A molecular sieve catalyst double-modified with a multi-metal oxide and platinum nanoparticles, and a preparation method and application thereof

Abstract

The present invention discloses a molecular sieve catalyst double-modified with a multi-metal oxide and platinum nanoparticles, and a preparation method and application thereof. The molecular sieve catalyst comprises FeCoO x -modified molecular sieve support and noble metal platinum nanoparticles uniformly embedded in the surface defect sites of the molecular sieve support; FeCoO x In the FeCoO x -modified molecular sieve support, Fe and Co are uniformly distributed in the pores of the molecular sieve support in the form of an oxide with an equal atomic ratio, and the Pt nanoparticles are embedded in the surface defect sites of the molecular sieve support and form a Schottky heterojunction structure with FeCoO. The Pt in the catalyst of the present invention has high activity and high selectivity for the hydrogenation of halogenated nitrobenzene to halogenated aniline under the action of Fe and Co promoters. At the same time, the preparation of the catalyst in the present invention innovatively uses a one-step instantaneous in-situ reduction method, which is simple and easy to operate, and provides a new idea for the catalyst design of a class of reactions for the highly selective preparation of corresponding halogenated anilines from halogenated nitrobenzenes.

Description

Technical Field

[0001] The present invention belongs to the technical fields of thermal catalysis technology and the preparation and application of catalysts, and particularly relates to a molecular sieve catalyst double-modified by a multi-metal oxide and platinum nanoparticles, and a preparation method and application thereof. Background Art

[0002] Halogenated anilines are widely used in the synthesis of fine chemicals such as pharmaceuticals, pesticides, and fuels, and are important organic chemical intermediates. Halogenated anilines are usually prepared by the reduction synthesis method of halogenated aromatic compounds, including chemical reduction methods such as sulfide reduction method, iron powder reduction method, and hydrazine hydrate reduction method. Although the technology is mature, it causes serious environmental pollution and high energy consumption. Compared with these methods, the catalytic hydrogenation method has less pollution, low energy consumption, and low cost, and thus has attracted much attention. How to improve the catalytic activity and selectivity of the catalytic hydrogenation of halogenated nitrobenzene to prepare halogenated anilines is a huge challenge in research and application. Among them, noble metals such as Pt, Pd, Au, and Rh are widely used in the selective hydrogenation of halogenated nitrobenzenes due to their excellent hydrogen (H2) dissociation ability. However, in the reaction process, the dehalogenation reaction is difficult to avoid. To achieve high catalytic activity for the hydrogenation of halogenated nitrobenzenes and selectivity for halogenated anilines, it is necessary to limit or completely inhibit the dehalogenation reaction to the greatest extent. Therefore, the development of highly selective catalysts is crucial.

[0003] Supported platinum-based catalysts are widely used in green catalytic hydrogenation reactions due to their mild reaction conditions and high activity. However, bromonitrobenzene is extremely prone to hydrogenolysis dehalogenation side reactions during the catalytic hydrogenation reaction, resulting in low selectivity of the target product. Therefore, in the selective hydrogenation of bromonitrobenzene, the development of supported platinum-based catalysts with high activity and high selectivity is the focus of this research direction. For supported catalysts, many researchers have carried out relevant research on the influencing factors of the carrier on the catalytic performance, such as: 1) the size effect of the supported metal nanoparticles; 2) the activation of the substrate by the carrier; 3) the structure sensitivity of the strong metal-carrier interaction, etc. These influencing factors determine the selectivity of halogenated anilines. Therefore, the development of highly selective and highly active catalysts is crucial. Summary of the Invention

[0004] The main object of the present invention is to provide a molecular sieve catalyst double-modified by a multi-metal oxide and platinum nanoparticles, and a preparation method and application thereof, so as to overcome the deficiencies of the prior art.

[0005] To achieve the foregoing invention object, the technical solutions adopted by the present invention include:

[0006] A molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles, comprising a molecular sieve carrier modified with a multi-metal oxide in the pore structure and noble metal nanoparticles uniformly embedded in the defect sites on the surface of the molecular sieve carrier; wherein, the molecular sieve carrier modified with the multi-metal oxide in the pore structure is FeCoO x modified molecular sieve carrier, and in the FeCoO x modified molecular sieve carrier, Fe and Co are uniformly distributed in the pores of the molecular sieve carrier in the form of an oxide with an equal atomic ratio. The noble metal nanoparticles are Pt nanoparticles and are embedded in the defect sites on the surface of the molecular sieve carrier and form a Schottky heterojunction structure with FeCoO x .

[0007] Furthermore, the particle size of the nano-platinum particles is 5-12 nm.

[0008] Furthermore, the content of nano-platinum particles in the molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles is 0.15 wt% to 1.0 wt%;

[0009] Furthermore, the atomic ratio of Pt:Fe:Co in the molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles is 1:0.4-1.6:0.4-1.6.

[0010] Furthermore, the FeCoO x modified molecular sieve carrier is an FeCoO x modified SSZ-13 carrier

[0011] A preparation method of a molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles, comprising the following steps: mixing a platinum source, an iron source, a cobalt source, a reducing agent and an SSZ-13 carrier for reaction, and instantaneously in-situ reducing in one step to obtain a molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles.

[0012] Furthermore, specifically, it includes the following steps:

[0013] Mix the SSZ-13 carrier with a solvent, ultrasonicate and stir to form a first mixed solution, then add the platinum source, iron source, and cobalt source and stir to mix to form a second mixed solution; add a reducing agent to the second mixed solution and stir thoroughly for reaction, and then perform rotary evaporation, washing, and drying treatments to obtain a molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles.

[0014] Furthermore, the platinum source is an inorganic compound of platinum, which is any one or a combination of chloroplatinic acid, potassium chloroplatinate, and sodium chloroplatinate;

[0015] and / or, the iron source is any one or a combination of iron bromide, ferrous bromide, and iron nitrate;

[0016] and / or, the cobalt source is cobalt bromide and / or cobalt nitrate;

[0017] and / or, the solvent is ethanol;

[0018] and / or, the reducing agent is any one or a combination of sodium borohydride, lithium borohydride, and sodium thiosulfate.

[0019] Furthermore, the temperature of the rotary evaporation treatment is 30 - 70 °C; the temperature of the drying treatment is 30 - 60 °C.

[0020] Application of a molecular sieve-supported catalyst dual-modified with a multi-metal oxide and platinum nanoparticles in the catalytic hydrogenation of halogenated nitrobenzene to prepare halogenated aniline.

[0021] In the present invention, the preparation method of the molecular sieve catalyst dual-modified with a multi-metal oxide and platinum nanoparticles innovatively adopts a one-step instantaneous in-situ reduction method, which is simple and easy to implement. The method in the present invention is a tandem synthesis of an instantaneous reduction and deposition method: the non-noble metal Fe and Co species are reduced to low-valence oxide species (FeCoO x ), and are dispersed and adsorbed in the internal pore channels of the SSZ-13 molecular sieve carrier through electrostatic interaction. The noble metal Pt is then reduced to form Pt nanoparticles anchored on the surface defect sites of the SSZ-13 molecular sieve modified by FeCoO x , and forms a Schottky heterojunction structure with FeCoO x . Different chemical compositions and crystal structures in the heterostructure will cause lattice strains such as stretching and compression, affect the adsorption energy of the sites for intermediates, and improve the catalytic activity of the material.

[0022] In the present invention, the advantages of the catalyst structure are that, on the one hand, the non-noble metal oxide FeCoO x stabilizes the active Pt nanoparticles in terms of geometric structure to a certain extent due to the modification of the SSZ-13 molecular sieve carrier; on the other hand, the Schottky heterojunction structure formed by the Pt nanoparticles and FeCoO x results in electron transfer, reducing the electron density of Pt, promoting the heterolytic dissociation of hydrogen, and H + and H - have stronger hydrogenation activity. By regulating the electronic structure of the Pt nanoparticles and the adsorption behavior of the substrate, the performance is optimized based on the synergistic effect.

[0023] The Pt in the catalyst of the present invention has high activity and high selectivity for the hydrogenation of halogenated nitrobenzene to halogenated aniline under the action of Fe and Co promoters. At the same time, the preparation of the catalyst in the present invention innovatively uses a one-step instantaneous in-situ reduction method, which is simple and easy to implement, providing a new idea for the catalyst design of a class of reactions for the selective preparation of corresponding halogenated anilines from halogenated nitrobenzenes.

[0024] In the present invention, the catalytic test is used to evaluate the efficacy of the catalyst. The reaction conditions are an atmospheric pressure H2 atmosphere and a reaction temperature of 40 °C.

[0025] The design of the molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles in the present invention will be further improved in the selective hydrogenation of halo nitrobenzene. This is because there is a significant synergistic effect between the Pt particles and the non-noble metal oxide species in the carrier, and the influence of the carrier on the catalytic effect can be controlled by changing the input amounts of Fe and Co. The modification of the carrier by metal oxides effectively regulates the molecular sieve-supported catalyst to have high activity and excellent selectivity in the selective hydrogenation of halo nitrobenzene.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) In the molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles in the present invention, the strong interaction between the Pt nanoparticles and the SSZ-13 modified with multi-metal oxides improves the adsorption ability of the reaction substrate and the adsorption and dissociation ability of H2, thereby improving the catalytic activity;

[0028] (2) In the molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles provided in the present invention, the nano-scale Pt particles are dispersed on the surface defect sites of the SSZ-13 molecular sieve, effectively reducing the dosage of the noble metal platinum, saving costs, and at the same time, Pt and FeCoO x form a Schottky heterojunction structure, reducing the mobility of nano-Pt and preventing the formation of large particles of Pt, thereby enhancing the catalytic effect;

[0029] (3) The FeCoO x modified SSZ-13 carrier in the molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles in the present invention changes the electron transport channel and the substrate adsorption configuration, improving the selectivity of the reaction for hydrogenating halo nitrobenzene to halo aniline. At the same time, the innovative one-step instantaneous reduction method is adopted in the present invention, and the experimental operation is simple and easy.

[0030] (4) Fe and Co oxides have rich valence changes and can flexibly adjust the electronic structure of the Pt active site. In addition, Fe and Co oxide species can also adsorb the electrophilic reaction substrate halo nitrobenzene, further enhancing the activity. Description of the Drawings

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is the transmission electron microscope image of the Pt / SSZ-13 catalyst prepared in Comparative Example 2 of the present invention;

[0033] Figure 2 It is the Pt-FeO x prepared in Comparative Example 3 of the present invention / SSZ-13 catalyst's transmission electron microscope image;

[0034] Figure 3 It is the Pt-FeCoO prepared in Example 1 of the present invention x / SSZ-13 catalyst's transmission electron microscope image;

[0035] Figure 4 It is the Pt-FeCoO prepared in Example 1 of the present invention x / SSZ-13's element mapping image;

[0036] Figure 5 It is the schematic diagram of the principle of the present invention. Detailed implementation manners

[0037] The following further elaborates in detail on the technical solutions of the present invention in combination with several preferred embodiments and the accompanying drawings. These embodiments are implemented on the premise of the technical solutions of the invention, and detailed implementation manners and specific operation procedures are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0038] The experimental materials used in the following embodiments can be obtained from conventional biochemical reagent companies without special instructions.

[0039] In the catalyst tests in the embodiments related to the present invention, 3-bromonitrobenzene is used as the model substrate molecule for halogenated nitrobenzenes. 3-bromonitrobenzene is a typical halogenated nitrobenzene. However, the application field of this catalyst can be directed to the selective hydrogenation field of other halogenated nitrobenzenes.

[0040] Calculation method for the selectivity of preparing 3-bromoaniline from 3-bromonitrobenzene: Analyze the products by gas chromatography, and the content of 3-bromoaniline in the products based on the relative correction factor is the selectivity.

[0041] Comparative Example 1

[0042] A preparation process of a Pt / SiO2 catalyst involved in this comparative example includes the following steps:

[0043] (1) Mix SiO2 and ethanol, ultrasonicate and stir evenly for 10 min to prepare suspension A.

[0044] (2) Add a certain amount of chloroplatinic acid (controlling the Pt loading to be 0.4 wt%) to suspension A, stir for 15 min to disperse evenly to form suspension B.

[0045] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir thoroughly for 2 h until the reaction occurs completely to form suspension C.

[0046] (4) Rotavaporize the reaction suspension C to remove the solvent, with the reaction temperature being 70 °C, cool to room temperature, wash the precipitate with ethanol, and dry at 60 °C to obtain the Pt / SiO2 catalyst.

[0047] Comparative Example 2

[0048] A preparation process of a Pt / SSZ-13 catalyst involved in this comparative example includes the following steps:

[0049] The operation steps and raw material dosages are the same as those in Comparative Example 1, the difference is that SSZ-13 is used as the carrier to replace SiO2 to obtain the Pt / SSZ-13 catalyst. The transmission electron micrograph of the Pt / SSZ-13 catalyst is as Figure 1 shown, and it can be found from Figure 1 that Pt is in the form of nanoparticle structure.

[0050] Comparative Example 3

[0051] A preparation process of a Pt-FeO x / SSZ-13 catalyst (Pt1-(Fe 0.75 O x )) / SSZ-13) includes the following steps (except for the additional iron source, the dosages of the remaining raw materials in the preparation process are the same as those in Comparative Example 2):

[0052] (1) Mix the SSZ-13 carrier and ethanol, ultrasonicate and stir evenly for 10 min to prepare suspension A;

[0053] (2) Add a certain amount of chloroplatinic acid and iron bromide to suspension A, stir evenly for 15 min to form suspension B (the atomic ratio of Pt:Fe is 1:1);

[0054] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir thoroughly for 2 h until the reaction occurs completely to form suspension C;

[0055] (4) Rotate evaporate the suspension C to remove the solvent to obtain the reaction product D, with the reaction temperature being 70 °C;

[0056] (5) Cool the reaction product D to room temperature, wash it with ethanol (there is a certain loss during the washing of non-noble metal elements), and dry it at 60 °C to obtain the Pt1-(Fe 0.75 O x ) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe is 1:0.75, and the transmission electron micrograph of the Pt1-(Fe 0.75 O x ) / SSZ-13 catalyst is as shown in Figure 2 . It can be found from Figure 2 that the introduction of Fe does not cause the structural collapse of the nanoparticles, and they are still nanoparticles, which is quite comparable to Pt / SSZ-13.

[0057] Comparative Example 4

[0058] A Pt-CoO x / SSZ-13 catalyst (Pt1-(Co 0.75 O x ) / SSZ-13) involved in this example has a preparation process including the following steps (except for the additional cobalt source, the dosages of the other raw materials in the preparation process are the same as those in Comparative Example 2):

[0059] (1) Mix the SSZ-13 support and ethanol, ultrasonically treat and stir evenly for 10 min to prepare suspension A;

[0060] (2) Add a certain amount of chloroplatinic acid and cobalt bromide to suspension A and stir evenly for 15 min to form suspension B (the atomic ratio of Pt:Co is 1:1);

[0061] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir thoroughly for 2 h until the reaction is complete to form suspension C;

[0062] (4) Rotate evaporate the suspension C to remove the solvent to obtain the reaction product D, with the reaction temperature being 70 °C;

[0063] (5) Cool the reaction product D to room temperature, wash it with ethanol (there is a certain loss during the washing of non-noble metal elements), and dry it at 60 °C to obtain the Pt1-(Co 0.75 O x ) / SSZ-13 catalyst, where the atomic ratio of Pt:Co is 1:0.75.

[0064] Comparative Example 5

[0065] A Pt-FeCoO x / SiO2 (Pt1-(Fe 0.7 Co 0.7 O x ) / SiO2) catalyst preparation process includes the following steps (except for the additional cobalt source and iron source, the dosage of the rest of the raw materials in the preparation process is the same as that in Comparative Example 2, and the dosage of SiO2 is the same as that in Comparative Example 1):

[0066] (1) Mix SiO2 and ethanol, ultrasonicate and stir evenly for 10 min to prepare suspension A;

[0067] (2) Add a certain amount of chloroplatinic acid, iron bromide, and cobalt bromide to solution A, and stir evenly for 15 min to form suspension B (Pt:Fe:Co atomic ratio is 1:1:1);

[0068] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir well for 2 h until the reaction is complete, and form suspension C;

[0069] (4) Rotavapor suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C;

[0070] (5) Cool reaction product D to room temperature, wash with ethanol (there is a certain loss during the washing of non-noble metal elements), and dry at 60 °C to obtain Pt1-(Fe 0.7 Co 0.7 O x ) / SiO2 catalyst, where the Pt:Fe:Co atomic ratio is 1:0.7:0.7.

[0071] Comparative Example 6

[0072] A Pt1-Fe 0.7 -Co 0.7 / SSZ-13 (Fe and Co species exist in the metallic state) catalyst preparation process includes the following steps:

[0073] (1) Dissolve a certain amount of ferric chloride hexahydrate in water to prepare solution A; dissolve a certain amount of cobalt chloride hexahydrate in water to prepare solution B; dissolve a certain amount of chloroplatinic acid hexahydrate in water to prepare solution C;

[0074] (2) Slowly drop solution A and solution B onto the SSZ-13 catalyst successively, and keep stirring for 15 min;

[0075] (3) Place the SSZ-13 with the aqueous solution of Fe and Co metal salts added at 80 o °C for 2 h for drying, and grind to obtain solid A;

[0076] (3) Solid A is placed in a muffle furnace at 550 oCalcine at 3 h to obtain solid B;

[0077] (4) Reduce solid B in a H2 / Ar mixed gas at 700 o °C for 3 h to obtain solid C;

[0078] (5) Slowly drip solution C into solid C, keep stirring for 15 min, then place it at 80 o °C for 2 h for drying, and obtain solid D after grinding;

[0079] (6) Calcinate solid D in a muffle furnace at 550 o °C for 3 h to obtain solid E;

[0080] (7) Reduce solid E in a H2 / Ar mixed gas at 350 o °C for 3 h; obtain Pt1-Fe 0.7 -Co 0.7 / SSZ-13, where the atomic ratio of Pt:Fe:Co is 1:0.7:0.7, and Pt, Fe, and Co are all in the metallic state.

[0081] Example 1

[0082] A preparation process of a Pt-FeCoO x / SSZ-13 catalyst (Pt1-(Fe 0.7 Co 0.7 O x ) / SSZ-13) includes the following steps (the raw material dosages in the preparation process are the same as those in Comparative Example 5, and the SSZ-13 support dosage is the same as that in Comparative Example 2):

[0083] (1) Mix the SSZ-13 support and ethanol, ultrasonically stir for 10 min to make it uniform, and prepare suspension A;

[0084] (2) Add a certain amount of chloroplatinic acid, iron bromide, and cobalt bromide to solution A, stir evenly for 15 min to form suspension B (the atomic ratio of Pt:Fe:Co is 1:1:1);

[0085] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir thoroughly for 2 h until the reaction is complete, and form suspension C;

[0086] (4) Rotate evaporate suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C;

[0087] (5) Cool reaction product D to room temperature, wash it with ethanol (there is a certain loss of non-precious metal elements during washing), and dry it at 60 °C to obtain Pt1-(Fe 0.7 Co 0.7 Ox ) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe:Co is 1:0.7:0.7, and the average particle size of Pt in the catalyst is 10.2 nm. Figure 3 is the transmission electron microscope image of the Pt-FeCoO x / SSZ-13 catalyst prepared in this example; Figure 4 is the mapping image of the Pt-FeCoO x / SSZ-13 prepared in this example. It can be seen from the figure that the nanoparticles are evenly dispersed. The principle of the present invention is as Figure 5 shown. In the molecular sieve support modified by FeCoO x , Fe and Co are evenly distributed in the pores of the molecular sieve support in the form of oxides with equal atomic ratios. Pt nanoparticles are embedded in the surface defect sites of the molecular sieve support and form a Schottky heterojunction structure with FeCoO x .

[0088] Example 2

[0089] A Pt-FeCoO x / SSZ-13 catalyst (Pt1-(Fe 2.7 Co 2.7 O x ) / SSZ-13) involved in this example has a preparation process including the following steps (except for the amounts of iron and cobalt sources, the amounts of other raw materials used in the preparation process are the same as those in Example 1):

[0090] (1) Mix the SSZ-13 support and ethanol, ultrasonicate and stir evenly for 10 min to prepare suspension A;

[0091] (2) Add a certain amount of chloroplatinic acid, iron bromide, and cobalt bromide to suspension A and stir evenly for 15 min to form solution B (the atomic ratio of Pt:Fe:Co is 1:3:3);

[0092] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir well for 2 h until the reaction is complete, and form suspension C;

[0093] (4) Rotate evaporate suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C;

[0094] (5) Cool reaction product D to room temperature, wash it with ethanol (there is a certain loss of non-precious metal elements during washing), and dry it at 60 °C to obtain the Pt1-(Fe 2.7 Co 2.7 O x ) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe:Co is 1:2.7:2.7.

[0095] Example 3

[0096] A Pt-FeCoO x / SSZ-13 catalyst (Pt1-(Fe 1.6 Co 1.6 O x )) / SSZ-13) has a preparation process including the following steps (except for the dosages of iron and cobalt sources, the dosages of the rest of the raw materials in the preparation process are the same as in Example 1):

[0097] (1) Mix the SSZ-13 support and ethanol, ultrasonically treat and stir evenly for 10 min to prepare suspension A;

[0098] (2) Add a certain amount of chloroplatinic acid, iron bromide, and cobalt bromide to solution A, and stir evenly for 15 min to form suspension B (the atomic ratio of Pt:Fe:Co is 1:2:2);

[0099] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be able to completely reduce platinum), stir thoroughly for 2 h until the reaction is complete, and form suspension C;

[0100] (4) Rotary evaporate suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C;

[0101] (5) Cool reaction product D to room temperature, wash it with ethanol (there is a certain loss of non-precious metal elements during washing), and dry it at 60 °C to obtain the Pt1-(Fe 1.6 Co 1.6 O x )) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe:Co is 1:1.6:1.6.

[0102] Example 4

[0103] A Pt-FeCoO x / SSZ-13 catalyst (Pt1-(Fe 0.4 Co 0.4 O x )) / SSZ-13) has a preparation process including the following steps (except for the dosages of iron and cobalt sources, the dosages of the rest of the raw materials in the preparation process are the same as in Example 1):

[0104] (1)Mix the SSZ-13 support and ethanol, ultrasonically treat and stir evenly for 10 min to prepare suspension A;

[0105] (2)Add a certain amount of chloroplatinic acid, iron bromide, and cobalt bromide to suspension A, and stir evenly for 15 min to form solution B (the atomic ratio of Pt:Fe:Co is 1:0.5:0.5);

[0106] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be sufficient to completely reduce platinum), and stir well for 2 h until the reaction is complete to form suspension C;

[0107] (4) Rotavapor suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C;

[0108] (5) Cool reaction product D to room temperature, wash it with ethanol (there is a certain loss during the washing of non-noble metal elements), and dry it at 60 °C to obtain the Pt1-(Fe 0.4 Co 0.4 O x ) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe:Co is 1:0.4:0.4.

[0109] Performance characterization:

[0110] For the Pt-FeCoO x / SSZ-13 catalysts with different Pt and FeCo ratios prepared in Examples 1-4 and the Pt / SiO2 catalysts, Pt / SSZ-13 catalysts, Pt1-(Fe 0.75 O x ) / SSZ-13 catalysts, Pt1-(Co 0.75 O x ) / SSZ-13, Pt1-(Fe 0.7 Co 0.7 O x ) / SiO2 prepared in Comparative Examples 1-5, perform catalytic performance tests. Using 3-bromonitrobenzene as a model catalyst for halogenated nitrobenzenes, during the test, the reaction conditions adopted are set as: normal pressure H2 atmosphere; 40 °C temperature; catalyst mass / 3-bromonitrobenzene mass is 1:5; high rotation speed to eliminate the influence of diffusion. The calculation method for the selectivity of preparing 3-bromoaniline from 3-bromonitrobenzene: Analyze the product by gas chromatography, and the content of 3-bromoaniline in the product is the selectivity. The test results are shown in Table 1.

[0111] Table 1 Catalytic performance results of the catalysts prepared in Examples 1-4 and Comparative Examples 1-5

[0112]

[0113] As can be seen from Table 1: In all the examples, the catalyst activity is closely related to the support. In the reaction of Pt / SSZ-13 catalyst, the conversion rate of 3-bromonitrobenzene and the selectivity of 3-bromoaniline both increase to a certain extent, and the conversion rate increases significantly. It can be known from Examples 1-4 and Comparative Examples 1-5 that the selectivity of the catalyst with SSZ-13 or SSZ-13 modified by metal oxides as the support for 3-bromoaniline all reaches more than 93%. However, the catalyst with SSZ-13 support modified by multi-metal oxides has a promoting effect on the conversion rate compared with the catalyst with SSZ-13 support modified by single-metal oxides and SSZ-13. In addition, it can be seen from Comparative Example 6 that compared with the molecular sieve catalyst modified by multi-metal oxides, the conversion rate of the molecular sieve catalyst modified by metallic Fe and Co promoters drops sharply. This is because metallic Fe and Co are in the reduced state, which will lead to an increase in the electron cloud density of Pt, and the ability to activate and dissociate H2 during the reaction becomes weaker. At the same time, Pt and the reduced Fe do not form a Schottky heterojunction structure tightly, further leading to a performance decline. The conversion rate of the catalyst with platinum-based SSZ-13 modified by iron and cobalt bimetal oxides for the catalytic reaction of 3-bromonitrobenzene even reaches 100%. When the platinum loading mass is certain, with the gradual increase of the loading amounts of iron oxide and cobalt oxide, both the selectivity and conversion rate of 3-bromoaniline first increase gradually and then decrease. Therefore, considering both the conversion rate and selectivity comprehensively, the performance of the Pt1-(Fe 0.7 Co 0.7 O x ) / SSZ-13 catalyst is the best.

[0114] The Pt active site has good H2 dissociation ability, which promotes its high selectivity in the hydrogenation reaction. However, its disadvantage is that the side reaction of dehalogenation reaction is relatively serious. Constructing a regular SSZ-13 molecular sieve as a reasonable support for Pt can effectively inhibit the occurrence of dehalogenation reaction. This is because SSZ-13 has abundant acidic sites provided by Al2O3, which can regulate the chemical acid-base environment and electronic structure of the Pt site, inhibit the activation of C-X (X: Cl, Br, I) bonds and promote the hydrogenation of -NO2. The use of SSZ-13 support also greatly promotes the nitro-tendency adsorption of halogenated nitrobenzene, which all leads to a double improvement in the activity and selectivity of nitro-hydrogenation.

[0115] Therefore, when SSZ-13 is selected as the support, the improvement of the catalyst performance can be attributed to the synergistic effect between the Pt site and the L acid site and B acid site of Al species. The transition metal oxides such as Fe oxide species introduced as modifying species can further regulate the electronic structure of Pt: the electrons of the Pt site can be transferred to the transition metal oxide. The electron-deficient Pt site can cause the heterolytic dissociation of H2 into H + and H -It promotes the hydrogenation of the polar group -NO2. When introducing multi-metal composite oxides for modification, compared with single metals, it has a more powerful multi-metal synergistic effect and multifunctionality. The multi-metal oxides can have multiple adsorption sites or activation sites, and can catalyze multiple reaction steps simultaneously in the reaction, improving the overall reaction efficiency and selectivity.

[0116] Select Fe and Co oxide species for modification. Fe and Co oxides have rich valence state changes and can flexibly adjust the electronic structure of the Pt active site. In addition, Fe and Co oxides can also adsorb the electrophilic reaction substrate halogenated nitrobenzene, further improving the activity. Generally speaking, this significant improvement in selectivity and activity is due to the presence of the Al species of the carrier and the synergistic effect of Pt and Fe and Co oxidizing species. At the same time, the regular porous molecular sieve structure also promotes the effective dispersion of Pt nanoparticles.

[0117] In addition, the inventors of this case also referred to the foregoing embodiments and conducted tests with other raw materials, process operations, and process conditions described in this specification, and all obtained relatively ideal results.

[0118] It should be understood that the technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention without departing from the purpose of the present invention and the scope protected by the claims falls within the protection scope of the present invention.

Claims

1. A molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles, characterized in that: The invention comprises a molecular sieve carrier with a pore structure modified by a multi-metal oxide and noble metal nanoparticles uniformly embedded in the defect sites on the surface of the molecular sieve carrier; wherein the molecular sieve carrier with a pore structure modified by a multi-metal oxide is FeCoO x The modified molecular sieve support, and the FeCoO x The Fe and Co in the modified molecular sieve carrier are uniformly distributed in the pores of the molecular sieve carrier in the form of oxides in an equiatomic ratio. The noble metal nanoparticles are Pt nanoparticles and are embedded in the defect sites on the surface of the molecular sieve carrier and are bonded to FeCoO x A Schottky heterojunction structure is formed.

2. The molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles according to claim 1, characterized in that: The particle size of the nano Pt particles is 5-12 nm.

3. The molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles according to claim 2, characterized in that: The content of the nano-platinum particles is 0.15wt% to 1.0wt%.

4. The molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles according to claim 1, characterized in that: FeCoO x The modified molecular sieve carrier is a SSZ-13 molecular sieve carrier.

5. The molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles according to claim 3, characterized in that: The atomic ratio of Pt:Fe:Co in the molecular sieve catalyst doubly modified with multi-metal oxides and platinum nanoparticles is 1:0.4-1.6:0.4-1.

6.

6. A method for preparing a molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing a platinum source, an iron source, a cobalt source, a reducing agent and an SSZ-13 carrier for reaction, and performing instantaneous in-situ reduction in one step to prepare a molecular sieve catalyst doubly modified with multi-metal oxides and platinum nanoparticles.

7. The preparation method according to claim 6, characterized in that: The specific steps include: The SSZ-13 carrier and the solvent are mixed by ultrasound and stirring to form a first mixed solution, and then a platinum source, an iron source and a cobalt source are added and stirred to form a second mixed solution; a reducing agent is added to the second mixed solution and the solution is stirred to react, and then the solution is subjected to rotary evaporation, washing and drying to obtain a molecular sieve catalyst doubly modified with multi-metal oxides and platinum nanoparticles.

8. The preparation method according to claim 7, characterized in that: The platinum source is an inorganic compound of platinum, which is any one or more combination of bromoplatinic acid, potassium bromoplatinate, and sodium bromoplatinate; the iron source is any one or more combination of ferric bromide, ferrous bromide, and ferric nitrate; the cobalt source is cobalt bromide and / or cobalt nitrate; the solvent is ethanol; and the reducing agent is any one or more combination of sodium borohydride, lithium borohydride, and sodium thiosulfate.

9. The preparation method according to claim 7, characterized in that: The temperature of the rotary evaporation treatment is 30~70℃; the temperature of the drying treatment is 30~60℃.

10. Use of a molecular sieve catalyst double-modified with a multi-metal oxide and platinum nanoparticles according to any one of claims 1 to 5 in catalyzing the hydrogenation of halonitrobenzene to prepare halogenated aniline.

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