Titanium silical molecular sieve and supported catalysts, methods for their preparation and use

Abstract

The application relates to the technical field of molecular sieves, and discloses a titanium-silicon molecular sieve, a supported catalyst and application, the titanium-silicon molecular sieve has a silicon-titanium molar ratio of 100:0.05-15; and the content of oxygen vacancies in the titanium-silicon molecular sieve is 0.35-2.2 mmol / g. The catalyst prepared by using the titanium-silicon molecular sieve with the specific oxygen vacancy content as a carrier has high thermal stability, and when the catalyst is used for catalyzing propylene gas phase method to prepare propylene oxide, the conversion rate of propylene, the selectivity of propylene oxide and the service life of the catalyst can be improved.

Description

Cross-references to related applications

[0001] This application claims the benefit of Chinese Patent Application No. 202411713351.7, filed on November 27, 2024, the contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of molecular sieve technology, specifically to a titanium-silicon molecular sieve and a supported catalyst, as well as their preparation methods and applications. Background Technology

[0003] Propylene oxide, one of the world's 50 largest-produced chemicals, has surpassed acrylonitrile to become the second largest propylene derivative after polypropylene. It is used to prepare polyurethanes and polyether polyols and is widely applied in chemical, light industry, textile, and pharmaceutical fields. Currently, the main production processes for propylene oxide (PO) include the chlorohydrin process, the co-oxidation process, and the liquid-phase direct oxidation process. The chlorohydrin process uses toxic chlorine gas and generates large amounts of harmful wastewater and waste residue, leading to extremely serious environmental and safety problems. The co-oxidation process is lengthy, requires large-scale investment, and its economic benefits are constrained by the market supply and demand of co-products. Liquid-phase direct oxidation processes, represented by HPPO and CHPPO, have advantages such as low emissions and mild reaction conditions, and are showing a clear trend towards green development in the propylene oxide industry. However, liquid-phase direct oxidation processes all require large-scale on-site peroxide production units, which significantly restricts the process layout.

[0004] The hydrogen-phase epoxidation route for propylene can fundamentally overcome this constraint: this process uses titanium-silicon molecular sieves loaded with gold nanoparticles as catalysts (Au / TS-1). Hydrogen and oxygen react with Au to generate *OOH, an active intermediate species, which is then in-situ catalyzed by Ti active sites on the same catalyst to oxidize propylene to PO, achieving a "one-step" PO production. Propylene gas-phase epoxidation technology simultaneously meets the development requirements of clean, efficient, green, and low-carbon practices, and is highly favored by both academia and industry.

[0005] Supported bifunctional catalysts, exemplified by Au / TS-1, have become a novel type of catalytic material and have been widely applied in chemical synthesis and industrial catalysis in recent years. These supported bifunctional catalytic materials are mostly molecular sieves, alumina, or cerium oxide supported on metal nanoparticles or metal oxide particles. In these materials, the molecular sieves, alumina, and other supports, along with the supported active metal species, catalyze two consecutive reactions, enabling significant integration of existing processes.

[0006] However, existing supported catalysts have poor thermal stability. Most chemical reactions are exothermic, and as the reaction time increases, the active components in the catalyst are prone to agglomeration, which seriously affects the catalytic performance of the catalyst. This not only affects the production efficiency of the plant, but may even lead to catalyst deactivation, forcing the plant to shut down and frequently replace the catalyst, which greatly increases the plant's production costs. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of poor thermal stability and easy agglomeration of active component particles in existing supported catalysts, and to provide a titanium-silicon molecular sieve, a supported catalyst, its preparation method, and its application. The titanium-silicon molecular sieve of this invention has a specific content of oxygen vacancies, which, when used as a support for a supported catalyst, can prevent the agglomeration of active component particles during the reaction and improve the thermal stability of the catalyst.

[0008] The first aspect of the present invention provides a titanium-silicon molecular sieve, wherein the silicon-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; and the oxygen vacancy content in the titanium-silicon molecular sieve is 0.35-2.2 mmol / g.

[0009] A second aspect of the present invention provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps: (1) A mixture containing silicon source, titanium source, alkali source, water and first organosilicon is subjected to hydrothermal crystallization; then solid-liquid separation, first drying and calcination are performed; the alkali source is at least one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and tetrapentylammonium hydroxide; the conditions for hydrothermal crystallization include: temperature of 135-185℃ and time of 12-64h; (2) The calcined product obtained in step (1) is brought into contact with a second organosilicon, and then subjected to a second drying process, wherein the drying conditions of the second drying process result in a drying rate of 0.015-1.015 g organosilicon / (cm³). 2 h·g of calcined product); the contact conditions include: a temperature of 20-60℃ and a time of 30-70min; The molar ratio of silicon source, titanium source, alkali source and water in the mixture is R1 of 100:0.005-80:0.5-180:25-900. The first organosilicon and the second organosilicon are each independently selected from at least one of methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, 3-aminopropyltriethoxysilane, trimethylsilyldiethylamine and tert-butyldimethylchlorosilane.

[0010] A third aspect of the present invention provides a supported catalyst comprising a support and an active component supported on the support, wherein the active component is a noble metal and the support is the aforementioned titanium-silicon molecular sieve.

[0011] A fourth aspect of the present invention provides a supported catalyst comprising a support and an active component supported on the support, wherein the active component is a noble metal, and the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; at least a portion of the active component is anchored to oxygen vacancies in the titanium-silicon molecular sieve.

[0012] The fifth aspect of this invention provides a method for preparing a supported catalyst, the method comprising the following steps: (a) A solid-liquid mixture is obtained by contacting a solution containing an active component precursor and an inorganic alkaline substance with a support; wherein the active component precursor includes a noble metal precursor; and the support is a titanium-silicon molecular sieve as described in any one of claims 1-6. (b) The solid-liquid mixture obtained in step (a) is dried and activated.

[0013] The sixth aspect of this invention provides the application of the above-described noble metal supported catalyst in the preparation of propylene oxide.

[0014] Through the above technical solution, the present invention achieves the following beneficial effects: (1) When the titanium-silicon molecular sieve with a specific oxygen vacancy content of the present invention is used as a support to prepare a catalyst, the active component in the catalyst can be anchored on the oxygen vacancy, thereby increasing the interaction force between the active component and the support, thus avoiding the aggregation of the active component and improving the thermal stability of the catalyst; at the same time, the active component and the oxygen vacancy work together to improve the catalytic performance of the catalyst, especially the performance of the catalyst in the gas-phase preparation of propylene oxide, for example, improving the conversion rate of propylene, the selectivity of propylene oxide, the utilization rate of hydrogen, reducing the selectivity of other by-products, and improving the service life of the catalyst, reducing the frequency of factory shutdowns to replace the catalyst, and reducing the production cost of the factory, etc.

[0015] (2) In a preferred embodiment, the titanium-silicon molecular sieve of the present invention can also increase the total loading of the active components in the catalyst, especially the total loading of the active component Au nanoparticles. In a further preferred embodiment, when the titanium-silicon molecular sieve of the present invention is used as a support for the preparation of the catalyst, it can make the active components of the catalyst uniformly dispersed, thereby further improving the catalytic performance of the catalyst. Attached Figure Description

[0016] Figure 1 This is a graph showing the change in oxygen hole content before and after the active component is loaded onto the supported catalyst of the present invention. Detailed Implementation

[0017] 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.

[0018] The first aspect of the present invention provides a titanium-silicon molecular sieve, wherein the silicon-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; and the oxygen vacancy content in the titanium-silicon molecular sieve is 0.35-2.2 mmol / g.

[0019] According to the present invention, the oxygen vacancy content in the titanium-silicon molecular sieve can be 0.35 mmol / g, 0.4 mmol / g, 0.5 mmol / g, 0.6 mmol / g, 0.7 mmol / g, 0.8 mmol / g, 0.9 mmol / g, 1 mmol / g, 1.5 mmol / g, 2 mmol / g, 2.2 mmol / g, or any two of the above ranges. Preferably, the oxygen vacancy content in the titanium-silicon molecular sieve is 0.35-1 mmol / g, more preferably 0.4-0.6 mmol / g.

[0020] According to the present invention, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve can be 100:0.05, 100:0.5, 100:0.52, 100:0.54, 100:0.56, 100:0.58, 100:0.6, 100:0.65, 100:1, 100:5, 100:10, 100:15, or any range of any two of the above. Preferably, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.5-1.

[0021] According to the present invention, preferably, the ratio of the hydroxyl density Q4 / Q3 of the titanium-silicon molecular sieve is 4-10; more preferably, it is 5.2-8. Wherein, Q4 / Q3 represents the hydroxyl density of the titanium-silicon molecular sieve. 29 The ratio of peak areas in the Si MAS NMR spectrum with chemical shifts near -113±1ppm and -103±1ppm. The ratio of the hydroxyl density Q4 / Q3 of the titanium-silicon molecular sieve can be 4, 5, 6, 7, 8, 9, 10, or any two of the above ranges.

[0022] According to the present invention, preferably, the amount of L-acid in the titanium-silicon molecular sieve is 0.001-2.5 mmol / g (e.g., 0.001 mmol / g, 0.01 mmol / g, 0.05 mmol / g, 0.08 mmol / g, 0.1 mmol / g, 1 mmol / g, 2 mmol / g, 2.5 mmol / g, and any two of the above ranges); more preferably, it is 0.06-0.3 mmol / g. Wherein, in the pyridine infrared spectrum of the titanium-silicon molecular sieve, 1540±5 cm⁻¹... -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

[0023] According to the present invention, preferably, the ratio of Brønsted acid to L-acid (the ratio of the amount of Brønsted acid to L-acid) in the titanium silicate molecular sieve is 0.05-2 (for example, it can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, and any two of the above-mentioned values), more preferably 0.4-1.

[0024] According to the present invention, preferably, the average particle size of the titanium-silicon molecular sieve is 60-145 nm (for example, it can be 60 nm, 80 nm, 100 nm, 120 nm, 145 nm, or any two of the above), more preferably 100-130 nm.

[0025] According to the present invention, preferably, the mesopore specific surface area of ​​the titanium-silicon molecular sieve is 80-225 m². 2 / g, the pore volume of the mesoporous tissue is 0.2-0.65cm³. 3 / g, the specific surface area of ​​the micropores is 150-510m² 2 / g, the pore volume of the micropores is 0.08-0.32cm³. 3 / g, with an average pore size of 0.4-2nm.

[0026] According to the present invention, preferably, the crystallinity of the titanium-silicon molecular sieve is 82-98%.

[0027] A second aspect of the present invention provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps: (1) A mixture containing silicon source, titanium source, alkali source, water and first organosilicon is subjected to hydrothermal crystallization; then solid-liquid separation, first drying and calcination are performed; the alkali source is at least one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and tetrapentylammonium hydroxide; the conditions for hydrothermal crystallization include: temperature of 135-185℃ and time of 12-64h; (2) The calcined product obtained in step (1) is brought into contact with a second organosilicon, and then subjected to a second drying process, wherein the drying conditions of the second drying process result in a drying rate of 0.015-1.015 g organosilicon / (cm³). 2 h·g of calcined product); the contact conditions include: a temperature of 20-60℃ and a time of 30-70min; The molar ratio R1 of silicon source, titanium source, alkali source and water in the mixture is 100:0.005-80:0.5-180:25-900. The first organosilicon and the second organosilicon are each independently selected from at least one of methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, 3-aminopropyltriethoxysilane, trimethylsilyldiethylamine and tert-butyldimethylchlorosilane.

[0028] The method for preparing titanium-silicon molecular sieves mainly involves a two-step process of modifying the titanium-silicon molecular sieve with organosilicon and controlling the drying rate of the solid-liquid mixture to obtain a titanium-silicon molecular sieve with a specific oxygen void content. The preferred method for preparing the molecular sieve of this invention can further reduce the hydroxyl density (acidic sites) in the titanium-silicon molecular sieve, reduce the average particle size of the titanium-silicon molecular sieve, and increase the titanium content in the titanium-silicon molecular sieve.

[0029] According to the present invention, preferably, the molar ratio R2 of the silicon source to the first organosilicon is 100:0.5-50; wherein the silicon source is SiO2. More preferably, the molar ratio R2 of the silicon source to the first organosilicon is 100:1-10 (for example, it can be 100:1, 100:2, 100:3, 100:4, 100:4.5, 100:5, 100:5.5, 100:6, 100:7, 100:8, 100:9, 100:10, and any two of the above), and even more preferably 100:1-5; wherein the silicon source is SiO2.

[0030] According to the present invention, preferably, the amount of the second organosilicon is 0.1-2g (e.g., 0.1g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g, 1g, 1.5g, 2g, and any two of the above) relative to each gram of calcined product, more preferably 0.5-2g, and even more preferably 0.5-1g.

[0031] According to the present invention, preferably, the molar ratio of silicon source, titanium source, alkali source and water in the mixture is R1 of 100:0.005-80:0.5-180:25-900, more preferably 100:0.15-15:15-100:150-750; wherein, the silicon source is calculated as SiO2 and the titanium source is calculated as TiO2.

[0032] According to the present invention, preferably, the silicon source is organosilicon, more preferably, it is an alkyl silicate, even 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.

[0033] According to the present invention, preferably, the titanium source is organotitanium, more preferably, it is an alkyl titanate, further 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.

[0034] According to the present invention, preferably, the conditions for hydrothermal crystallization include: a temperature of 150-180°C and a time of 20-50 hours.

[0035] According to the present invention, preferably, the conditions for the first drying include: a temperature of 20-80°C and a time of 6-24 hours.

[0036] According to the present invention, preferably, the calcination conditions include: a temperature of 475-625°C and a time of 6-12 hours.

[0037] According to the present invention, preferably, step (1) further includes: before hydrothermal crystallization, the aqueous solution containing silicon source, titanium source and alkali source is subjected to alcohol removal treatment, and then the product of alcohol removal treatment is mixed with the first organosilicon to obtain a mixture.

[0038] According to the present invention, preferably, in step (2), the contact conditions include: a temperature of 20-40°C and a time of 50-70 minutes. The contact method can be a commonly used contact method in the art, such as immersion or wetting.

[0039] According to the present invention, preferably, the second drying conditions result in a drying rate of 0.2-0.6 g organosilicon / (cm³) for the solid-liquid mixture. 2 h·g calcination product), for example, can be 0.2g organosilicon / (cm³). 2 h·g calcination product), 0.3g organosilicon / (cm 2 h·g calcination product), 0.4g organosilicon / (cm) 2 h·g calcination product), 0.5g organosilicon / (cm) 2 h·g calcination product), 0.6g organosilicon / (cm) 2The drying rate refers to the evaporation rate of organosilicon in the solid-liquid mixture, i.e., the weight of organosilicon volatilized in the solid-liquid mixture per unit time and unit area of ​​container, relative to a unit weight of carrier. The drying rate is tested as follows: the mass of the carrier in the solid-liquid mixture is denoted as M; the solid-liquid mixture is placed in a glass petri dish with a bottom area of ​​S (in cm²). 2 Weigh the glass petri dish containing the solid-liquid mixture before drying, and record the mass as M1 (g). Then, dry the glass petri dish containing the solid-liquid mixture under a certain temperature and humidity environment until constant weight is reached. Stop drying at this point. Record the drying time as T (h). Weigh the glass petri dish containing the solid after drying, and record the mass as M2 (g). The drying rate of the solid-liquid mixture is calculated using the formula: (M1-M2) / (S×T×M).

[0040] According to the present invention, the drying rate can be controlled by adjusting the drying temperature, the relative humidity of the drying environment, and the vacuum degree. Preferably, the conditions for the second drying include: a temperature of 30-70°C, a vacuum degree of ≤40 kPa, preferably 1-35 kPa, and a relative humidity of ≤60%. The relative humidity can be 60%, 50%, 45%, 35%, 25%, 15%, 10%, 5%, or any two of the above values, for example, 5-20%.

[0041] In this invention, the 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 to the saturated vapor pressure at the same temperature during the drying process of the solid-liquid mixture.

[0042] According to the present invention, preferably, the fluctuation range of relative humidity during the second drying process is ≤5%. The fluctuation range of relative humidity can be 5%, 4%, 3%, 2%, 1%, 0.5%, or a range consisting of any two of the above points, such as 2-3%.

[0043] The titanium-silicon molecular sieve described in this invention can be used to prepare methylphenol.

[0044] A third aspect of the present invention provides a supported catalyst comprising a support and an active component supported on the support, wherein the active component is a noble metal and the support is the aforementioned titanium-silicon molecular sieve.

[0045] According to the present invention, preferably, at least a portion of the active component is anchored to oxygen vacancies in the titanium-silicon molecular sieve; more preferably, the content of the oxygen vacancies-anchored active component in the catalyst is 0.04-0.08% by weight. In the present invention, anchoring refers to the formation of chemical bonds between the active component and the lone pair electrons in the oxygen vacancies.

[0046] According to the present invention, the precious metal may be gold, silver and platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), preferably, the precious metal is Au and / or Pd; more preferably, the precious metal is Au.

[0047] According to the present invention, the loading of the active component is not particularly limited and can be the conventional amount used in the art. Preferably, the content of the active component, based on the total weight of the catalyst and the metal element, is 0.01-1.15% by weight (e.g., 0.01-1% by weight); more preferably, it is 0.06-0.1% by weight.

[0048] According to the present invention, preferably, in any 100nm×100nm region on the catalyst, the proportion of noble metal particles with a diameter of 2-5nm to the total number of noble metal particles with a diameter of 1-10nm is greater than 50%, more preferably greater than 80%, for example 80-90%.

[0049] According to the present invention, preferably, the ratio of the hydroxyl density Q4 / Q3 of the catalyst is 3-13.5, more preferably 3-12, more preferably 3.5-10, and even more preferably 6-8; wherein, Q4 / Q3 represents the hydroxyl density of the catalyst. 29 The ratio of peak areas with chemical shifts near -113±1ppm and -103±1ppm in the Si MAS NMR spectrum. In this invention, the ratio of the hydroxyl density Q4 / Q3 of the catalyst can be 4.5-5.5, or even 5-5.5.

[0050] According to the present invention, preferably, the weight ratio of reduced metal to oxidized metal in the active component is 1:0.1-10, more preferably 1:0.1-2, and even more preferably 1:0.1-1. In the present invention, the reduced metal is represented by zero valence; for example, Au, the reduced state of Au is represented as Au. 0 .

[0051] According to the present invention, preferably, when the noble metal is Au, Au comprises reduced Au and oxidized Au, wherein the weight ratio of reduced Au to oxidized Au is 1:0.1-10, more preferably 1:0.1-1. More preferably, the oxidized Au comprises Au... 1+ and Au 3+ More preferably, the valence state of Au includes Au 0 Au 1+ and Au3+ .

[0052] More preferably, Au 0 Au 1+ Au 3+ The weight ratio is 1:0.1-0.7:0.01-0.5, and more preferably 1:0.1-0.35:0.01-0.27.

[0053] According to the present invention, preferably, the amount of L acid in the catalyst is 0.005-0.4 mmol / g, more preferably 0.05-0.15 mmol / g; the acid ratio of Brønsted acid to L acid is less than 1.1, more preferably 0.02-0.9, and even more preferably 0.3-0.6, wherein, in the pyridine infrared spectrum of the catalyst, at 1540±5 cm⁻¹... -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

[0054] A fourth aspect of the present invention provides a supported catalyst comprising a support and an active component supported on the support, wherein the active component is a noble metal, and the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; at least a portion of the active component is anchored to oxygen vacancies in the titanium-silicon molecular sieve.

[0055] According to the present invention, preferably, the content of the oxygen vacancy anchoring active component in the catalyst is 0.04-0.08% by weight.

[0056] According to the present invention, preferably, the content of the active component, calculated as metal element, is 0.01-1.15% by weight based on the total weight of the catalyst.

[0057] According to the present invention, preferably, the noble metal is Au and / or Pd.

[0058] According to the present invention, preferably, in any 100nm×100nm region on the catalyst, the proportion of noble metal particles with a diameter of 2-5nm to the total number of noble metal particles with a diameter of 1-10nm is greater than 50%, more preferably greater than 80%.

[0059] According to the present invention, preferably, the ratio of the hydroxyl density Q4 / Q3 of the catalyst is 3-13.5, more preferably 3-12, even more preferably 3.5-10, and even more preferably 6-8; wherein, Q4 / Q3 represents the hydroxyl density of the catalyst. 29 The ratio of peak areas of peaks with chemical shifts near -113±1ppm and -103±1ppm in the Si MAS NMR spectrum.

[0060] According to the present invention, preferably, the weight ratio of reduced metal to oxidized metal in the active component is 1:0.1-2; more preferably, the valence state of Au includes Au. 0 Au 1+ and Au 3+ Further preferably, Au 0 Au 1+ Au 3+ The weight ratio is 1:0.1-0.7:0.01-0.8, more preferably 1:0.1-0.7:0.01-0.5, and even more preferably 1:0.1-0.35:0.01-0.25.

[0061] According to the present invention, preferably, the amount of L acid in the catalyst is 0.005-0.4 mmol / g, and the acid-to-L acid ratio is less than 1.1, more preferably 0.02-0.9, wherein, in the pyridine infrared spectrum of the catalyst, at 1540±5 cm⁻¹... -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

[0062] The fifth aspect of this invention provides a method for preparing a supported catalyst, the method comprising the following steps: (a) A solid-liquid mixture is obtained by contacting a solution containing an active component precursor and an inorganic alkaline substance with a support; wherein the active component precursor includes a noble metal precursor; and the support is the titanium-silicon molecular sieve described above. (b) The solid-liquid mixture obtained in step (a) is dried and activated.

[0063] In this invention, the catalyst is prepared by excessively impregnating a support with a solution containing an active component precursor and an inorganic alkaline substance to obtain a solid-liquid mixture, and then controlling the evaporation rate of the solvent in the solid-liquid mixture. The catalyst obtained by this method can further increase the proportion of active components with a particle size of 2-5 nm in the catalyst.

[0064] According to the present invention, preferably, in step (b), the drying conditions are such that the drying rate of the solid-liquid mixture is 0.025-0.955 g water / (cm³). 2 h·g carrier), more preferably 0.2-0.6 g water / (cm³) 2 (h·g carrier). In this invention, the drying rate refers to the evaporation rate of water in the solid-liquid mixture, that is, the weight of water that evaporates from the solid-liquid mixture per unit time and unit area of ​​container, relative to a unit weight of carrier. The method for testing the drying rate is as follows: the mass of the carrier in the solid-liquid mixture is denoted as M; the solid-liquid mixture is placed in a glass petri dish, the bottom area of ​​which is S, in cm².2 Weigh the glass petri dish containing the solid-liquid mixture before drying, and record the mass as M1 (g). Then, dry the glass petri dish containing the solid-liquid mixture under a certain temperature and humidity environment until constant weight is reached. Stop drying at this point. Record the drying time as T (h). Weigh the glass petri dish containing the solid after drying, and record the mass as M2 (g). The drying rate of the solid-liquid mixture is calculated using the formula: (M1-M2) / (S×T×M).

[0065] The inventors of this invention further discovered that limiting the drying rate of the solid-liquid mixture within the above-mentioned range can not only increase the proportion of active components with a particle size of 2-5 nm in the catalyst, thereby improving the catalytic performance and thermal stability of the catalyst, but also improve the utilization rate of raw materials, especially the utilization rate of precious metals, and reduce the production cost of the catalyst.

[0066] According to the present invention, the drying rate can be controlled by adjusting the drying temperature and the relative humidity of the drying environment. The inventors further discovered that drying at lower temperatures and lower relative humidity can further increase the proportion of active components with a particle size of 2-5 nm in the catalyst, thereby improving the catalytic performance and thermal stability of the catalyst. Preferably, the drying conditions include a temperature of 30-70°C and a relative humidity ≤60%; more preferably, the drying conditions include a temperature of 30-40°C and a relative humidity of 5-30%.

[0067] In this invention, the 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 to the saturated vapor pressure at the same temperature during the drying process of the solid-liquid mixture.

[0068] According to the present invention, preferably, the fluctuation range of relative humidity during the drying process is ≤5%; more preferably, the fluctuation range of relative humidity during the drying process is ≤3%. Controlling the fluctuation range of relative humidity within the above range can further increase the proportion of active components with a particle size of 2-5 nm in the catalyst, thereby improving 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.

[0069] According to the present invention, preferably, the drying in step (b) is carried out in the presence of a first alkaline substance.

[0070] According to the present invention, preferably, under drying conditions, when the first alkaline substance is a gas, the amount of the first alkaline substance used increases the vacuum degree of the drying system by 5-100 kPa after the first alkaline substance is introduced.

[0071] In this invention, before drying, the system is first adjusted to a low vacuum level. Then, a first alkaline substance (gas) is introduced into the system to increase the vacuum level. The amount of the first alkaline substance (gas) is controlled by adjusting the vacuum level before and after the introduction of the first alkaline substance (gas). For example, before introducing the first alkaline substance (gas), the vacuum level of the system is set to 1-50 kPa. After introducing the first alkaline substance (gas), the vacuum level of the system increases to 6-150 kPa.

[0072] According to the present invention, preferably, under dry conditions, when the first alkaline substance is a liquid, the amount of the first alkaline substance is 0.1-2.5 g relative to each gram of solid-liquid mixture.

[0073] According to the present invention, preferably, the activation described in step (b) is carried out in the presence of a second alkaline substance.

[0074] According to the present invention, preferably, under activation conditions, when the second alkaline substance is a gas, the amount of the second alkaline substance increases the vacuum degree of the drying system by 10-150 kPa after the second alkaline substance is introduced. Similarly, the method of controlling the vacuum degree of the system during the activation process is similar to that during the drying process. For example, before the second alkaline substance (gas) is introduced, the vacuum degree of the system is set to 1-50 kPa, and after the second alkaline substance (gas) is introduced, the vacuum degree of the system increases to 11-200 kPa.

[0075] According to the present invention, preferably, under activation conditions, when the second alkaline substance is a liquid, the amount of the second alkaline substance is 0.1-2.5 g relative to each gram of dried product.

[0076] According to the present invention, preferably, the first alkaline substance and the second alkaline substance are each independently a nitrogen-containing alkaline substance; more preferably, the nitrogen-containing alkaline substance includes ammonia and / or a nitrogen-containing organic amine; wherein the nitrogen-containing organic amine may have 1-5 carbon atoms and 1-3 nitrogen atoms; the nitrogen-containing organic amine may be a dialkylamine and / or an alkyldiamine. Even more preferably, the nitrogen-containing organic amine includes dimethylamine and / or ethylenediamine.

[0077] This invention, in preparing the catalyst, involves drying and / or activating a solid-liquid mixture containing a support, an active component precursor, and an inorganic alkaline substance in the presence of a nitrogen-containing alkaline substance. This further reduces the acid content and the Brønsted acid / Low acid ratio in the catalyst, increases the loading of the active component, improves the utilization rate of precious metals, and lowers the synthesis cost of the catalyst. When used in the propylene epoxidation reaction, it significantly reduces the selectivity of the byproducts propionaldehyde and acetone, greatly simplifies the separation and purification process of propylene oxide products, and reduces the amount of adsorbent and extractant used in the separation process, as well as the energy consumption for product separation; simultaneously, it achieves high propylene conversion and high propylene oxide selectivity.

[0078] According to the present invention, preferably, step (a) further includes adding an alkali metal auxiliary agent; the alkali metal auxiliary agent is a strong acid salt of an alkali metal and / or a weak acid salt of an alkali metal.

[0079] According to the present invention, preferably, the strong acid salt of the alkali metal includes at least one of alkali metal chloride, alkali metal sulfate and alkali metal nitrate; more preferably, the strong acid salt of the alkali metal is at least one of sodium nitrate, potassium nitrate, sodium chloride and potassium chloride.

[0080] According to the present invention, preferably, the weak acid salt of the alkali metal is an alkali metal sulfide, such as potassium sulfide or sodium sulfide.

[0081] According to the present invention, preferably, the amount of the alkali metal auxiliary agent, calculated as metal element, is 0.02-1g per 100g of carrier.

[0082] This invention utilizes a combination of inorganic alkaline substances and strong acid salts of alkali metals during catalyst preparation, which further increases the content of reduced states in the catalyst.

[0083] In this invention, the solid-liquid mixture is obtained by an impregnation method. The impregnation method involves first mixing an aqueous solution of the active component precursor with an aqueous solution of an inorganic alkaline substance to obtain an impregnation solution, and then contacting the impregnation solution with a carrier to obtain the solid-liquid mixture. According to this invention, preferably, in step (a), the solid-liquid mixture is obtained by first mixing an aqueous solution of the active component precursor with an aqueous solution of an inorganic alkaline substance to obtain a solution containing the active component precursor and the inorganic alkaline substance, and then contacting the solution with a carrier to obtain the solid-liquid mixture.

[0084] According to the present invention, preferably, the solution containing the active component precursor and the inorganic alkaline substance further includes a dispersant.

[0085] According to the present invention, preferably, the solution containing the active component precursor, dispersant and inorganic alkaline substance is obtained by: mixing the aqueous solution of the active component precursor with the dispersant to obtain solution B1; then adjusting the pH value of solution B1 to 5-8 (for example, it can be 5, 5.5, 6, 6.5, 7, 7.5, 8, or any two of the above points) using the aqueous solution of the inorganic alkaline substance to obtain solution B2; then aging solution B2 under aging conditions such that the pH value of solution B2 is 6.5-9 (for example, it can be 6, 6.5, 7, 7.5, 8, 8.5, 9, or any two of the above points).

[0086] According to the present invention, the active component in the active component precursor can be gold, silver, or platinum group metals (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.

[0087] According to the present invention, the concentration of the aqueous solution of the active component precursor can be selected within a wide range. Preferably, the concentration of the aqueous solution of the active component precursor, calculated as metal element, is 0.1-5 g / L.

[0088] According to the present invention, preferably, the amount of the active component precursor, calculated in terms of metal element, is 0.01-2g relative to each 100g of carrier (for example, it can be 0.01g, 0.1g, 0.3g, 0.5g, 0.7g, 0.9g, 1.1g, 1.3g, 1.5g, 2g, and any two of the above ranges).

[0089] According to the present invention, the dispersant is a ligand that has a weak complexing interaction with Au, wherein the cumulative stability constant of the complex formed by the ligand and Au is <2. 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.

[0090] According to the present invention, preferably, the amount of dispersant used is 0.005-1g relative to 100g of carrier (for example, it can be 0.008g, 0.05g, 0.5g, 0.1g, 0.5g, 1g, 1.2g, and any two of the above ranges).

[0091] According to the present invention, preferably, the inorganic alkaline substance is selected from at least one of alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, and ammonia water; preferably at least one of Na2CO3, K2CO3, Cs2CO3, NaHCO3, and KHCO3. The inventors of the present invention have further discovered that when a weak acid salt of an alkali metal is used as the alkaline substance, the particle size of the active component in the catalyst can be further reduced.

[0092] According to the present invention, preferably, the concentration of the aqueous solution of the inorganic alkaline substance is 0.005-0.25 mol / L.

[0093] According to the present invention, the aging can be carried out using aging methods commonly used in catalyst preparation processes, as long as the components in the solution containing the active component precursor, dispersant, and alkaline substance are fully mixed and reacted. The aging temperature is not particularly limited and is typically carried out at room temperature. The aging time is sufficient to ensure that the pH value of solution B2 meets the aforementioned range; preferably, the aging time is 0.75-7.5 hours. In this invention, the room temperature is approximately 20°C. The aging can be carried out with stirring or by standing; typically, the aging is carried out with stirring.

[0094] According to the present invention, the contact method can be a commonly used contact method in the art, such as equal volume impregnation, excessive impregnation, etc., preferably, the contact method is excessive impregnation. The specific implementation of the impregnation is not particularly limited, but to ensure sufficient contact between the impregnation liquid and the carrier, more preferably, in step (a), the contact method is ultrasonic impregnation and oscillating impregnation; wherein, the ultrasonic impregnation time is 0.5-2.5 h; the oscillating impregnation is performed under light-shielding conditions, and the oscillating impregnation time is 8-28 h. 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.

[0095] Compared to the deposition method, the impregnation method used in this invention can effectively control the loading of active components, while avoiding the waste of precious metals in the active components and reducing the production cost of the catalyst.

[0096] According to the present invention, preferably, the activation conditions include: a temperature of 150-350°C and a time greater than 2 hours, preferably 2.5-10 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. In the prior art, supported catalysts typically require activation in a reducing atmosphere to obtain the reduced active component. However, when using the titanium-silicon molecular sieve of the present invention as a support for loading the active component, a supported catalyst containing the reduced active component can be directly prepared in an oxidizing atmosphere.

[0097] The sixth aspect of this invention provides the application of the above-described noble metal supported catalyst in the preparation of propylene oxide.

[0098] The noble metal supported catalyst of the present invention can reduce the temperature of the catalytic reaction when used to prepare propylene oxide.

[0099] According to the present invention, preferably, the raw material gas used in the preparation of propylene oxide includes propylene, hydrogen and oxygen, and more preferably, the volume ratio of propylene, hydrogen and oxygen is 1:0.1-5:0.1-2.

[0100] According to the present invention, preferably, the flow rate of the propylene is 1-700 mL / min.

[0101] According to the present invention, preferably, the temperature for preparing propylene oxide is 160-225°C.

[0102] 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.

[0103] The present invention will be described in detail below through embodiments. In the following embodiments, The following preparation examples illustrate the preparation method of the titanium-silicon molecular sieve in this invention. Preparation Example 1 (1-1) Preparation of a solution containing silicon, titanium, and alkali sources: Weigh tetraethyl silicate and pour it into a beaker equipped with a magnetic stirrer, stirring vigorously. Then, add tetrabutyl titanate dropwise to the beaker containing tetraethyl silicate, maintaining a stirring rate of 400-600 r / min and stirring vigorously for 30 min to mix them evenly. The transparent solution is recorded as A1. Slowly add tetrapropylammonium hydroxide solution (the concentration of tetrapropylammonium hydroxide in the tetrapropylammonium hydroxide solution is 25% by weight) to A1. It initially becomes turbid and gradually turns into a milky white opaque suspension, recorded as A2. Increase the speed of the magnetic stirrer to 600-800 r / min, add a certain amount of distilled water to A2, and continue stirring for 60 min. The milky white opaque suspension then turns back into a colorless and transparent solution, recorded as A3. In the mixture A3, the molar ratio R1 of tetraethyl silicate, tetrabutyl titanate, tetrapropylammonium hydroxide and water is 100:0.65:80:700.

[0104] (1-2) De-alcoholization treatment: The solution A3 is heated to 80℃ to distill off the ethanol and butanol produced by the hydrolysis of the titanium silica sol. The liquid level of solution A3 in the beaker drops. At this time, the same amount of distilled water is added to maintain the liquid level. After 4-5 hours of alcohol distillation treatment, the liquid level of solution A3 remains basically stable and no longer drops. The solution at this time is recorded as A4.

[0105] (1-3) Pour solution A4 into a high-pressure hydrothermal synthesis reactor, and simultaneously add the first organosilicon (tert-butyldimethylchlorosilane) to the reactor. Start stirring (50 r / min) for hydrothermal crystallization. The molar ratio R2 of the silicon source to the first organosilicon is 100:5. The hydrothermal crystallization conditions include a temperature of 170℃ and a time of 48 h. After hydrothermal crystallization is complete, allow the reactor to cool naturally to 30℃. Open the reactor and remove the milky white suspension material, which is recorded as A5. Centrifuge A5 in a high-speed centrifuge, discard the supernatant, and leave the solid material, which is recorded as A6. Wash A6 with distilled water and repeat the centrifugation process 3-4 times until the pH of the supernatant is <8. Discard the supernatant, leaving the solid material A6. Treat A6 in an oven at 50℃ for 20 h. At this point, the free water on A6 is basically removed, and A6 appears as irregular clumps, which is recorded as A7. After grinding and pulverizing A7, it was calcined at 550℃ for 6.5 hours to remove crystal water and template agent, thus obtaining the calcined product.

[0106] (2) Place the roasted product obtained in step (1-3) in a container with a bottom area of ​​80 cm². 2The calcined product was immersed in a glass petri dish for 70 minutes at room temperature (27°C) using a second organosilicon (tert-butyldimethylchlorosilane). The amount of the second organosilicon was 0.5 g per gram of calcined product. After immersion, the product was transferred directly to a vacuum drying oven without solid-liquid separation. The drying conditions were: temperature 30°C, vacuum 2 kPa, relative humidity 15%, with a maximum relative humidity fluctuation of 2%. Drying was stopped after reaching constant weight to obtain titanium-silicon molecular sieves. The parameters of the constant temperature and humidity oven resulted in a drying rate of 0.383 g organosilicon / (cm²). 2 h·g roasting product).

[0107] Preparation Example 2 (1-1) Preparation of a solution containing silicon, titanium, and alkali sources: Weigh tetraethyl silicate and pour it into a beaker equipped with a magnetic stirrer, stirring vigorously. Then, add tetrabutyl titanate dropwise to the beaker containing tetraethyl silicate, maintaining a stirring rate of 400-600 r / min and stirring vigorously for 30 min to mix them evenly. The transparent solution is recorded as A1. Slowly add tetrapropylammonium hydroxide solution (the concentration of tetrapropylammonium hydroxide in the tetrapropylammonium hydroxide solution is 25% by weight) to A1. It initially becomes turbid and gradually turns into a milky white opaque suspension, recorded as A2. Increase the speed of the magnetic stirrer to 600-800 r / min, add a certain amount of distilled water to A2, and continue stirring for 60 min. The milky white opaque suspension then turns back into a colorless and transparent solution, recorded as A3. In the mixture A3, the molar ratio R1 of tetraethyl silicate, tetrabutyl titanate, tetrapropylammonium hydroxide and water is 100:1:50:600.

[0108] (1-2) De-alcoholization treatment: The solution A3 is heated to 80℃ to distill off the ethanol and butanol produced by the hydrolysis of the titanium silica sol. The liquid level of solution A3 in the beaker drops. At this time, the same amount of distilled water is added to maintain the liquid level. After 4-5 hours of alcohol distillation treatment, the liquid level of solution A3 remains basically stable and no longer drops. The solution at this time is recorded as A4.

[0109] (1-3) Pour solution A4 into a high-pressure hydrothermal synthesis reactor, and simultaneously add the first organosilicon (tert-butyldimethylchlorosilane) to the reactor. Start stirring (50 r / min) for hydrothermal crystallization. The molar ratio R2 of the silicon source to the first organosilicon is 100:4. The hydrothermal crystallization conditions include a temperature of 180℃ and a time of 28 h. After hydrothermal crystallization is complete, allow the reactor to cool naturally to 30℃. Open the reactor and remove the milky white suspension material, which is recorded as A5. Centrifuge A5 in a high-speed centrifuge, discard the supernatant, and leave the solid material, which is recorded as A6. Wash A6 with distilled water and repeat the centrifugation process 3-4 times until the pH of the supernatant is <8. Discard the supernatant, leaving the solid material A6. Treat A6 in an oven at 50℃ for 20 h. At this point, the free water on A6 is basically removed, and A6 appears as irregular clumps, which is recorded as A7. After grinding and pulverizing A7, it was calcined at 550℃ for 6.5 hours to remove crystal water and template agent, thus obtaining the calcined product.

[0110] (2) Place the roasted product obtained in step (1-3) in a container with a bottom area of ​​80 cm². 2 The calcined product was immersed in a glass petri dish for 50 minutes at room temperature (27°C) using a second organosilicon (tert-butyldimethylchlorosilane). The amount of the second organosilicon was 0.5 g per gram of calcined product. After immersion, the product was directly transferred to a vacuum drying oven without solid-liquid separation. The drying conditions were: temperature 55°C, vacuum 20 kPa, relative humidity 20%, with a maximum relative humidity fluctuation of 3%. Drying was stopped after reaching constant weight to obtain titanium-silicon molecular sieves. The parameters of the constant temperature and humidity oven resulted in a drying rate of 0.569 g organosilicon / (cm³). 2 h·g roasting product).

[0111] Preparation Example 3 Molecular sieves were prepared according to the method of Preparation Example 1, except that the soaking time in step (2) was 30 min.

[0112] Preparation Example 4 Molecular sieves were prepared according to the method of Preparation Example 1, except that in step (2), the drying temperature was 60°C, the relative humidity was 20%, the maximum fluctuation of the relative humidity was 3%, and the drying rate was 0.539 organosilicon / (cm). 2 h·g roasting product).

[0113] Preparation Example 5 Molecular sieves were prepared according to the method of Preparation Example 1, except that the vacuum degree in step (2) was 40 kPa and the drying rate was 0.223 organosilicon / (cm). 2h·g roasting product).

[0114] Preparation Example 6 Molecular sieves were prepared according to the method of Preparation Example 1, except that the types of the first and second organosilicones were both replaced with trimethylsilyldiethylamine.

[0115] Preparation Example 7 Molecular sieves were prepared according to the method of Preparation Example 1, except that the molar ratio R2 of silicon source to first organosilicon was 100:0.4.

[0116] Preparation Example 8 Molecular sieves were prepared according to the method of Preparation Example 1, except that the alcohol removal process in steps (1-2) was not included, and solution A3 was directly poured into a high-pressure hydrothermal synthesis reactor.

[0117] Preparation Example 9 Molecular sieves were prepared according to the method of Preparation Example 1, except that the amount of the second organosilicon was 0.08 g relative to each gram of calcined product.

[0118] Comparative Preparation Example 1 The molecular sieve was prepared according to the method of Preparation Example 1, except that the first organosilicon was not added in steps (1-3); that is, solution A4 was poured into a high-pressure hydrothermal synthesis reactor for hydrothermal crystallization.

[0119] Comparative Preparation Example 2 The molecular sieve was prepared according to the method of Preparation Example 1, except that in step (2), the drying conditions included: a temperature of 100°C, a relative humidity of 65%, and a maximum relative humidity fluctuation of 10%; the parameters of the constant temperature and humidity oven were set such that the drying rate was 1.15 g organosilicon / (cm). 2 h·g roasting product).

[0120] Comparative preparation example 3 The molecular sieve was prepared according to the method of Preparation Example 1, except that step (2) was not included, that is, the calcined product obtained in step (1-3) was used as the titanium silicon molecular sieve.

[0121] Comparative preparation example 4 The molecular sieve was prepared according to the method of Preparation Example 2, except that the molar ratio R2 of silicon source to first organosilicon in steps (1-3) was 100:51; the hydrothermal crystallization conditions included a temperature of 200℃ and a time of 72h. Meanwhile, in step (2), the amount of second organosilicon used was 5g; the soaking time was 120min and the soaking temperature was 50℃.

[0122] Test Example 1 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 1, Table 1-1, and Table 1-2.

[0123] The hydroxyl density of titanium-silicon molecular sieves was tested using silicon nuclear magnetic resonance (NMR) on a VARIANV NMR 400WB 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 were used 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.

[0124] The method for testing the oxygen hole content of titanium-silicon molecular sieves is as follows: Electron paramagnetic resonance (EPR) spectroscopy is used to test the unpaired electrons of the substance. A 100% crystallinity all-silicon molecular sieve is used as a reference, with an oxygen hole content of 0. The unpaired electron concentration is calculated by the difference in spectral area between the sample and the standard. The oxygen hole value of the sample is then quantitatively converted (1 mol oxygen hole = 2 mol unpaired electron) based on the unpaired electron concentration to obtain the oxygen hole value of the substance.

[0125] The method for testing the silicon-titanium molar ratio in titanium-silicon molecular sieves is as follows: the content of titanium and silicon elements in the molecular sieves is tested by combining inductively coupled plasma optical emission spectroscopy (ICP-OES) to obtain the silicon-titanium ratio of the molecular sieves.

[0126] Method for testing the crystallinity of titanium-silicon molecular sieves: The crystallinity of titanium-silicon molecular sieves was tested using Bruker D8 Advance X-ray diffraction. The tube voltage was 40 kV, the tube current was 40 mA, and the scanning speed was 2° / min. The diffraction patterns of the samples were recorded within the range of 2θ = 5-35°. The JCPDS standard card was used as the standard sample (its crystallinity was known, denoted as X). s ), tested its range of 2θ = 5~35 o The XRD diffraction peaks of the crystalline phase were obtained, and several characteristic peaks were 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 test was performed at 2θ=24.5. o The half-peak width at that time is denoted as W. S The characteristic peaks at the positions corresponding to the characteristic peaks of the molecular sieve being tested and the standard sample, as determined by XRD, are 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 test was performed at 2θ=24.5. o The half-peak width at that time is denoted as W. i Among them, several characteristic diffraction peaks are at 2θ = 7.9°, 8.8°, 23.2°, 24.0°, and 24.5°. The crystallinity X of the molecular sieve sample to be tested... i The calculation formula is as follows: X i =X s (W) i ΣH ii / (W) S ΣH Si )).

[0127] The method for testing the average particle size of titanium-silicon molecular sieves is as follows: The average particle size of the molecular sieves is tested using a laser particle size analyzer. 0.1g of the sample to be tested is mixed with 10ml of an aqueous solution with an ethanol content of 30vol% to obtain a dispersion of the molecular sieve. The dispersion is placed in the laser particle size analyzer, and the laser wavelength of the laser particle size analyzer is set to 466nm, the scattering angle is 90-144°, and the test temperature is room temperature. Then the average particle size of the molecular sieve is tested.

[0128] The pore structure and specific surface area of ​​titanium-silicon molecular sieves were tested using a nitrogen physical adsorption instrument. The specific surface area of ​​the molecular sieves was analyzed using the BET (Brunauer-Emmett-Teller) method, and the pore size distribution and pore volume were calculated using the BJH (Barrett-Joiner-Halenda) model.

[0129] The method for testing the acidity of titanium silicate molecular sieves is as follows: pyridine infrared spectroscopy is used. The sample is placed in a vacuum cell and pretreated for 1 hour at 500℃ and a vacuum of 0.001 Pa. The temperature is then lowered to 200℃, and pyridine vapor is allowed to flow for 30 minutes. Excess unadsorbed pyridine vapor is then degassed at 200℃. Subsequently, the temperature is lowered to 100℃, and the desorption peak of pyridine at the corresponding acidic sites is collected. The peak value at 1540 cm⁻¹ in the corresponding spectrum is [missing value]. -1 The peak at 1450 cm⁻¹ is designated as the characteristic peak of Brønsted acid. -1 The peak is denoted as the L acid characteristic peak. The amount of Brønsted acid (B acid) and L acid (L acid) is calculated based on the integrated peak area of ​​the spectrum, and the ratio of B acid to L acid is obtained. The total acid amount is calculated as: total B acid amount + L acid amount.

[0130] Table 1

[0131] Table 1-1

[0132] Table 1-2

[0133] The following examples illustrate the preparation method of the catalyst of the present invention. Example 1 (1-1) Preparation of impregnation solution containing active component precursor, dispersant and alkaline substance: Take 17.24 mL of HAuCl4 aqueous solution (the concentration of Au 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 slowly 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 6.78. Then continue to stir solution B2 for 3.5 h to obtain impregnation solution, the pH value of impregnation solution is 8.25.

[0134] (1-2) Impregnation of the carrier with impregnation solution: Take 5g of the titanium-silicon molecular sieve prepared in Example 1 and place it in a container with a bottom area of ​​80cm². 2 The impregnation solution prepared in step (1-1) 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.

[0135] (2) Drying: The solid-liquid mixture after shaking and impregnation was placed in a constant temperature and humidity oven with a blower for drying. The oven settings were: temperature 30℃, relative humidity 15%, maximum relative humidity fluctuation 3%, vacuum degree 2kPa before drying, and then vacuum degree 65kPa after ammonia gas was introduced; drying was stopped after constant weight was achieved, resulting in block solids, which were then ground to a particle size of less than 0.06mm. The parameters of the constant temperature and humidity oven resulted in a drying rate of 0.589g water / (cm³). 2 h·g carrier).

[0136] (3) Activation: Then the solid after grinding in step (2) is placed in a muffle furnace and activated in an air atmosphere. The activation treatment is carried out at 200°C for 2.5 h to obtain the catalyst.

[0137] Examples 2-9 and Comparative Examples 1-4 The catalyst was prepared according to the method of Example 1, except that the titanium-silicon molecular sieve obtained in Preparation Example 1 was replaced with the titanium-silicon molecular sieves obtained in Preparation Examples 2-9 and Comparative Preparation Examples 1-4, respectively.

[0138] Example 10 The catalyst was prepared according to the method of Example 1, except that the drying temperature was 60°C, the relative humidity was 20%, the maximum fluctuation of the relative humidity was 4%, and the drying rate was 0.709 g water / (cm³). 2 h•g carrier).

[0139] Example 11 The catalyst was prepared according to the method in Example 1, except that the vacuum degree before drying was 20 kPa and the drying rate was 0.492 g water / (cm²). 2 h•g carrier).

[0140] Example 12 The catalyst was prepared according to the method of Example 1, except that the KHCO3 aqueous solution was replaced with an aqueous solution of NaOH of equal concentration and volume. The pH values ​​of solution B2 and the impregnation solution were 8.17 and 7.01, respectively.

[0141] Example 13 The catalyst was prepared according to the method of Example 1, except that the dispersant was replaced with an equal amount of ethylenediamine.

[0142] Example 14 The catalyst was prepared according to the method in Example 1, except that the amount of KHCO3 aqueous solution used was increased so that the pH of solution B2 was 3.98. Solution B2 was then stirred for another 3 hours to obtain an impregnation solution with a pH of 6.05.

[0143] Example 15 The catalyst was prepared according to the method of Example 1, except that ammonia was not introduced during the drying process in step (2).

[0144] Example 16 The catalyst was prepared according to the method of Example 1, except that in step (3), activation was carried out in the presence of an alkaline substance, specifically: The solid ground in step (2) was placed in a vacuum oven for activation. The vacuum degree was 2 kPa before activation began. Then, a mixture of dimethylamine and air (the volume ratio of dimethylamine to air was 1:3) was introduced, and the vacuum degree was 70 kPa. Under this atmosphere, the catalyst was activated at 200°C for 2.5 h to obtain the catalyst.

[0145] Example 17 The catalyst was prepared according to the method of Example 16, except that step (1-1) also included the addition of an alkali metal promoter, namely, the addition of a saturated potassium chloride aqueous solution simultaneously with the addition of KHCO3 aqueous solution to obtain solution B2, the pH of which was 6.72. The amount of potassium chloride used, calculated as metal element, was 0.26 g per 100 g of carrier.

[0146] Test Example 2 The catalysts prepared in the above examples and comparative examples were characterized by parameters, and the test results are shown in Table 2.

[0147] The method for determining the Au content of the active component in the catalyst is inductively coupled plasma optical emission spectroscopy (ICP-OES), which measures the total Au content in the catalyst. The total Au content in the catalyst is denoted as Au1.

[0148] Test method for the content of Au anchored by oxygen vacancies in the catalyst: Calculated based on the difference in oxygen vacancies content in the catalyst before and after Au nanoparticle loading, as shown in the attached figure. Figure 1 As shown, the EPR characterization of the catalyst before and after loading in Example 1 provides a direct visual indication of the change in oxygen hole content. The formula for calculating the content of Au anchored by oxygen holes in the catalyst is: (Oxygen hole content in the titanium silicate molecular sieve - Oxygen hole content in the catalyst) × 0.001 × 2 ÷ 1.56 × 197 × 100%.

[0149] The method for testing the ratio of Au particles with a diameter of 2-5 nm to the total number of noble metal particles with a diameter of 1-10 nm in the catalyst is as follows: TEM electron microscopy is used to measure and count the total number of Au particles with a diameter of 1-10 nm in any 100 nm × 100 nm region, denoted as N1; at the same time, the number of Au particles with a diameter of 2-5 nm in the same region is counted and denoted as N2; then the ratio of N2 / N1 is calculated.

[0150] 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 The peak area is used to calculate Au. 3+ Au 1+ and Au 0 The content ratio.

[0151] 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.

[0152] The method for testing the acidity in the catalyst is as follows: pyridine infrared spectroscopy is used. The sample is placed in a vacuum cell and pretreated for 1 h at 500℃ and a vacuum of 0.001 Pa. The temperature is then lowered to 200℃, and pyridine vapor is allowed to flow for 30 min. Excess unadsorbed pyridine vapor is then degassed at 200℃. Subsequently, the temperature is lowered to 100℃, and the desorption peak of pyridine at the corresponding acidic sites is collected. The peak value at 1540 cm⁻¹ in the corresponding spectrum is [missing value]. -1 The peak at 1450 cm⁻¹ is designated as the characteristic peak of Brønsted acid. -1 The peak is denoted as the L acid characteristic peak. Based on the spectrum, the amount of Brønsted acid and L acid is calculated by integrating the peak areas, and the ratio of Brønsted acid to L acid is obtained. The total acid amount is calculated as: total Brønsted acid amount + L acid amount.

[0153] Table 2

[0154] Note: Au1 represents the total content of the active component Au in the catalyst; Au2 represents the content of oxygen-hole anchored Au in the catalyst.

[0155] Test Example 3 The performance of the catalysts prepared in the above examples and comparative examples in the preparation of propylene oxide was tested. 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 3.

[0156] Propylene conversion rate (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 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) acrolein selectivity (S C3H4O = Amount of acrolein in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product) Acetone selectivity (S) CH3COCH3 = Amount of acetone in the product / (Amount of C3 product + 2 / 3 of C2 product + 1 / 3 of C1 product) Hydrogen utilization rate (Y) H2 = Amount of propylene oxide in the product / (Amount of hydrogen in the feed gas - Amount of hydrogen in the product) PO space-time yield = propylene conversion (C C3H6 *Propylene oxide selectivity (S) PO ) *Airspeed (GHSV).

[0157] Table 3

[0158] 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 titanium-silicon molecular sieve, characterized in that, The silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; the oxygen vacancy content in the titanium-silicon molecular sieve is 0.35-2.2 mmol / g.

2. The titanium-silicon molecular sieve according to claim 1, wherein, The oxygen vacancy content in the titanium-silicon molecular sieve is 0.4-0.6 mmol / g; And / or, the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.5-1.

3. The titanium-silicon molecular sieve according to claim 1 or 2, wherein, The ratio of the hydroxyl density Q4 / Q3 of the titanium-silicon molecular sieve is 4-10, preferably 5.2-8; wherein, Q4 / Q3 represents the hydroxyl density of the titanium-silicon molecular sieve. 29 The ratio of peak areas of peaks with chemical shifts near -113±1ppm and -103±1ppm in the Si MAS NMR spectrum.

4. The titanium-silicon molecular sieve according to any one of claims 1-3, wherein, The L acid content in the titanium-silicon molecular sieve is 0.001-2.5 mmol / g, preferably 0.06-0.3 mmol / g; the Brønsted acid / L acid ratio in the titanium-silicon molecular sieve is 0.05-2, preferably 0.4-1; wherein, in the pyridine infrared spectrum of the titanium-silicon molecular sieve, at 1540±5 cm⁻¹... -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

5. The titanium-silicon molecular sieve according to any one of claims 1-4, wherein, The mesopores of the titanium-silicon molecular sieve have a specific surface area of ​​80-225 m². 2 / g, the pore volume of the mesoporous tissue is 0.2-0.65cm³. 3 / g, the specific surface area of ​​the micropores is 150-510m² 2 / g, the pore volume of the micropores is 0.08-0.32cm³. 3 / g, with an average pore size of 0.4-2nm and a crystallinity of 82-98%.

6. The titanium-silicon molecular sieve according to any one of claims 1-5, wherein, The average particle size of the titanium-silicon molecular sieve is 60-145 nm.

7. A method for preparing titanium-silicon molecular sieves, characterized in that, The method includes the following steps: (1) A mixture containing silicon source, titanium source, alkali source, water and first organosilicon is subjected to hydrothermal crystallization; then solid-liquid separation, first drying and calcination are performed; the alkali source is at least one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and tetrapentylammonium hydroxide; the conditions for hydrothermal crystallization include: temperature of 135-185℃ and time of 12-64h; (2) The calcined product obtained in step (1) is contacted with a second organosilicon, and then subjected to a second drying process, wherein the drying conditions of the second drying process result in a drying rate of 0.015-1.015 g organosilicon / (cm³). 2 h·g of calcined product); the contact conditions include: a temperature of 20-60℃ and a time of 30-70min; The molar ratio of silicon source, titanium source, alkali source and water in the mixture is R1 of 100:0.005-80:0.5-180:25-900. The first organosilicon and the second organosilicon are each independently selected from at least one of methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldiethoxysilane, 3-aminopropyltriethoxysilane, trimethylsilyldiethylamine and tert-butyldimethylchlorosilane.

8. The method according to claim 7, wherein, The molar ratio R2 of the silicon source to the first organosilicon is 100:0.5-50; more preferably 100:1-10; wherein the silicon source is SiO2. And / or, relative to each gram of calcined product, the amount of the second organosilicon is 0.1-2g, more preferably 0.5-2g; And / or, the molar ratio of silicon source, titanium source, alkali source and water in the mixture is R1 of 100:0.15-15:15-100:150-750; wherein, the silicon source is calculated as SiO2 and the titanium source is calculated as TiO2; And / or, the silicon source is an alkyl silicate, preferably, the alkyl group in the alkyl silicate is a C1-C6 alkyl group; And / or, the titanium source is an alkyl titanate, preferably, the alkyl group in the alkyl titanate is a C1-C6 alkyl group; And / or, the conditions for hydrothermal crystallization include: a temperature of 150-180°C and a time of 20-50 hours; And / or, the calcination conditions include: a temperature of 475-625°C and a time of 6-12 hours.

9. The method according to claim 7 or 8, wherein, Step (1) also includes: before hydrothermal crystallization, the aqueous solution containing silicon source, titanium source and alkali source is subjected to alcohol removal treatment, and then the product of alcohol removal treatment is mixed with the first organosilicon to obtain a mixed solution; And / or, in step (2), the contact conditions include: a temperature of 20-40°C and a time of 50-70 min.

10. A supported catalyst, characterized in that, The catalyst comprises a support and an active component loaded on the support, wherein the active component is a noble metal and the support is the titanium-silicon molecular sieve according to any one of claims 1-9.

11. The catalyst according to claim 10, wherein, The content of the active component, calculated by metal element, is 0.01-1.15% by weight of the total weight of the catalyst. And / or, at least a portion of the active component is anchored to oxygen vacancies in the titanium-silicon molecular sieve; more preferably, the content of the oxygen vacan-anchored active component in the catalyst is 0.04-0.08% by weight. And / or, the precious metal is Au and / or Pd.

12. The catalyst according to claim 10 or 11, wherein, Within any 100nm × 100nm region on the catalyst, the proportion of noble metal particles with a diameter of 2-5nm to the total number of noble metal particles with a diameter of 1-10nm is greater than 50%, preferably greater than 80%. And / or, the ratio of the hydroxyl density Q4 / Q3 of the catalyst is 3-13.5, preferably 3-12, more preferably 3.5-10, and even more preferably 6-8; wherein Q4 / Q3 represents the hydroxyl density of the catalyst. 29 The ratio of peak areas of peaks with chemical shifts near -113±1ppm and -103±1ppm in the Si MAS NMR spectrum.

13. The catalyst according to claim 11 or 12, wherein, The weight ratio of reduced metal to oxidized metal in the active component is 1:0.1-2; more preferably, the valence state of Au includes Au. 0 Au 1+ and Au 3+ Further preferably, Au 0 Au 1+ Au 3+ The weight ratio is 1:0.1-0.7:0.01-0.5, and more preferably 1:0.1-0.35:0.01-0.25; And / or, the amount of L acid in the catalyst is 0.005-0.4 mmol / g, and the acid-to-L acid ratio is less than 1.1, preferably 0.02-0.9, wherein, in the pyridine infrared spectrum of the catalyst, at 1540±5 cm⁻¹... -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

14. A supported catalyst, characterized in that, The catalyst comprises a support and an active component supported on the support, wherein the active component is a noble metal, and the silicon-to-titanium molar ratio in the titanium-silicon molecular sieve is 100:0.05-15; at least a portion of the active component is anchored to oxygen vacancies in the titanium-silicon molecular sieve. Preferably, the content of the oxygen vacancy anchoring active component in the catalyst is 0.04-0.08% by weight. Preferably, the content of the active component, calculated as metal element, is 0.01-1.15% by weight, based on the total weight of the catalyst. Preferably, the noble metal is Au and / or Pd; Preferably, within any 100nm × 100nm region on the catalyst, the proportion of noble metal particles with a diameter of 2-5nm to the total number of noble metal particles with a diameter of 1-10nm is greater than 50%, and more preferably greater than 80%. Preferably, the ratio of the hydroxyl density Q4 / Q3 of the catalyst is 3-13.5, more preferably 3-12, more preferably 3.5-10, and even more preferably 6-8; wherein Q4 / Q3 represents the hydroxyl density of the catalyst. 29 The ratio of peak areas of peaks with chemical shifts near -113±1ppm and -103±1ppm in the Si MAS NMR spectrum; Preferably, the weight ratio of reduced metal to oxidized metal in the active component is 1:0.1-2; more preferably, the valence state of Au includes Au. 0 Au 1+ and Au 3+ Further preferably, Au 0 Au 1+ Au 3+ The weight ratio is 1:0.1-0.7:0.01-0.5, and more preferably 1:0.1-0.35:0.01-0.25; Preferably, the amount of L acid in the catalyst is 0.005-0.4 mmol / g, and the acid-to-L acid ratio is less than 1.1, preferably 0.02-0.

9. The catalyst's pyridine infrared spectrum is [value missing] at 1540±5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the acidity of Brønsted acid, 1450 ± 5 cm⁻¹. -1 The integral area of ​​the characteristic peak at that location is the amount of L acid.

15. A method for preparing a supported catalyst, characterized in that, The method includes the following steps: (a) A solid-liquid mixture is obtained by contacting a solution containing an active component precursor and an inorganic alkaline substance with a support; wherein the active component precursor includes a noble metal precursor; and the support is a titanium-silicon molecular sieve as described in any one of claims 1-6. (b) The solid-liquid mixture obtained in step (a) is dried and activated.

16. The method according to claim 15, wherein, In step (a), the solid-liquid mixture is obtained by first mixing an aqueous solution of the active component precursor with an aqueous solution of an inorganic alkaline substance to obtain a solution containing the active component precursor and the inorganic alkaline substance, and then contacting it with a carrier to obtain a solid-liquid mixture. And / or, the solution containing the active component precursor and the inorganic alkaline substance further includes a dispersant; preferably, the solution containing the active component precursor, dispersant and inorganic alkaline substance is obtained by: mixing an aqueous solution of the active component precursor with a dispersant to obtain solution B1; then adjusting the pH of solution B1 to 5-8 using an aqueous solution of the inorganic alkaline substance to obtain solution B2; then aging solution B2 under aging conditions so that the pH of solution B2 is 6.5-9; more preferably, the amount of dispersant used is 0.005-1g relative to 100g of carrier; the dispersant includes at least one selected from ethylenediamine, ethylene glycol, urea, disodium ethylenediaminetetraacetate, bipyridine, glycerol, N,N dimethylformamide, acetone, toluene, tannic acid and cyclohexane; And / or, the inorganic alkaline substance is selected from at least one of alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates and ammonia water; preferably at least one of Na2CO3, K2CO3, Cs2CO3, NaHCO3 and KHCO3; And / or, the active component precursor includes an Au precursor and / or a Pd precursor; more preferably an Au precursor; And / or, relative to each 100g carrier, the amount of the active component precursor, calculated as metal element, is 0.01-2g.

17. The method according to claim 15 or 16, wherein, In step (b), the drying conditions are such that the drying rate of the solid-liquid mixture is 0.025-0.955 g water / (cm³). 2 h·g carrier), preferably 0.2-0.6 g water / (cm³) 2 h·g carrier); And / or, the drying described in step (b) is carried out in the presence of a first alkaline substance; And / or, the activation conditions include: a temperature of 150-350°C and a time of more than 2 hours, preferably 2.5-10 hours; And / or, the activation described in step (b) is carried out in the presence of a second basic substance; Preferably, the first alkaline substance and the second alkaline substance are each independently a nitrogen-containing alkaline substance; more preferably, the nitrogen-containing alkaline substance includes ammonia and / or a nitrogen-containing organic amine; even more preferably, the nitrogen-containing organic amine includes dimethylamine and / or ethylenediamine.

18. The method according to claim 15 or 16, wherein, Step (a) further includes adding an alkali metal auxiliary agent; the alkali metal auxiliary agent is a strong acid salt of an alkali metal and / or a weak acid salt of an alkali metal; preferably, the strong acid salt of the alkali metal is at least one of sodium nitrate, potassium nitrate, sodium chloride and potassium chloride; Preferably, the amount of the alkali metal auxiliary agent, calculated as metal element, is 0.02-1g per 100g of carrier.

19. The application of the noble metal supported catalyst according to any one of claims 10-14 in the preparation of propylene oxide; preferably, the feed gas used in the preparation of propylene oxide includes propylene, hydrogen, and oxygen, and the volume ratio of propylene, hydrogen, and oxygen is 1:0.1-5:0.1-2; the temperature for preparing propylene oxide is 160-225°C.

Images