Molecular sieve catalyst double-modified by multi-element metal oxide and platinum nanoparticles as well as preparation method and application of molecular sieve catalyst

Abstract

The invention discloses a multi-element metal oxide and platinum nano-particle dual-modified molecular sieve catalyst as well as a preparation method and application of the multi-element metal oxide and platinum nano-particle dual-modified molecular sieve catalyst. The molecular sieve catalyst comprises a FeCoOx modified molecular sieve carrier and precious metal platinum nanoparticles uniformly embedded in defect sites on the surface of the molecular sieve carrier, fe and Co in the FeCoOx-modified molecular sieve carrier form an oxide in an equal atomic ratio and are uniformly distributed in pore channels of the molecular sieve carrier, Pt nanoparticles are embedded in surface defect sites of the molecular sieve carrier, and the Pt nanoparticles and FeCoOx form a Schottky heterojunction structure. The Pt in the catalyst has high activity and high selectivity for preparing halogenated aniline through hydrogenation of halogenated nitrobenzene under the action of the Fe and Co auxiliaries, and meanwhile, a one-step instantaneous in-situ reduction method is innovatively used for preparation of the catalyst, and the method is simple and easy to implement; and a new thought is provided for the design of a catalyst for one-class reaction for preparing corresponding halogen-containing aniline from halogen-containing nitrobenzene with high selectivity.

Description

Technical Field

[0001] The present invention belongs to the field of thermal catalysis technology and the preparation and application technology of catalysts, and specifically relates to a molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles, and its preparation method and application. Background Technology

[0002] Haloaniline is widely used in the synthesis of fine chemicals such as medicines, pesticides, and fuels. It is an important organic chemical intermediate. Halogenated aniline is usually prepared by the reduction synthesis method of halogenated aromatic compounds, including chemical reduction methods such as alkali sulfide reduction method, iron powder reduction method, and hydrazine hydrate reduction method. Although the technology is mature, it has serious environmental pollution and high energy consumption. Compared with these methods, catalytic hydrogenation has attracted much attention due to its low pollution, low energy consumption, and low cost. How to improve the catalytic activity and selectivity of catalytic hydrogenation of halogenated nitrobenzenes to prepare halogenated aniline is a huge challenge faced in research and application. Among them, precious metals, such as Pt, Pd, Au, and Rh, have excellent hydrogen (H 2 ) dissociation ability, widely used in the selective hydrogenation of halonitrobenzenes. However, dehalogenation reaction is difficult to avoid during the reaction. To achieve high catalytic activity for hydrogenation of halonitrobenzenes and selectivity for halogenated anilines, it is necessary to limit or completely inhibit the dehalogenation reaction to the maximum extent. Therefore, it is crucial to develop a highly selective catalyst.

[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 very prone to hydrogenation dehalogenation side reactions during the catalytic hydrogenation reaction, resulting in low selectivity for the target product. Therefore, in the selective hydrogenation of bromonitrobenzene, the research and development of supported platinum-based catalysts with high activity and selectivity is the focus of this research direction. For supported catalysts, many researchers have conducted relevant research on the factors affecting the catalytic performance of the support, such as: 1) the size effect of the supported metal nanoparticles; 2) the activation of the substrate by the support; 3) the structural sensitivity of the strong metal-support interaction, etc. These factors determine the selectivity of the halogenated aniline. Therefore, it is crucial to develop highly selective and active catalysts. SUMMARY OF THE INVENTION

[0004] The main purpose of the present invention is to provide a molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles and its preparation method and application, so as to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned invention purpose, the technical solution adopted by the present invention includes: A molecular sieve catalyst double-modified by multi-metal oxides and platinum nanoparticles, comprising a molecular sieve carrier with a pore structure modified by multi-metal oxides and noble metal nanoparticles uniformly embedded in the surface defect sites of the molecular sieve carrier; wherein the molecular sieve carrier with a pore structure modified by multi-metal oxides is FeCoO x Modified molecular sieve carrier, and the FeCoO x In the modified molecular sieve carrier, Fe and Co 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, which are embedded in the defect sites on the surface of the molecular sieve carrier and are combined with FeCoO x Forming a Schottky heterojunction structure.

[0006] Furthermore, the particle size of the nano-platinum particles is 5-12nm.

[0007] Furthermore, the content of nano-platinum particles in the molecular sieve catalyst double-modified with multi-metal oxides and platinum nano-particles is 0.15wt% to 1.0wt%; Furthermore, the atomic ratio of Pt:Fe:Co in the molecular sieve catalyst double-modified by multi-metal oxides and platinum nanoparticles is 1:0.4-1.6:0.4-1.6.

[0008] Furthermore, FeCoO x The modified molecular sieve carrier is FeCoO x Modified SSZ-13 vector A method for preparing a molecular sieve catalyst double-modified by multi-metal oxides 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 performing instantaneous in-situ reduction in one step to obtain a molecular sieve catalyst double-modified by multi-metal oxides and platinum nanoparticles.

[0009] Further, the method specifically includes the following steps: The SSZ-13 carrier and the solvent are mixed by ultrasonication 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 stirred to react, and then subjected to rotary evaporation, washing, and drying to obtain a molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles.

[0010] Furthermore, the platinum source is an inorganic compound of platinum, which is any one or more of bromoplatinic acid, potassium bromoplatinate, and sodium bromoplatinate; And / or, the iron source is any one or more of ferric bromide, ferrous bromide, and ferric nitrate; And / or, the cobalt source is cobalt bromide and / or cobalt nitrate; And / or, the solvent is ethanol; And / or, the reducing agent is any one or more combinations of sodium borohydride, lithium borohydride, and sodium thiosulfate.

[0011] Furthermore, the temperature of the rotary evaporation treatment is 30-70°C; the temperature of the drying treatment is 30-60°C.

[0012] The application of a molecular sieve-supported catalyst dually modified with multi-metal oxides and platinum nanoparticles in the hydrogenation of halonitrobenzenes to prepare halogenated anilines.

[0013] The preparation method of the molecular sieve catalyst double modified by multi-metal oxides and platinum nanoparticles in the present invention 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 instantaneous reduction and deposition methods: non-precious metal Fe and Co species are reduced to low-valent oxide species (FeCoO x ), dispersed and adsorbed in the internal pores of the SSZ-13 molecular sieve carrier through electrostatic interaction, and the precious metal Pt is reduced to form Pt nanoparticles anchored on FeCoO x The modified SSZ-13 molecular sieve has surface defects and is combined with FeCoO x Forming a Schottky heterojunction structure. The different chemical compositions and crystal structures in the heterostructure will cause lattice strains such as tension and compression, affecting the adsorption energy of the site to the intermediate and improving the catalytic activity of the material.

[0014] In the present invention, the advantage of the catalyst structure is that on the one hand, the non-precious metal oxide FeCoO x Due to the modification of SSZ-13 molecular sieve carrier, the active Pt nanoparticles are stabilized in geometric structure to a certain extent; on the other hand, the Pt nanoparticles and FeCoO x The Schottky heterojunction structure formed produces electron transfer, which reduces the electron density of Pt and promotes the heterolysis of hydrogen. + With H - It has stronger hydrogenation activity. By regulating the electronic structure of Pt nanoparticles and the adsorption behavior of the substrate, the performance is optimized based on synergy.

[0015] The Pt in the catalyst of the present invention has high activity and selectivity in hydrogenating halogenated nitrobenzene to halogenated aniline under the action of Fe and Co additives. At the same time, the preparation of the catalyst of the present invention innovatively uses a one-step instantaneous in-situ reduction method, which is simple and easy to implement, and provides a new idea for the catalyst design of a type of reaction for selectively preparing the corresponding halogenated aniline from halogenated nitrobenzene.

[0016] The catalytic test in the present invention is used to evaluate the performance of the catalyst, and the reaction conditions are normal pressure H 2 Atmosphere, reaction temperature is 40℃. ​​

[0017] The design of the molecular sieve catalyst double modified by multi-metal oxides and platinum nanoparticles in the present invention will further improve the selective hydrogenation of halonitrobenzenes. This is because the Pt particles have a significant synergistic effect with the non-precious metal oxide species in the carrier and the influence of the carrier on the catalytic effect can be controlled by changing the input amount 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 halonitrobenzenes.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The strong interaction between Pt nanoparticles and SSZ-13 modified with multiple metal oxides and platinum nanoparticles in the molecular sieve catalyst of the present invention improves the adsorption capacity of reaction substrates and H 2 's adsorption and dissociation ability, thereby improving the catalytic activity; (2) In the molecular sieve catalyst double-modified with multi-metal oxides and platinum nanoparticles provided in the present invention, nano-scale Pt particles are dispersed on the surface defect sites of SSZ-13 molecular sieve, which effectively reduces the amount of precious metal platinum and saves costs. x The formation of Schottky heterojunction structure reduces the mobility of nano-Pt, prevents the formation of large Pt particles, and improves the catalytic effect; (3) FeCoO in the molecular sieve catalyst double modified by multi-metal oxides and platinum nanoparticles in the present invention x The modified SSZ-13 carrier changes the electron transfer channel and substrate adsorption configuration, improving the selectivity of the catalytic halogenated nitrobenzene hydrogenation to halogenated aniline reaction. At the same time, the present invention innovatively adopts a one-step instantaneous reduction method, and the experimental operation is simple and easy.

[0019] (4) Fe and Co oxides have rich valence changes and can flexibly adjust the electronic structure of Pt active sites. In addition, Fe and Co oxide species can also adsorb the electrophilic reaction substrate halogenated nitrobenzene, further improving the activity. Brief Description of the Figures

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is a transmission electron microscope image of the Pt / SSZ-13 catalyst prepared in Comparative Example 2 of the present invention;​ Figure 2 Pt-FeO prepared in Comparative Example 3 of the present invention x / Transmission electron microscope image of SSZ-13 catalyst; Figure 3 Pt-FeCoO prepared in Example 1 of the present invention x / Transmission electron microscope image of SSZ-13 catalyst; Figure 4 Pt-FeCoO prepared in Example 1 of the present invention x / SSZ-13 element mapping diagram; Figure 5 This is a schematic diagram of the principle of the present invention. Specific implementation method

[0022] The following is a further detailed description of the technical solution of the present invention in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0023] The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0024] In the catalyst test in the embodiment of the present invention, 3-bromonitrobenzene is used as the model substrate molecule of halogenated nitrobenzene. 3-bromonitrobenzene is a typical halogenated nitrobenzene. However, the application field of the catalyst can be targeted at the selective hydrogenation field of other halogenated nitrobenzenes.

[0025] Calculation method for the selectivity of preparing 3-bromoaniline from 3-bromonitrobenzene: Analyze the product by gas chromatography, and the 3-bromoaniline content in the product based on the relative correction factor is the selectivity.

[0026] Comparative Example 1 This comparative example involves a Pt / SiO 2 The preparation process of the catalyst includes the following steps: (1) SiO 2 , ethanol, ultrasonic, stir evenly for 10 minutes to prepare suspension A.

[0027] (2) Add a certain amount of bromoplatinic acid (control the Pt loading to 0.4wt%) to suspension A, stir for 15min, and disperse evenly to form suspension B.

[0028] (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C.

[0029] (4) The reaction suspension C was evaporated to remove the solvent at 70°C, cooled to room temperature, and the precipitate was washed with ethanol and dried at 60°C to obtain Pt / SiO 2 Catalyst.

[0030] Comparative Example 2 The preparation process of a Pt / SSZ-13 catalyst involved in this comparative example includes the following steps: The operation steps and raw material dosage are the same as those in Comparative Example 1, except that SSZ-13 is used as the carrier to replace SiO 2 , Pt / SSZ-13 catalyst was obtained, and the transmission electron microscope image of Pt / SSZ-13 catalyst is shown in Figure 1 As shown, from Figure 1 It can be found that Pt is a nanoparticle structure.

[0031] Comparative Example 3 A Pt-FeO x / SSZ-13 catalyst (Pt 1 -(Fe 0.75 O x ) / SSZ-13) preparation process comprises the following steps (except for the additional iron source, the amount of other raw materials in the preparation process is the same as that of comparative example 2): (1) Mix the SSZ-13 carrier and ethanol, stir evenly under ultrasonication for 10 minutes, and prepare suspension A; (2) Add a certain amount of bromoplatinic acid and ferric bromide to suspension A and stir for 15 minutes to form suspension B (the atomic ratio of Pt:Fe is 1:1); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Fe 0.75 O x ) / SSZ-13 catalyst catalyst, wherein the atomic ratio of Pt:Fe is 1:0.75, Pt 1 -(Fe 0.75 O x ) / SSZ-13 catalyst transmission electron microscope picture as shown in Figure 2 As shown, from Figure 2 It can be found that the introduction of Fe does not cause the structure of the nanoparticles to collapse, and they are still nanoparticles, which are quite comparable to Pt / SSZ-13.

[0032] Comparative Example 4 A Pt-CoO x / SSZ-13 catalyst (Pt 1 -(Co 0.75 O x ) / SSZ-13) preparation process comprises the following steps (except for the additional cobalt source, the amount of other raw materials used in the preparation process is the same as that of comparative example 2): (1) Mix the SSZ-13 carrier and ethanol, stir evenly under ultrasonication for 10 minutes, and prepare suspension A; (2) Add a certain amount of bromoplatinic acid and cobalt bromide to suspension A and stir for 15 minutes to form suspension B (Pt:Co atomic ratio is 1:1); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Co 0.75 O x ) / SSZ-13 catalyst, wherein the atomic ratio of Pt:Co is 1:0.75.

[0033] Comparative Example 5 This comparative example involves a Pt-FeCoO x / SiO 2 (Pt 1 -(Fe 0.7 Co 0.7 O x ) / SiO 2 ) The preparation process of the catalyst comprises the following steps (except for the additional cobalt source and iron source, the amounts of other raw materials used in the preparation process are the same as those in Comparative Example 2, SiO 2 Dosage is the same as in Comparative Example 1): (1) SiO 2 , ethanol, ultrasonic, stir evenly for 10 minutes to prepare suspension A; (2) Add a certain amount of bromoplatinic acid, ferric bromide and cobalt bromide to solution A and stir for 15 minutes to form suspension B (the atomic ratio of Pt:Fe:Co is 1:1:1); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Fe 0.7 Co 0.7 O x ) / SiO 2 Catalyst, wherein the atomic ratio of Pt:Fe:Co is 1:0.7:0.7.

[0034] Comparative Example 6 This comparative example involves a Pt 1 -Fe 0.7 -Co 0.7 / The preparation process of SSZ-13 (Fe and Co species exist in metallic state) catalyst includes the following steps: (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; (2) Slowly add solution A and solution B to the SSZ-13 catalyst and keep stirring for 15 minutes; (3) Add Fe and Co metal salt aqueous solution to SSZ-13 and place it at 80 o C was kept for 2 hours for drying, and solid A was obtained after grinding; (3) Solid A was heated in a muffle furnace at 550°C. o C was roasted for 3h to obtain solid B; (4) Solid B in H 2 / Ar mixed gas with 700 o C was reduced for 3 h to obtain solid C; (5) Slowly add solution C to solid C, keep stirring for 15 minutes and place at 80 o C was kept for 2 hours to dry, and solid D was obtained after grinding; (6) Solid D was heated in a muffle furnace at 550 o C was calcined for 3h to obtain solid E; (7) Solid E in H 2 / Ar mixed gas with 350 o C reduction for 3h; Pt was obtained after grinding 1 -Fe 0.7 -Co 0.7 / SSZ-13, in which the atomic ratio of Pt:Fe:Co is 1:0.7:0.7, and Pt, Fe, and Co are all in metallic state.

[0035] Example 1 ​​​​​​​​​​​​​​​​​​​

[0036] A Pt-FeCoO x / SSZ-13 catalyst (Pt 1 -(Fe 0.7 Co 0.7 O x ) / SSZ-13) preparation process comprises the following steps (the amount of raw materials used in the preparation process is the same as that in comparative example 5, and the amount of SSZ-13 carrier used is the same as that in comparative example 2): (1) Mix the SSZ-13 carrier and ethanol, stir evenly under ultrasonication for 10 minutes, and prepare suspension A; (2) Add a certain amount of bromoplatinic acid, ferric bromide and cobalt bromide to solution A and stir for 15 minutes to form suspension B (the atomic ratio of Pt:Fe:Co is 1:1:1); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Fe 0.7 Co 0.7 O x ) / SSZ-13 catalyst, in which the atomic ratio of Pt:Fe:Co is 1:0.7:0.7, and the average particle size of Pt in the catalyst is 10.2nm. Figure 3 is Pt-FeCoO prepared in this example x / Transmission electron microscope image of SSZ-13 catalyst; Figure 4 is Pt-FeCoO prepared in this example x / SSZ-13 mapping diagram, from which it can be seen that the nanoparticles are evenly dispersed. The principle of the present invention is as follows Figure 5 As shown, FeCoO x In the modified molecular sieve carrier, Fe and Co form oxides in equal atomic proportions and are evenly distributed in the pores of the molecular sieve carrier. Pt nanoparticles are embedded in the surface defects of the molecular sieve carrier and react with FeCoO x Forming a Schottky heterojunction structure.

[0037] Example 2

[0038] A Pt-FeCoO x / SSZ-13 catalyst (Pt 1 -(Fe 2.7 Co 2.7 Ox ) / SSZ-13) preparation process comprises the following steps (except the amount of iron and cobalt sources, the amount of other raw materials in the preparation process is the same as that in Example 1): (1) Mix the SSZ-13 carrier and ethanol, stir evenly under ultrasonication for 10 minutes, and prepare suspension A; (2) Add a certain amount of bromoplatinic acid, ferric bromide and cobalt bromide to suspension A and stir for 15 minutes to form solution B (the atomic ratio of Pt:Fe:Co is 1:3:3); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Fe 2.7 Co 2.7 O x ) / SSZ-13 catalyst, in which the atomic ratio of Pt:Fe:Co is 1:2.7:2.7.

[0039] Example 3

[0040] A Pt-FeCoO x / SSZ-13 catalyst (Pt 1 -(Fe 1.6 Co 1.6 O x ) / SSZ-13) preparation process comprises the following steps (except the amount of iron and cobalt sources, the amount of other raw materials in the preparation process is the same as that in Example 1): (1) Mix the SSZ-13 carrier and ethanol, stir evenly under ultrasonication for 10 minutes, and prepare suspension A; (2) Add a certain amount of bromoplatinic acid, ferric bromide and cobalt bromide to solution A and stir for 15 minutes to form suspension B (the atomic ratio of Pt:Fe:Co is 1:2:2); (3) Add a certain amount of sodium borohydride to suspension B (the amount of sodium borohydride should be enough to reduce all the platinum), stir thoroughly for 2 hours until the reaction is complete, and form suspension C; (4) The suspension C was subjected to rotary evaporation to remove the solvent to obtain the reaction product D, and the reaction temperature was 70°C; (5) The reaction product D was cooled to room temperature, washed with ethanol (there was a certain loss of non-precious metal elements during washing), and dried at 60°C to obtain Pt 1 -(Fe 1.6 Co1.6 O x ) / SSZ-13 catalyst, where the atomic ratio of Pt:Fe:Co is 1:1.6:1.6.

[0041] Example 4

[0042] A Pt-FeCoO x / SSZ-13 catalyst (Pt 1 -(Fe 0.4 Co 0.4 O x ) / SSZ-13) has a preparation process including the following steps (except for the amounts of iron and cobalt sources, the amounts of the rest of the raw materials in the preparation process are the same as in Example 1): (1) Mix the SSZ-13 support and ethanol, sonicate and stir evenly for 10 min to prepare suspension A; (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); (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; (4) Rotavaporate suspension C to remove the solvent to obtain reaction product D, and the reaction temperature is 70 °C; (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 Pt 1 -(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.

[0043] Performance characterization: For the Pt-FeCoO x / SSZ-13 catalysts with different Pt and FeCo ratios prepared in Examples 1-4 and the Pt / SiO 2 catalysts, Pt / SSZ-13 catalysts, Pt 1 -(Fe 0.75 O x ) / SSZ-13 catalysts, Pt 1 -(Co 0.75 O x ) / SSZ-13, Pt 1 -(Fe 0.7 Co 0.7 O x ) / SiO 2The catalytic performance test was carried out, using 3-bromonitrobenzene as a model catalyst for halogenated nitrobenzene. In the test, the reaction conditions used were set as follows: atmospheric pressure H 2 Atmosphere; 40℃ temperature; catalyst mass / 3-bromonitrobenzene mass is 1:5; high speed eliminates the diffusion effect. Calculation method of selectivity of 3-bromonitrobenzene to 3-bromoaniline: The product is analyzed by gas chromatography, and the content of 3-bromoaniline in the product is the selectivity. The test results are shown in Table 1.

[0044] Table 1 Catalytic performance results of catalysts prepared in Examples 1-4 and Comparative Examples 1-5

[0045] It can be seen from Table 1 that in all the embodiments, the catalyst activity is closely related to the carrier. The conversion rate of 3-bromonitrobenzene and the selectivity of 3-bromoaniline in the Pt / SSZ-13 catalyst reaction are improved to a certain extent, among which the conversion rate is significantly improved. From Examples 1-4 and Comparative Examples 1-5, it can be seen that the selectivity of the catalysts with SSZ-13 or SSZ-13 modified by metal oxides as carriers for 3-bromoaniline is more than 93%, but the SSZ-13 carrier catalyst modified by multi-metal oxides has a promoting effect on the conversion rate of SSZ-13 and SSZ-13 carriers modified by single metal oxides. 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 additives drops sharply. This is because the metallic Fe and Co are in a reduced state, which will lead to an increase in the electron cloud density of Pt, and the reaction process will increase the H 2 The activation and dissociation ability weakened, and Pt and reduced Fe did not tightly combine to form a Schottky heterojunction structure, which further led to a decline in performance. The conversion rate of 3-bromonitrobenzene catalyzed by the platinum-based catalyst with SSZ-13 modified with iron and cobalt bimetallic oxides as the carrier even reached 100%. Under the condition of a certain platinum loading mass, the loading amount of iron oxide and cobalt oxide gradually increased, and the selectivity and conversion rate of 3-bromoaniline gradually increased and then decreased. Therefore, considering the conversion rate and selectivity, Pt 1 -(Fe 0.7 Co 0.7 O x ) / SSZ-13 catalyst has the best performance.

[0046] Pt active sites have good H 2 The dissociation ability of SSZ-13 leads to its high selectivity in hydrogenation reaction. However, its disadvantage is that the side reaction of dehalogenation is more serious. The regular SSZ-13 molecular sieve as a reasonable carrier of Pt can effectively inhibit the occurrence of dehalogenation reaction. This is because SSZ-13 has Al 2O 3 The abundant acidic sites provided can adjust the chemical acid-base environment and electronic structure of the Pt site, inhibit the activation of CX (X: Cl, Br, I) bonds and promote -NO 2 Hydrogenation. The use of SSZ-13 carrier also greatly promotes the nitro-oriented adsorption of halogenated nitrobenzene, which doubles the activity and selectivity of nitro hydrogenation.

[0047] Therefore, the selection of SSZ-13 as the carrier can attribute the improvement of catalyst performance to the synergistic effect of Pt sites and Al species L acid sites and B acid sites. Transition metal oxides such as Fe oxide species introduced as modifying species can further regulate the electronic structure of Pt: electrons at Pt sites can be transferred to transition metal oxides. Electron-deficient Pt sites can lead to H 2 Differentiation into H + With H - Promotes the polar group -NO 2 Hydrogenation. When multi-metal composite oxides are introduced for modification, they have stronger multi-metal synergy and multifunctionality compared to single metals. Multi-metal oxides can have multiple adsorption sites or activation sites, which can catalyze multiple reaction steps simultaneously in the reaction, improving the overall reaction efficiency and selectivity.

[0048] Fe and Co oxide species are selected for modification. Fe and Co oxides have rich valence changes and can flexibly adjust the electronic structure of Pt active sites. In addition, Fe and Co oxides can also adsorb the electrophilic reaction substrate halogenated nitrobenzene, further improving the activity. In general, this significant selectivity and activity improvement is due to the presence of Al species on 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.

[0049] In addition, the inventor of this case also referred to the above embodiments and conducted experiments with other raw materials, process operations and process conditions described in this specification, and obtained relatively ideal results.

[0050] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall 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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