Supported catalysts, methods for their preparation and use

Abstract

The present application relates to the technical field of propylene oxide, and discloses a method for preparing a supported catalyst, which comprises: impregnating a titanium-silicon molecular sieve with a solution containing a precursor of an active component and an inorganic alkaline substance, and then drying and activating; wherein the active component comprises a group VIII and / or group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element entering the framework structure of the titanium-silicon molecular sieve, the bond length between the doped metal element and O atoms in the framework of the titanium-silicon molecular sieve is 0.02-0.55 nm, and the doped metal element comprises a group VIII and / or group IB metal element. The catalyst prepared by the method can improve the conversion rate of propylene and the selectivity of propylene oxide when used for preparing propylene oxide.

Description

Technical Field

[0001] This invention relates to the field of propylene oxide technology, specifically to a supported catalyst, its preparation method, and its application. Background Technology

[0002] Propylene oxide, as an important chemical raw material, is widely used in food, textiles, pharmaceuticals, and chemical industries. Currently, the main industrial methods for producing propylene oxide include the chlorohydrin process, the co-oxidation process, and the direct oxidation process. Among these, the chlorohydrin process, due to the use of toxic chlorine gas, causes severe equipment corrosion and generates large amounts of chlorine-containing wastewater, polluting the environment and failing to meet green environmental protection requirements. The co-oxidation process requires large upfront investment, and its economic benefits are significantly affected by the price fluctuations of co-products. The direct oxidation process, using hydrogen peroxide or its derivatives as the oxidant and titanium-silicon molecular sieves as the catalyst, is a relatively novel propylene oxide production process, represented by the HPPO and CHPPO processes. The HPPO process offers mild reaction conditions (room temperature - 100℃), high selectivity, and is environmentally friendly and clean. However, due to the risk of decomposition and explosion during the transportation and storage of hydrogen peroxide, this technology requires the construction of a dedicated hydrogen peroxide production unit.

[0003] To address the problems existing in the above-mentioned process, domestic and international research reports have found that loading Au nanoparticles onto TiO2 can catalyze the epoxidation reaction of hydrogen, oxygen, and propylene to produce propylene oxide. The specific reaction equation is as follows:

[0004]

[0005] In the Au@TiO2 catalyst, Au nanoparticles serve as the first-step catalytic active center in a tandem reaction. They initially catalyze the reaction of H2 with O2 to generate H2O2 or -OOH species. Then, the intermediate species H2O2 or -OOH reacts with the framework titanium (Ti). 4+The reaction forms Ti-OOH, which further reacts with propylene adsorbed on the titanium framework in an epoxidation reaction to produce propylene oxide. This work has attracted widespread attention from academia and industry, and researchers have conducted extensive research on it, developing various supported bifunctional catalysts. These catalysts utilize metal nanoparticles including Au, Ag, and Cu, and supports including TiO2, TS-1, Ti-HMS, Ti-MWW, Ti-MCM-41, and Ti-MCM-48. The outstanding advantages of this reaction are its mild reaction conditions, high selectivity, and environmentally friendly nature. However, as an emerging technology, the direct gas-phase epoxidation of propylene faces several challenges. Safety concerns include the risk of gas-phase explosion due to the presence of combustible gases (propylene and hydrogen) and oxidizers. Catalyst concerns include the difficulty in balancing reactivity and stability with existing catalysts. To address safety issues, most researchers have opted to dope with a large amount of inert protective gas (e.g., 70-95% by volume) and improve reactor types to avoid system explosions, such as using microchannel reactors.

[0006] Despite significant efforts by researchers to optimize bifunctional catalysts, resulting in some improvement in initial catalyst activity, the direct gas-phase epoxidation of propylene still faces challenges. Propylene reacts with oxygen to form propylene oxide, but also undergoes α-H oxidation to acrolein, and hydrogenation to propane. These side reactions negatively impact the selectivity of the target product in the direct gas-phase epoxidation of propylene, thus hindering its industrial application. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of high production of byproducts such as acrolein and propane and low selectivity of propylene oxide during the direct epoxidation of propylene in the gas phase in the existing technology, and to provide a supported catalyst, its preparation method and application.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a supported catalyst, the method comprising: impregnating a titanium-silicon molecular sieve with a solution containing an active component precursor and an inorganic alkaline substance, followed by drying and activation; wherein the active component comprises a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, and the doped metal element comprises a Group VIII and / or Group IB metal element.

[0009] A second aspect of the present invention provides a bifunctional catalyst prepared by the method described above.

[0010] A third aspect of the present invention provides a supported catalyst comprising a titanium-silicon molecular sieve and an active component supported on the titanium-silicon molecular sieve, wherein the active component comprises a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, and the doped metal element comprises a Group VIII and / or Group IB metal element.

[0011] The fourth aspect of this invention provides the application of the above-described supported catalyst in the preparation of propylene oxide.

[0012] Through the above technical solution, the present invention achieves the following beneficial effects:

[0013] (1) When the titanium-silicon molecular sieve of the present invention is used as a support to load the active component in the process of preparing the catalyst, it can not only improve the dispersibility of the active component, but also increase the proportion of the reduced active component in the active component.

[0014] (2) Preferably, the present invention can further improve the dispersibility of the active components and increase the proportion of reduced active components in the active components by using specific inorganic alkaline substances.

[0015] (3) When the catalyst prepared by the present invention is used to prepare propylene oxide, it can improve the conversion rate of propylene, the selectivity of propylene oxide, and reduce the selectivity of other by-products. Attached Figure Description

[0016] Figure 1 This is a TEM image of the catalyst prepared in Example 1;

[0017] Figure 2 This is a TEM image of the catalyst prepared in Example 12;

[0018] Figure 3 This is a TEM electron microscope image of the catalyst prepared in Comparative Example 1;

[0019] Figure 4 This is a STEM mapping image of the catalyst prepared in Example 1;

[0020] Figure 5 This is a STEM mapping image of the catalyst prepared in Example 2;

[0021] Figure 6 This is a TEM electron microscope image of the catalyst after the reaction in Example 1;

[0022] Figure 7 This is a TEM image of the catalyst after the reaction in Example 12;

[0023] Figure 8 This is a TEM electron microscope image of the catalyst after the reaction in Comparative Example 1. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of this invention provides a method for preparing a supported catalyst, the method comprising: impregnating a titanium-silicon molecular sieve with a solution containing an active component precursor and an inorganic alkaline substance, followed by drying and activation; wherein the active component comprises a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, preferably 0.15-0.25 nm, and the doped metal element comprises a Group VIII and / or Group IB metal element.

[0026] According to the present invention, preferably, the silicon-to-titanium molar ratio in the molecular sieve is 100:0.1-10. In the present invention, the silicon-to-titanium molar ratio in the molecular sieve can be 100:0.1, 100:0.4, 100:0.5, 100:0.6, 100:1, 100:5, 100:10, or any range consisting of any two of the above.

[0027] According to the present invention, preferably, the doped metal element includes Pd and / or Pt.

[0028] According to the present invention, preferably, the content of the doped metal element is 0.01-0.5% by weight, more preferably 0.04-0.06% by weight, based on the total weight of the titanium-silicon molecular sieve.

[0029] According to the present invention, preferably, the molecular sieve has an average particle size of 80-300 nm and a mesopore specific surface area of ​​50-200 m². 2 / g, the pore volume of the mesoporous tissue is 0.2-0.5cm³. 3 / g, the specific surface area of ​​the micropores is 200-500m² 2 / g, the pore volume of the micropores is 0.05-0.25cm³. 3 / g, with a crystallinity of 85-99%.

[0030] According to the present invention, preferably, the preparation method of titanium-silicon molecular sieve includes the following steps:

[0031] (1) The aqueous solution containing silicon source, titanium source and alkali source is brought into first contact with the solution containing metal salt; wherein the metal salt includes Group VIII and / or Group IB metal salt;

[0032] (2) The solution obtained from the first contact is brought into a second contact with a dispersion containing metal particles; wherein the metal particles include Group VIII and / or Group IB metal particles;

[0033] (3) The solution obtained from the second contact is subjected to hydrothermal crystallization, solid-liquid separation and calcination in sequence.

[0034] According to the present invention, the molar ratio of the silicon source, titanium source, alkali source and water can be selected within a wide range. Preferably, in step (1), the molar ratio R1 of the silicon source, titanium source, alkali source and water in the aqueous solution containing the silicon source, titanium source and alkali source is 100:0.002-60:1-200:50-1000, more preferably 100:0.1-10:20-120:100-800; wherein the silicon source is SiO2 and the titanium source is TiO2.

[0035] According to the present invention, the silicon source can be any substance in the field of molecular sieve preparation that can provide silicon. Preferably, the silicon source is organosilicon, more preferably an alkyl silicate, more preferably an alkyl group of C1-C6, and even more preferably, the silicon source includes at least one of tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, and tetrapentyl silicate.

[0036] According to the present invention, the titanium source can be any substance in the field of molecular sieve preparation that can provide titanium. Preferably, the titanium source is organotitanium, more preferably an alkyl titanate, more preferably an alkyl group of C1-C6, and even more preferably, the titanium source includes at least one of tetrabutyl titanate, tetraethyl titanate, tetrapropyl titanate, and tetrapentyl titanate.

[0037] According to the present invention, preferably, the alkali source is an organic ammonium, more preferably an alkyl ammonium hydroxide, more preferably, the alkyl group in the alkyl ammonium hydroxide is a C1-C6 alkyl group, and even more preferably, the alkali source is at least one selected from tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrapentylammonium hydroxide.

[0038] According to the present invention, preferably, the metal salt comprises a palladium salt and / or a platinum salt. For example, the metal salt can be any metal salt capable of providing Pd ions or Pt ions; preferably, the cation in the metal salt is Pd. 2+ and / or Pt 2+More preferably, the metal salt includes at least one selected from PdCl2, Pd(NO3)2, PtCl2, and Pt(NO3)2. The inventors have further discovered that when a divalent metal salt (PdCl2) is used… 2+ and / or Pt 2+ This can further improve the uniformity of the loading of active components on the molecular sieve. The inventors speculate that this may be because the divalent metal salt is dicoordinated, and after entering the molecular sieve framework structure, it easily generates oxygen vacancies, thereby promoting the loading of active components. At the same time, the divalent metal salt acts as an electrophilic center to attack the hydroxyl groups on the titanium-silicon molecular sieve, and then the active component (taking Au as an example) couples with the electrophilic center as a nucleophilic center, effectively loading Pd 2+ / Pt 2+ The surrounding area forms PdAu / PtAu alloy clusters, thereby increasing the density and number of active centers. Furthermore, the formation of PdAu / PtAu alloy clusters helps weaken the hydroxyl groups on the titanium-silicon molecular sieve, reducing the hydroxyl density and effectively decreasing the occurrence of the propylene oxide ring-opening isomerization side reaction.

[0039] According to the present invention, in order to promote the uniform distribution of active components on the molecular sieve and improve the conversion rate of propylene and the selectivity of propylene oxide in the gas-phase preparation of propylene oxide, preferably, the molar ratio R2 of the silicon source to the metal salt is 1000:0.02-5, more preferably 1000:0.1-2, and even more preferably 1000:0.1-0.5; wherein the silicon source is calculated as SiO2 and the metal salt is calculated as a metal element. In the present invention, the molar ratio R2 of the silicon source to the metal salt can be 1000:0.02, 1000:0.2, 1000:0.25, 1000:0.4, 1000:0.5, 1000:1, 1000:2, and any two of the above ranges.

[0040] According to the present invention, preferably, the concentration of the metal salt in the solution containing the metal salt is 0.001-1 mol / L, more preferably 0.01-0.1 mol / L.

[0041] According to the present invention, preferably, the solvent in the solution containing the metal salt is water.

[0042] According to the present invention, the duration of the first contact can be selected within a wide range. However, in order to promote the entry of the metal salt into the molecular sieve framework and the uniform distribution of metal ions within the molecular sieve, the duration of the first contact is preferably 10-120 min, more preferably 40-80 min. Typically, the temperature of the first contact is room temperature. In the present invention, unless otherwise specified, room temperature is typically 15-40°C.

[0043] According to the present invention, in order to promote the uniform distribution of active components on the molecular sieve and improve the conversion rate of propylene and the selectivity of propylene oxide in the gas-phase preparation of propylene oxide, preferably, the molar ratio R3 of the metal salt in step (1) to the metal particles in step (2) is 1:0.001-1, more preferably 1:0.005-0.1, and even more preferably 1:0.005-0.01, where the metal salt and the metal particles are calculated as metal elements. In the present invention, the molar ratio R3 of the metal salt to the metal particles can be 1:0.001, 1:0.005, 1:0.008, 1:0.01, 1:0.015, 1:0.05, 1:0.5, 1:1, and any two of the above ranges.

[0044] According to the present invention, preferably, the metal particles include palladium particles and / or platinum particles. The inventors of the present invention speculate that the introduction of metal particles during the molecular sieve preparation process can improve the uniform distribution of the active components because: according to frontier orbital theory, the 4d orbitals of Pd / Pt atoms can partially coincide with the 6s orbitals of the active components, and electrons in the 4d orbitals of Pd / Pt atoms can fill the empty 6s orbitals of the active component atoms, forming a stable interaction. Therefore, the metal particles can effectively anchor the active components dispersed around them; on the one hand, this can improve the dispersion of the active components; on the other hand, according to the lattice dynamics theory of solid-state physics, Pd / Pt atoms have a high Taman temperature, which can reduce the fluidity of the active components and reduce the degree of Austaunch ripening during the reaction.

[0045] According to the present invention, preferably, the concentration of metal particles in the dispersion containing metal particles is 0.001-0.1 mol / L.

[0046] According to the present invention, preferably, the solvent in the dispersion containing metal particles is water.

[0047] According to the present invention, preferably, the particle size of the metal particles in the dispersion containing metal particles is 1-20 nm, more preferably 1-3 nm.

[0048] According to the present invention, preferably, the method for preparing the metal particles is as follows: mixing an aqueous solution of a metal precursor, an aqueous solution of sodium citrate, and an aqueous solution of tannic acid, and then heating at 60-120°C for 2-6 hours to obtain metal particles (colloids), wherein the metal precursor includes a Group VIII metal salt and / or a Group IB metal salt. Preferably, the metal precursor includes a palladium salt and / or a platinum salt. More preferably, the amounts of the aqueous solution of the metal precursor, the aqueous solution of sodium citrate, and the aqueous solution of tannic acid are such that the molar ratio of the metal precursor, sodium citrate, and tannic acid is 1:0.02-0.2:0.025-0.25. The concentration of the aqueous solution of the metal precursor can be 0.005-0.1 mol / L, the concentration of the aqueous solution of sodium citrate can be 0.05-0.5 mol / L, and the concentration of the aqueous solution of tannic acid can be 0.005-0.1 mol / L. In this invention, the amounts of the metal precursor aqueous solution, sodium citrate aqueous solution, and tannic acid aqueous solution are adjusted such that the molar ratio of the metal precursor, sodium citrate, and tannic acid can be 1:0.08-0.12:0.15-0.2.

[0049] According to the present invention, preferably, the second contact time is 20-100 minutes. Typically, the temperature of the second contact is room temperature.

[0050] According to the present invention, preferably, the conditions for hydrothermal crystallization include: a temperature of 120-200°C and a time of 10-80 hours.

[0051] According to the present invention, preferably, the calcination conditions include a temperature of 500-650°C and a time of 4-10 hours. More preferably, the calcination atmosphere is air.

[0052] According to the present invention, preferably, the aqueous solution containing silicon source, titanium source and alkali source is obtained by: first mixing silicon source and titanium source to obtain a first mixture, then mixing the first mixture with alkali source to obtain a second mixture, and then mixing the second mixture with water to obtain the aqueous solution containing silicon source, titanium source and alkali source.

[0053] According to the present invention, preferably, the preparation method further includes: subjecting the product of the first contact to alcohol removal treatment before performing step (2). The inventors of the present invention have further discovered that subjecting the product of the first contact to alcohol removal treatment before performing step (2) can further promote the entry of doped metals into the framework of the molecular sieve, thereby improving the crystallinity, specific surface area, and pore volume of the titanium-silicon molecular sieve.

[0054] According to the present invention, preferably, the conditions for the alcohol removal treatment include: a temperature of 70-100°C and a time of 2-8 hours.

[0055] According to the present invention, since some water will evaporate during the de-alcoholization process, it is preferable to replenish water during the de-alcoholization process to maintain the liquid level.

[0056] According to the present invention, preferably, the solution containing the active component precursor and the inorganic alkaline substance further includes a dispersant. More preferably, the solution containing the active component precursor, the dispersant, and the inorganic alkaline substance is obtained by: mixing the solution containing the active component precursor with the dispersant to obtain solution B1; then adjusting the pH of solution B1 to 5-8 using the solution containing the inorganic alkaline substance to obtain solution B2; and then aging solution B2 to obtain an impregnation solution.

[0057] According to the present invention, preferably, the concentration of the solution containing the active component precursor is 0.1-5 g / L. In the present invention, the solution containing the active component precursor can be prepared directly by mixing the active component precursor with a solvent; alternatively, the active component precursor can be first mixed with a portion of the solvent to obtain a solution of a certain concentration, and then the solution can be diluted with the remaining solvent to obtain the solution containing the active component precursor.

[0058] According to the present invention, the active component in the active component precursor can be a Group VIII metal element, gold, silver, or a platinum group metal (ruthenium, rhodium, palladium, osmium, iridium, platinum). Preferably, the active component precursor includes an Au precursor and / or a Pd precursor; more preferably, it is an Au precursor. The active component precursor can be any substance capable of providing a noble metal element to the catalyst, such as a noble metal, a salt of a noble metal, or an oxide of a noble metal. The Au precursor can be at least one of HAuCl4, AuCl3, and Au(NO3)3; the Pd precursor can be at least one of Pd(NO3)2, PdCl2, and PdSO4.

[0059] According to the present invention, the type of dispersant is not particularly limited and can be a commonly used dispersant in the art. Preferably, the dispersant includes at least one of ethylenediamine, ethylene glycol, urea, disodium ethylenediaminetetraacetate, bipyridine, glycerol, N,N dimethylformamide, acetone, toluene, tannic acid and cyclohexane.

[0060] According to the present invention, preferably, the concentration of the solution containing the inorganic alkaline substance is 0.005-0.25 mol / L.

[0061] According to the present invention, preferably, the inorganic alkaline substance includes at least one of alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, and ammonia water. More preferably, the inorganic alkaline substance includes at least one of NaOH, KOH, Na₂CO₃, K₂CO₃, Cs₂CO₃, NaHCO₃, and KHCO₃; even more preferably, the inorganic alkaline substance includes at least one of Na₂CO₃, K₂CO₃, Cs₂CO₃, NaHCO₃, and KHCO₃. The inventors have further discovered that, in the method of the present invention, compared with organic bases (e.g., urea), using inorganic bases (alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates) can further improve the uniformity of the loading of active components and improve the propylene conversion rate and the selectivity of propylene oxide.

[0062] According to the present invention, preferably, the solution containing the active component precursor is mixed with the dispersant for 0.5-6 hours.

[0063] According to the present invention, preferably, the aging conditions result in an impregnation solution pH of 7-9.3. More preferably, the aging time is 3-8 hours. The aging can be carried out with stirring (stirring speed of 200-800 r / min) or by standing. Typically, the aging temperature is room temperature.

[0064] According to the present invention, preferably, the amount of the active component precursor, calculated as metal element, is 0.01-1g per 100g of titanium silicate molecular sieve, and the amount of the dispersant is 0.005-1g. In this invention, the amount of the active component precursor, calculated as metal element, is 0.01g, 0.1g, 0.3g, 0.5g, 0.7g, 0.9g, 1g, or any two of the above values, relative to 100g of carrier; the amount of the dispersant can be 0.005g, 0.05g, 0.08g, 0.1g, 0.5g, 1g, or any two of the above values.

[0065] According to the present invention, preferably, the impregnation method includes ultrasonic impregnation and oscillatory impregnation; wherein, the ultrasonic impregnation time is 0.2-2 hours; the oscillatory impregnation is carried out under light-shielding conditions, and the oscillatory impregnation time is 8-24 hours. The oscillation frequency can be 50-1200 r / min; the ultrasonic frequency can be a commonly used ultrasonic frequency in the art, such as 25 kHz-100 kHz.

[0066] According to the present invention, preferably, the solid-liquid mixture obtained after impregnation can be dried after solid-liquid separation, or it can be dried directly without solid-liquid separation. More preferably, the solid-liquid mixture is dried directly without solid-liquid separation.

[0067] According to the present invention, preferably, the drying conditions are such that the drying rate of the solid-liquid mixture is 0.025-0.955 g water / (cm³). 2 More preferably, the drying conditions include a temperature of 30-70°C and a relative humidity of ≤60%. The drying time is not particularly limited, as long as the moisture in the solid-liquid mixture is fully evaporated under the drying conditions and the weight no longer changes.

[0068] In this invention, relative humidity is measured using a thermo-hygrometer (model: Alarm-Hygrometer testo 608-H2). Specifically, in this system, relative humidity refers to the ratio of the partial pressure of water vapor in the air during the drying process of the solid-liquid mixture to the saturated vapor pressure at the same temperature. In the catalyst preparation process, drying is usually carried out at temperatures above 100°C to facilitate water evaporation. However, the inventors of this invention have further discovered that drying at lower temperatures can further improve the dispersibility of the active components. The inventors speculate that this may be because drying at lower temperatures reduces the rate of water evaporation, preventing excessively rapid evaporation from causing segregation and aggregation of the active components, thereby improving the dispersibility of the active components and reducing their average particle size.

[0069] According to the present invention, preferably, the relative humidity fluctuation range during the drying process is ≤5%; more preferably, the relative humidity fluctuation range during the drying process is ≤3%. Controlling the relative humidity fluctuation range within the above range can further increase the content of small-particle-size active components in the catalyst, improve the dispersibility of active components in the catalyst, increase active centers, and improve the catalytic performance of the catalyst; and when the catalyst is used for the gas-phase production of propylene oxide, it can achieve higher propylene conversion rate, propylene oxide selectivity, and hydrogen utilization rate.

[0070] According to the present invention, preferably, the activation conditions include: a temperature of 150-350°C and a time greater than 2 hours, preferably 2-8 hours. The activation atmosphere can be an inert atmosphere or an oxygen-containing atmosphere, wherein the inert atmosphere can be provided by at least one of nitrogen, argon, helium, and neon, preferably nitrogen. The oxygen-containing atmosphere can be an air atmosphere.

[0071] A second aspect of the present invention provides a supported catalyst prepared by the method described above.

[0072] A third aspect of the present invention provides a supported catalyst comprising a titanium-silicon molecular sieve and an active component supported on the titanium-silicon molecular sieve, wherein the active component comprises a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, preferably 0.15-0.25 nm, and the doped metal element comprises a Group VIII and / or Group IB metal element.

[0073] According to the present invention, preferably, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.1-10. In the present invention, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve can be 100:0.1, 100:0.4, 100:0.5, 100:0.6, 100:1, 100:5, 100:10, or any range consisting of any two of the above.

[0074] According to the present invention, preferably, the doped metal element includes Pd and / or Pt.

[0075] According to the present invention, preferably, the content of the doped metal element is 0.01-0.5% by weight, more preferably 0.04-0.06% by weight, based on the total weight of the titanium-silicon molecular sieve.

[0076] According to the present invention, preferably, the titanium-silicon molecular sieve has an average particle size of 80-300 nm and a mesopore specific surface area of ​​50-200 m². 2 / g, the pore volume of the mesoporous tissue is 0.2-0.5cm³. 3 / g, the specific surface area of ​​the micropores is 200-500m² 2 / g, the pore volume of the micropores is 0.05-0.25cm³. 3 / g, with a crystallinity of 85-99%.

[0077] According to the present invention, preferably, the active component is Au.

[0078] According to the present invention, preferably, the content of the active component is 0.01-1% by weight, based on the total weight of the catalyst.

[0079] According to the present invention, preferably, the hydroxyl density of the catalyst is Q4 / Q3 = 3-10.

[0080] In the catalyst, Au exists in the form of PdAu alloy clusters and / or PtAu alloy clusters.

[0081] According to the present invention, preferably, the number of Au nanoparticles with a diameter of 2-5 nm in any 100 nm × 100 nm region on the gold nanoparticle-supported titanium-silicon molecular sieve does not differ by more than 40%, and the spacing between any metal nanoparticles is >3 nm; more preferably, the number of Au nanoparticles with a diameter of 2-5 nm in any 100 nm × 100 nm region on the gold nanoparticle-supported titanium-silicon molecular sieve does not differ by more than 20%, and the spacing between any metal nanoparticles is >5 nm.

[0082] The fourth aspect of this invention provides the application of the above-described supported catalyst in the preparation of propylene oxide.

[0083] According to the present invention, preferably, the raw material gas used in the preparation of propylene oxide includes propylene, hydrogen and oxygen, and preferably, the volume ratio of propylene, hydrogen and oxygen is 1:0.1-5:0.1-2.

[0084] According to the present invention, preferably, the flow rate of the propylene is 2-70 mL / min.

[0085] According to the present invention, preferably, the temperature for preparing propylene oxide is 160-220°C.

[0086] Typically, heat treatment of catalysts at high temperatures accelerates the aggregation of active components. In this invention, to verify the heat resistance stability of the catalyst, it is heat-treated before the preparation of propylene oxide. The heat treatment conditions may include: a temperature of 250-370°C, a pressure of 0.2-0.6 MPa, and a time of 1-20 hours.

[0087] The present invention will be described in detail below through embodiments. In the following embodiments,

[0088] Preparation Example 1

[0089] This preparation example illustrates the preparation process of molecular sieves.

[0090] (1-1) Preparation of an aqueous solution containing silicon, titanium and alkali sources: Weigh 41.67 g of tetraethyl silicate and pour it into a beaker containing a magnetic stir bar, and keep stirring vigorously; then add tetrabutyl titanate dropwise to the beaker containing tetraethyl silicate, and keep stirring at a stirring rate of 400 r / min for 30 min to obtain a transparent liquid, which is recorded as mixture A1; then slowly add tetrapropylammonium hydroxide solution (the concentration of tetrapropylammonium hydroxide in the tetrapropylammonium hydroxide solution is 25% by weight) to mixture A1. The solution begins to become turbid and gradually turns into a milky white opaque suspension, which is recorded as mixture A2; adjust the stirring speed to 600 r / min, add distilled water to mixture A2, and continue stirring for 60 min. The milky white opaque suspension turns into a colorless and transparent solution again, which is the aqueous solution containing silicon, titanium and alkali sources, recorded as mixture A3. In the mixture A3, the molar ratio R1 of tetraethyl silicate, tetrabutyl titanate, tetrapropylammonium hydroxide and water is 100:0.5:80:555.

[0091] (1-2) Add 0.1 mol / L PdCl2 solution to mixture A3 and continue stirring at a stirring rate of 600 r / min for 60 min. The resulting solution is denoted as mixture A4. Then, heat mixture A4 to 80℃ for alcohol removal treatment to distill off the ethanol and butanol produced by the hydrolysis of the titanium silica sol. During the alcohol removal treatment, the liquid level in the beaker drops, and the same amount of distilled water needs to be added to maintain the liquid level. After 6 h of alcohol removal treatment, the liquid level of mixture A4 basically stabilizes and no longer drops. The alcohol removal treatment is then ended, and the resulting solution is denoted as mixture A5. The amount of PdCl2 solution added makes the molar ratio R2 of silicon source to metal salt 1000:0.5.

[0092] (2-1) Preparation of nano-sized Pd particles: A 0.003 mol / L PdCl2 aqueous solution was placed in a beaker and heated to 70 °C. Then, a 0.1 mol / L sodium citrate aqueous solution and a 0.05 mol / L tannic acid aqueous solution were added to the beaker. After stirring at 600 r / min for 4 h, palladium nanoparticles were obtained. The Pd nanoparticles in the colloid had a particle size of 1-3 nm. The amounts of PdCl2 aqueous solution, sodium citrate aqueous solution, and tannic acid aqueous solution were such that the molar ratio of PdCl2, sodium citrate, and tannic acid was 1:0.1:0.2.

[0093] (2-2) The palladium nanocolloids prepared in step (2-1) were mixed with water to obtain an aqueous dispersion of Pd nanoparticles with a concentration of 0.01 mol / L. The aqueous dispersion of Pd nanoparticles with a concentration of 0.01 mol / L was added to mixture A5, and stirring was continued at a stirring rate of 600 r / min for 60 min. The resulting solution was denoted as mixture A6. The amount of the nanoparticle dispersion added was such that the molar ratio R3 of the metal salt to the metal particles was 1:0.01.

[0094] (3) The mixture A6 was transferred to a high-pressure hydrothermal reactor and heated to 170°C at a rate of 0.5°C / min for hydrothermal crystallization for 72 hours. After hydrothermal crystallization, the reactor was allowed to cool naturally to 30°C. The milky white suspension was then removed from the reactor and centrifuged in a high-speed centrifuge. The supernatant was discarded, leaving the solid material. The solid material was washed with distilled water and centrifuged repeatedly until the pH of the supernatant was <8. The solid material was then dried in an oven at 50°C for 20 hours to obtain an irregularly shaped agglomerated solid material. The agglomerated solid material was ground and pulverized to obtain a particle size of less than 0.075 mm. The calcined solid material was then calcined at 550°C for 6.5 hours in air to obtain a Pd-modified titanium silicate molecular sieve, designated as molecular sieve-1.

[0095] Preparation Examples 2-6

[0096] The method of preparation example 1 is the same, except that R1, R2, R3, the types of metal salts, and the types of metal particles are shown in Table 1.

[0097] Table 1

[0098] R1 Metal salts R2 Types of metal particles R3 Molecular sieve Preparation Example 2 100:0.5:80:555 <![CDATA[PtCl2]]> 1000:0.5 Pt 1:0.01 Molecular sieve-2 Preparation Example 3 100:0.5:80:555 <![CDATA[PdCl2]]> 1000:0.25 Pd 1:0.005 Molecular sieve-3 Preparation Example 4 100:0.5:80:555 <![CDATA[Pd(NO3)2]]> 1000:0.5 Pd 1:0.01 Molecular sieve-4 Preparation Example 5 100:1:80:555 <![CDATA[PdCl2]]> 1000:0.5 Pd 1:0.01 Molecular sieve-5 Preparation Example 6 100:0.5:40:555 <![CDATA[PdCl2]]> 1000:0.5 Pd 1:0.01 Molecular sieve-6

[0099] Note: The preparation method of Pt metal particles in Preparation Example 2 is the same as that of Pd nanoparticles in Preparation Example 1, except that PdCl2 is replaced with PtCl2. The particle size of Pt metal particles obtained in Preparation Example 2 is 1-3 nm. The preparation methods of Pd metal particles in Preparation Examples 3-6 are the same as those of Pd nanoparticles in Preparation Example 1.

[0100] Preparation Example 7

[0101] The preparation method was the same as in Preparation Example 1, except that the solution containing silicon, titanium, and alkali sources was prepared by directly mixing silicon, titanium, alkali, and water in the same molar ratio as in Preparation Example 1 to obtain mixture A3. The resulting molecular sieve was designated as molecular sieve-7.

[0102] Preparation Example 8

[0103] The preparation method was carried out according to Example 1, except that the dealcoholization step was not included. The resulting molecular sieve is designated as molecular sieve-8.

[0104] Preparation Example 9

[0105] The preparation method was followed as in Example 1, except that tannic acid was not added in step (2-1) when preparing the nano-sized Pd particles. The resulting nano-sized Pd particles had a particle size of 5-10 nm. The resulting molecular sieve is designated as Molecular Sieve-9.

[0106] Preparation Example 10

[0107] The preparation method was followed as in Example 1, except that R3 = 1:0.1. The resulting molecular sieve is designated as Molecular Sieve-10.

[0108] Comparative Preparation Example 1

[0109] The preparation method was carried out according to Example 1, except that steps (1-2), (2-1), and (2-2) were not included. The resulting molecular sieve is denoted as molecular sieve-D1.

[0110] Comparative Preparation Example 2

[0111] The preparation method of Example 1 was followed, except that steps (2-1) and (2-2) were not included; in step (1-2), an aqueous solution of metal salt was added to mixture A3 along with an aqueous dispersion of nano-metal particles (the type, concentration, and amount of the aqueous dispersion of nano-metal particles were the same as in step (2-2) of Example 1). The resulting molecular sieve was designated as molecular sieve-D2.

[0112] Comparative preparation example 3

[0113] The preparation method was carried out according to Example 7, except that step (1-2) did not include the alcohol removal process, and steps (2-1) and (2-2) were not included. The resulting molecular sieve is designated as molecular sieve-D3.

[0114] Example 1

[0115] This example illustrates the catalyst preparation process.

[0116] (1) Preparation of impregnation solution containing active component precursor, dispersant and alkaline substance: Take 17.24 mL of HAuCl4 aqueous solution (Au concentration in HAuCl4 aqueous solution is 0.29 g / L), then add 0.033 g of ethylene glycol to HAuCl4 aqueous solution, and stir at a stirring rate of 400 r / min for 30 min to obtain solution B1. Maintain the stirring rate of 400 r / min, and then add 0.1 mol / L KHCO3 aqueous solution to solution B1, with the dropping rate controlled at 1 mL / min to obtain solution B2, the pH value of solution B2 is 6.92. Then continue to stir solution B2 for 3.5 h to obtain impregnation solution, the pH value of impregnation solution is 8.59.

[0117] (2) Impregnating the carrier with an impregnation solution: Take 5g of the molecular sieve obtained in Example 1 and place it in a container with a bottom area of ​​80cm². 2 The impregnation solution prepared in step (1) was slowly injected into the glass petri dish, with the drop rate controlled at 2 mL / min. The resulting solid-liquid mixture was then subjected to ultrasonic impregnation in an ultrasonic cleaner and oscillation impregnation on an oscillator at room temperature. The ultrasonic impregnation time was 30 min, and the oscillation impregnation time was 24 h. The oscillation frequency was 100 r / min, and the solid-liquid mixture was shielded from light during the oscillation.

[0118] (3) Drying and activation: The shaken solid-liquid mixture was placed in a constant temperature and humidity oven with forced air to dry and obtain a blocky solid. The oven settings were: temperature 30℃, relative humidity 15%, and maximum relative humidity fluctuation of 3%. Drying was stopped after reaching constant weight, and the blocky solid was then ground to a particle size of less than 0.06 mm. The solid was then activated in a muffle furnace at 200℃ for 2.5 h in air atmosphere to obtain the catalyst. The constant temperature and humidity oven settings resulted in a drying rate of 0.275 g water / (cm³). 2 h·g carrier).

[0119] The scanning electron microscope image of the catalyst prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 It can be seen that the active component Au has a small particle size and high dispersibility.

[0120] Examples 2-14 and Comparative Examples 1-3

[0121] The method was carried out in accordance with Example 1, except that the type of carrier, the amount of HAuCl4, the solution B2, and the pH value of the impregnation solution were as shown in Table 2.

[0122] Table 2

[0123]

[0124] Example 15

[0125] The procedure was carried out according to Example 1, except that the KHCO3 aqueous solution was replaced with an equal concentration and volume of KOH aqueous solution. The pH values ​​of solution B2 and the impregnation solution were 8.26 and 7.06, respectively.

[0126] Example 16

[0127] The method was followed as in Example 1, except that the drying conditions in step (3) were: a temperature of 100°C and a relative humidity of 10%. The parameters of the constant temperature and humidity oven were set such that the drying rate was 1.2 g water / (cm³).2 h·g carrier).

[0128] Example 17

[0129] (1) Preparation of impregnation solution containing active component precursor, dispersant and alkaline substance: 8.62 mL of HAuCl4 aqueous solution (Au concentration in HAuCl4 aqueous solution is 0.29 g / L) was transferred, and then 0.01 mL of ethylene glycol was added to the HAuCl4 aqueous solution. After stirring at a rate of 400 r / min for 30 min, solution B1 was obtained. While maintaining the stirring rate of 400 r / min, 0.1 mol / L KHCO3 aqueous solution was added to solution B1, with a dropping rate controlled at 1 mL / min, to obtain solution B2. The pH value of solution B2 was 6.86. Solution B2 was then stirred for another 4 h to obtain the impregnation solution, with a pH of 8.88.

[0130] (2) Impregnating the carrier with an impregnation solution: Take 5g of the molecular sieve obtained in Example 5 and place it in a container with a bottom area of ​​80cm². 2 The impregnation solution prepared in step (1) was slowly injected into the glass petri dish, with the drop rate controlled at 2 mL / min. The resulting solid-liquid mixture was then subjected to ultrasonic impregnation in an ultrasonic cleaner and oscillation impregnation on an oscillator at room temperature. The ultrasonic impregnation time was 20 min, and the oscillation impregnation time was 20 h. The oscillation frequency was 100 r / min, and the solid-liquid mixture was shielded from light during the oscillation.

[0131] (3) Drying and activation: The shaken solid-liquid mixture was placed in a constant temperature and humidity oven with forced air to dry and obtain a blocky solid. The oven settings were: temperature 40℃, relative humidity 25%, and maximum relative humidity fluctuation of 3%. Drying was stopped after reaching constant weight, and the blocky solid was then ground to a particle size of less than 0.06 mm. The solid was then activated in a muffle furnace at 300℃ for 2 hours in air atmosphere to obtain the catalyst. The constant temperature and humidity oven settings resulted in a drying rate of 0.325 g water / (cm³). 2 h·g carrier).

[0132] Comparative Example 4

[0133] The procedure was carried out according to Example 1, except that the KHCO3 aqueous solution was replaced with an aqueous solution of urea of ​​equal concentration and volume. The pH values ​​of solution B2 and the impregnation solution were 4.31 and 5.76, respectively.

[0134] Test case

[0135] (I) The molecular sieves prepared in the above preparation examples and comparative preparation examples were characterized by parameters, and the test results are shown in Table 3.

[0136] The presence of dopants in titanium-silicon molecular sieves was tested using synchrotron X-ray absorption fine structure spectroscopy (XAFS). The atomic nearest-neighbor structures of different elements in the analyte were studied by adjusting the incident X-ray energy. Specifically, the X-ray energy was adjusted to match the inner electron shell of the element under study before being used to probe the sample. The relationship between the number of absorbed X-rays and their energy was then monitored. The obtained spectral structures were analyzed using software to determine the spacing between absorbing atoms and their neighboring atoms, the number and type of atoms, and the oxidation state of the absorbing elements. The Si-O bond length in the titanium-silicon molecular sieve is 0.18-0.19 nm, the Ti-O bond length is 0.19-0.20 nm, and the -O bond lengths of the dopants are shown in Table 3. Specifically, when the bond length between the dopant metal and the O atom is comparable to the Si-O bond length (or Ti-O bond length) (the smaller the difference), it indicates that the dopant element has entered the framework of the titanium-silicon molecular sieve and can maintain the framework structure of the titanium-silicon molecular sieve well. As the difference increases, the dopant element may enter the framework of the titanium-silicon molecular sieve, but it will cause the framework to deform. As the difference further increases (the bond length between the dopant metal and the O atom is greater than 1 nm), the dopant element cannot enter the framework of the titanium-silicon molecular sieve.

[0137] The method for testing the silicon-titanium molar ratio in molecular sieves is as follows: the content of titanium and silicon elements in molecular sieves is tested by combining inductively coupled plasma optical emission spectroscopy (ICP-OES) to obtain the overall silicon-titanium ratio of the molecular sieve.

[0138] The method for determining the Pd / Pt content in molecular sieves is as follows: based on inductively coupled plasma optical emission spectroscopy (ICP-OES), the metal content in the catalytic material is tested. Specifically, after sample digestion, the solution is introduced into the plasma optical emission spectrometer, and the intensity is measured at the corresponding elemental wavelengths. The elemental content in the sample is calculated using the standard curve method. Then, the Pd / Pt content is obtained based on the relevant component data.

[0139] The method for testing the crystallinity of molecular sieves is as follows: using a JCPDS standard card as the standard sample (whose crystallinity is known, denoted as X). s The XRD diffraction peaks of its crystalline phase in the 2θ = 5-35° range were measured, and several characteristic peaks were obtained, denoted as P. S1 -P Sn Its corresponding peak height is H S1 -H Sn The sum of the peak heights is denoted as ΣH. Si The full width at half maximum (FWHM) at 2θ = 24.5° is denoted as W. S XRD analysis revealed a characteristic peak at the position corresponding to the characteristic peak of S-1 in the molecular sieve being tested; this peak is denoted as P. i1 -P in Its corresponding peak height is H i1-H in The sum of the peak heights is denoted as ΣH. ii The full width at half maximum (FWHM) at 2θ = 24.5° is denoted as W. i Crystallinity X of the molecular sieve sample to be tested i The calculation formula is as follows:

[0140] X i =X s *(W i *ΣH ii / (W S *ΣH Si )).

[0141] The method for testing the average particle size of molecular sieves is as follows: The average particle size of molecular sieves is tested using a laser particle size analyzer. The sample to be tested is diluted to a certain extent to obtain a high degree of dispersion. By setting conditions such as laser wavelength, scattering angle, and test temperature, the intensity distribution of the scattered light of the particles to the laser is determined, and the particle size distribution information is calculated based on the intensity distribution of the scattered light.

[0142] The pore structure and specific surface area of ​​the molecular sieve were tested using a nitrogen physical adsorption instrument. The specific surface area of ​​the molecular sieve was analyzed using the BET (Brunauer-Emmett-Teller) method, and the pore size distribution was calculated using the BJH (Barrett-Joiner-Halenda) model.

[0143] Table 3

[0144]

[0145]

[0146] (II) The catalysts prepared in the above examples and comparative examples were characterized by parameters, and the test results are shown in Table 4.

[0147] The method for testing the content of Au, the active component in the catalyst, is inductively coupled plasma optical emission spectroscopy (ICP-OES) to test the Au element content in the catalyst material.

[0148] The method for determining the form of Au in the catalyst is X-ray photoelectron spectroscopy (XPS). Based on the different electron binding energies of Au in different valence states, Au is obtained after peak separation. 3+ Au 1+ and Au 0 Au in different valence states exhibits a relative size of morphological peak area.

[0149] The method for testing the average particle size of Au nanoparticles in the catalyst is as follows: in the obtained TEM image, randomly select the diameter of 100 Au nanoparticles in any region, and then take the average value of the sample.

[0150] The hydroxyl density of the catalyst was tested using silicon nuclear magnetic resonance (NMR) on a VARIAN VNMRS 400WB NMR spectrometer. The single-pulse method was employed, with (CH3)3Si(CH2)3SO3Na as the chemical shift reference, and a rotation rate of 3 kHz and a cycle delay of 60 s, at a frequency of 79.43 MHz. 29 Si MAS nuclear magnetic resonance spectroscopy measurements. The peak areas near -113 ppm and -103 ppm in the corresponding spectra represent the relative contents of the silicon framework structures Q4:Si(OSi)4 and Q3:Si(OSi)3OH in the molecular sieve, respectively. The ratio Q4 / Q3 represents the relative content of silanol groups in the molecular sieve. The larger the Q4 / Q3 ratio, the lower the hydroxyl content.

[0151] The method for testing the dispersion of Au in the catalyst is as follows: Transmission electron microscopy (TEM) is generally used to characterize the dispersion of nanoparticles on the molecular sieve support. For higher precision requirements and to characterize the Au dispersion under conditions of smaller metal nanoparticle distribution, small-angle dark-field scanning transmission electron microscopy (HADDF-STEM) can be used. In this method, the metal exists as bright spots, while the support is in a dark field, providing a clear contrast. Figure 1-3 It can be seen that the Au / TS-1 catalyst obtained in the preferred embodiment 1 of the present invention has small Au nanoparticle size, small size difference between each nanoparticle, and very uniform overall dispersion on the TS-1 support; the Au / TS-1 catalyst obtained in the non-preferred embodiment 12 has Au nanoparticle size of varying sizes, large size difference between each nanoparticle, and poorer overall dispersion uniformity on the TS-1 support than in embodiment 1; the Au / TS-1 catalyst obtained in comparative example 1 has large Au nanoparticle size, large size difference between each nanoparticle, and very uneven overall dispersion on the TS-1 support, with obvious agglomeration.

[0152] The method for testing the Pd / Pt dispersion in the catalyst was as follows: transmission electron microscopy combined with EDS energy dispersive spectroscopy area scanning (TEM-mapping) was used to obtain the distribution of different element contents. Figure 4 It can be seen that the elemental distribution of Pd-induced Au nanoparticles on the TS-1 support is almost completely consistent with the distribution of the inducing element Pd, indicating that a relatively stable PdAu alloy structure has been formed. Figure 5It can be seen that the elemental distribution of Pt-induced Au nanoparticles on the TS-1 support is almost completely consistent with the distribution of the inducing element Pt, indicating that the two form a relatively stable PtAu alloy structure.

[0153] Table 4

[0154]

[0155]

[0156] Note: Dispersion of Au a

[0157] 1) Excellent dispersibility of Au: The number of Au nanoparticles with diameters of 2-5 nm in any 100 nm × 100 nm region on the nano-gold supported titanium-silicon molecular sieve does not differ by more than 20%, and the spacing between any metal nanoparticles is >5 nm.

[0158] 2) Good dispersibility of Au: The number of Au nanoparticles with diameters of 2-5 nm in any 100 nm × 100 nm region on the nano-gold supported titanium-silicon molecular sieve does not differ by more than 40%, and the spacing between any metal nanoparticles is >3 nm.

[0159] 3) Poor dispersion of Au: The number of Au nanoparticles with diameters of 2-5 nm in any 100 nm × 100 nm region on the nano-gold supported titanium silicon molecular sieve does not differ by more than 50%, and the spacing between any metal nanoparticles is >2 nm.

[0160] (III) Test the performance of the catalysts prepared in the above examples and comparative examples in the preparation of propylene oxide.

[0161] Weigh 0.1 g of catalyst and load it into the middle of a fixed-bed reactor, with both ends of the catalyst filled with quartz sand. Then, purge the reactor with nitrogen gas at a flow rate of 14 ml / min. Set the temperature program to increase from room temperature to 350°C at a rate of 1°C / min, and set the reaction pressure to 0.5 MPa. Perform heat treatment on the catalyst for 10 hours. Then, cool the reactor to 170°C, set the reaction pressure to 0.1 MPa, and introduce gases in a volume ratio of propylene, hydrogen, oxygen, and nitrogen of 1:1:1:7 to begin the direct propylene gas-phase epoxidation reaction. The propylene flow rate is set to 2 ml / min. The gaseous components such as hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, and methane in the reaction process were analyzed using an Agilent 7890B gas chromatograph equipped with a TCD detector. Organic compounds such as propylene, propane, propionaldehyde, acrolein, acetone, acetaldehyde, and propylene oxide were analyzed using an Agilent 7890B gas chromatograph equipped with an FID detector. Based on the detection results, the propylene conversion rate, propylene oxide selectivity, propane selectivity, acrolein selectivity, propionaldehyde selectivity, acetone selectivity, carbon dioxide selectivity, and selectivity of other byproducts were calculated. The test results for propylene conversion rate, propylene oxide selectivity, propane selectivity, and acrolein selectivity after 15 hours of reaction are shown in Table 5.

[0162] propylene conversion (C) C3H6 = (Amount of C3 product + 2 / 3 amount of C2 product + 1 / 3 amount of C1 product) / Amount of propylene in the feed gas;

[0163] propylene oxide selectivity (S PO = Amount of propylene oxide in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product);

[0164] Propane selectivity (S) C3H8 = Amount of propane in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product);

[0165] acrolein selectivity (S C3H4O = Amount of acrolein in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product);

[0166] Propionaldehyde selectivity (S) CH3CH2CHO = Amount of propionaldehyde in the product / (Amount of C3 product + 2 / 3 Amount of C2 product + 1 / 3 Amount of C1 product);

[0167] Acetone selectivity (S) CH3COCH3 = Amount of acetone in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product).

[0168] Table 5

[0169]

[0170]

[0171] (IV) After the propylene oxide preparation reaction in (III) is completed, and the reaction temperature is lowered to room temperature, the catalyst is removed and characterized by transmission electron microscopy (TEM). Bright-field scanning transmission electron microscopy (STEM) is used for characterization, where the metal appears as black dots, while the support is gray, providing a clear contrast. Figure 6 As shown, in Example 1, after 100 hours of direct propylene vapor-phase epoxidation, the Au / TS-1 catalyst maintained stable Au nanoparticle size, with small individual nanoparticle sizes, minimal size differences between nanoparticles, and relatively uniform dispersion on the TS-1 support; Figure 7 As shown in Example 12, after 100 hours of direct propylene vapor-phase epoxidation, the Au / TS-1 catalyst exhibited changes in Au nanoparticle size, agglomeration, and increased size differences between different Au nanoparticles, resulting in uneven overall dispersion on the TS-1 support. Figure 8 As shown, in Comparative Example 1, after 100 hours of direct propylene vapor-phase epoxidation reaction, the Au / TS-1 catalyst exhibits larger Au nanoparticle sizes, significant agglomeration of metal nanoparticles, large size differences between nanoparticles, and uneven overall dispersion on the TS-1 support.

[0172] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a supported catalyst, characterized in that, The method includes: impregnating a titanium-silicon molecular sieve with a solution containing an active component precursor and an inorganic alkaline substance, followed by drying and activation; wherein the active component includes a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve includes a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, and the doped metal element includes a Group VIII and / or Group IB metal element.

2. The method according to claim 1, wherein, The doped metal element includes Pd and / or Pt; And / or, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.1-10; And / or, based on the total weight of the titanium-silicon molecular sieve, the content of the doped metal element is 0.01-0.5% by weight; And / or, the average particle size of the titanium-silicon molecular sieve is 80-300 nm, and the specific surface area of ​​the mesopores is 50-200 m². 2 / g, the pore volume of the mesoporous tissue is 0.18-0.5cm³. 3 / g, the specific surface area of ​​the micropores is 180-500m² 2 / g, the pore volume of the micropores is 0.05-0.25cm³. 3 / g, with a crystallinity of 85-99%.

3. The method according to claim 1, wherein, The preparation method of the titanium-silicon molecular sieve includes the following steps: (1) The aqueous solution containing silicon source, titanium source and alkali source is brought into first contact with the solution containing metal salt; wherein the metal salt includes Group VIII and / or Group IB metal salt; (2) The solution obtained from the first contact is brought into a second contact with a dispersion containing metal particles; wherein the metal particles include Group VIII and / or Group IB metal particles; (3) The solution obtained from the second contact is subjected to hydrothermal crystallization, solid-liquid separation and calcination in sequence.

4. The method according to claim 3, wherein, In step (1), the metal salt includes palladium salt and / or platinum salt; And / or, the molar ratio R1 of silicon source, titanium source, alkali source and water in the aqueous solution containing silicon source, titanium source and alkali source is 100:0.002-60:1-200:50-1000, preferably 100:0.1-10:20-120:100-800; wherein, the silicon source is calculated as SiO2 and the titanium source is calculated as TiO2; And / or, the silicon source is organosilicon, preferably an alkyl silicate, more preferably, the alkyl group in the alkyl silicate is a C1-C6 alkyl group, and even more preferably, the silicon source includes at least one of tetraethyl silicate, tetrapropyl silicate, tetrabutyl silicate, and tetrapentyl silicate. And / or, the titanium source is organic titanium, preferably an alkyl titanate, more preferably, the alkyl group in the alkyl titanate is a C1-C6 alkyl group, and even more preferably, the titanium source includes at least one of tetrabutyl titanate, tetrapropyl titanate, tetraethyl titanate, and tetrapentyl titanate. And / or, the alkali source is an organic ammonium, preferably an alkyl ammonium hydroxide, more preferably, the alkyl group in the alkyl ammonium hydroxide is a C1-C6 alkyl group, and even more preferably, the alkali source is at least one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrapentylammonium hydroxide; And / or, the molar ratio R2 of the silicon source to the metal salt is 1000:0.02-5, preferably 1000:0.1-2; wherein the silicon source is calculated as SiO2 and the metal salt is calculated as a metal element; And / or, the metal salt includes at least one of PdCl2, Pd(NO3)2, PtCl2 and Pt(NO3)2; And / or, the concentration of the metal salt in the solution containing the metal salt is 0.001-1 mol / L, preferably 0.01-0.1 mol / L; And / or, the solvent in the metal salt-containing solution is water; And / or, the duration of the first contact is 10-120 min, preferably 40-80 min.

5. The method according to claim 3, wherein, The molar ratio R3 of the metal salt in step (1) to the metal particles in step (2) is 1:0.001-1, preferably 1:0.005-0.1, wherein the metal salt is calculated as a metal element and the metal particles are calculated as a metal element. And / or, in step (2), the metal particles include palladium particles and / or platinum particles; And / or, the concentration of metal particles in the dispersion containing metal particles is 0.001-0.1 mol / L; And / or, the solvent in the dispersion containing metal particles is water; And / or, the particle size of the metal particles in the dispersion containing metal particles is 1-20 nm, preferably 1-3 nm; Preferably, the metal particles are prepared by mixing an aqueous solution of a metal precursor, an aqueous solution of sodium citrate, and an aqueous solution of tannic acid, and then heating the mixture at 60-120°C for 2-6 hours; wherein the metal precursor includes a Group VIII metal salt and / or a Group IB metal salt. More preferably, the amounts of the metal precursor aqueous solution, sodium citrate aqueous solution, and tannic acid aqueous solution are such that the molar ratio of the metal precursor, sodium citrate, and tannic acid is 1:0.02-0.2:0.025-0.25; And / or, the second contact time is 20-100 min.

6. The method according to claim 3, wherein, The conditions for hydrothermal crystallization include: a temperature of 120-200℃ and a time of 10-80h; And / or, the calcination conditions include: a temperature of 500-650°C and a time of 4-10 hours.

7. The method according to claim 3, wherein, The aqueous solution containing silicon source, titanium source and alkali source is obtained by: first mixing silicon source and titanium source to obtain a first mixture, then mixing the first mixture with alkali source to obtain a second mixture, and then mixing the second mixture with water to obtain the aqueous solution containing silicon source, titanium source and alkali source.

8. The method according to claim 3, wherein, The preparation method of the titanium-silicon molecular sieve further includes: before step (2), the product of the first contact is subjected to alcohol removal treatment; Preferably, the conditions for the alcohol removal treatment include: a temperature of 70-100℃ and a time of 2-8 hours.

9. The method according to claim 1, wherein, The active component is Au; And / or, the solution containing the active component precursor and the inorganic alkaline substance also includes a dispersant; Preferably, the solution containing the active component precursor, dispersant, and inorganic alkaline substance is obtained by mixing the solution containing the active component precursor with the dispersant to obtain solution B1; The pH of solution B1 is then adjusted to 5-8 using a solution containing an inorganic alkaline substance to obtain solution B2; solution B2 is then aged to obtain the impregnation solution. Preferably, the dispersant comprises at least one selected from ethylenediamine, ethylene glycol, urea, disodium ethylenediaminetetraacetate, bipyridine, glycerol, N,N dimethylformamide, acetone, toluene, tannic acid, and cyclohexane. Preferably, the inorganic alkaline substance includes at least one of alkali metal hydroxide, alkali metal carbonate, alkali metal bicarbonate, and ammonia water. More preferably, the concentration of the solution containing the active component precursor is 0.1-5 g / L; More preferably, the concentration of the solution containing the inorganic alkaline substance is 0.005-0.25 mol / L; More preferably, the solution containing the active component precursor is mixed with the dispersant for 0.5-6 hours; More preferably, the aging conditions result in an impregnation solution with a pH of 7-9.3; More preferably, the amount of the active component precursor, calculated as metal element, is 0.01-1g and the amount of the dispersant is 0.005-1g per 100g of titanium-silicon molecular sieve.

10. The method according to claim 1, wherein, The impregnation methods include ultrasonic impregnation and vibration impregnation; wherein, ultrasonic impregnation takes 0.2-2 hours; vibration impregnation is carried out under light-proof conditions and takes 8-24 hours.

11. The method according to claim 1, wherein, The drying conditions include: a temperature of 30-70℃ and a relative humidity of ≤60%. And / or, the activation conditions include: a temperature of 150-350°C and a time of more than 2 hours, preferably 2-8 hours.

12. The supported catalyst prepared by the method according to any one of claims 1-11.

13. A supported catalyst, characterized in that, The catalyst comprises a titanium-silicon molecular sieve and an active component supported on the titanium-silicon molecular sieve, wherein the active component comprises a Group VIII and / or Group IB metal element; the titanium-silicon molecular sieve comprises a doped metal element incorporated into the framework structure of the titanium-silicon molecular sieve, wherein the bond length between the doped metal element and the O atom in the titanium-silicon molecular sieve framework is 0.02-0.55 nm, and the doped metal element comprises a Group VIII and / or Group IB metal element.

14. The supported catalyst according to claim 13, wherein, The active component is Au; And / or, based on the total weight of the catalyst, the content of the active component is 0.01-1% by weight; And / or, the hydroxyl density of the catalyst is Q4 / Q3 = 3-10, where Q4 / Q3 represents the hydroxyl density of the catalyst. 29 The ratio of peak areas of the peaks with chemical shifts near -113 ppm and -103 ppm in the Si MAS NMR spectrum; And / or, the number of Au nanoparticles with a diameter of 2-5 nm in any 100 nm × 100 nm region on the nano-gold supported titanium silicon molecular sieve does not differ by more than 40%, and the spacing between any metal nanoparticles is >3 nm.

15. The supported catalyst according to claim 13, wherein, The doped metal element includes Pd and / or Pt; And / or, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.1-10; And / or, based on the total weight of the titanium-silicon molecular sieve, the content of the doped metal element is 0.01-0.5% by weight; And / or, the average particle size of the titanium-silicon molecular sieve is 80-300 nm, and the specific surface area of ​​the mesopores is 50-200 m². 2 / g, the pore volume of the mesoporous tissue is 0.18-0.5cm³. 3 / g, the specific surface area of ​​the micropores is 180-500m² 2 / g, the pore volume of the micropores is 0.05-0.25cm³. 3 / g, with a crystallinity of 85-99%.

16. The use of the supported catalyst according to any one of claims 13-15 in the preparation of propylene oxide.

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