solution is 0.032 to 0.040 mol / L.

[0016] The present invention is further configured such that step (1) and step (2) are continuously performed in the same reaction place, and the temperature of the reaction system is controlled to be 55-75° C., comprising the following process:

[0017] Under stirring conditions, magnesium aluminum nitrate solution and M precursor solution are added to the precipitant in sequence, the addition rate of the two metal salt solutions is controlled to be 0.8-1.2 mL / min, and the pH value of the reaction system is controlled to be 10±1 by a pH regulator; after the addition is completed, the stirring reaction is continued for 10-20 hours, and finally the M / Mg / Al ternary layered hydroxide J is obtained by filtering, washing and drying.

[0018] The present invention is further configured as follows: in step (1), the nitrates of magnesium and aluminum are Mg(NO3)2·6H2O and Al(NO3)3·9H2O respectively; the Pd precursor is selected from one of PdCl2 and H2PdCl4; the Pt precursor is selected from one of H2PtCl6·6H2O and Pt(NO3)2; the Rh precursor is selected from one of K3RhCl6·6H2O and RhCl3·3H2O; the Ir precursor is selected from one of 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 0.3-0.5 mol / L.

[0020] The present invention is further configured such that the pH regulator is selected from a NaOH solution or a KOH solution, and the molar concentration of the pH regulator is 0.8 to 1.2 mol / L.

[0021] The present invention is further configured such that the drying conditions in step (2) are: a temperature of 80 to 150° C. and a drying time of 12 to 20 hours; preferably, the drying temperature is 100 to 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:Sb of 1:(0.9-1.2).

[0023] The present invention is further configured such that the conditions for the thermal reduction treatment in step (4) are reduction at 800-1000° C. for 3-5 hours in a H 2 / Ar atmosphere.

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

[0025] The present invention also provides an application of the M-Sb intermetallic compound catalyst or the M-Sb intermetallic compound catalyst prepared by the 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 the present invention forms an M2Sb2 site structure of electron-deficient Sb and isolated electron-rich M through the strong hybridization effect between the d orbital of the active metal M and the p orbital of the inert metal Sb at the Fermi level, which can simultaneously promote the adsorption and activation of the electrophilic nitro group in dinitrobenzene at the M site and the timely desorption of the nucleophilic amino group in phenylenediamine from the M site, thereby achieving complete conversion of the nitro group at low temperature and showing excellent amino selectivity and catalytic stability.

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

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

[0029] Compared with the prior art, the present invention has the following beneficial effects: compared with the traditional M-based catalyst, the M-Sb intermetallic compound catalyst prepared by the present invention changes the electronic structure and spatial structure of the M active site due to the introduction of the inert metal Sb, and the M site after high-temperature thermal reduction treatment is isolated by the Sb atom, which significantly improves the atomic utilization of the active component M, and effectively regulates the adsorption behavior between H2, o-DNB, m-DNB, p-DNB and the M-Sb intermetallic catalyst. The M-Sb intermetallic compound catalyst exhibits extremely excellent o-DNB, m-DNB, p-DNB conversion rates and OPD, MPD, PPD selectivity, and the reaction conditions are mild, and it can be recycled for multiple times, and has an ideal industrial application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the XRD spectrum of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention.

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

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

[0033] Figure 4 A high-angle annular dark-field scanning transmission electron microscope image of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention and a corresponding line-scan element distribution map.

[0034] Figure 5 A high-angle annular dark-field scanning transmission electron microscope image of the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention and a corresponding surface scanning element distribution map.

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

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

[0037] Figure 8 This is the adsorption configuration of m-dinitrobenzene and m-phenylenediamine on the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The present invention is described in detail and completely with specific embodiments and in conjunction with the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0039] Example 1

[0040] Preparation of Pd-Sb Intermetallic Compound Catalyst

[0041] The specific steps include:

[0042] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as magnesium aluminum nitrate solution; 0.1496 g PdCl2 and 0.141 mL concentrated hydrochloric acid were dissolved in 25 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as chloropalladic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as pH adjuster.

[0043] The precipitant was transferred to a 500 mL three-necked flask and placed in a 65°C oil bath for constant temperature treatment for 1 hour. The magnesium aluminum nitrate solution and the chloropalladic acid solution were added dropwise to the three-necked flask at a speed of 120 r / min, and a constant flow pump was used to control the feeding speed to be 1.0 mL / min. At the same time, a constant flow pump was used to add the pH regulator to control the pH of the reaction system in the three-necked flask to be constant at 10.5. After the feeding was completed, the mixture was continuously stirred at 65°C for 12 hours, then vacuum filtered, and washed several times until the pH was neutral to obtain a dark brown block solid.

[0044] (2) The dark brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pd / Mg / Al ternary LDH material, which was labeled as J1.

[0045] (3) The Pd / Mg / Al ternary LDH material J1 obtained in step (2) was mixed with 0.103 g of inert metal Sb powder and ground thoroughly to obtain a molar ratio of Pd to Sb of 1:1 to obtain a Pd / Sb / Mg / Al quaternary LDH material, labeled J1Y1.

[0046] (4) The quaternary layered hydroxide J1Y1 prepared in step (3) was reduced at 900° C. in a 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%, which was labeled J1Y1-900.

[0047] Example 2

[0048] Preparation of Pd-Sb Intermetallic Compound Catalyst

[0049] The specific steps include:

[0050] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as magnesium aluminum nitrate solution; 0.0756 g PdCl2 and 0.141 mL concentrated hydrochloric acid were dissolved in 25 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as chloropalladic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed by ultrasonic wave, which was recorded as pH adjuster.

[0051] The required precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65°C for 1 hour. Then, the magnesium aluminum nitrate solution and the chloropalladic acid solution were added dropwise to the three-necked flask at a speed of 120 r / min, and the flow rate was controlled to 1.0 mL / min using a constant flow pump; at the same time, a pH regulator was added using a constant flow pump to control the pH of the reaction system in the three-necked flask to be constant at 10.5. After the feeding was completed, the reaction was continued at a synthesis temperature of 65°C for 12 hours, and then vacuum filtered and washed several times until the pH was neutral to obtain a dark brown block solid.

[0052] (2) The dark brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pd / Mg / Al ternary LDH material, which was labeled as J2.

[0053] (3) The Pd / Mg / Al ternary LDH material J2 prepared in step (1) was mixed with 0.0519 g of inert metal Sb powder and ground thoroughly to obtain a molar ratio of Pd to Sb of 1:1 to obtain a Pd / Sb / Mg / Al quaternary LDH material, labeled J2Y2.

[0054] (4) The quaternary layered hydroxide J2Y2 prepared in step (3) was reduced at 900° C. in a 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%, which was labeled J2Y2-900.

[0055] Comparative Example 1

[0056] Preparation of Pd monometallic catalyst

[0057] The specific steps include:

[0058] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.1336 g PdCl2 and 0.141 mL concentrated hydrochloric acid were dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare chloropalladic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a pH regulator.

[0059] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloropalladic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH value was neutral, and a dark brown block solid was finally obtained.

[0060] (2) The dark brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pd / Mg / Al ternary LDH material, labeled as J3.

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

[0062] Example 3

[0063] Preparation of Pt-Sb Intermetallic Compound Catalyst

[0064] The specific steps include:

[0065] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave to prepare a magnesium aluminum nitrate solution. 0.437 g H2PtCl6·6H2O was dissolved in 25 mL ultrapure water and dispersed by ultrasonic wave to prepare a chloroplatinic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed by ultrasonic wave to prepare a pH regulator.

[0066] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloroplatinic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH value was neutral, and a brown block solid was finally obtained.

[0067] (2) The brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pt / Mg / Al ternary LDH material, labeled as J4.

[0068] (3) The Pt / Mg / Al ternary LDH material J4 prepared in step (2) was mixed with 0.103 g of inert metal Sb powder and ground thoroughly to obtain a molar ratio of Pt to Sb of 1:1 to obtain a Pt / Sb / Mg / Al quaternary LDH material, labeled J4Y4.

[0069] (4) The quaternary layered hydroxide J4Y4 prepared in step (3) was reduced at 900° C. in a 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%, which was labeled J4Y4-900.

[0070] Example 4

[0071] Preparation of Pt-Sb Intermetallic Compound Catalyst

[0072] The specific steps include:

[0073] (1) 7.69 g of Mg(NO3)2·6H2O and 3.75 g of Al(NO3)3·9H2O were dissolved in 50 mL of ultrapure water and dispersed by ultrasonic wave to prepare a magnesium aluminum nitrate solution; 0.0441 g of H2PtCl6·6H2O was dissolved in 25 mL of ultrapure water and dispersed by ultrasonic wave to prepare a chloroplatinic acid solution; 2.12 g of Na2CO3 powder was dissolved in 50 mL of ultrapure water and dispersed by ultrasonic wave to prepare a precipitant; 6.00 g of NaOH powder was dissolved in 150 mL of ultrapure water and dispersed by ultrasonic wave to prepare a pH regulator.

[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. At a stirring speed of 120 r / min, the magnesium aluminum nitrate solution and the chloroplatinic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added through a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH value was neutral, and finally a brown block solid was obtained.

[0075] (2) The brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pt / Mg / Al ternary LDH material, which was labeled as J5.

[0076] (3) The brown-gray block solid J5 obtained in step (1) was mixed with 0.0275 g of inert metal Sb powder and ground thoroughly to make the molar ratio of Pt to Sb be 1:1, thereby obtaining a Pt / Sb / Mg / Al quaternary LDH material, which was labeled as J5Y5.

[0077] (4) The quaternary layered hydroxide J5Y5 prepared in step (3) was reduced at 900° C. in a H 2 / 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%, which was labeled J5Y5-900.

[0078] Comparative Example 2

[0079] Preparation of Pt monometallic catalyst

[0080] The specific steps include:

[0081] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.2129 g H2PtCl6·6H2O was dissolved in 25 mL ultrapure water and dispersed by ultrasonic wave to prepare chloroplatinic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed by ultrasonic wave to prepare a pH regulator.

[0082] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloroplatinic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH value was neutral, and a brown block solid was finally obtained.

[0083] (2) The brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Pt / Mg / Al ternary LDH material, labeled as J6.

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

[0085] Example 5

[0086] Preparation of Rh-Sb Intermetallic Compound Catalyst

[0087] The specific steps include:

[0088] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.365 g K3RhCl6 was dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare potassium chlororhodiumate solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a pH regulator.

[0089] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for constant temperature treatment for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and potassium chlororhodate solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and a dark brown block solid was finally obtained.

[0090] (2) The dark brown solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Rh / Mg / Al ternary LDH material, which was labeled as J7.

[0091] (3) The Rh / Mg / Al ternary LDH material J7 prepared in step (2) was mixed with 0.103 g of inert metal Sb powder and ground thoroughly to make the molar ratio of Rh to Sb be 1:1 to obtain a Rh / Sb / Mg / Al quaternary LDH material, which was labeled J7Y7.

[0092] (4) The quaternary layered hydroxide J7Y7 prepared in step (3) was reduced at 900° C. in a H 2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Rh-Sb intermetallic compound catalyst with a Rh loading of about 9%, which was labeled J7Y7-900.

[0093] Example 6

[0094] Preparation of Rh-Sb Intermetallic Compound Catalyst

[0095] The specific steps include:

[0096] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution. 0.1913 g K3RhCl6 was dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare potassium chlororhodiumate solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a pH regulator.

[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. At a stirring speed of 120 r / min, the magnesium aluminum nitrate solution and the potassium chlororhodate solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added through a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and finally a dark brown block solid was obtained.

[0098] (2) The dark brown solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Rh / Mg / Al ternary LDH material, which was labeled as J8.

[0099] (3) The dark brown block solid J8 obtained in step (1) was mixed with 0.0538 g of inert metal Sb powder and ground thoroughly to make the molar ratio of Rh to Sb be 1:1, thereby obtaining a Rh / Sb / Mg / Al quaternary LDH material, which was labeled as J8Y8.

[0100] (4) The quaternary layered hydroxide J8Y8 prepared in step (3) was reduced at 900° C. in a H 2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain a Rh-Sb intermetallic compound catalyst with a Rh loading of about 5%, which was labeled J8Y8-900.

[0101] Comparative Example 3

[0102] Preparation of Rh monometallic catalyst

[0103] The specific steps include:

[0104] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.3373 g K3RhCl6 was dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare potassium chlororhodiumate solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a pH regulator.

[0105] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for constant temperature treatment for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and potassium chlororhodate solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and a dark brown block solid was finally obtained.

[0106] (2) The dark brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain a Rh / Mg / Al ternary LDH material, which was labeled as J9.

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

[0108] Example 7

[0109] Preparation of Ir-Sb Intermetallic Compound Catalyst

[0110] The specific steps include:

[0111] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed evenly by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.435 g H2IrCl6·6H2O was dissolved in 25 mL ultrapure water and dispersed evenly by ultrasonic wave to prepare chloroiridic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed evenly by ultrasonic wave to prepare precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed evenly by ultrasonic wave to prepare pH regulator.

[0112] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for constant temperature treatment for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloroiridic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and a brown block solid was finally obtained.

[0113] (2) The brown-gray block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain an Ir / Mg / Al ternary LDH material, which was labeled as J10.

[0114] (3) The Ir / Mg / Al ternary LDH material J10 prepared in step (2) was mixed with 0.103 g of inert metal Sb powder and ground thoroughly to make the molar ratio of Ir to Sb be 1:1 to obtain an Ir / Sb / Mg / Al quaternary LDH material, which was labeled J10Y10.

[0115] (4) The quaternary layered hydroxide J10Y10 prepared in step (3) was reduced at 900° C. in a H 2 / 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%, which was labeled J10Y10-900.

[0116] Example 8

[0117] Preparation of Ir-Sb Intermetallic Compound Catalyst

[0118] The specific steps include:

[0119] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution. 0.0441 g H2IrCl6·6H2O was dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare chloroiridic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare pH regulator.

[0120] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for constant temperature treatment for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloroiridic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and a brown block solid was finally obtained.

[0121] (2) The brown-gray block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain an Ir / Mg / Al ternary LDH material, which was labeled as J11.

[0122] (3) The brown-gray block solid J11 obtained in step (1) was mixed with 0.028 g of inert metal Sb powder and ground thoroughly to make the molar ratio of Ir to Sb be 1:1, thereby obtaining an Ir / Sb / Mg / Al quaternary LDH material, which was labeled as J11Y11.

[0123] (4) The quaternary layered hydroxide J11Y11 prepared in step (3) was reduced at 900° C. in a H 2 / 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%, which was labeled J11Y11-900.

[0124] Comparative Example 4

[0125] Preparation of Ir monometallic catalysts

[0126] The specific steps include:

[0127] (1) 7.69 g Mg(NO3)2·6H2O and 3.75 g Al(NO3)3·9H2O were dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare magnesium aluminum nitrate solution; 0.2148 g H2IrCl6·6H2O was dissolved in 25 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare chloroiridic acid solution; 2.12 g Na2CO3 powder was dissolved in 50 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a precipitant; 6.00 g NaOH powder was dissolved in 150 mL ultrapure water and dispersed uniformly by ultrasonic wave to prepare a pH regulator.

[0128] The precipitant was transferred to a 500 mL three-necked flask and placed in an oil bath at 65 ° C for constant temperature treatment for 1 hour. At a stirring speed of 120 r / min, magnesium aluminum nitrate solution and chloroiridic acid solution were added dropwise to the three-necked flask in turn, and the feeding rate was controlled to be 1.0 mL / min using a constant flow pump. At the same time, a pH regulator was added by a constant flow pump to ensure that the pH value of the reaction system was constant at 10.5. After the feeding was completed, stirring was continued at a synthesis temperature of 65 ° C for 12 hours. After the reaction was completed, vacuum filtration was performed, and the reaction product was washed several times until the pH was neutral, and a brown block solid was finally obtained.

[0129] (2) The brown block solid obtained in step (1) was dried at 110° C. for 12 hours, and then fully mechanically ground to obtain an Ir / Mg / Al ternary LDH material, which was labeled as J12.

[0130] (3) The ternary layered hydroxide J12 prepared in step (2) was reduced at 900° C. in a H 2 / Ar atmosphere (volume ratio of 1:4) for 3 hours to obtain an Ir monometallic catalyst with an Ir loading of approximately 9%, which was labeled J12-900.

[0131] Control group

[0132] The Pd-Sn intermetallic compound catalyst provided by patent CN118059957A is used, and the loading amount of Pd is 9%.

[0133] Characterization of M-Sb intermetallic compound catalysts

[0134] The M-Sb intermetallic compound catalysts prepared in the above examples were characterized. Figure 1 As shown, the XRD spectrum results of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 show that the intermetallic compound synthesized by the present invention has a distinct crystal structure, and the diffraction intensity of the (102) crystal plane is the highest, indicating that this crystal plane accounts for the largest proportion in the surface distribution of the medium entropy alloy particles. Figure 2 It shows that the Pd-Sb intermetallic compound catalyst J1Y1-900 has clear lattice fringes, which also verifies Figure 1 The XRD results in Figure 4 prove that the catalyst has an obvious crystalline structure. Figure 3 The particle size diagram results show that the synthesized Pd-Sb intermetallic compound catalyst has uniform particle size, with an average particle size of about 10 nm. Figure 4 The results show that Pd and Sb elements are evenly distributed. Figure 5 The high-angle annular dark field scanning transmission electron microscopy image and the corresponding surface scanning element distribution map of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 show that the Pd, Sb, Mg, and Al elements are uniformly distributed. Figure 4 The analysis results are consistent with those in .

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

[0136] Figure 8 Schematic diagram of the catalytic hydrogenation of m-dinitrobenzene using the Pd-Sb catalyst J1Y1-900 prepared in Example 1 of the present invention. A unique Pd2Sb2 site structure of electron-deficient Sb isolated electron-rich Pd is formed in the PdSb catalyst, which simultaneously promotes the adsorption and activation of the electrophilic nitro group in m-dinitrobenzene on the Pd site and the timely desorption of the nucleophilic amino group in m-phenylenediamine from the Pd site, thereby achieving complete conversion of the nitro group at low temperature, demonstrating excellent amino selectivity and catalytic stability.

[0137] Test Example 1

[0138] Evaluation of o-DNB Catalytic Hydrogenation Performance over M-Sb Intermetallic Compound Catalysts

[0139] The catalytic hydrogenation activity of o-DNB was evaluated using the M-Sb intermetallic compound catalysts prepared in Examples 1 to 8 and the M monometallic catalysts prepared in Comparative Examples 1 to 4. The evaluation of the o-DNB hydrogenation reaction performance was carried out in a high-pressure hydrogenation reactor of Yanzheng Instruments, with methanol as the solvent, a reaction 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 25mL of o-DNB solution to the inner tank of a 100mL reactor. Before the reaction starts, continue to pass argon gas and observe whether the pressure is constant to ensure that the equipment is airtight. Then, under an inert atmosphere, raise the temperature to the temperature required for the reaction. After the temperature stabilizes, switch the inert gas to 1.15MPa hydrogen and start stirring, at which point the reaction begins. Maintain constant temperature and pressure and react for 2 hours. After the reaction is completed, sample about 1.5mL from the sampling port. The components of the reactants and products were 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 , to evaluate the catalytic performance of the catalyst prepared by the present invention for the selective hydrogenation of o-DNB to OPD, the calculation formula is as follows:

[0142]

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

[0144] Table 1 Catalytic performance evaluation results of catalysts

[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 can be seen from Table 1, the Pd monometallic catalyst prepared in Comparative Example 1 shows extremely high activity in the conversion of o-DNB, but the OPD selectivity is only 21.5%, and most of the product still stays on the monoamino intermediate o-NA. However, when an appropriate amount of Sb element 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% when o-DNB is completely converted. When the Pd loading in the Pd-Sb intermetallic catalyst prepared in Example 2 is 5%, its OPD selectivity for catalytic hydrogenation reaction also reaches 98.8%. It is easy for those skilled in the art to understand that the Pd-Sb intermetallic compound catalyst prepared by the present invention effectively optimizes the surface structure of the Pd-Sb site through the pd orbital hybridization between Sb and Pd, so that the Pd-based catalyst has a higher OPD selectivity under low temperature conditions.

[0147] Further studies have found that by introducing the inert component Sb into the 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, and these catalysts also exhibit excellent low-temperature selective hydrogenation performance. A horizontal comparison of these eight M-Sb intermetallic compound catalysts showed that the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 had the best performance. Under the condition of complete conversion of o-DNB, the OPD selectivity was as high as 99.1%, indicating that the synergistic catalytic effect between the Pd sites isolated by the Sb sites was the most effective. In summary, the M-Sb intermetallic compound catalyst prepared by the present invention exhibits excellent low-temperature hydrogenation activity and OPD selectivity, providing an effective way for the industrial application of intermetallic compound catalysts.

[0148] Test Example 2

[0149] Evaluation of the stability of o-DNB catalytic hydrogenation over M-Sb intermetallic compound catalysts

[0150] The stability of the Pd-Sb intermetallic compound catalyst prepared in Example 1 was evaluated for the selective hydrogenation of o-DNB. According to the catalyst performance evaluation method of Example 1, the catalyst and the product after the reaction were centrifuged, and the catalyst was continuously put into the next batch of reactions under the same conditions, and the cycle was repeated five times. The results are shown in Table 2:

[0151] Table 2 Evaluation of J1Y1-900 catalytic hydrogenation stability

[0152] Cycle times <![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] It can be seen from the data in Table 2 that after 5 cycles, the conversion rate of o-DNB of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 was always maintained at 100%, and the selectivity of OPD was also stable at more than 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 monometallic catalysts prepared in Examples 1 to 8 and Comparative Examples 1 to 4. The evaluation of the m-DNB hydrogenation reaction performance was carried out in a high-pressure hydrogenation reactor of a Yanzheng instrument, with ethanol as the solvent, 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 as follows: the same as those in Test Example 1, except that the reaction raw material is 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 selective S m-NA and product MPD selectivity S MPD , to evaluate the catalytic performance of the catalyst prepared by the present invention for the reaction of selective hydrogenation of m-DNB to MPD, the catalytic performance evaluation results of the catalysts prepared in various embodiments and comparative examples are shown in Table 3 below:

[0158] Table 3 Catalytic performance evaluation results of catalysts

[0159] serial number catalyst Reaction temperature / ℃ <![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 can be seen from Table 1, the Pd monometallic catalyst prepared in Comparative Example 1 shows extremely high activity in the conversion of m-DNB, but the MPD selectivity is only 19.5%, and most of the products still remain on the monoamino intermediate m-NA. However, when an appropriate amount of Sb element 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% when m-DNB is completely converted; when the Pd loading in the Pd-Sb intermetallic compound catalyst prepared in Example 2 is 5%, the MPD selectivity of the catalytic hydrogenation reaction also reaches 99.2%. It is easy for those skilled in the art to understand that the Pd-Sb intermetallic compound catalyst prepared in the present invention effectively optimizes the surface structure of the Pd-Sb site through the pd orbital hybridization between Sb and Pd, so that the Pd-based catalyst has a 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 a similar M-Sb site structure, as shown in Examples 3 to 8. These catalysts also exhibit excellent low-temperature selective hydrogenation performance.

[0162] Test Example 4

[0163] Evaluation of the stability 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. According to the catalyst performance evaluation method of Example 1, the catalyst and the product after the reaction were centrifuged, and the catalyst was continuously put into the next batch of reactions under the same conditions, and the cycle was repeated five times. The results are shown in Table 4:

[0165] Table 4 Evaluation of J1Y1-900 catalytic hydrogenation stability

[0166] Cycle times <![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] It can be seen from the data in Table 4 that after 5 cycles, the conversion rate of m-DNB of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 was always maintained at 100%, and the selectivity of MPD was also stable at more than 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 monometallic catalysts prepared in Examples 1 to 8 and Comparative Examples 1 to 4. The evaluation of the p-DNB hydrogenation reaction performance was carried out in a high-pressure hydrogenation reactor of a Yanzheng instrument, with ethanol as the solvent, a reaction concentration of 16 mg (p-DNB) / mL (tetrahydrofuran), 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.

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

[0171] The p-DNB conversion rate C of the above M single metal catalyst and M-Sb intermetallic compound catalyst was tested. p-DNB , intermediate p-NA selective S p-NA and product PPD selectivity S PPD , to evaluate the catalytic performance of the catalyst prepared by the present invention for the reaction of selective hydrogenation of p-DNB to PPD, the catalytic performance evaluation results of the catalysts prepared in various embodiments and comparative examples are shown in Table 5 below:

[0172] Table 5 Catalytic performance evaluation results of catalysts

[0173]

[0174]

[0175] As can be seen from Table 5, the Pd monometallic catalyst prepared in Comparative Example 1 shows extremely high activity in the conversion of p-DNB, but the PPD selectivity is only 20.8%, and most of the product still stays on the monoamino intermediate p-NA. However, when an appropriate amount of Sb element 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 99.7% PPD selectivity when p-DNB is fully converted; when the Pd loading in the Pd-Sb intermetallic compound catalyst prepared in Example 2 is 5%, the PPD selectivity of the catalytic hydrogenation reaction also reaches 99.2%. It is easy for those skilled in the art to understand that the Pd-Sb intermetallic compound catalyst prepared in the present invention effectively optimizes the surface structure of the Pd-Sb site through the pd orbital hybridization between Sb and Pd, so that the Pd-based catalyst has a 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 a similar M-Sb site structure, as shown in Examples 3 to 8. These catalysts also exhibit excellent low-temperature selective hydrogenation performance.

[0177] Test Example 6

[0178] Evaluation of the stability 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. According to the catalyst performance evaluation method of Example 1, the catalyst and the product after the reaction were centrifuged, and the catalyst was continuously put into the next batch of reactions under the same conditions, and the cycle was repeated five times. The results are shown in Table 6:

[0180] Table 6 Evaluation of J1Y1-900 catalytic hydrogenation stability

[0181] Cycle times <![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] It can be seen from the data in Table 6 that after 5 cycles, the conversion rate of p-DNB of the Pd-Sb intermetallic compound catalyst J1Y1-900 prepared in Example 1 was always maintained at 100%, and the selectivity of PPD was also stable at more than 95.9%, which indicates 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 their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

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

1.

2. A method for preparing a M-Sb intermetallic compound catalyst, characterized in that: The steps include: (1) using magnesium and aluminum nitrates as carrier precursors, preparing a magnesium aluminum nitrate solution, and preparing Mg / Al layered hydroxide by a coprecipitation method; (2) adding the M precursor solution to the Mg / Al layered hydroxide suspension prepared in step (1), performing ion exchange, filtering, washing and drying to obtain the M / Mg / Al ternary layered hydroxide J; (3) grinding and mixing the M / Mg / Al ternary layered hydroxide J and the inert metal Sb powder to obtain the M / Sb / Mg / Al quaternary layered hydroxide JY; (4) subjecting the M / Sb / Mg / Al quaternary layered hydroxide JY to thermal reduction treatment to obtain an M-Sb intermetallic compound catalyst; Wherein, the metal M is selected from one of Pd, Pt, Rh or Ir.

3. The method for preparing a 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 a M-Sb intermetallic compound catalyst according to claim 2, characterized in that: Step (1) and step (2) are continuously carried out in the same reaction place, and the temperature of the reaction system is controlled to be 55-75° C., comprising the following process: under stirring conditions, magnesium aluminum nitrate solution and M precursor solution are sequentially added to the precipitant, the addition rate of the two metal salt solutions is controlled to be 0.8-1.2 mL / min, and the pH value of the reaction system is controlled to be 10±1 by a pH regulator; after the addition is completed, the stirring reaction is continued for 10-20 hours, and finally the M / Mg / Al ternary layered hydroxide J is obtained by filtering, washing and drying.

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

6. The method for preparing a 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:(0.9-1.2).

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

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

9. Use of the M-Sb intermetallic compound catalyst according to claim 1 or the M-Sb intermetallic compound catalyst prepared by the preparation method 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, and the dinitrobenzene includes o-dinitrobenzene, m-dinitrobenzene or p-dinitrobenzene.

10. The use according to claim 9, characterized in that: The conditions for the hydrogenation reaction are: temperature 30-60°C and pressure 1.0-2.0MPa.

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