A composite catalyst of supported Ti-MWW molecular sieve and metal oxide and its preparation and application

Abstract

The present invention belongs to the field of catalytic material preparation and application, and specifically relates to a composite catalyst of a Ti-MWW molecular sieve loaded with a metal oxide and its preparation and application. The preparation method of the composite catalyst comprises the following steps: adding a loaded Ti-MWW molecular sieve to a metal nitrate solution for impregnation to obtain a loaded composite catalyst. The composite catalyst catalyzes hydrogen peroxide and styrene to prepare styrene oxide, and the conversion rate of styrene and the selectivity of styrene oxide are 72.61% and 51.37%, respectively. The loaded Ti-MWW molecular sieve and metal oxide composite catalyst provided by the present invention has a high specific surface area and multi-stage pores, which can effectively promote the diffusion of reactants in the pores, and significantly improves the catalytic performance of the Ti-MWW molecular sieve, the reaction rate of the target reaction, and the yield of the target product.

Description

Technical Field

[0001] The invention belongs to the field of preparation and application of catalytic materials, and specifically relates to a composite catalyst of a supported Ti-MWW molecular sieve and a metal oxide, and a preparation and application thereof. Background Art

[0002] Epoxystyrene (SO), also known as styrene oxide, is an important organic synthesis intermediate, widely used in fine chemical synthesis, pharmaceuticals, dyes, fragrances, pesticides and other industries. Domestic epoxystyrene enterprises have small production scale, low technical level and backward production process. The quantity and quality of epoxystyrene produced cannot meet market demand. In recent years, the market demand for epoxystyrene has been growing, showing a situation of supply exceeding demand.

[0003] At present, the main SO processes for industrial production include the halogen alcohol method, co-oxidation method, peroxyacid oxidation method, hydrogen peroxide epoxidation method, etc. The halogen alcohol method has serious equipment corrosion when applied, and produces a large amount of high-salt, highly oxidizing, and highly acidic wastewater during the production process, which has serious environmental problems; the co-oxidation method (Halcon) has a complex process flow, high requirements for reaction purity, and its production capacity is heavily dependent on co-products, resulting in high production costs; the hydrogen peroxide epoxidation method uses hydrogen peroxide as a green oxygen source for olefin catalytic epoxidation to overcome the shortcomings of the above two methods, and requires the use of high-concentration hydrogen peroxide, but the problem is that high-concentration hydrogen peroxide is very likely to cause explosions during industrial production, and its storage and use have great safety hazards. When the concentration of hydrogen peroxide is reduced, its effect in the olefin epoxidation reaction is almost negligible.

[0004] In the prior art, molecular sieves are usually used as catalysts to solve the problem of unsatisfactory yield of styrene oxide during low-concentration hydrogen peroxide reaction. Chinese patent CN113731485A discloses a method for preparing a supported multi-level porous titanium silicon molecular sieve, comprising mixing a silicon source, a titanium source, a template agent and deionized water to obtain a synthetic sol of a supported multi-level porous titanium silicon molecular sieve, placing the synthetic sol and a carrier pre-coated with molecular sieve seeds in a reactor for dynamic hydrothermal crystallization, and washing and calcining the crystallized supported molecular sieve to obtain a supported multi-level porous titanium silicon molecular sieve. Nano-scale titanium silicon molecular sieves have high specific surface area and excellent catalytic performance, but due to the influence of factors such as substrate molecular size, solvent properties, grain size and pore structure, the catalytic performance of titanium silicon molecular sieves is subject to certain limitations. On the one hand, there are problems of separation and recovery difficulties in the molecular sieve catalysis industry; on the other hand, the micropore diameter of the molecular sieve is small, which makes it difficult for macromolecular reactants to diffuse in a single and narrow channel and unable to contact with titanium active sites, which greatly limits the catalytic performance of titanium silicon molecular sieves. In addition, metal oxides have attracted much attention as heterogeneous catalysts in the selective oxidation of olefins. For example, CuO has the characteristics of low cost, natural abundance, environmental friendliness and good catalytic performance, and is widely used in various processes. However, at the same time, the aggregation and reorganization of metal oxides are still defects that limit their application. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a method for preparing styrene oxide by using a supported Ti-MWW molecular sieve / metal oxide, which solves the problem that it is difficult to achieve olefin epoxidation reaction with low-concentration hydrogen peroxide, significantly improves the catalytic performance of the Ti-MWW molecular sieve, the reaction rate of the target reaction and the yield of the target product, and realizes the green and sustainable production of styrene oxide, and effectively increases the output of styrene oxide.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] One of the purposes of the present invention is to provide a method for preparing a composite catalyst of a supported Ti-MWW molecular sieve and a metal oxide, the preparation method comprising the following steps:

[0008] (1) SiO2, TiO2, B2O3, HMI, NH4F and H2O are fully mixed in a first preset ratio to obtain a gel; and the gel and the loaded Ti-MWW molecular sieve layer are transferred to a reactor for crystallization reaction to obtain a loaded Ti-MWW molecular sieve;

[0009] (2) The supported Ti-MWW molecular sieve is added to a metal nitrate solution prepared with ethanol as a solvent and ultrasonically impregnated to obtain a supported composite catalyst.

[0010] In summary, according to the prepared supported Ti-MWW molecular sieve and metal oxide composite catalyst, on the one hand, the molecular sieve with its own nano-scale pores aggregates and covers the surface of the porous material to form micropores and carrier pore bodies, thereby reducing the steric hindrance and improving the molecular diffusion rate. When the flow rate of the raw material liquid is constant, the higher the molecular diffusion rate, the more binding sites can be brought into contact with the reactants, thereby increasing the styrene oxidation reaction rate; on the other hand, the metal oxide is carried on the porous carrier to avoid the aggregation of metal oxide nanoparticles, that is, the metal oxide is evenly distributed in the molecular sieve nanosheet layer, thereby forming metal oxide catalytic sites, effectively increasing the active sites for catalyzing the epoxidation of styrene, and also increasing the styrene oxidation reaction rate; therefore, the composite catalyst composed of the supported Ti-MWW molecular sieve and the metal oxide has dual catalytic active sites, thereby having a synergistic catalytic effect, greatly increasing the yield of styrene oxide.

[0011] Preferably, the first preset molar ratio is 1:0.035-0.06:0.67:0.7-1.4:0.21:30-60.

[0012] Preferably, the crystallization reaction temperature is 170-180° C., and the crystallization reaction time is 6-8 days.

[0013] Preferably, the metal nitrate solution is any one of iron nitrate, copper nitrate, cobalt nitrate, nickel nitrate, magnesium nitrate and lanthanum nitrate solutions, and the concentration of the metal nitrate solution is 0.05-0.1 mol / L.

[0014] Preferably, the size of the Ti-MWW molecular sieve and the TiO2 / SiO2 ratio on the supported Ti-MWW molecular sieve are 0.10-2.00 μm and 0.032, respectively.

[0015] Preferably, the size of the metal oxide and the ratio of TiO2 to the metal oxide are 10-200 nm and 0.2-0.8, respectively.

[0016] Preferably, the immersion time is 5-80 min.

[0017] Preferably, the ultrasonic treatment time is 10-40 min.

[0018] The second object of the present invention is to provide a composite catalyst of supported Ti-MWW molecular sieve and metal oxide prepared by the above preparation method.

[0019] The third object of the present invention is to provide an application of the composite catalyst in the preparation of styrene oxide.

[0020] In the above technical scheme, the composite catalyst of the supported Ti-MWW molecular sieve and metal oxide comprises the following steps when preparing styrene oxide:

[0021] In the presence of a molecular sieve and a metal oxide composite catalyst, styrene, hydrogen peroxide and a solvent are added to a raw material bottle in a second preset ratio, mixed and heated, and after mixing, the raw material liquid is transferred to a fixed bed reactor to react with the composite catalyst in a third preset ratio. After the reaction, the reaction liquid is circulated back to the raw material bottle from the fixed bed reactor, and styrene oxide is obtained after several cycles.

[0022] The circulation operation in the step is to effectively ensure that the raw material liquid is fully in contact with the supported Ti-MWW molecular sieve in the fixed bed reactor.

[0023] Preferably, the flow rate of the raw material liquid during the circulation operation is 2 ml / min.

[0024] Preferably, in the second preset ratio, the molar ratio of styrene to hydrogen peroxide is 1:1-4; the volume ratio of styrene to solvent is 1:5-20, wherein the solvent is any one of acetonitrile and / or methanol.

[0025] Preferably, the volume ratio of the raw material liquid to the mass ratio of the composite catalyst in the third preset ratio is 1-4:1.

[0026] Preferably, the fixed bed reactor is placed in a constant temperature water bath for reaction, the reaction temperature and reaction time are 40-90° C. and 4-10 h respectively, and the reaction pressure is 1 atmosphere.

[0027] Preferably, the fixed bed reactor and the raw material bottle are placed under a constant temperature of 30-100° C. for heating reaction, and the reaction time is 2-10 h.

[0028] Preferably, the filler in the fixed bed reactor is a composite catalyst supported by a porous microsphere carrier, wherein the porous microsphere carrier is one or more of porous alumina / silicon dioxide / silicon carbide beads, and the diameter of the porous microsphere carrier is 1-10 mm.

[0029] When the composite catalyst prepared by the present invention catalyzes hydrogen peroxide and styrene to prepare styrene oxide, it not only avoids the problems of difficulty in catalyst separation and recovery and waste residue emission pollution in the production process, but also improves the molecular diffusion rate and the reaction efficiency of styrene epoxidation, thereby ensuring a high selectivity of styrene oxide while obtaining the product styrene oxide in the catalytic reaction.

[0030] Compared with the prior art, the present invention has the following characteristics:

[0031] The fixed reactor composed of supported Ti-MWW molecular sieve and metal oxide can effectively solve the problem of separation and recovery difficulties in the molecular sieve catalysis industry. Its high specific surface area and multi-level pores can effectively promote the diffusion of reactants in the pores, significantly improving the catalytic performance of Ti-MWW molecular sieve, the reaction rate of the target reaction and the yield of the target product. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The schematic diagram of the device for continuously producing styrene oxide using a composite catalyst of supported Ti-MWW molecular sieve and metal oxide in a fixed bed reactor;

[0033] Figure 2 The SEM and TEM images of the composite catalyst of supported Ti-MWW molecular sieve and iron oxide are shown;

[0034] Figure 3 XRD patterns of supported Ti-MWW molecular sieve and composite catalyst of supported Ti-MWW molecular sieve and iron oxide;

[0035] Figure 4 The gas chromatogram and analysis results of Example 4 are shown below:

[0036] Figure 5 The gas chromatogram and analysis results of Example 5 are shown below:

[0037] Figure 6 The gas chromatogram and analysis results of Example 6 are shown below:

[0038] Figure 7 The gas chromatogram and analysis results of Example 7 are shown below:

[0039] Figure 8 The gas chromatogram and analysis results of Example 8 are shown below:

[0040] Fig. 9 The gas chromatogram and analysis results of Example 9 are shown in FIG. DETAILED DESCRIPTION

[0041] In order to facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are provided in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0043] like Figure 1 As shown, the raw material liquid (a certain molar ratio of styrene, hydrogen peroxide and solvent) is first added to the raw material bottle and mixed evenly and preheated to the reaction temperature in a constant temperature water bath a. After mixing, the raw material liquid flows into a fixed bed reactor b filled with a composite catalyst of a supported Ti-MWW molecular sieve and a metal oxide under the drive of a peristaltic pump d. The stainless steel conduit c at the reactor outlet is connected to the raw material bottle e. The cyclic operation ensures that the raw material liquid medium is fully in contact with the supported Ti-MWW molecular sieve in the fixed bed reactor b. The fixed bed reactor b and the three-necked flask are placed in a constant temperature water bath a. After the reaction time is over, the peristaltic pump d is turned off, and the product after the reaction is collected for gas chromatography analysis of the components.

[0044] Example 1

[0045] The synthetic gel was prepared according to the preset molar ratio of SiO2:TiO2:B2O3:HMI:NH4F:H2O at 1:0.035:0.67:1.4:0.21:30, and the synthesis temperature and synthesis time were 180℃ and 6 days respectively. The crystallized supported Ti-MWW molecular sieve was washed and dried for use. With ethanol as solvent, a metal ferric nitrate solution with a concentration of 0.05mol / L was prepared, and the supported Ti-MWW molecular sieve was immersed in the above solution for 30min under ultrasonic conditions, filtered after immersion, dried in an oven at 80℃ overnight, and calcined in a high-temperature muffle furnace at a calcination temperature and time of 550℃ and 10h respectively to obtain a composite catalyst.

[0046] Example 2

[0047] The synthetic gel was prepared according to the preset molar ratio of SiO2:TiO2:B2O3:HMI:NH4F:H2O at 1:0.025:0.67:0.7:0.21:30, and the synthesis temperature and synthesis time were 180℃ and 8 days respectively. The crystallized supported Ti-MWW molecular sieve was washed and dried for use. With ethanol as solvent, a metal ferric nitrate solution with a concentration of 0.1mol / L was prepared, and the supported Ti-MWW molecular sieve was immersed in the above solution for 30min under ultrasonic conditions, filtered after immersion, dried in an oven at 80℃ overnight, and calcined in a high-temperature muffle furnace at a calcination temperature and time of 550℃ and 10h respectively to obtain a composite catalyst.

[0048] Example 3

[0049] The synthetic gel was prepared by mixing SiO2:TiO2:B2O3:HMI:NH4F:H2O in a preset molar ratio of 1:0.06:0.67:1.4:0.21:60, and the synthesis temperature and synthesis time were 170℃ and 7 days respectively. The crystallized supported Ti-MWW molecular sieve was washed and dried for use. Using ethanol as solvent, a metal copper nitrate solution with a concentration of 0.05mol / L was prepared, and the supported Ti-MWW molecular sieve was immersed in the above solution for 30min under ultrasonic conditions, filtered after immersion, dried in an oven at 80℃ overnight, and calcined in a high-temperature muffle furnace. The calcination temperature and time were 550℃ and 10h respectively to obtain a composite catalyst.

[0050] The structure of the composite catalyst of supported Ti-MWW molecular sieve and iron oxide prepared in the above embodiment is as follows: Figure 2 , Figure 2 a, b are SEM images of the composite catalyst of supported Ti-MWW molecular sieve and iron oxide; Figure 2 c and d are TEM images of the composite catalyst of supported Ti-MWW molecular sieve and iron oxide. It can be seen from the figure that the molecular sieve with pure phase MWW structure and the metal oxide constitute lamellae, while the composite catalyst of supported Ti-MWW molecular sieve and iron oxide is composed of many ordered lamellae stacked as above, and the lamellae are dense and continuous. The surface of the composite catalyst is mottled, and the metal oxide is evenly distributed in the molecular sieve nanosheet, which increases the catalytic sites of the metal oxide.

[0051] Figure 3 Figure 2 is the XRD spectrum of the supported Ti-MWW molecular sieve and the composite catalyst of supported Ti-MWW molecular sieve and iron oxide. As shown in the figure, the molecular sieve exhibits typical characteristic peaks of Ti-MWW molecular sieve, and the characteristic peak intensity of the composite catalyst of supported Ti-MWW molecular sieve and iron oxide is consistent with that of the supported Ti-MWW molecular sieve.

[0052] Example 4

[0053] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(acetonitrile)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and iron oxide supported by porous alumina beads with a diameter of 2mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / iron oxide ratio are 1.35 and 0.82 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and iron oxide is 30g, and the reaction temperature is 80℃. After 7h of reaction, the conversion rate of styrene is 72.61%, the selectivity of styrene oxide is 51.37%, and the utilization rate of hydrogen peroxide is 96.40%.

[0054] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Figure 4 shown.

[0055] Example 5

[0056] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(acetonitrile)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and iron oxide supported by porous alumina beads with a diameter of 2mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / iron oxide ratio are 1.35 and 0.82 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and iron oxide is 30g, and the reaction temperature is 70℃. After 7h of reaction, the conversion rate of styrene is 52.00%, the selectivity of styrene oxide is 60.38%, and the utilization rate of hydrogen peroxide is 97.04%.

[0057] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Figure 5 shown.

[0058] Example 6

[0059] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(methanol)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and iron oxide supported by porous alumina beads with a diameter of 2mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / iron oxide ratio are 1.35 and 0.82 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and iron oxide is 30g, and the reaction temperature is 80℃. After 7h of reaction, the conversion rate of styrene is 5.50%, the selectivity of styrene oxide is 51.45%, and the utilization rate of hydrogen peroxide is 95.89%.

[0060] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Figure 6 shown.

[0061] Example 7

[0062] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(acetonitrile)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and iron oxide supported by porous alumina beads with a diameter of 2mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / iron oxide ratio are 1.35 and 0.82 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and iron oxide is 20g, and the reaction temperature is 80℃. After 7h of reaction, the conversion rate of styrene is 49.01%, the selectivity of styrene oxide is 71.25%, and the utilization rate of hydrogen peroxide is 95.75%.

[0063] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Figure 7 shown.

[0064] Example 8

[0065] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(acetonitrile)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and copper oxide supported by porous alumina beads with a diameter of 2mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / copper oxide ratio are 1.35 and 0.82 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and copper oxide is 30g, and the reaction temperature is 80℃. After 7h of reaction, the conversion rate of styrene is 25.82%, the selectivity of styrene oxide is 77.11%, and the utilization rate of hydrogen peroxide is 95.24%.

[0066] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Figure 8 shown.

[0067] Example 9

[0068] In the raw material liquid, n(styrene):n(hydrogen peroxide):V(acetonitrile)=0.1mol:0.1mol:30mL. The filler in the fixed bed reactor is a composite catalyst of Ti-MWW molecular sieve and iron oxide supported by porous alumina / silicon dioxide / silicon carbide beads with a diameter of mm. The size of the Ti-MWW molecular sieve on the supported Ti-MWW molecular sieve is 0.2μm, and the TiO2 / SiO2 ratio and TiO2 / iron oxide ratio are 1.35 and 0.64 respectively. The mass of the composite catalyst of the supported Ti-MWW molecular sieve and iron oxide is 30g, and the reaction temperature is 80℃. After 7h of reaction, the conversion rate of styrene is 55.62%, the selectivity of styrene oxide is 62.53%, and the utilization rate of hydrogen peroxide is 96.40%.

[0069] The gas chromatogram and analysis results of the products prepared in the above examples are as follows: Fig. 9 shown.

[0070] Table 1 Summary of application variable conditions

[0071]

[0072] Table 2 Styrene epoxidation performance under different conditions

[0073] Example Styrene conversion rate (%) Epoxystyrene selectivity (%) Hydrogen peroxide utilization rate (%) Example 4 72.61％ 51.37％ 96.40％ Example 5 52.00％ 60.38％ 97.04％ Example 6 5.50％ 51.45％ 95.89％ Example 7 49.01％ 71.25％ 95.75％ Example 8 25.82％ 77.11％ 95.24％ Example 9 55.62％ 62.53％ 96.40％

[0074] According to the comparative analysis of the experimental results, in the embodiments of several control variables, when the solvent in the raw material liquid is acetonitrile and the metal oxide in the composite catalyst is copper oxide, the selectivity of styrene oxide is the highest, which can reach 77.11%. That is, when the solvent in the raw material liquid is acetonitrile and the metal oxide in the composite catalyst is copper oxide, the yield of styrene oxide is the highest, which significantly improves the catalytic performance of the composite catalyst, the reaction rate of the styrene epoxidation reaction, and the yield of the target product.

[0075] Although the description of the present invention has been quite detailed and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A method for preparing a composite catalyst of a Ti-MWW molecular sieve loaded with a metal oxide, characterized in that: The preparation method comprises the following steps: (1) SiO2, TiO2, B2O3, HMI, NH4F and H2O are fully mixed in a first preset ratio to obtain a gel; and the gel and the loaded Ti-MWW molecular sieve layer are transferred to a reactor for crystallization reaction to obtain a loaded Ti-MWW molecular sieve; (2) adding the supported Ti-MWW molecular sieve into a metal nitrate solution prepared with ethanol as solvent and performing ultrasonic impregnation to obtain a supported composite catalyst; Wherein, the metal nitrate solution is any one of iron nitrate, copper nitrate, cobalt nitrate, nickel nitrate, magnesium nitrate, and lanthanum nitrate solutions; the concentration of the metal nitrate solution is 0.05-0.1 mol / L; The Ti-MWW molecular sieve loaded with metal oxide composite catalyst obtained by the preparation method is a Ti-MWW molecular sieve and metal oxide composite catalyst loaded with a porous microsphere carrier, wherein the porous microsphere carrier is one or more of porous alumina / silicon dioxide / silicon carbide beads, and the diameter of the porous microsphere carrier is 1-10 mm; The composite catalyst of Ti-MWW molecular sieve loaded with metal oxide has a pure phase MWW structure molecular sieve and metal oxide to form a sheet, and the composite catalyst of supported Ti-MWW molecular sieve and metal oxide is formed by stacking many of the above ordered sheets, and the sheets are dense and continuous; the surface of the composite catalyst is mottled, and the metal oxide is evenly distributed in the molecular sieve nanosheets; The size of the Ti-MWW molecular sieve on the composite catalyst is 0.2 μm, the SiO2 / TiO2 ratio is 1.35, the TiO2 / iron oxide ratio is 0.82 or 0.64, and the TiO2 / copper oxide ratio is 0.

82.

2. The method for preparing a supported composite catalyst according to claim 1, wherein In the step of fully mixing SiO2, TiO2, B2O3, HMI, NH4F and H2O according to a first preset molar ratio to prepare a gel: The first preset molar ratio is 1: 0.035-0.06: 0.67: 0.7-1.4: 0.21: 30-60.

3. The method for preparing a supported composite catalyst according to claim 1, characterized in that: In the step of transferring the gel and the loaded Ti-MWW molecular sieve layer to a reactor for crystallization reaction to obtain the loaded Ti-MWW molecular sieve: The crystallization reaction time is 6-8 days, and the reaction temperature of the crystallization reaction is 170-180 °C.

4. A supported composite catalyst, characterized in that The supported composite catalyst is obtained by the preparation method according to any one of claims 1 to 3.

5. Use of the supported composite catalyst as claimed in claim 4 in the preparation of styrene oxide.

6. The use according to claim 5, characterized in that: The applications include: In the presence of a composite catalyst, styrene, hydrogen peroxide and a solvent are added to a raw material bottle in a second preset ratio, mixed and heated, and after mixing, the raw material liquid is transferred to a fixed bed reactor to react with the composite catalyst in a third preset ratio. After the reaction, the reaction liquid is circulated back to the raw material bottle from the fixed bed reactor, and styrene oxide is obtained after the cyclic operation.

7. The use according to claim 6, characterized in that: In the step of adding styrene, hydrogen peroxide and solvent into the raw material bottle according to the second preset ratio and mixing and heating: In the second preset ratio, the molar ratio of styrene to hydrogen peroxide is 1:1-4; the volume ratio of styrene to solvent is 1:5-20, wherein the solvent is any one of acetonitrile and / or methanol.

8. The use according to claim 6, characterized in that: In the step of transferring the raw material liquid to the fixed bed reactor to react with the composite catalyst in a second preset ratio: The third preset ratio of the volume of the raw material liquid to the mass of the composite catalyst is 1-4:1.

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