A pd@ti-utl molecular sieve catalyst, a preparation method and application thereof

Abstract

The application discloses a Pd@Ti-UTL molecular sieve catalyst and a preparation method and application thereof, and the catalyst is prepared through the following steps: step (1): raw materials are mixed to prepare a reaction liquid A, wherein the raw materials comprise UTL molecular sieve, a titanium source and an NH4F aqueous solution; step (2): Ti-UTL molecular sieve obtained after reaction of the reaction liquid A in step (1) is mixed with a chloropalladic acid aqueous solution to prepare a reaction liquid B; and step (3): a product obtained after reaction of the reaction liquid B in step (2) is dried, calcined and reduced to obtain the required Pd@Ti-UTL molecular sieve catalyst. The Pd@Ti-UTL molecular sieve catalyst prepared by the application can catalyze in-situ synthesis of hydrogen peroxide and coupling reaction of propylene epoxidation to generate propylene oxide, a high propylene oxide yield can be obtained at a mild reaction temperature (60 DEG C), and efficient and green synthesis of propylene oxide is realized.

Description

Technical Field

[0001] This invention relates to the fields of zeolite molecular sieves and industrial catalysis, specifically to a Pd@Ti-UTL molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] Propylene oxide is a very important cyclic ether compound, with a global annual production of 10 million tons. It is the third largest propylene derivative after polypropylene and acrylonitrile, and is mainly used as a raw material for the synthesis of polyether polyols, propylene glycol, and alcohol ethers, playing a vital role in industries such as textiles, construction, automobiles, and coatings. Currently, industrial production routes for propylene oxide include the chlorohydrin process, the tert-butyl hydroperoxide process, the ethylbenzene hydroperoxide process, the cumene hydroperoxide process, and the direct oxidation of hydrogen peroxide (Microporous and Mesoporous Materials, 2021, 328:111492).

[0003] The direct oxidation of hydrogen peroxide refers to the epoxidation of propylene with pre-prepared hydrogen peroxide using titanium-silicon molecular sieve catalysis to produce propylene oxide. Compared to other propylene oxide production routes, it has advantages such as mild reaction conditions and high selectivity. However, industrially, over 95% of hydrogen peroxide is produced using the anthraquinone process, which suffers from problems such as low atom economy, large equipment investment, complex process flow, and significant environmental pollution. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a Pd@Ti-UTL molecular sieve catalyst for the preparation of propylene oxide, its preparation method, and its applications. Pd@Ti-UTL indicates that titanium (Ti) atoms are first implanted into the UTL molecular sieve framework to form a Ti-UTL molecular sieve, and then palladium (Pd) atoms are deposited and distributed on the surface of the Ti-UTL molecular sieve. UTL is a structural code assigned by the Structure Committee of the International Molecular Sieve Association to molecular sieves with a specific type of topology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of this invention provides a method for preparing a Pd@Ti-UTL molecular sieve catalyst, comprising the following steps:

[0007] Step (1): Mix the raw materials to prepare reaction solution A, wherein the raw materials include UTL molecular sieve, titanium source and NH4F aqueous solution;

[0008] Step (2): After the reaction solution A obtained in step (1) is completely reacted, the Ti-UTL molecular sieve obtained is mixed with an aqueous solution of palladium chloride to prepare reaction solution B;

[0009] Step (3): After the reaction solution B obtained in step (2) is completely reacted, the product obtained is dried, calcined and reduced to obtain the desired Pd@Ti-UTL molecular sieve catalyst.

[0010] In one embodiment of the present invention, the mass ratio of UTL molecular sieve, titanium source and NH4F aqueous solution in step (1) is 1:0.05:10-50.

[0011] In one embodiment of the present invention, the UTL molecular sieve in step (1) is a germanium-containing UTL silicon-germanium molecular sieve with a germanium content of 5-10 wt.%; the titanium source is one or more of tetrabutyl titanate, titanium methoxide, titanium trichloride, titanium tetrachloride and titanium sulfate; and the concentration of the NH4F aqueous solution is 0.1-2 M.

[0012] In one embodiment of the present invention, the reaction conditions of reaction solution A in step (2) are 0.5 to 6 hours at 60 to 100°C.

[0013] In one embodiment of the present invention, the mass ratio of Ti-UTL molecular sieve to palladium chloride aqueous solution in step (2) is 1:5 to 50.

[0014] In one embodiment of the present invention, the palladium chloride aqueous solution in step (2) is a palladium chloride hydrochloric acid aqueous solution, wherein the concentration of palladium chloride is 0.001 to 0.01 wt.% and the concentration of hydrochloric acid is 0.1 to 1 M.

[0015] In one embodiment of the present invention, the reaction conditions of reaction solution B in step (3) are 0.5 to 24 hours at 40 to 100°C.

[0016] In one embodiment of the present invention, the calcination conditions in step (3) are heating at 200-400°C in an air atmosphere for 4-12 hours; the reduction conditions are heating at 300-500°C in a hydrogen atmosphere for 1-6 hours.

[0017] A second aspect of the present invention provides a Pd@Ti-UTL molecular sieve catalyst, which is prepared by the above-described preparation method.

[0018] A third aspect of the present invention provides the application of the above-mentioned Pd@Ti-UTL molecular sieve catalyst in the preparation of propylene oxide, wherein preferably, the reaction temperature for preparing propylene oxide is 60°C.

[0019] The principle of preparing propylene oxide using the Pd@Ti-UTL molecular sieve catalyst is as follows:

[0020] Hydrogen and oxygen are activated at the Pd catalytic active site to generate hydrogen peroxide; the generated hydrogen peroxide is transferred from the Pd active site to the Ti catalytic active site and activated to generate Ti-OOH species, which then react with adsorbed propylene to generate propylene oxide. Figure 1 ).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The Pd@Ti-UTL molecular sieve catalyst provided by the present invention is prepared by mixing and reacting the product obtained by mixing and reacting UTL molecular sieve, titanium source and NH4F aqueous solution with palladium chloride aqueous solution and then heat-treating it at high temperature. For the first time, Pd atoms are deposited and distributed on the surface of Ti-UTL molecular sieve, and Pd atoms have good dispersion. Finally, a Pd@Ti-UTL molecular sieve catalyst with high catalytic activity was prepared.

[0023] (2) This invention is the first to use Pd@Ti-UTL molecular sieve catalyst for the preparation of propylene oxide. Propylene oxide is generated by in-situ synthesis of hydrogen peroxide and coupling reaction with propylene epoxidation. High propylene oxide yield can be obtained at a mild reaction temperature (60°C). At the same time, this invention uses Pd to activate hydrogen and oxygen to generate hydrogen peroxide, replacing the traditional anthraquinone method for producing hydrogen peroxide, effectively solving the problem of hydrogen peroxide supply and realizing the efficient and green synthesis of propylene oxide. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the in-situ synthesis of hydrogen peroxide catalyzed by Pd@Ti-UTL molecular sieve catalyst and coupled reaction with propylene epoxidation to synthesize propylene oxide;

[0025] Figure 2 This is the UV-vis spectrum of the Pd@Ti-UTL molecular sieve catalyst obtained in Example 1 of this invention;

[0026] Figure 3 These are the XRD diffraction patterns of the Pd@Ti-UTL molecular sieve catalysts obtained in Example 1 and Comparative Example 3 of this invention.

[0027] Figure 4 This is the gas chromatogram of Embodiment 1 of the present invention;

[0028] Figure 5 This is the gas chromatogram of Comparative Example 3 of the present invention. Detailed Implementation

[0029] The following is a description of the embodiments and appendices. Figure 1-5 The present invention will be further described below.

[0030] Except for the specific details mentioned below, the processes, conditions, and experimental methods for implementing this invention are all common knowledge and general knowledge in the field, and this invention does not have any particular limitations. All embodiments are operated according to the above-described technical solution steps.

[0031] In the examples and comparative examples, UTL silicon-germanium molecular sieves were prepared according to the literature method (Chemistry of Materials, 2010, 22:3482).

[0032] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0033] Example 1

[0034] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:10 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 5wt.%, the titanium source is titanium tetrachloride, and the concentration of NH4F aqueous solution is 1M.

[0035] (2) The reaction solution A obtained in step (1) is reacted at 80°C for 6 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:20 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.002 wt.% and a hydrochloric acid concentration of 0.1 M.

[0036] (3) The reaction solution B obtained in step (2) is reacted at 60°C for 12 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 400°C in air for 6 hours and the reduction conditions are heating at 350°C in hydrogen for 2 hours.

[0037] Characterization results of ultraviolet-visible absorption spectroscopy (UV-vis) Figure 2 The results show that the Pd@Ti-UTL molecular sieve catalyst has a framework of four-coordinated titanium species at 210 nm, indicating that Ti was successfully implanted into the UTL molecular sieve framework.

[0038] X-ray diffraction (XRD) characterization results Figure 3 The results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to a typical UTL structure.

[0039] XRD characterization results ( Figure 3The results show that the Pd@Ti-UTL molecular sieve catalyst does not have the characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd is highly dispersed on the UTL molecular sieve.

[0040] Example 2

[0041] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:30 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 7wt.%, the titanium source is titanium trichloride, and the concentration of NH4F aqueous solution is 2M.

[0042] (2) The reaction solution A obtained in step (1) is reacted at 60°C for 4 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:5 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.01 wt.% and a hydrochloric acid concentration of 1 M.

[0043] (3) The reaction solution B obtained in step (2) is reacted at 40°C for 24 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 200°C in air for 12 hours and the reduction conditions are heating at 500°C in hydrogen for 1 hour.

[0044] UV-vis characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a framework of four-coordinated titanium species at 210 nm, indicating that Ti was successfully implanted into the UTL molecular sieve framework.

[0045] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0046] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst did not have the characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd was highly dispersed on the UTL molecular sieve.

[0047] Example 3

[0048] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:50 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 10wt.%, the titanium source is titanium sulfate, and the concentration of NH4F aqueous solution is 1M.

[0049] (2) The reaction solution A obtained in step (1) is reacted at 100°C for 6 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:50 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.001 wt.% and a hydrochloric acid concentration of 0.5 M.

[0050] (3) The reaction solution B obtained in step (2) is reacted at 100°C for 0.5 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 300°C in air atmosphere for 4 hours and the reduction conditions are heating at 300°C in hydrogen atmosphere for 6 hours.

[0051] UV-vis characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a framework of four-coordinated titanium species at 210 nm, indicating that Ti was successfully implanted into the UTL molecular sieve framework.

[0052] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0053] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst did not have the characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd was highly dispersed on the UTL molecular sieve.

[0054] Example 4

[0055] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:25 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 8wt.%, the titanium source is tetrabutyl titanate, and the concentration of NH4F aqueous solution is 0.1M.

[0056] (2) The reaction solution A obtained in step (1) is reacted at 100°C for 0.5 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:25 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.005 wt.% and a hydrochloric acid concentration of 0.3 M.

[0057] (3) The reaction solution B obtained in step (2) is reacted at 60°C for 6 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 400°C in air atmosphere for 12 hours and the reduction conditions are heating at 350°C in hydrogen atmosphere for 6 hours.

[0058] UV-vis characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a framework of four-coordinated titanium species at 210 nm, indicating that Ti was successfully implanted into the UTL molecular sieve framework.

[0059] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0060] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst did not have the characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd was highly dispersed on the UTL molecular sieve.

[0061] Example 5

[0062] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:50 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 10wt.%, the titanium source is titanium ethanol, and the concentration of NH4F aqueous solution is 1M.

[0063] (2) The reaction solution A obtained in step (1) is reacted at 100°C for 6 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:50 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.005 wt.% and a hydrochloric acid concentration of 0.5 M.

[0064] (3) The reaction solution B obtained in step (2) is reacted at 100°C for 0.5 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 300°C in air atmosphere for 4 hours and the reduction conditions are heating at 350°C in hydrogen atmosphere for 6 hours.

[0065] UV-vis characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a framework of four-coordinated titanium species at 210 nm, indicating that Ti was successfully implanted into the UTL molecular sieve framework.

[0066] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0067] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst did not have the characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd was highly dispersed on the UTL molecular sieve.

[0068] Comparative Example 1

[0069] (1) Mix UTL molecular sieve, titanium source and water in a mass ratio of 1:0.05:10 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 5wt.% and the titanium source is titanium tetrachloride.

[0070] (2) The reaction solution A obtained in step (1) is reacted at 80°C for 6 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:20 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.002 wt.% and a hydrochloric acid concentration of 0.1 M.

[0071] (3) The reaction solution B obtained in step (2) is reacted at 60°C for 12 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 400°C in air for 6 hours and the reduction conditions are heating at 350°C in hydrogen for 2 hours.

[0072] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0073] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a characteristic peak attributable to Pd crystals, 2θ = 45.3°, indicating that Pd was poorly dispersed on the UTL molecular sieve.

[0074] Comparative Example 2

[0075] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:30 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 7wt.%, the titanium source is titanium trichloride, and the concentration of the NH4F aqueous solution is 2M.

[0076] (2) The reaction solution A obtained in step (1) is reacted at 60°C for 4 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:5 to prepare reaction solution B, wherein the concentration of palladium chloride is 0.01 wt.%.

[0077] (3) The reaction solution B obtained in step (2) is reacted at 40°C for 24 hours. After the reaction is completed, the product is dried, calcined and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The calcination conditions are heating at 200°C in air for 12 hours and the reduction conditions are heating at 500°C in hydrogen for 1 hour.

[0078] XRD characterization results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to the typical UTL structure.

[0079] XRD characterization results showed that the Pd@Ti-UTL molecular sieve catalyst had a characteristic peak attributable to Pd crystals, 2θ = 45.3°, indicating that Pd was poorly dispersed on the UTL molecular sieve.

[0080] Comparative Example 3

[0081] (1) Mix UTL molecular sieve, titanium source and NH4F aqueous solution in a mass ratio of 1:0.05:50 to prepare reaction solution A, wherein the UTL molecular sieve is UTL silicon-germanium molecular sieve with a germanium content of 10wt.%, the titanium source is titanium sulfate, and the concentration of NH4F aqueous solution is 1M.

[0082] (2) The reaction solution A obtained in step (1) is reacted at 100°C for 6 hours. After the reaction is completed, the Ti-UTL molecular sieve obtained is mixed with the palladium chloride aqueous solution at a mass ratio of 1:50 to prepare the reaction solution B. The palladium chloride aqueous solution is a palladium chloride hydrochloric acid aqueous solution with a palladium chloride concentration of 0.001 wt.% and a hydrochloric acid concentration of 0.5 M.

[0083] (3) The reaction solution B obtained in step (2) is reacted at 100°C for 0.5 hours. After the reaction is completed, the product is dried and reduced to obtain Pd@Ti-UTL molecular sieve catalyst. The reduction condition is heating at 300°C under a hydrogen atmosphere for 6 hours.

[0084] XRD characterization results ( Figure 3 The results show that the Pd@Ti-UTL molecular sieve catalyst has characteristic peaks 2θ = 6.3°, 7.0°, 7.4°, 8.4°, 9.7°, 12.6°, 17.0°, 17.9°, 22.8°, 25.3°, 26.4°, and 29.3°, which belongs to a typical UTL structure.

[0085] XRD characterization results ( Figure 3 The results show that the Pd@Ti-UTL molecular sieve catalyst has a characteristic peak 2θ = 45.3° attributable to Pd crystals, indicating that Pd is poorly dispersed on the UTL molecular sieve.

[0086] All examples and comparative examples were applied to the in-situ synthesis of hydrogen peroxide coupled with propylene epoxidation to prepare propylene oxide: First, 0.1 g of catalyst, 10 g of acetonitrile, and 1 g of water were added to a high-pressure reactor with a 45 mL polytetrafluoroethylene liner. Propylene was then introduced into the reactor to replace the air, and this process was repeated three times while maintaining the reaction pressure at 0.4 MPa. Then, hydrogen and oxygen were introduced into the reactor in a molar ratio of 1:1, and the pressure inside the reactor was controlled at 2 MPa. Finally, the reaction was carried out at 60 °C for 2 hours under vigorous stirring, and the liquid mixture was obtained by centrifugation. Finally, the reactants and products were analyzed by gas chromatography (Agilent 7890B, DB-Wax capillary column 30 m × 0.25 mm × 0.25 μm), with isopropanol as an internal standard.

[0087] The reaction results of the in-situ synthesis of hydrogen peroxide catalyzed by the catalyst in the examples and comparative examples and the coupled reaction with propylene epoxidation to prepare propylene oxide are shown in Table 1.

[0088] Table 1. Reaction results of ethylene oxide preparation using catalysts in the examples and comparative examples.

[0089] Example 1 99.5％ Example 2 99.3％ Example 3 99.4％ Example 4 99.3％ Example 5 99.2％ Comparative Example 1 10.5％ Comparative Example 2 0％ Comparative Example 3 22.3％

[0090] As shown in Table 1, compared with Comparative Examples 1-3, the Pd@Ti-UTL molecular sieve catalyst prepared by the present invention in Examples 1-5 has better catalytic activity. It catalyzes the in-situ synthesis of hydrogen peroxide and the coupled reaction with propylene epoxidation to produce propylene oxide. A high yield of propylene oxide can be obtained under the reaction conditions of 60°C, realizing the efficient and green synthesis of propylene oxide.

[0091] Figure 4 and Figure 5 The figures show the gas chromatograms of Example 1 and Comparative Example 3, respectively. As can be seen from the figures, the Pd@Ti-UTL molecular sieve catalyst prepared in Example 1 has a much higher catalytic activity than the catalyst prepared in Comparative Example 3 in the in-situ synthesis of hydrogen peroxide and the coupled reaction with propylene epoxidation to prepare propylene oxide.

[0092] The specific embodiments described above are only used to explain and illustrate the present invention, and are not intended to limit the present invention. Any changes and substitutions made to the present invention without creative effort within the scope of the inventive concept and claims shall fall within the protection scope of the present invention patent.

Claims

1. A method for preparing a Pd@Ti-UTL molecular sieve catalyst, characterized in that, Includes the following steps: Step (1): Mix the raw materials to prepare reaction solution A, wherein the raw materials include UTL molecular sieve, titanium source and NH4F aqueous solution, and the UTL molecular sieve is a germanium-containing UTL silicon-germanium molecular sieve; Step (2): React the reaction solution A obtained in step (1) at 60~100℃ for 0.5~6 hours. After the reaction is completed, mix the Ti-UTL molecular sieve obtained with an aqueous solution of palladium chloride to prepare reaction solution B. The aqueous solution of palladium chloride is an aqueous solution of palladium chloride hydrochloric acid. Step (3): After the reaction solution B obtained in step (2) is completely reacted, the product obtained is dried, calcined and reduced to obtain the desired Pd@Ti-UTL molecular sieve catalyst.

2. The preparation method according to claim 1, characterized in that, The mass ratio of UTL molecular sieve, titanium source and NH4F aqueous solution in step (1) is 1:0.05:10~50.

3. The preparation method according to claim 1, characterized in that, In step (1), the germanium content in the germanium-containing UTL silicon-germanium molecular sieve is 5~10 wt.%; the titanium source is one or more of tetrabutyl titanate, titanium methoxide, titanium trichloride, titanium tetrachloride and titanium sulfate; the concentration of the NH4F aqueous solution is 0.1~2M.

4. The preparation method according to claim 1, characterized in that, The mass ratio of Ti-UTL molecular sieve to palladium chloride aqueous solution in step (2) is 1:5~50.

5. The preparation method according to claim 1, characterized in that, In step (2), the concentration of palladium chloride in the hydrochloric acid aqueous solution is 0.001~0.01 wt.%, and the concentration of hydrochloric acid is 0.1~1 M.

6. The preparation method according to claim 1, characterized in that, The reaction conditions for reaction solution B in step (3) are 40~100℃ for 0.5~24 hours.

7. The preparation method according to claim 1, characterized in that, The calcination conditions in step (3) are heating at 200~400℃ in an air atmosphere for 4~12 hours; the reduction conditions are heating at 300~500℃ in a hydrogen atmosphere for 1~6 hours.

8. A Pd@Ti-UTL molecular sieve catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the Pd@Ti-UTL molecular sieve catalyst according to claim 8 in the preparation of propylene oxide.

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