CuO X / Ti-MWW composite catalysts, their preparation methods and applications

Abstract

The application belongs to the technical field of catalyst preparation, and particularly relates to a CuOx / Ti-MWW composite catalyst and a preparation method and application thereof. The method comprises the following steps: mixing and stirring hexamethyleneimine, water, tetrabutyl titanate and silica sol, and irradiating a precursor solution by using an ultraviolet light assisted method; placing the precursor solution and porous alpha-Al2O3 particles coated with Ti-MWW molecular sieves in a reaction kettle to perform a hydrothermal synthesis crystallization reaction, then placing the particles in a fluoride solution for impregnation, washing, drying, calcining to obtain a monolithic multi-level hole Ti-MWW molecular sieve; finally, mixing the molecular sieve with a Cu(OH)2 suspension and placing the mixture in a reaction kettle, then placing the reaction kettle in an oven to perform a reaction, after the reaction, washing, drying and calcining, and the catalyst is obtained. The catalyst provided by the application not only improves the dispersion degree of CuOx, but also enhances the interaction between CuOx and the Ti-MWW carrier, thereby significantly improving the activity and stability of the catalyst.

Description

Technical Field

[0001] This application belongs to the field of catalyst preparation technology, specifically relating to a CuOx / Ti-MWW composite catalyst, its preparation method, and its application. Background Technology

[0002] Epoxyphenylene oxide, as an important chemical intermediate, is widely used in the synthesis of resins, surfactants, and pharmaceutical intermediates. Traditional processes such as the halohydrin method and peroxyacid oxidation method suffer from severe equipment corrosion, numerous byproducts, and high costs. In recent years, green catalytic processes using hydrogen peroxide (H2O2) as an oxygen source have become a research hotspot due to their environmental friendliness. However, this system faces challenges such as insufficient catalyst active sites, low H2O2 utilization, and poor product selectivity. Ti-MWW molecular sieves, due to their unique MWW topology (containing ten-membered ring sinusoidal channels and twelve-membered ring supercages), exhibit excellent diffusion performance and catalytic activity for macromolecular substrates (such as styrene) and have been widely used in olefin epoxidation reactions.

[0003] However, traditional methods for synthesizing Ti-MWW molecular sieves mainly include post-treatment synthesis, hydrothermal synthesis, dry gel synthesis, and dual-template synthesis. However, these methods all have limitations. For example, post-treatment synthesis typically involves harsh conditions and complex operations, and easily forms non-framework titanium species, leading to poor stability; hydrothermal synthesis requires the addition of excessive boric acid, and boron species can affect the catalytic performance of the titanium active centers; while the dry gel method reduces the amount of boric acid used, it increases the diffusion resistance of substrate and product molecules, resulting in reduced catalytic performance; and although the dual-template method can synthesize boron-free Ti-MWW molecular sieves, the synthesis process is relatively complex. Therefore, developing a novel and efficient method for synthesizing Ti-MWW molecular sieves is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a CuOx / Ti-MWW composite catalyst, its preparation method, and its application. Specifically, the following technical solution is adopted:

[0005] In a first aspect, the present invention provides a method for preparing a CuOx / Ti-MWW composite catalyst, comprising the following steps:

[0006] S1. Mix and stir hexamethyleneimine, water, tetrabutyl titanate and silica sol, and then irradiate with ultraviolet light to obtain a precursor solution;

[0007] S2. The precursor solution and porous α-Al2O3 particles coated with Ti-MWW molecular sieve are placed in a reaction vessel to carry out a hydrothermal synthesis crystallization reaction. After washing, drying and calcining, an integral Ti-MWW molecular sieve is obtained.

[0008] S3. The monolithic Ti-MWW molecular sieve is immersed in a fluoride solution, washed, dried and calcined to obtain a monolithic hierarchical porous Ti-MWW molecular sieve.

[0009] S4. The monolithic multi-level porous Ti-MWW molecular sieve is mixed with Cu(OH)2 suspension and placed in a reaction vessel. Then, the reaction vessel is placed in an oven for reaction. After the reaction is completed, the mixture is washed, dried, and calcined to obtain the CuOx / Ti-MWW composite catalyst.

[0010] This invention proposes a strategy for preparing monolithic CuOx / Ti-MWW composite catalysts using a UV-etching-deposition method. Firstly, UV-assisted crystallization technology accelerates the framework assembly of Ti-MWW molecular sieves, shortening the synthesis time to 4 days, while simultaneously suppressing anatase formation and significantly increasing the proportion of titanium species in the framework. Secondly, this invention employs fluoride etching of the molecular sieve to form a monolithic Ti-MWW molecular sieve with a hierarchical porous structure. CuOx nanoparticles are introduced onto the surface and within the hierarchical channels of the monolithic Ti-MWW molecular sieve using Cu(OH)2 deposition, achieving precise confinement of CuOx nanoparticles within these channels. The monolithic CuOx / Ti-MWW composite catalyst effectively solves the mass transfer limitation problem, achieving high-efficiency catalysis under mild conditions. This provides a new approach for designing high-performance non-precious metal catalysts and is expected to promote the green upgrading of styrene epoxidation processes.

[0011] This invention first uses ultraviolet light irradiation to excite active species in the molecular sieve precursor, promoting their structural transformation and crystallization during synthesis, thereby shortening the crystallization time of Ti-MWW molecular sieves. Then, NH4F is used as a mild etchant, whose etching process is more easily controlled by gradient regulation of fluoride ion concentration, solving the problem of framework collapse caused by traditional HF etching. Finally, combined with the precise controllability of Cu(OH)2 deposition, highly dispersed CuOx nanoparticles and strong interactions can be achieved on the Ti-MWW surface, forming a "defect site-metal oxide" synergistic catalytic system. Studies have shown that the introduction of CuOx can not only promote the activation of H2O2 to generate hydroxyl radicals through electron transfer (… The basic sites on the surface of Ti-MWW can also inhibit the ring-opening of epoxide phenylene oxide, thereby simultaneously improving styrene conversion and product selectivity. In addition, the hierarchical porous structure of Ti-MWW combined with the high redox activity of CuOx can effectively solve the mass transfer limitation problem and achieve efficient catalysis under mild conditions.

[0012] As a further preferred embodiment, the molar ratio of SiO2, TiO2, B2O3, hexamethyleneimine (HMI), and H2O in the precursor solution in S1 is 1:0.035:0.67:1.4:30.

[0013] As a further preferred embodiment, the ultraviolet light intensity during ultraviolet-assisted irradiation is 40 W / m². 2 -160W / m 2 The duration is 4 h to 20 h.

[0014] As a further preferred embodiment, the crystallization reaction in S2 is carried out at a temperature of 160 ℃-200 ℃ for 2 to 6 days, and at a calcination temperature of 450 ℃-550 ℃.

[0015] As a further preferred embodiment, the fluoride solution in S3 is an NH4F solution.

[0016] As a further preferred embodiment, the concentration of the fluoride solution is 1 wt%-4 wt%; the immersion time is 0.5 h-5 h.

[0017] As a further preferred embodiment, the Cu(OH)2 suspension in S4 is obtained by mixing ammonia water and Cu(NO3)2·3H2O solution and adjusting the pH to 6;

[0018] The reaction is carried out in an oven at a temperature of 30℃-100℃ for 2 h-24 h.

[0019] The calcination temperature is 250℃-350℃, and the time is 6 h-10 h.

[0020] Secondly, the present invention provides a CuOx / Ti-MWW composite catalyst, which is prepared by the above-described preparation method.

[0021] Thirdly, the present invention provides the application of the above-mentioned CuOx / Ti-MWW composite catalyst in the synthesis of epoxide phenylene oxide.

[0022] Fourthly, the present invention provides a method for synthesizing epoxide phenylene oxide, comprising the following steps:

[0023] Styrene, hydrogen peroxide and acetonitrile solution were mixed to obtain a reaction solution, which was then placed in a reaction flask and heated. At the same time, the CuOx / Ti-MWW composite catalyst mentioned above was added to carry out the reaction. After the reaction was completed, the mixture was centrifuged to obtain the epoxy phenyl ethane.

[0024] The molar ratio of styrene to hydrogen peroxide is 1:2; the volume ratio of styrene to solvent is 1:5-20; and the amount of CuOx / Ti-MWW composite catalyst added is 5%~20% of the mass percentage of the reaction solution.

[0025] As a further preferred embodiment, the reaction temperature is 40℃-90℃ and the reaction time is 4 h-9 h.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The preparation method provided by this invention, on the one hand, greatly shortens the crystallization time of the monolithic Ti-MWW molecular sieve by ultraviolet irradiation and can significantly increase the proportion of framework titanium species; on the other hand, the monolithic Ti-MWW molecular sieve is etched with fluoride to form a pitted structure on the surface of the molecular sieve, and then Cu oxide nanoparticles are uniformly loaded onto the surface and multi-level channels of the Ti-MWW molecular sieve by deposition. The monolithic CuOx / Ti-MWW composite catalyst prepared by the "ultraviolet-assisted-etching-deposition" method of this invention not only improves the dispersion of CuOx, but also enhances the interaction between CuOx and the Ti-MWW support, thereby significantly improving the activity and stability of the catalyst. Therefore, the monolithic CuOx / Ti-MWW composite catalyst can not only efficiently activate H2O2 through the framework titanium sites of the monolithic Ti-MWW molecular sieve to generate highly reactive oxygen species (such as... CuOx provides a sufficient oxygen source for styrene epoxidation and can accelerate the conversion of reaction intermediates through the redox cycle of CuOx. It also utilizes its surface basic sites to inhibit the ring-opening side reaction of epoxide phenylene oxide, thus exhibiting a synergistic catalytic effect and greatly enhancing the efficiency of styrene epoxidation.

[0028] (2) The process for preparing epoxide phenylene oxide adopted in this invention is green and environmentally friendly, reducing the generation of harmful solvents and by-products, and conforming to the current concept of sustainable development. By precisely controlling the reaction conditions and raw material ratios, efficient utilization of resources and minimized emissions of waste are achieved, providing an environmentally friendly solution for industrial production. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The image shows the XRD patterns of the monolithic Ti-MWW molecular sieve and the monolithic CuOx / Ti-MWW composite catalyst before and after NH4F impregnation and etching in Example 1 of the present invention.

[0031] Figure 2 The image shown is a transmission electron microscope (TEM) image of the monolithic Ti-MWW molecular sieve and the monolithic CuOx / Ti-MWW composite catalyst before and after NH4F impregnation and etching in Example 1 of the invention.

[0032] Figure 3The image shows the UV-vis spectra of the monolithic Ti-MWW molecular sieve and the monolithic CuOx / Ti-MWW composite catalyst before and after NH4F impregnation and etching in Example 1 of the invention.

[0033] Figure 4 The figures shown are the N2 adsorption-desorption curves and pore size distribution diagrams of the monolithic Ti-MWW molecular sieve and the monolithic CuOx / Ti-MWW composite catalyst before and after NH4F impregnation and etching in Example 1 of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1

[0036] A method for preparing a CuOx / Ti-MWW composite catalyst, specifically comprising the following steps:

[0037] (1) Preparation of monolithic Ti-MWW molecular sieves by UV-assisted method and hydrothermal synthesis method

[0038] A precursor solution was prepared by mixing and stirring hexamethyleneimine, deionized water, tetrabutyl titanate, silica sol, and boric acid (the molar ratio of SiO2, TiO2, B2O3, hexamethyleneimine, and H2O in the precursor solution was 1:0.035:0.67:1.4:30). Then, the precursor solution was subjected to UV-assisted light at an intensity of 80 W / m². 2 Irradiation for 16 hours;

[0039] Porous α-Al2O3 particles (1 mm in diameter) coated with Ti-MWW molecular sieve and a precursor solution irradiated with ultraviolet light (the mass ratio of porous α-Al2O3 particles of Ti-MWW molecular sieve to precursor solution was 100:1) were transferred together to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal synthesis. Crystallization was carried out at 180℃ for 4 days. After the reaction was completed, the sample was cleaned, dried and calcined at 550℃ for 10 h to obtain monolithic Ti-MWW molecular sieve.

[0040] (2) Preparation of monolithic hierarchical porous Ti-MWW molecular sieve by fluoride etching

[0041] The monolithic Ti-MWW molecular sieve obtained above was immersed in an NH4F solution with a concentration of 2wt% at 50℃ for 1h, with a solid-liquid ratio of 1:100 (g / mL). After immersion, the sample was washed, dried, and calcined at 300℃ for 10h to obtain a monolithic hierarchical porous Ti-MWW molecular sieve (denoted as Ti-MWW-2-60).

[0042] (3) Preparation of monolithic CuOx / Ti-MWW composite catalyst by deposition-calcination

[0043] Ammonia was added dropwise to a 3wt% copper nitrate solution to adjust the pH to 6, forming a Cu(OH)2 suspension. The etched monolithic hierarchical porous Ti-MWW molecular sieve and the Cu(OH)2 suspension were then placed in a stainless steel reactor with a polytetrafluoroethylene liner at a ratio of 1:10 (w / v). The reactor was then placed in an 80℃ rotary oven for 24 h at a rotation speed of 15 rpm. After etching, the sample was removed, cleaned, dried, and calcined (at a temperature of 300℃ for 5 h), and then dried to obtain a CuOx / Ti-MWW composite catalyst (denoted as 3Cu / Ti-MWW-2-60).

[0044] The CuOx / Ti-MWW composite catalyst prepared above was characterized and tested. Specific results are as follows: Figures 1-4 As shown;

[0045] Figure 1 XRD patterns of the monolithic Ti-MWW molecular sieve, monolithic hierarchical Ti-MWW molecular sieve, and monolithic CuOx / Ti-MWW composite catalyst prepared in the above embodiments, with the precursor solution at 80 W / m 2 Under ultraviolet irradiation, the sample exhibited characteristic peaks of the typical MWW structure (2θ = 7.20°, 7.92°, 9.66°, 20.06°, 22.44°, and 26.42°), confirming that highly crystalline MWW molecular sieves can be prepared in 4 days with ultraviolet light assistance. Furthermore, the monolithic CuOx / Ti-MWW composite catalyst, after fluoride etching and metal CuOx deposition, not only exhibited characteristic peaks of the MWW structure (2θ = 7.20°, 7.92°, 9.66°, 20.06°, 22.44°, and 26.42°), but also showed typical CuO structure characteristic peaks (2θ = 35.9°, 39.2°, and 66.5°).

[0046] Figure 2These are transmission electron microscopy (TEM) images of a monolithic Ti-MWW molecular sieve and a monolithic CuOx / Ti-MWW composite catalyst. The Ti-MWW molecular sieve exhibits a distinct layered structure. In the monolithic CuOx / Ti-MWW composite catalyst, after fluoride etching and CuOx deposition, numerous pitting structures appear on the surface of the layered molecular sieve, and obvious CuOx nanoparticles are present on the surface. Therefore, the monolithic CuOx / Ti-MWW composite catalyst retains the MWW molecular sieve structure, and CuOx is successfully loaded onto the Ti-MWW molecular sieve surface after the fluoride etching and deposition process.

[0047] Figure 3 The UV-Vis spectra of monolithic Ti-MWW molecular sieves, monolithic hierarchical porous Ti-MWW molecular sieves, and CuOx / Ti-MWW composite catalysts are shown. Compared to Ti-MWW molecular sieves, the monolithic CuOx / Ti-MWW composite catalyst exhibits enhanced intensity of characteristic absorption peaks in the 210-230 nm range, indicating increased Ti tetracoordination. Conversely, the absorption peaks at 260 nm-280 nm, belonging to non-framework six-coordination Ti (TiO6), are significantly weakened. This may be due to the selective removal of amorphous silicon species from the molecular sieve surface during etching, effectively stripping away the silica-oxygen layer surrounding the framework Ti and exposing more previously masked tetracoordination Ti active sites. Furthermore, the monolithic CuOx / Ti-MWW composite catalyst exhibits a wider absorption range in the 230 nm-340 nm range, corresponding to charge transfer transitions in oligomeric CuOx nanoparticles. This phenomenon indicates that the etched Ti-MWW molecular sieve surface provides stable anchoring points for CuOx species, achieving high dispersion loading of CuOx on the support surface.

[0048] Figure 4This section presents the N2 adsorption-desorption curves and pore size distribution diagrams for monolithic Ti-MWW molecular sieves, monolithic hierarchical Ti-MWW molecular sieves, and monolithic CuOx / Ti-MWW composite catalysts. In the lower relative pressure range, the adsorption isotherms of the Ti-MWW molecular sieves, monolithic hierarchical Ti-MWW molecular sieves, and monolithic CuOx / Ti-MWW composite catalysts exhibit a sharp upward trend, indicating the presence of numerous microporous structures within the materials. Conversely, in the higher relative pressure range, the adsorption capacity of the monolithic hierarchical Ti-MWW molecular sieves and the CuOx / Ti-MWW composite catalysts shows a significant increase, indicating that the fluoride etching process can create macropores or macropores in the Ti-MWW molecular sieves. The pore size distribution curves show that the pore size of the monolithic Ti-MWW molecular sieves is mainly concentrated around 2 nm, while the monolithic hierarchical Ti-MWW molecular sieves exhibit a distinct bipore distribution characteristic, with macropores of approximately 2 nm and 20 nm-40 nm respectively. After CuOx nanoparticles are deposited, the BET specific surface area and total pore volume of the CuOx / Ti-MWW composite catalyst decrease compared to the monolithic hierarchical Ti-MWW molecular sieve. This can be attributed to the fact that the deposition of CuOx nanoparticles in the pores occupies part of the pore space.

[0049] Based on the above characterization results, it can be concluded that fluoride etching is an effective post-processing method for preparing hierarchical porous molecular sieves, capable of precisely controlling the pore structure and surface chemical properties of Ti-MWW molecular sieves. The process of depositing CuOx nanoparticles in this invention not only preserves the "micropore-macropore" hierarchical pore framework constructed during the etching process, but also ensures the high-efficiency mass transfer between styrene and H2O2 by maintaining the integrity of the 20nm-40nm macropore range. Furthermore, the broad absorption peaks of 230nm-340nm in UV-vis characterization confirm that CuO is anchored in a highly dispersed state within the pores, avoiding pore blockage caused by particle agglomeration. This controllability provides a powerful tool for designing and preparing high-performance molecular sieve catalysts.

[0050] The CuOx / Ti-MWW composite catalyst prepared above was used to catalyze the epoxidation reaction of styrene, as detailed below:

[0051] Styrene, hydrogen peroxide, and acetonitrile were added to a reaction flask at a molar ratio of styrene to hydrogen peroxide of 1:2 and a volume ratio of styrene to acetonitrile of 1:10. The mixture was heated to 80°C, and 10% (by mass) of a monolithic CuOx / Ti-MWW composite catalyst was added to the reaction solution. The reaction was carried out for 8 hours at a standard atmosphere. After the reaction was completed, the solid catalyst and the reaction solution were separated by centrifugation. The component content in the separated reaction solution was analyzed by gas chromatography, and the styrene conversion rate and epoxide selectivity were calculated.

[0052] The composition of the reaction solution separated by gas chromatography showed that the styrene conversion rate and the selectivity for epoxide were 88.98% and 80.11%, respectively.

[0053] Example 2

[0054] A method for preparing a CuOx / Ti-MWW composite catalyst is described. The specific preparation process is similar to that in Example 1, except that "impregnation in a 2wt% NH4F solution at 50°C for 1 hour" is replaced with "impregnation in a 2wt% NH4F solution at 50°C for 30 minutes". All other processes remain unchanged, and the CuOx / Ti-MWW composite catalyst is obtained.

[0055] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation of styrene, and the styrene conversion and epoxide selectivity were 83.76% and 79.01%, respectively.

[0056] Example 3

[0057] A method for preparing a CuOx / Ti-MWW composite catalyst is described. The specific preparation process is similar to that in Example 1, except that "impregnation in a 2wt% NH4F solution at 50°C for 1 hour" is replaced with "impregnation in a 1wt% NH4F solution at 50°C for 1 hour". All other processes remain unchanged, and the CuOx / Ti-MWW composite catalyst is obtained.

[0058] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation of styrene, and the styrene conversion and epoxide selectivity were 80.36% and 77.15%, respectively.

[0059] Example 4

[0060] A method for preparing a CuOx / Ti-MWW composite catalyst is described, the specific preparation process of which is similar to that of Example 1, the only difference being that the precursor solution is prepared using an ultraviolet light-assisted method under ultraviolet light intensity of 80 W / m². 2 Replace "16 h of irradiation" with "The precursor solution was irradiated with ultraviolet light using an ultraviolet light-assisted method at an ultraviolet light intensity of 120 W / m²". 2 After irradiating for 16 h, with the rest of the process unchanged, CuOx / Ti-MWW composite catalyst was obtained.

[0061] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation of styrene, and the styrene conversion and epoxide selectivity were 86.23% and 76.16%, respectively.

[0062] Example 5

[0063] A method for preparing a CuOx / Ti-MWW composite catalyst is described, the specific preparation process of which is similar to that of Example 1, the only difference being that the precursor solution is prepared using an ultraviolet light-assisted method under ultraviolet light intensity of 80 W / m². 2 Replace "16 h of irradiation" with "The precursor solution was irradiated with ultraviolet light using an ultraviolet light-assisted method at an ultraviolet light intensity of 80 W / m²". 2 After irradiating for 24 h with the rest of the process unchanged, CuOx / Ti-MWW composite catalyst was obtained.

[0064] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation of styrene, and the styrene conversion and epoxide selectivity were 87.28% and 79.68%, respectively.

[0065] Comparative Example 1

[0066] A method for preparing a monolithic hierarchical porous Ti-MWW molecular sieve is described. The preparation process is similar to that in Example 1, except that the monolithic Ti-MWW molecular sieve is immersed in an NH4F solution with a concentration of 2wt% at 50℃ for 1 hour without reacting with Cu(OH)2 suspension (without loading Cu metal oxides) to obtain the monolithic hierarchical porous Ti-MWW molecular sieve.

[0067] The obtained monolithic hierarchical porous Ti-MWW molecular sieve was used to catalyze the epoxidation reaction of styrene, with a styrene conversion rate of 59.16% and an epoxide selectivity of 79.35%.

[0068] Comparative Example 2

[0069] A method for preparing monolithic Ti-MWW molecular sieves is described. The specific preparation process is similar to that in Example 1, except that an ultraviolet-assisted method and a hydrothermal synthesis method are used to obtain monolithic Ti-MWW molecular sieves (catalytic performance is tested directly without fluoride etching and Cu oxide loading).

[0070] The monolithic Ti-MWW molecular sieve prepared by this method was used to catalyze the epoxidation reaction of styrene, with a styrene conversion rate of 56.87% and an epoxide selectivity of 77.98%.

[0071] Comparative Example 3

[0072] A method for preparing a CuOx / Ti-MWW composite catalyst is described. The specific preparation process is similar to that in Example 1, except that "the precursor solution is not irradiated with ultraviolet light and reacts directly with porous α-Al2O3 particles coated with Ti-MWW molecular sieves". All other processes remain unchanged, resulting in an integral Ti-MWW molecular sieve catalyst.

[0073] The monolithic Ti-MWW molecular sieve catalyst prepared by this method was used to catalyze the epoxidation reaction of styrene, with a styrene conversion rate of 44.72% and an epoxide selectivity of 61.53%.

[0074] Comparative Example 4

[0075] A method for preparing a CuOx / Ti-MWW composite catalyst is described. The specific preparation process is similar to that in Example 1, except that the "NH4F solution" is replaced with "NaF solution". All other processes remain unchanged to obtain the CuOx / Ti-MWW composite catalyst.

[0076] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation reaction of styrene, with a styrene conversion rate of 68.53% and an epoxide selectivity of 59.66%.

[0077] Comparative Example 5

[0078] A method for preparing a CuOx / Ti-MWW composite catalyst is similar to that in Example 1. The only difference is that the monolithic Ti-MWW molecular sieve obtained in step (1) is not fluorinated and is directly placed with Cu(OH)2 suspension in a stainless steel reactor with a polytetrafluoroethylene liner for subsequent reaction. The rest of the process remains unchanged, and the CuOx / Ti-MWW composite catalyst is obtained.

[0079] The CuOx / Ti-MWW composite catalyst prepared by this method was used to catalyze the epoxidation reaction of styrene, with a styrene conversion rate of 70.81% and an epoxide selectivity of 74.28%.

[0080] Table 1 shows the styrene epoxidation performance data of Examples 1-5 and Comparative Examples 1-5;

[0081] Table 1. Data on the epoxidation performance of styrene in Examples 1-5 and Comparative Examples 1-5

[0082]

[0083] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A CuO x The method for preparing the / Ti-MWW composite catalyst is characterized by, Includes the following steps: S1. Mix and stir hexamethyleneimine, water, tetrabutyl titanate, silica sol and boric acid, and then irradiate with ultraviolet light to obtain a precursor solution. S2. The precursor solution and porous α-Al2O3 particles coated with Ti-MWW molecular sieve are placed in a reaction vessel to carry out a hydrothermal synthesis crystallization reaction. After washing, drying and calcining, an integral Ti-MWW molecular sieve is obtained. S3. The monolithic Ti-MWW molecular sieve is immersed in a fluoride solution, washed, dried and calcined to obtain a monolithic hierarchical porous Ti-MWW molecular sieve. S4. The monolithic multi-level porous Ti-MWW molecular sieve is mixed with Cu(OH)2 suspension and placed in a reaction vessel. The reaction vessel is then placed in an oven for reaction. After the reaction is completed, the mixture is washed, dried, and calcined to obtain CuO. x / Ti-MWW composite catalyst; The molar ratio of SiO2, TiO2, B2O3, hexamethyleneimine, and H2O in the precursor solution described in S1 is 1:0.035:0.67:1.4:30; The ultraviolet light intensity during ultraviolet-assisted irradiation is 40 W / m. 2 -160W / m 2 The time frame is 4 hours to 20 hours. The fluoride solution in S3 is an NH4F solution.

2. The preparation method according to claim 1, characterized in that, The crystallization reaction in S2 takes place at a temperature of 160℃-200℃ for 2-6 days, and at a calcination temperature of 450℃-550℃.

3. The preparation method according to claim 1, characterized in that, The concentration of the fluoride solution is 1 wt%-4 wt%; the immersion time is 0.5 h-5 h.

4. The preparation method according to claim 1, characterized in that, The Cu(OH)2 suspension in S4 was obtained by mixing ammonia water and Cu(NO3)2·3H2O solution and adjusting the pH to 6; The reaction is carried out in an oven at a temperature of 30℃-100℃ for 2 h-24 h. The calcination temperature is 250℃-350℃, and the time is 6 h-10 h.

5. A CuO x / Ti-MWW composite catalyst, characterized in that It is prepared by the preparation method according to any one of claims 1-4.

6. The CuO according to claim 5 x Application of / Ti-MWW composite catalyst in the synthesis of epoxide phenylene oxide.

7. A method for synthesizing epoxide phenylene oxide, characterized in that, Includes the following steps: A reaction solution was prepared by mixing styrene, hydrogen peroxide, and acetonitrile solution, and then placed in a reaction flask and heated while adding CuO as described in claim 5. x The reaction was carried out using the / Ti-MWW composite catalyst, and centrifugation was performed after the reaction was completed to obtain the epoxy phenyl ethane. The molar ratio of styrene to hydrogen peroxide is 1:2; the volume ratio of styrene to solvent is 1:5-20; the CuO... x The amount of the / Ti-MWW composite catalyst added is 5% to 20% of the mass percentage of the reaction solution.

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