Propylene epoxidation catalyst, process for the preparation thereof and process for the gas phase epoxidation of propylene

Abstract

The present application relates to the technical fields of propylene epoxidation catalyst, and discloses a propylene epoxidation catalyst, characterized in that the propylene epoxidation catalyst comprises a hierarchical pore titanium silicalite molecular sieve and nano gold loaded on the hierarchical pore titanium silicalite molecular sieve; wherein the content of the nano gold is 0.01wt%-1wt% based on the total amount of the propylene epoxidation catalyst; wherein the total pore volume of the propylene epoxidation catalyst is 0.18-0.56cm 3 / g, the particle size is 100-250nm, and the crystallinity is greater than or equal to 50%. By loading nano gold particles on the titanium silicalite molecular sieve with specific physical parameters under the condition of inert gas pressurization, the obtained catalyst has high catalytic activity when applied to propylene gas phase epoxidation reaction, the propylene conversion rate is increased to 10%-20%, and the selectivity of propylene oxide is increased to 90%-95%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of propylene epoxidation, in particular to a propylene epoxidation catalyst, a preparation method thereof and a propylene gas phase epoxidation method. BACKGROUND

[0002] Propylene oxide is a very important organic chemical intermediate, and its downstream industry chain is long and its terminal application is wide. Propylene oxide can be used to prepare products such as propylene glycol, polyether polyol and dimethyl carbonate, which can be used to produce polyurethane resin, unsaturated polyester resin, plasticizer, flame retardant, lubricating oil and other derivatives, and finally applied to furniture, home appliances, automobiles, building insulation materials, coatings and other fields closely related to people's life.

[0003] The method of preparing propylene oxide by propylene gas phase direct epoxidation is more green, environmentally friendly, economical and efficient than the traditional chlorohydrination method and co-oxidation method, meets the requirements of laws and regulations on environmental protection, and also meets people's pursuit of economic benefits. At the same time, compared with the liquid phase epoxidation method, the process layout is more flexible because the hydrogen peroxide production device is reduced. The propylene gas phase epoxidation process usually uses metal (Au, Ag, Pd) supported titanium-containing carrier (TiO2, TiO2-SiO2, TS-1, HTS, TS-2, Ti-MCM-41, etc.) as catalyst. In recent years, more research has been conducted on Au / TS-1 catalyst. On the one hand, Au nanoparticles play a good catalytic role in the in-situ synthesis of hydrogen peroxide from hydrogen and oxygen; on the other hand, TS-1 molecular sieve has a stable MFI framework structure and four-coordinated Ti active center, which is beneficial to the propylene epoxidation reaction.

[0004] Although the TS-1 molecular sieve has a large number of framework Ti atoms, the ten-membered ring channel of the MFI structure is relatively narrow, and the micropore with a pore size of 0.55 nm occupies the main part. When the reaction molecules or product molecules diffuse in the pore, accumulation may occur, which further leads to the plugging and deactivation of the catalyst. In addition, the narrow pore structure also makes it difficult to accommodate Au nanoparticles dispersed therein to play a synergistic catalytic role with the more Ti active centers in the bulk phase. Therefore, there is a need for improved propylene epoxidation catalysts. SUMMARY

[0005] The purpose of the present application is to overcome the problem of poor catalytic performance of the propylene epoxidation catalyst in the prior art, and to provide a propylene epoxidation catalyst, a preparation method thereof and a propylene gas phase epoxidation method.

[0006] To achieve the above object, the present application provides a propylene epoxidation catalyst in the first aspect, wherein the propylene epoxidation catalyst comprises a hierarchical porous titanosilicate molecular sieve and nano-gold supported on the hierarchical porous titanosilicate molecular sieve; wherein the content of the nano-gold is 0.01wt%-1wt% based on the total amount of the propylene epoxidation catalyst; wherein the total pore volume of the propylene epoxidation catalyst is 0.18-0.56cm 3 / g, the particle size is 100-250nm, and the crystallinity is ≥50%.

[0007] The present application provides a preparation method of a propylene epoxidation catalyst in the second aspect, which comprises the following steps:

[0008] (1) mixing a silicon source, an alkaline template agent, a titanium source, water and isopropyl alcohol uniformly to obtain a titanosilica sol;

[0009] (2) adding a compound represented by formula (I) into the titanosilica sol, and subjecting the obtained mixture to hydrothermal crystallization and calcination to obtain a hierarchical porous titanosilicate molecular sieve;

[0010]

[0011] wherein i is an integer of 0-10; R1, R2 and R3 are each independently selected from C1-C6 alkyl;

[0012] (3) mixing the hierarchical porous titanosilicate molecular sieve with an aqueous solution containing a gold-containing compound, and then adding a pH adjusting agent to adjust the pH of the obtained mixture to 6-10 to obtain a first suspension;

[0013] (4) subjecting the first suspension to pressurized mixing under the protection of an inert gas to obtain a second suspension;

[0014] (5) filtering the second suspension, and subjecting the obtained filter residue to calcination to obtain the propylene epoxidation catalyst.

[0015] The present application provides a propylene epoxidation catalyst prepared by the method according to the second aspect in the third aspect.

[0016] The present application provides a method for propylene gas phase epoxidation in the fourth aspect, which comprises: mixing hydrogen, oxygen and propylene under the protection of an inert gas and in the presence of a catalyst to obtain propylene oxide; the catalyst is the propylene epoxidation catalyst according to the first and third aspects.

[0017] By the technical scheme, the catalyst obtained by loading nano gold particles on the titanium-silicon molecular sieve with specific physical parameters under the condition of inert gas pressurization has high catalytic activity when applied to the propylene gas phase epoxidation reaction, the propylene conversion rate is increased to 10%-20%, and the selectivity of propylene oxide is increased to 90%-95%. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the reaction path diagram of the propylene gas phase epoxidation in the application;

[0019] Figure 2 is the pore size distribution diagram of the titanium-silicon molecular sieve obtained in preparation example 1 of the application;

[0020] Figure 3 is the TEM diagram of the titanium-silicon molecular sieve obtained in preparation example 1 of the application;

[0021] Figure 4 is the XRD diagram of the titanium-silicon molecular sieve obtained in preparation example 1 of the application;

[0022] Figure 5 is the XRD diagram of the titanium-silicon molecular sieve obtained in preparation example 5 of the application;

[0023] Figure 6 is the pore size distribution diagram of the titanium-silicon molecular sieve obtained in preparation example 6 of the application. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly included within the range. The ranges are understood to be shorthand for describing each and every value that falls within the range. Any value within the range, including the endpoints, can be combined with any other value or claim to make a new claim intended to fall within the scope of the application. The endpoints of all ranges and any values between the endpoints are included as are individual values unless specifically stated otherwise.

[0025] The first aspect of the application provides a propylene epoxidation catalyst, wherein the propylene epoxidation catalyst comprises a hierarchical pore titanium-silicon molecular sieve, and nano gold loaded on the hierarchical pore titanium-silicon molecular sieve; wherein the content of the nano gold is 0.01wt%-1wt% based on the total amount of the propylene epoxidation catalyst; wherein the total pore volume of the propylene epoxidation catalyst is 0.18-0.56cm 3 / g, the particle size is 100-250nm, and the crystallinity is ≥50%.

[0026] According to the application, preferably, the molar ratio of titanium to silicon in the propylene epoxidation catalyst is 0.001-0.04:1; preferably 0.005-0.025:1.

[0027] In the present application, in the infrared spectrum of the propylene epoxidation catalyst, the peak at a wave number of 960 cm -1 is a characteristic peak of a skeleton Ti atom, the peak at a wave number of 800 cm -1 is a characteristic peak of a Si-O-Si structure, the ratio of the peak area at a wave number of 960 cm -1 to the peak area at a wave number of 800 cm -1 is too small, which indicates that the content of the skeleton Ti atom in the propylene epoxidation catalyst is insufficient, and the catalytic performance is low, and vice versa, which indicates that part of the Ti atoms are aggregated into TiO2 which is not a skeleton, and side reactions occur; under the preferred condition, the ratio of the peak area at a wave number of 960 cm -1 to the peak area at a wave number of 800 cm -1 is 0.7-2.

[0028] According to the present application, under the preferred condition, more than 90% of the gold in the nano-gold has a valence of 0.

[0029] In the present application, the particle size of the nano-gold particles is determined by a transmission electron microscope (TEM), and the valence of the nano-gold particles is determined by XPS characterization.

[0030] The present application provides a preparation method of a propylene epoxidation catalyst.

[0031] (1) uniformly mixing a silicon source, an alkaline template agent, a titanium source, water and isopropyl alcohol to obtain a titanium silicon sol;

[0032] (2) adding a compound represented by formula (I) to the titanium silicon sol, and hydrothermally crystallizing and calcining the obtained mixture to obtain a hierarchical pore titanium silicon molecular sieve;

[0033]

[0034]

[0035] wherein i is an integer of 0-10; R1, R2 and R3 are each independently selected from C1-C6 alkyl;

[0036] (3) mixing the hierarchical pore titanium silicon molecular sieve with an aqueous gold-containing compound, and then adding a pH adjusting agent to adjust the pH of the obtained mixture to 6-10 to obtain a first suspension;

[0037] (4) mixing the first suspension under the protection of an inert gas to obtain a second suspension;

[0038] (5) filtering the second suspension, and calcining the obtained residue to obtain the propylene epoxidation catalyst.

[0039] In the present application, C1-C6 alkyl refers to alkyl with total number of carbon atoms being 1-6, for example, it can be one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl and n-hexyl.

[0040] In the present application, the number of methylene between the phenyl and the methyl is 0-10; in some preferred embodiments of the present application, i is an integer of 1-5, for example, it can be 1, 2, 3, 4 or 5; that is, the number of methylene between the phenyl and the methyl is 1-5.

[0041] In some preferred embodiments of the present application, R1, R2 and R3 are each independently selected from C1-C3 alkyl, which can be methyl, ethyl, n-propyl or isopropyl, preferably, R1, R2 and R3 are each independently selected from methyl, ethyl or n-propyl. In the present application, R1, R2 and R3 can be the same or different, preferably, R1, R2 and R3 are all the same.

[0042] In the present application, the compound shown in formula (I) is used as a silanization agent, one end of which is a phenyl complex alkyl group. In the hydrothermal crystallization process, the phenyl group can play a supporting role in the hydrolysis and condensation of the titanium silica sol as a strong supporting layer structure, so that the molecular sieve crystal has both microporous structure and mesoporous structure; at the same time, the flexible alkyl group can fine-tune the mesoporous structure obtained by the supporting layer, so that the mesoporous pore size is relatively concentrated. The mesopore size obtained by using the silanization agent shown in formula (I) is conducive to the loading of nano gold particles inside the molecular sieve crystal, avoiding the migration and aggregation of nano gold particles due to the excessively large mesopore size, and also avoiding the occurrence of pore plugging caused by the accumulation of reaction molecules or product molecules in the pores due to the larger mesopore than micropore; thereby improving the propylene conversion rate and the selectivity of propylene oxide in the propylene gas phase direct epoxidation reaction catalyzed by the propylene epoxidation catalyst.

[0043] According to the present application, too high amount of the silanization agent (compound shown in formula (I)) will result in poor crystallization performance of the titanium silica sol; and too low amount of the silanization agent (compound shown in formula (I)) will reduce the specific surface area of the obtained titanium silica molecular sieve, and the mesoporous structure of the titanium silica molecular sieve is also changed, affecting the mass transfer effect, and further affecting the catalytic activity of the finally prepared propylene epoxidation catalyst; preferably, in step (1), the molar ratio of the silicon source to the compound shown in formula (I) is 1:(0.01-0.3), preferably 1:(0.01-0.2); more preferably 1:(0.05-0.12) in terms of SiO2.

[0044] In some preferred embodiments of the present application, the molar ratio of the silicon source, the basic template agent and water is 1:(0.05-0.4):(5-40) in terms of SiO2, N and OH respectively when the basic template agent contains nitrogen element, and in terms of SiO2 and OH respectively when the basic template agent does not contain nitrogen element. - In some preferred embodiments of the present application, the molar ratio of the silicon source, the basic template agent and water is 1:(0.05-0.4):(5-40) in terms of SiO2, N and OH respectively when the basic template agent contains nitrogen element, and in terms of SiO2 and OH respectively when the basic template agent does not contain nitrogen element.

[0045] According to the present application, preferably, the silicon source is selected from at least one of tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, silica gel, white carbon black and silica sol.

[0046] According to the present application, preferably, the basic template agent is selected from at least one of quaternary ammonium base, aliphatic amine and aliphatic alcohol amine, and preferably at least one of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide and tetrabutyl ammonium hydroxide.

[0047] In some preferred embodiments of the present application, the molar ratio of the silicon source, the titanium source and isopropyl alcohol is 1:(0.001-0.04):(0.1-10) in terms of SiO2, TiO2 and isopropyl alcohol respectively.

[0048] According to the present application, preferably, the titanium source is selected from at least one of organic titanium source and / or inorganic titanium source; further preferably, the titanium source is selected from at least one of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate.

[0049] According to the present application, preferably, step (1) further comprises: mixing the silicon source, the basic template agent and water by first stirring to obtain a mixed system; and then adding a mixed solution of the titanium source and isopropyl alcohol dropwise into the mixed system by second stirring to obtain a mixed solution.

[0050] In the present application, the dropping speed of the mixed solution is preferably 0.01-0.5 mL / min; further preferably 0.1-0.5 mL / min.

[0051] In the present application, preferably, the first stirring time is 0.1-2 h.

[0052] In the present application, preferably, the second stirring time is 0.5-6 h, preferably 0.5-3 h.

[0053] In the present application, preferably, step (1) further comprises: alcohol removal is performed on the mixed solution; the alcohol removal can remove the alcohol generated by hydrolysis of the silicon source and the titanium source; in the present application, the alcohol generated in the system is removed by azeotropic distillation, and water is supplemented in the process of alcohol removal to ensure that the ratio of the substances in the titanium silicon sol meets the above requirements; preferably, the alcohol removal conditions include: temperature of 30-100℃, time of 2-10h; preferably, temperature of 40-90℃, time of 4-10h.

[0054] According to the present application, in order to uniformly disperse the silylating agent in the titanium silicon sol; under the preferred conditions, step (1) further comprises: a compound represented by formula (I) is added to the titanium silicon sol for third stirring for 0.1-24h, preferably, the third stirring time is 0.5-10h, more preferably, 1-5h.

[0055] In the present application, the rapid heating can control the nucleation and growth rate of the molecular sieve at low temperature, so that smaller molecular sieve particles are obtained, which, after loading with nano-gold, can shorten the internal diffusion path of product molecules and is beneficial to improve the selectivity; under the preferred conditions, in step (2), the hydrothermal crystallization conditions include: the mixture is heated to 50-200℃ within 0.1-1h, and then hydrothermal crystallization is performed at 50-200℃ for 10-100h; preferably, the hydrothermal crystallization is performed at 100-200℃ for 20-80h; further preferably, the heating time is 0.3-1h; more preferably, the hydrothermal crystallization conditions include: temperature of 120-180℃, time of 20-80h; under the above preferred conditions, the crystallinity, specific surface area and pore volume of the molecular sieve can be balanced; and the molecular sieve with specific crystallinity, specific surface area and pore volume is prepared.

[0056] The pressure of the hydrothermal crystallization in the present application is not particularly limited and can be the autogenous pressure of the crystallization system.

[0057] According to the present application, under the preferred conditions, the method further comprises: the product obtained by hydrothermal crystallization is washed, filtered and dried; wherein the washing, filtering and drying processes can be known by those skilled in the art. Exemplarily, the washing temperature can be 20-50℃, the washing solvent can be water, and the amount of the washing solvent is 1-20 times the mass of the crystallization product; the drying conditions can be: temperature of 40-150℃, time of 0.5-24h.

[0058] In a preferred embodiment of the present application, in step (2), the calcination conditions include: temperature of 400-800℃, time of 1-15h; preferably, temperature of 500-600℃, time of 4-10h.

[0059] The multi-level pore titanosilicate molecular sieve prepared in the application has abundant mesoporous channels, which is beneficial to diffusion of Au nanoparticles into the inside of the carrier crystal, close to the active sites of the framework titanium in the crystal, and is beneficial to exerting the synergistic catalysis of the double active sites. In addition, the increase of the surface area of the molecular sieve caused by the mesopores is beneficial to contact of the reaction molecules with the active sites in the crystal, and the increase of the pore volume is beneficial to desorption of the product molecules, thereby avoiding side reactions. Preferably, the mesopore size of the multi-level pore titanosilicate molecular sieve is 5-10 nm, the specific surface area is 500-650 m 2 / g, the total pore volume is 0.45-0.80 cm 3 / g, the external surface area is 120-300 m 2 / g, the micropore volume is 0.12-0.20 cm 3 / g, the particle size is 100-250 nm, and the crystallinity of the molecular sieve is ≥50%. In the application, the external surface area of the multi-level pore titanosilicate molecular sieve refers to the surface area of the external surface of the multi-level pore titanosilicate molecular sieve, which can be obtained by BET method. The specific surface area of the multi-level pore titanosilicate molecular sieve refers to the BET specific surface area.

[0060] In a preferred embodiment of the application, the molar ratio of titanium to silicon in the multi-level pore titanosilicate molecular sieve is 0.001-0.04:1, preferably 0.005-0.025:1.

[0061] In a preferred embodiment of the application, in the infrared spectrum of the multi-level pore titanosilicate molecular sieve, the ratio of the peak area at a wave number of 960 cm -1 to the peak area at a wave number of 800 cm -1 is 0.7-2.

[0062] In the application, too high an amount of chloroauric acid will cause aggregation of gold nanoparticles, and will cause side reactions in the propylene gas phase epoxidation reaction process, thereby reducing the selectivity of propylene oxide. Too low an amount of chloroauric acid will cause a decrease in the catalytic activity of the prepared propylene epoxidation catalyst. Under preferred conditions, the amount of the chloroauric acid aqueous solution, calculated as gold, is 0.01wt%-5wt% of the titanosilicate molecular sieve.

[0063] In order to further optimize the catalytic performance of the propylene epoxidation catalyst, under preferred conditions, the concentration of the chloroauric acid aqueous solution is 0.0001-0.1M.

[0064] The application does not have special limitations on the type of the pH regulator, as long as the pH of the mixed system can be adjusted to a specific range. Preferably, the pH regulator is at least one selected from alkali metal bicarbonates and ammonia water, for example, at least one selected from NaHCO3, CsHCO3, KHCO3 and ammonia water.

[0065] To improve the loading efficiency of the nano-gold, further preferably, the pH of the mixed system is 7-9.

[0066] In the present application, the inert gas in step (4) is selected from at least one of nitrogen, argon and helium.

[0067] In the present application, too high inert gas pressure causes too many nano-gold particles to enter the pore channels of the hierarchical pore titanosilicate molecular sieve, resulting in pore channel blockage and thus reduced internal diffusion efficiency and reaction effect; too low inert gas pressure cannot ensure sufficient Au active sites to enter the pore channels of the molecular sieve and approach the intracrystalline titanium active centers. Under the preferred conditions, in step (4), the nitrogen pressure is 0.5-2 MPa.

[0068] The nitrogen pressure promotes partial Au active sites to enter the hierarchical pore titanosilicate molecular sieve intracrystalline, so that the Au active sites and the abundant titanium active centers in the intracrystalline are close to each other. When the reactants enter the intracrystalline of the titanosilicate molecular sieve, the two kinds of active centers can fully exert the synergistic catalytic effect, so that the reactants are rapidly converted into products.

[0069] In some preferred embodiments of the present application, in step (4), the time for the pressurized mixing is 10-24 h.

[0070] In some preferred embodiments of the present application, to improve the catalytic activity of the propylene epoxidation catalyst, in step (5), the calcination conditions include: temperature of 150-300℃ and time of 1-4 h.

[0071] The third aspect of the present application provides a propylene epoxidation catalyst prepared by the method according to the preceding second aspect.

[0072] In a preferred embodiment of the present application, the propylene epoxidation catalyst comprises a hierarchical pore titanosilicate molecular sieve and nano-gold loaded on the hierarchical pore titanosilicate molecular sieve; wherein the content of the nano-gold is 0.01wt%-1wt% based on the total amount of the propylene epoxidation catalyst; wherein the total pore volume of the propylene epoxidation catalyst is 0.18-0.56 cm 3 / g, the particle size is 100-250 nm, and the crystallinity is ≥50%.

[0073] In a preferred embodiment of the present application, the molar ratio of titanium to silicon in the propylene epoxidation catalyst is 0.001-0.04:1, preferably 0.005-0.025:1.

[0074] In a preferred embodiment of the present application, in the infrared spectrum of the propylene epoxidation catalyst, the peak area at a wave number of 960 cm -1 is greater than the peak area at a wave number of 800 cm -1The ratio of peak area to peak area is 0.7-2.

[0075] In this invention, the higher the content of 0-valent gold in the propylene epoxidation catalyst, the higher the catalytic activity of the gold nanoparticle-supported titanium-silicon molecular sieve; preferably, more than 90% of the gold in the gold nanoparticles has a valence of 0.

[0076] In a preferred embodiment of the present invention, the propylene epoxidation catalyst has high catalytic activity, and when catalyzing the gas-phase epoxidation reaction of propylene, the propylene conversion rate is increased to 10%-20%, and the selectivity of propylene oxide is increased to 90%-95%.

[0077] A fourth aspect of the present invention provides a method for gas-phase epoxidation of propylene, the method comprising: reacting hydrogen, oxygen and propylene in a mixture under inert gas protection and in the presence of a catalyst to obtain propylene oxide; wherein the catalyst is the propylene epoxidation catalyst described in the first and third aspects above.

[0078] According to the present invention, under preferred conditions, the reaction conditions include: the flow rate ratio of hydrogen, oxygen and propylene is 0.5-2:0.5-2:1; more preferably, the flow rate ratio of propylene and inert gas is 1:1-10.

[0079] In some preferred embodiments of the present invention, the reaction conditions further include: a temperature of 100-250°C, a time of 1-1000 h, and a pressure of 0.1-6 MPa; more preferably, the temperature is 120-200°C, the time is 1-500 h, and the pressure is 0.1-3 MPa.

[0080] In this invention, the reaction pathway for the gas-phase epoxidation of propylene is as follows: Figure 1 As shown, from Figure 1 It can be seen that Au catalyzes the reaction of H2 and O2 to generate H2O2, and then H2O2 and TS-1 form Ti-OOH active sites. Ti-OOH catalyzes the formation of propylene oxide from propylene.

[0081] In this invention, the method for gas-phase epoxidation of propylene can be carried out in a continuous operation mode. Specifically, after the catalyst is loaded into the reactor, a mixture of hydrogen, oxygen, propylene and inert gas is continuously added to carry out the reaction.

[0082] The present invention does not have any special requirements on the morphology of the catalyst. The catalyst can be the propylene epoxidation catalyst described in the first and third aspects above, or it can be further loaded onto a support for use. Those skilled in the art can select the catalyst according to the type of reactor.

[0083] In the present application, the separation of the propylene gas phase epoxidation product from the catalyst can be adjusted according to the form of the catalyst and the actual needs; for example, when the catalyst is the propylene epoxidation catalyst powder as described in the aforementioned first and third aspects, the separation of the product and the recycling of the catalyst can be achieved by means of sedimentation, filtration, centrifugation, evaporation, membrane separation, etc.; when the catalyst is the propylene epoxidation catalyst supported on a carrier (shaped catalyst) as described in the aforementioned first and third aspects, the shaped catalyst can be loaded into a fixed bed reactor, and the catalyst can be recovered after the reaction is completed.

[0084] The present application will be described in detail below through examples. In the following examples, room temperature refers to 25±5℃.

[0085] The raw materials used in the following examples are all chemical pure reagents, except for special instructions.

[0086] In each of the following examples and comparative examples, the X-ray diffraction (XRD) crystal phase pattern of the sample was determined on a Siemens D5005 X-ray diffractometer, with a Cu Kα tube voltage of 40 kV, a tube current of 40 mA, a scanning speed of 0.5° / min, and a scanning range of 2θ = 5°-35°.

[0087] According to the XRD spectrum, the crystallinity was obtained by fitting with the software eva of BRUKER;

[0088] Both the external surface area and the specific surface area were obtained by BET fitting of the adsorption curve after measuring the static N2 adsorption-desorption curve of the sample at liquid nitrogen temperature (77.4 K) using the ASAP2405J static nitrogen adsorption instrument of Micromeritics Company;

[0089] The pore volume was determined according to the method described in RIPP151-90 in Petroleum Chemical Industry Analysis Methods (published by Science Press in September 1990, first edition) edited by Yang Cuiding et al.;

[0090] The pore size distribution was calculated according to the BJH formula;

[0091] The particle size was determined by JEOL JEM-2100 transmission electron microscope (TEM);

[0092] The valence of the gold nanoparticles was determined by XPS characterization.

[0093] In the following preparation examples, the chemical structural formula of the silylating agent used is shown in Table 1; wherein, compound 1, compound 2 and compound 3 are all commercially available.

[0094] Table 1

[0095]

[0096] Preparation Example 1-6 is used to illustrate the preparation of the hierarchical porous titanosilicate molecular sieve.

[0097] Preparation Example 1

[0098] (1) White carbon black, tetrabutylammonium hydroxide and water were mixed at room temperature for 0.5 h by first stirring to obtain a mixed system, and during the stirring, a mixture of titanium tetrachloride and isopropyl alcohol was added dropwise into the mixed system at a rate of 0.5 mL / min, and second stirring was carried out for 1 h to obtain a mixed solution; the molar ratio of white carbon black (calculated as SiO2), tetrabutylammonium hydroxide (calculated as N) and titanium tetrachloride (calculated as TiO2) was 1:0.15:20; the molar ratio of white carbon black, titanium tetrachloride and isopropyl alcohol was 1:0.005:5;

[0099] The mixed solution was then subjected to alcohol removal at 80°C for 5 h to obtain a titanosilica sol;

[0100] (2) Compound (1) was added into the titanosilica sol, and third stirring was carried out at room temperature for 1 h to obtain a mixture, wherein the molar ratio of compound (1) to white carbon black was 0.05:1;

[0101] (3) The mixture was heated to 120°C for 0.5 h, and then subjected to hydrothermal crystallization at 120°C for 72 h to obtain a crystallization product; the crystallization product was subjected to water leaching, filtration and drying at 120°C for 2 h in sequence;

[0102] The dried product was calcined at 550°C for 6 h to obtain a titanosilicate molecular sieve;

[0103] The pore size distribution of the titanosilicate molecular sieve obtained in this preparation example is shown in Figure 2 From Figure 2 it can be seen that the titanosilicate molecular sieve obtained in this preparation example contains both microporous structure and mesoporous structure with a pore size of about 8 nm;

[0104] The TEM image of the titanosilicate molecular sieve obtained in this preparation example is shown in Figure 3 From the image, it can be seen that the particle size of the titanosilicate molecular sieve obtained in this example is about 100-200 nm;

[0105] The XRD spectrum of the titanosilicate molecular sieve obtained in this preparation example is shown in Figure 4 From the image, it can be seen that the titanosilicate molecular sieve obtained in this example has MFI structure and good crystallization performance;

[0106] The physical property parameters of the titanosilicate molecular sieve obtained in this preparation example are shown in Table 3.

[0107] Preparation Example 2-4

[0108] The titanium silicalite molecular sieve was prepared according to the method of Preparation Example 1, and the ratio and synthesis conditions are shown in Table 2. The physical property parameters of the prepared molecular sieve are shown in Table 3.

[0109] Table 2

[0110]

[0111]

[0112] Note: 1-mole ratio; 2-mole ratio; 3-mole ratio

[0113] Preparation Example 5

[0114] A tetrapropylammonium hydroxide solution (TPAOH, concentration 20 wt%, purchased from Aldrich, USA) was added to a tetraethyl orthosilicate (TEOS) solution, and then anhydrous isopropanol solution of n-butyl titanate [Ti(OBu)4] was added dropwise to the obtained liquid mixture under vigorous stirring. After stirring for 15 min, a clear liquid was obtained. The clear liquid was subjected to alcohol removal at 75℃ for 3h to obtain a sol. The mole ratio of tetraethyl orthosilicate (calculated as SiO2) : n-butyl titanate (calculated as TiO2) : tetrapropylammonium hydroxide (calculated as N) : deionized water was 1:0.03:0.36:35.

[0115] The sol was crystallized at 170℃ for 3 days. The obtained solid was filtered, washed with distilled water, and then dried at 100℃ for 5h, and then calcined at 550℃ for 10h to obtain a titanium silicalite molecular sieve TS-1-5. The physical property parameters of the titanium silicalite molecular sieve TS-1-5 are shown in Table 3. The XRD characterization results of the titanium silicalite molecular sieve TS-1-5 are shown in Figure 5 From Figure 5 it can be seen that the titanium silicalite molecular sieve obtained in the present preparation example has the MFI structure characteristic peak, and is crystallized as a TS-1 molecular sieve.

[0116] Preparation Example 6

[0117] The titanium silicalite molecular sieve was prepared according to the method of CN106145151B Example 1, and the specific method is as follows:

[0118] A mixture of tetraethyl orthosilicate, tetrapropylammonium hydroxide, tetrabutyl titanate and deionized water was prepared to obtain a mixture with a molar ratio of SiO2:structure directing agent:TiO2:H2O=1:0.2:0.025:50. Then, according to a molar ratio of SiO2 to silanization agent of 1:0.1 and a weight ratio of SiO2 to natural polymer compound of 1:0.1, quaternary aminated cellulose and N-phenyl-3-aminopropyl trimethoxysilane were added into the titanium silicalite molecular sieve precursor gel mixture. After stirring, the obtained titanium silicalite molecular sieve precursor treated with silanization agent and modified natural polymer compound was transferred into a pressure-resistant stainless steel autoclave. Under stirring, the temperature was raised to 170°C and crystallization was carried out under autogenous pressure for 24 h. After the stainless steel pressure-resistant autoclave was cooled to room temperature, the obtained uncalcined titanium silicalite molecular sieve was recovered, dried at 110°C for 6 h, and then calcined at 550°C for 4 h to obtain hierarchical pore titanium silicalite molecular sieve TS-1-6. The physical property parameters of the obtained hierarchical pore titanium silicalite molecular sieve TS-1-6 are shown in Table 3, and the pore size distribution is shown in Figure 2. Figure 6 As can be seen from Figure 6 , the titanium silicalite molecular sieve obtained in the present preparation example has a mesoporous structure with a pore size of 3 nm.

[0119] Table 3

[0120]

[0121] Note: In the infrared spectrum of the hierarchical pore titanium silicalite molecular sieve, the ratio of the peak area at a wave number of 960 cm-1 to the peak area at a wave number of 800 cm-1 -1 . -1

[0122] Example 1

[0123] 5 g of titanium silicalite molecular sieve TS-1-1 was added into 50 mL of chloroauric acid (HAuCl4) solution (0.0025 M) under stirring. During stirring, NaHCO3 was slowly added to adjust the pH of the mixture to 7.5. The first suspension with adjusted pH was transferred into a stainless steel pressure-resistant autoclave, and nitrogen was filled into the autoclave to maintain a pressure of 1.0 MPa while stirring was maintained for 15 h to obtain a second suspension. The second suspension was filtered to obtain a filter residue, which was calcined at 200°C for 2 h in an air atmosphere to obtain a propylene epoxidation catalyst Au / TS-1-1. The reaction conditions and raw materials are shown in Table 4, and the physical property parameters of the obtained propylene epoxidation catalyst are shown in Table 5. As can be seen from the data in Table 3, the titanium silicalite molecular sieve support was loaded with nano-gold to obtain the propylene epoxidation catalyst, and the particle size, I 960 / I 800 , crystallinity, and molar ratio of silicon to titanium of the two did not change.

[0124] Examples 2-9 and Comparative Examples 1-6

[0125] ​The method of Example 1 was followed except that the reaction conditions and raw materials were as shown in Table 4, and the physical property parameters of the propylene epoxidation catalyst obtained were as shown in Table 5.

[0126] Table 4

[0127]

[0128] Table 5

[0129]

[0130]

[0131] Note: In the infrared spectrum of the propylene epoxidation catalyst, the ratio of the peak area at a wave number of 960 cm -1 to the peak area at a wave number of 800 cm -1

[0132] Test Example

[0133] The propylene epoxidation catalysts prepared in Examples 1-9 and Comparative Examples 1-6 were respectively loaded into a tubular reactor with an inner diameter of 6 mm, and then heated to 180°C in a N2 atmosphere, and the reaction was started by passing in hydrogen, oxygen and propylene. After 1 h of reaction, the product was analyzed on-line. The amount of catalyst used was 0.3 g, the flow rates of the gases, the reaction pressure and the temperature are shown in Table 6, and the results of the catalytic reaction are shown in Table 7.

[0134] In the present application, gas chromatography was used to analyze the reactants and products in the evaluation system. The analysis conditions for the gas chromatography were as follows: Agilent-6890 chromatograph, molecular sieve 5A and PoraBON DU chromatographic column, FID and TCD detectors.

[0135] Propylene conversion % = (moles of propylene in the raw material - moles of propylene in the product) / moles of propylene in the raw material x 100%

[0136] Propylene oxide selectivity % = moles of propylene oxide in the product / (moles of propylene in the raw material - moles of propylene in the product) x 100%

[0137] Table 6

[0138]

[0139]

[0140] Table 7

[0141]

[0142] ​

[0143] From the results of Test Examples 1-12 and Test Examples 19-23 in Table 7, it can be seen that the propylene epoxidation catalysts of the embodiments of the present application have high catalytic activity for propylene gas-phase epoxidation, so that the conversion of propylene is increased to 10.2% or more, and the selectivity of the product propylene oxide is increased to 90.2% or more.

[0144] From the comparison between Test 1 and Test Examples 13-16, it can be seen that the conditions for propylene gas-phase epoxidation also affect the conversion of propylene and the selectivity of propylene oxide.

[0145] From the comparison between Test 1 and Test Examples 17-18, it can be seen that when the pore volume of the titanium silicalite molecular sieve does not meet the requirements, the prepared propylene epoxidation catalyst has significantly reduced catalytic activity for propylene gas-phase epoxidation, and it is difficult to simultaneously meet the requirements of high propylene conversion and high propylene oxide selectivity.

[0146] From the comparison between Test 1 and Test Examples 24-25, it can be seen that during the preparation of the propylene epoxidation catalyst, too high or too low calcination temperature will reduce the catalytic activity of the propylene epoxidation catalyst for propylene gas-phase epoxidation.

[0147] From the comparison between Test 1 and Test Examples 26-27, it can be seen that during the preparation of the propylene epoxidation catalyst, too low nitrogen pressure will reduce the loading amount of the nano gold particles, and in turn reduce the catalytic activity of the propylene epoxidation catalyst for propylene gas-phase epoxidation.

[0148] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A propylene epoxidation catalyst, characterized in that, The propylene epoxidation catalyst comprises a hierarchical porous titanium silicate molecular sieve and gold nanoparticles supported on the hierarchical porous titanium silicate molecular sieve; wherein, based on the total amount of the propylene epoxidation catalyst, the content of the gold nanoparticles is 0.01wt%-1wt%; wherein, the total pore volume of the propylene epoxidation catalyst is 0.18-0.56 cm³. 3 / g, particle size 100-250nm, crystallinity ≥50%; The preparation method of the propylene epoxidation catalyst includes: (1) Mix silicon source, alkaline template agent, titanium source, water and isopropanol evenly to obtain titanium silica sol; (2) The compound shown in formula (I) is added to the titanium silica sol, and the resulting mixture is subjected to hydrothermal crystallization and calcination to obtain a multi-level porous titanium silica molecular sieve; Formula (I) Where i is an integer from 0 to 10; R1, R2 and R3 are each independently selected from C1-C6 alkyl groups; (3) The multi-level porous titanium silica molecular sieve is mixed with an aqueous solution containing gold compounds, and then a pH adjuster is added to adjust the pH of the mixture to 6-10 to obtain the first suspension; (4) The first suspension is mixed under pressure under inert gas protection to obtain the second suspension; (5) The second suspension is filtered, and the resulting filter residue is calcined to obtain the propylene epoxidation catalyst.

2. The propylene epoxidation catalyst according to claim 1, wherein, The molar ratio of titanium to silicon in the propylene epoxidation catalyst is 0.001-0.04:

1.

3. The propylene epoxidation catalyst according to claim 2, wherein, The molar ratio of titanium to silicon in the propylene epoxidation catalyst is 0.005-0.025:

1.

4. The propylene epoxidation catalyst according to claim 1, wherein, The infrared spectrum of the propylene epoxidation catalyst has a wavenumber of 960 cm⁻¹. -1 Peak area and wavenumber at 800cm -1 The ratio of peak area to peak area is 0.7-2.

5. The propylene epoxidation catalyst according to claim 1, wherein, More than 90% of the gold in the nano-gold has a valence of 0.

6. A method for preparing the propylene epoxidation catalyst according to claim 1, characterized in that, The method includes: (1) Mix silicon source, alkaline template agent, titanium source, water and isopropanol evenly to obtain titanium silica sol; (2) The compound shown in formula (I) is added to the titanium silica sol, and the resulting mixture is subjected to hydrothermal crystallization and calcination to obtain a multi-level porous titanium silica molecular sieve; Formula (I) Where i is an integer from 0 to 10; R1, R2 and R3 are each independently selected from C1-C6 alkyl groups; (3) The multi-level porous titanium silica molecular sieve is mixed with an aqueous solution containing gold compounds, and then a pH adjuster is added to adjust the pH of the mixture to 6-10 to obtain the first suspension; (4) The first suspension is mixed under pressure under inert gas protection to obtain the second suspension; (5) The second suspension is filtered, and the resulting filter residue is calcined to obtain the propylene epoxidation catalyst.

7. The method according to claim 6, wherein, i is an integer from 1 to 5; R1, R2, and R3 are each independently selected from methyl, ethyl, or propyl.

8. The method according to claim 6, wherein, The silicon source is SiO2, and the molar ratio of the silicon source to the compound shown in formula (I) is 1:(0.01-0.3).

9. The method according to claim 8, wherein, The silicon source is SiO2, and the molar ratio of the silicon source to the compound shown in formula (I) is 1:(0.01-0.2).

10. The method according to any one of claims 6-9, wherein, The silicon source is calculated as SiO2, the alkaline template agent is calculated as N when it contains nitrogen, and the alkaline template agent is calculated as OH when it does not contain nitrogen. - count, The molar ratio of the silicon source, the alkaline template agent, and water is 1:(0.05-0.4):(5-40).

11. The method according to claim 10, wherein, The molar ratio of the silicon source, the alkaline template agent, and water is 1:(0.1-0.3):(5-25).

12. The method according to any one of claims 6-9, wherein, The silicon source is calculated as SiO2, and the titanium source is calculated as TiO2. The molar ratio of the silicon source, the titanium source, and isopropanol is 1:(0.001-0.04):(0.1-10).

13. The method according to claim 12, wherein, The molar ratio of the silicon source, the titanium source, and isopropanol is 1:(0.005-0.025):(0.1-5).

14. The method according to any one of claims 6-9, wherein, The silicon source is selected from at least one of tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, silica gel, silica fume, and silica sol.

15. The method according to any one of claims 6-9, wherein, The alkaline template agent is selected from at least one of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines.

16. The method according to claim 15, wherein, The alkaline template agent is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

17. The method according to any one of claims 6-9, wherein, The titanium source is selected from organic titanium sources and / or inorganic titanium sources.

18. The method according to claim 17, wherein, The titanium source is selected from at least one of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.

19. The method according to any one of claims 6-9, wherein, Step (1) is as follows: the silicon source, alkaline template agent and water are stirred and mixed to obtain a mixed system; then the mixture of titanium source and isopropanol is added dropwise to the mixed system to obtain a mixed solution; then the mixed solution is subjected to alcohol removal to obtain titanium silica sol.

20. The method according to claim 19, wherein, The dropping rate of the mixture is 0.01-0.5 mL / min.

21. The method according to claim 19, wherein, The conditions for alcohol removal include: a temperature of 30-100℃ and a time of 2-10h.

22. The method according to claim 21, wherein, The conditions for alcohol removal include: a temperature of 40-90℃ and a time of 4-10h.

23. The method according to any one of claims 6-9, wherein, In step (2), the conditions for hydrothermal crystallization include: heating the mixture to 50-200°C within 0.1-1h, and then crystallizing at 50-200°C for 10-100h.

24. The method according to claim 23, wherein, In step (2), the conditions for hydrothermal crystallization include: heating the mixture to 100-200°C within 0.1-1h, and then crystallizing at 100-200°C for 20-80h.

25. The method according to any one of claims 6-9, wherein, In step (2), the calcination conditions include: a temperature of 400-800℃ and a time of 1-15h.

26. The method according to any one of claims 6-9, wherein, The mesopore size of the hierarchical porous titanium-silicon molecular sieve is 5-10 nm, and the specific surface area is 500-650 m². 2 / g, total pore volume is 0.45-0.80cm³ 3 / g, with an external surface area of ​​120-300m² 2 / g, micropore volume is 0.12-0.20cm³ 3 / g, with a particle size of 100-250nm and a molecular sieve crystallinity ≥50%.

27. The method according to any one of claims 6-9, wherein, The molar ratio of titanium to silicon in the multi-level porous titanium-silicon molecular sieve is 0.001-0.04:

1.

28. The method according to claim 27, wherein, The molar ratio of titanium to silicon in the multi-level porous titanium-silicon molecular sieve is 0.005-0.025:

1.

29. The method according to any one of claims 6-9, wherein, The infrared spectrum of the hierarchical porous titanium-silicon molecular sieve has a wavenumber of 960 cm⁻¹. -1 Peak area and wavenumber at 800cm -1 The ratio of peak area to peak area is 0.7-2.

30. The method according to any one of claims 6-9, wherein, The aqueous solution containing the gold compound is selected from an aqueous solution of chloroauric acid; the concentration of the aqueous solution of chloroauric acid is 0.0001-0.1M.

31. The method according to claim 30, wherein, The chloroauric acid aqueous solution is calculated as gold, and the amount of the chloroauric acid aqueous solution is 0.01wt%-5wt% of the titanium-silicon molecular sieve.

32. The method according to any one of claims 6-9, wherein, In step (3), the pH adjuster is selected from at least one of NaHCO3, CsHCO3, KHCO3, and ammonia water.

33. The method according to any one of claims 6-9, wherein, Adjust the pH to 7-9.

34. The method according to any one of claims 6-9, wherein, In step (4), the pressure of the inert gas is 0.5-2 MPa.

35. The method according to any one of claims 6-9, wherein, The pressurized mixing time is 10-24 hours.

36. The method according to any one of claims 6-9, wherein, In step (5), the calcination conditions include a temperature of 150-300℃ and a time of 1-4h.

37. A propylene epoxidation catalyst prepared by the method of any one of claims 6-36.

38. A method for propylene vapor-phase epoxidation, the method comprising: Hydrogen, oxygen, and propylene are mixed and reacted under the protection of an inert gas and in the presence of a catalyst to obtain propylene oxide. The catalyst is the propylene epoxidation catalyst according to any one of claims 1-5 and 37.

39. The method according to claim 38, wherein, The reaction conditions include a volume flow rate ratio of hydrogen, oxygen, and propylene of 0.5-2:0.5-2:

1. The volumetric flow rate ratio of propylene to inert gas is 1:1-10.

40. The method according to claim 38 or 39, wherein, The reaction conditions include: temperature of 100-250℃, time of 1-1000h, and pressure of 0.1-6MPa.

41. The method according to claim 40, wherein, The reaction conditions include: a temperature of 120-220℃, a time of 1-500h, and a pressure of 0.1-3MPa.

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