Titanium silicalite molecular sieve, preparation method thereof and application of titanium silicalite molecular sieve in organic catalytic reaction

Abstract

The invention relates to a titanium silicalite molecular sieve and a preparation method and application thereof in organic catalytic reaction, and the preparation method comprises the following steps: (1) mixing a titanium source, a crown ether compound and an optional solvent to obtain a titanium-containing precursor solution; (2) performing hydrolysis treatment on the titanium-containing precursor solution, a silicon source and a template agent in a contact manner to obtain a hydrolysis mixture; and (3) carrying out hydrothermal crystallization treatment, drying treatment and roasting treatment on the hydrolysis mixture. The problem that the content of non-framework titanium of the titanium silicalite molecular sieve is high can be effectively solved, and the catalytic activity of the titanium silicalite molecular sieve in an organic catalytic reaction is improved.

Description

Technical Field

[0001] This application relates to the field of inorganic material preparation technology, specifically to a titanium-silicon molecular sieve, its preparation method, and its application in organic catalytic reactions. Background Technology

[0002] Since Enichem developed the TS-1 titanium-silicon molecular sieve with an MFI structure in 1983, a series of Ti-containing heteroatom molecular sieves with different framework structures have been developed. They have shown excellent catalytic oxidation performance in the selective oxidation of hydrocarbons and have been widely used in industrial production such as epoxidation of olefins, ammonium oximeation of ketones, and hydroxylation of phenols.

[0003] TS-1 titanium-silicon molecular sieve is currently the most widely used titanium-containing molecular sieve. Its pore size is about 0.56 nm, and it has a unique confinement effect and shape selection effect in the conversion of low molecular weight hydrocarbons.

[0004] CN1167082A discloses a method for preparing TS-1 molecular sieves. This method involves dissolving a titanium source in an aqueous solution of tetrapropylammonium hydroxide (TPAOH) and mixing it uniformly with solid silica gel microspheres to obtain a reaction mixture. This reaction mixture is then hydrothermally crystallized in an autoclave, followed by filtration, washing, drying, and calcination using conventional methods. However, this invention does not investigate the effective titanium content and catalytic oxidation activity of the TS-1 molecular sieve. The titanium-silicon molecular sieves prepared by existing processes still contain a large amount of non-framework titanium, resulting in unsatisfactory performance in catalytic oxidation reactions. Summary of the Invention

[0005] The purpose of this disclosure is to provide a titanium-silicon molecular sieve, its preparation method, and its application in organic catalytic reactions. This method can effectively solve the problem of high non-framework titanium content in titanium-silicon molecular sieves and improve the catalytic activity of titanium-silicon molecular sieves in organic catalytic reactions.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing titanium-silicon molecular sieves, comprising the following steps:

[0007] (1) Mix the titanium source, crown ether compound and optional solvent to obtain a titanium-containing precursor solution;

[0008] (2) The titanium-containing precursor solution, silicon source and template agent are contacted and hydrolyzed to obtain a hydrolyzed mixture;

[0009] (3) The hydrolyzed mixture is subjected to hydrothermal crystallization, drying and calcination.

[0010] Optionally, in step (1), the crown ether compound is selected from one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, dicyclohexano-18-crown ether-6 and dibenzo-18-crown ether-6; preferably selected from one or more of 12-crown ether-4, 15-crown ether-5 and 18-crown ether-6.

[0011] Optionally, the titanium source is selected from one or more of inorganic titanium sources and organic titanium sources.

[0012] Optionally, the inorganic titanium source is selected from one or more of titanium tetrafluoride, titanium tetrachloride, titanium tetrabromide, titanium trichloride, and titanium sulfate; the organic titanium source is selected from one or more of tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.

[0013] Preferably, the titanium source is an inorganic titanium source, more preferably titanium sulfate.

[0014] Optionally, the silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol; preferably, it is selected from at least one of silicone grease, solid silica gel, and fumed silica.

[0015] Optionally, the silicone grease is selected from one or more compounds with the structure shown in formula (1):

[0016]

[0017] R a R b R c and R d Each is independently selected from alkyl groups having 1 to 4 carbon atoms, wherein the alkyl group is branched or straight-chain alkyl; preferably, the R a R b R c and R d Each of the following is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; more preferably, the organosilicon grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silyl ester; even more preferably, it is selected from one or more of tetramethyl silicate, tetraethyl silicate, and dimethyl diethyl silyl ester.

[0018] Optionally, the template agent is selected from one or more of organic quaternary ammonium salts and organic bases;

[0019] Optionally, the organic quaternary ammonium salt is selected from one or more of tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium bromide;

[0020] Optionally, the organic base is selected from one or more of organic quaternary ammonium bases and organic amines; preferably, the organic quaternary ammonium base is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the organic amine is selected from one or more of ethylamine, n-butylamine, butanediamine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, theanine, toluidine, and p-phenylenediamine.

[0021] Optionally, the solvent is selected from one or more of polar protic solvents and aprotic solvents; preferably, the polar protic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol; the aprotic solvent is selected from one or more of dichloromethane, dichloroethane, allyl chloride, methylchloropropene, 1-chlorobutane, acetonitrile, N,N-dimethylformamide, toluene, acetone, propylene glycol methyl ether and dimethyl sulfoxide; preferably, the solvent is selected from one or more of polar protic solvents, more preferably n-propanol.

[0022] Optionally, in step (1), the molar ratio of titanium source: crown ether compound: solvent is 1:(0.5-5):(0-100), preferably 1:(1-4):(5-50).

[0023] Optionally, in step (2), the molar ratio of silicon source: titanium-containing precursor solution: organic base: water is (0.001~0.5):(0.001~0.8):(5~100), preferably 1:(0.01~0.4):(0.01~0.5):(5~50), wherein the silicon source is calculated as SiO2 and the titanium-containing precursor solution is calculated as TiO2.

[0024] Optionally, in step (2), the conditions for the hydrolysis treatment include: first heating to 60-100°C at a first heating rate, and then hydrolyzing at a constant temperature for 0.5-10 hours; preferably, first heating to 70-90°C at a first heating rate, and then hydrolyzing at a constant temperature for 1-5 hours.

[0025] Optionally, the first heating rate is 5 to 30°C / h, preferably 10 to 20°C / h.

[0026] Optionally, in step (3), the conditions for the hydrothermal crystallization treatment include:

[0027] First, the temperature is increased to 80–200°C at a second heating rate, and then crystallized at a constant temperature for 2–360 hours; preferably, the temperature is increased to 120–180°C at a second heating rate, and then crystallized at a constant temperature for 10–240 hours.

[0028] Optionally, the second heating rate is 0.3 to 1.7 °C / min, preferably 0.5 to 1.4 °C / min.

[0029] Optionally, in step (3), the drying conditions include: a drying temperature of 80–120°C and a drying time of 2–30 h; preferably, a drying temperature of 90–110°C and a drying time of 5–10 h.

[0030] Optionally, the calcination conditions include: a calcination temperature of 450–650°C and a calcination time of 1–10 h; preferably, the calcination temperature is 480–620°C and the calcination time is 2–6 h.

[0031] The second aspect of this disclosure provides a titanium-silicon molecular sieve prepared according to the method described in the first aspect of this disclosure.

[0032] This disclosure provides a third aspect regarding the application of the titanium-silicon molecular sieve described in the second aspect of this disclosure in organic catalytic reactions.

[0033] Optionally, the organocatalytic reaction includes the epoxidation of 1-hexene to produce hexane oxide;

[0034] Optionally, the epoxidation reaction of 1-hexene to produce hexane includes: reacting the titanium-silicon molecular sieve with 1-hexene and hydrogen peroxide.

[0035] Preferably, the conditions for the epoxidation reaction of 1-hexene to hexane oxide include: a mass ratio of titanium silicate molecular sieve to hydrogen peroxide of 0.01 to 10:1, preferably 0.02 to 2:1; and a molar ratio of hydrogen peroxide to 1-hexene of 0.5 to 2:1, preferably 1 to 1.2:1.

[0036] Optionally, the reaction temperature is 30–60°C and the reaction time is 1–10 h; preferably, the reaction temperature is 35–50°C and the reaction time is 2–6 h.

[0037] Through the above technical solutions, this disclosure provides a titanium-silicon molecular sieve, its preparation method, and its application in organic catalytic reactions. In the method for preparing the titanium-silicon molecular sieve, a titanium-containing precursor solution formed by a titanium source, a crown ether compound as a ligand, and a solvent is used as the titanium source for the synthesis of the molecular sieve. This inhibits the self-polymerization of titanium salts, thereby minimizing the formation of TiO2 from the hydrolysis and self-polymerization of the titanium source, reducing the generation of non-framework titanium, and ensuring that more titanium is located within the pores of the molecular sieve. Compared with existing technologies, the titanium-containing molecular sieve synthesized in this disclosure exhibits better catalytic oxidation activity and selectivity, while also possessing better catalytic activity stability. In the epoxidation of 1-hexene to hexane, the titanium-silicon molecular sieve provided by this disclosure can achieve higher feed conversion rates and product selectivity.

[0038] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 The UV-Vis spectra of the molecular sieve products obtained in Example 1, Comparative Example 1, and Comparative Example 2 are shown below.

[0041] Figure 2 The peak fitting result of the ultraviolet-visible (UV-vis) spectrum of the titanium-containing molecular sieve sample synthesized in Example 1 is shown.

[0042] Figure 3 The peak fitting results of the ultraviolet-vis (UV-vis) spectrum of the titanium-containing molecular sieve sample synthesized in Comparative Example 1 are shown.

[0043] Figure 4 The peak fitting results of the ultraviolet-vis (UV-vis) spectrum of the titanium-containing molecular sieve sample synthesized in Comparative Example 2 are shown.

[0044] Figure 5 The XRD patterns are of the molecular sieve products obtained in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0045] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0046] The first aspect of this disclosure provides a method for preparing titanium-silicon molecular sieves, comprising the following steps:

[0047] (1) Mix the titanium source, crown ether compound and optional solvent to obtain a titanium-containing precursor solution;

[0048] (2) The titanium-containing precursor solution, silicon source and template agent are contacted and hydrolyzed to obtain a hydrolyzed mixture;

[0049] (3) The hydrolyzed mixture is subjected to hydrothermal crystallization, drying and calcination.

[0050] This disclosure provides a method for preparing titanium-silicon molecular sieves. By using a titanium source, a crown ether compound as a ligand, and a solvent to form a titanium-containing precursor solution as the synthetic titanium source for the molecular sieve, the self-polymerization of titanium salts can be suppressed, thereby minimizing the formation of TiO2 from the hydrolysis and self-polymerization of the titanium source, reducing the generation of non-framework titanium, and ensuring that more titanium is located within the pores of the molecular sieve. Compared with existing technologies, the titanium-containing molecular sieve synthesized by this disclosure exhibits better catalytic oxidation activity and selectivity, as well as better catalytic activity stability. In the epoxidation of 1-hexene to hexane, the titanium-silicon molecular sieve provided by this disclosure can achieve higher feed conversion and product selectivity.

[0051] In one embodiment, in step (1), the crown ether compound has 12 to 18 atoms on its ring.

[0052] In a preferred embodiment, in step (1), the crown ether compound is selected from one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, dicyclohexano-18-crown ether-6, and dibenzo-18-crown ether-6. This disclosure uses crown ether compounds as synthetic ligands for titanium silicate molecular sieves, which has the advantages of simple synthesis methods and stable synthesis processes.

[0053] In a preferred embodiment, the crown ether compound is selected from one or more of 12-crown ether-4, 15-crown ether-5, and 18-crown ether-6. Using the preferred crown ether compound in this embodiment as a ligand for the synthesis of titanium-silicon molecular sieves can further reduce the generation of non-framework titanium in the molecular sieve and improve the catalytic performance of the titanium-silicon molecular sieve.

[0054] In one embodiment, the titanium source is selected from one or more of inorganic titanium sources and organic titanium sources;

[0055] Optionally, the inorganic titanium source is selected from one or more of titanium tetrafluoride, titanium tetrachloride, titanium tetrabromide, titanium trichloride, and titanium sulfate; the organic titanium source is selected from one or more of tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.

[0056] In a preferred embodiment, the titanium source is an inorganic titanium source, preferably titanium sulfate. The inorganic titanium source preferred in this disclosure, especially titanium sulfate, is more suitable for preparing titanium-silicon molecular sieves with crown ether ligand compounds, and can further reduce the generation of non-framework titanium and increase the framework titanium content of the molecular sieve.

[0057] In one embodiment, the silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol; preferably, it is selected from at least one of silicone grease, solid silica gel, and fumed silica.

[0058] Optionally, the silicone grease is selected from one or more compounds with the structure shown in formula (1):

[0059]

[0060] R a R b R c and R d Each is independently selected from alkyl groups having 1 to 4 carbon atoms, wherein the alkyl group is branched or straight-chain alkyl; preferably, the R a R b R c and R d Each of the following is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; more preferably, the organosilicon grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silyl ester; even more preferably, it is selected from one or more of tetramethyl silicate, tetraethyl silicate, and dimethyl diethyl silyl ester.

[0061] In one embodiment, the template agent is selected from one or more of organic quaternary ammonium salts and organic bases;

[0062] Optionally, the organic quaternary ammonium salt is selected from one or more of tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium bromide;

[0063] Optionally, the organic base is selected from one or more of organic quaternary ammonium bases and organic amines; preferably, the organic quaternary ammonium base is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and the organic amine is selected from one or more of ethylamine, n-butylamine, butanediamine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, theanine, toluidine, and p-phenylenediamine.

[0064] In one embodiment, the solvent is selected from one or more of polar protic solvents and aprotic solvents; preferably, the polar protic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; the aprotic solvent is selected from one or more of dichloromethane, dichloroethane, allyl chloride, methylchloropropene, 1-chlorobutane, acetonitrile, N,N-dimethylformamide, toluene, acetone, propylene glycol methyl ether, and dimethyl sulfoxide. In a more preferred embodiment, the solvent is selected from one or more of polar protic solvents, more preferably n-propanol. When the polar protic solvent (especially n-propanol) provided in this embodiment is used in the synthesis of titanium sources, it can exert a superior effect in reducing the formation of TiO2 from the self-polymerization of titanium source hydrolysis and reducing the generation of non-framework titanium when it interacts with titanium sources and crown ether ligand compounds.

[0065] In one embodiment, in step (1), the molar ratio of titanium source: crown ether compound: solvent is 1:(0.5-5):(0-100), preferably 1:(1-4):(5-50). The titanium-silicon molecular sieve prepared from the titanium-containing precursor solution obtained according to the preferred molar ratio in this embodiment has a higher framework titanium content, and can have higher feed conversion rate and product selectivity in organic catalytic reactions.

[0066] In one embodiment, in step (2), the molar ratio of silicon source: titanium-containing precursor solution: organic base: water is (0.001-0.5):(0.001-0.8):(5-100), preferably 1:(0.01-0.4):(0.01-0.5):(5-50), wherein the silicon source is calculated as SiO2 and the titanium-containing precursor solution is calculated as TiO2. The titanium-silicon molecular sieve obtained according to the preferred molar ratio in this embodiment has better catalytic activity and can have higher feed conversion rate and product selectivity in organic catalytic reactions.

[0067] In one embodiment, the conditions for the hydrolysis treatment in step (2) include:

[0068] First, heat to 60-100°C at a first heating rate, then hydrolyze at a constant temperature for 0.5-10 hours; preferably, heat to 70-90°C at a first heating rate, then hydrolyze at a constant temperature for 1-5 hours.

[0069] Optionally, the first heating rate is 5 to 30°C / h, preferably 10 to 20°C / h.

[0070] In one embodiment, the conditions for the hydrothermal crystallization treatment in step (3) include:

[0071] First, the temperature is raised to 80-200°C at a second heating rate, and then crystallized at a constant temperature for 2-360 hours; preferably, the temperature is raised to 120-180°C at a second heating rate, and then crystallized at a constant temperature for 10-240 hours.

[0072] Optionally, the second heating rate is 20–100 °C / h, preferably 30–80 °C / h.

[0073] In one embodiment, the drying conditions in step (3) include: a drying temperature of 80-120°C and a drying time of 2-30 hours; preferably, the drying temperature is 90-110°C and the drying time is 5-10 hours.

[0074] In one embodiment, the conditions for the calcination treatment in step (3) include: a calcination temperature of 450-650°C and a calcination time of 1-10h; preferably, the calcination temperature is 480-620°C and the calcination time is 2-6h.

[0075] The titanium-silicon molecular sieve prepared according to the preferred process conditions in this disclosure can have better catalytic performance.

[0076] The second aspect of this disclosure provides a titanium-silicon molecular sieve prepared according to the method described in the first aspect of this disclosure.

[0077] In a preferred embodiment, the titanium-silicon molecular sieve has the following UV-Vis characteristics:

[0078] The UV-Vis spectrum of the titanium-silicon molecular sieve exhibits peaks at positions of 210±10 nm, 270±10 nm, and 330±10 nm, respectively; the peak area of ​​the peak at position 210±10 nm in the UV-Vis spectrum of the titanium-silicon molecular sieve is denoted as A. 210 Let A denote the peak area of ​​the spectral peak at position 270±10nm. 270 Let A denote the peak area of ​​the spectral peak at position 330±10nm. 330 The titanium-silicon molecular sieve, as defined in formula (2), has an X1 value that is any value within the range of 30% to 100%.

[0079] X1=(A 210 +A 270 ) / (A 210 +A 270 +A 330 Formula (2) is 100% × 100%.

[0080] The titanium-silicon molecular sieve disclosed herein has a higher framework titanium content and a lower non-framework titanium content, resulting in better catalytic oxidation activity and selectivity. In this disclosure, a spectral peak at 210±10 nm represents a four-coordinated framework titanium species in the titanium-silicon molecular sieve, a peak at 270±10 nm represents a six-coordinated framework titanium species, and a peak at 330±10 nm represents anatase titanium species. Furthermore, the content of each titanium species in the titanium-silicon molecular sieve is obtained by calculating the proportion of the area of ​​the three peaks in the total area.

[0081] In a preferred embodiment, X1 is any value in the range of 60% to 100%, and more preferably any value in the range of 70% to 90%.

[0082] In one embodiment, the molar ratio of silicon to titanium in the titanium-silicon molecular sieve is 1:0.01 to 0.2, more preferably 1:0.015 to 0.06.

[0083] In one specific embodiment, the average particle size of the titanium-silicon molecular sieve particles is 50–400 nm, preferably 100–300 nm; the BET specific surface area is 300–550 m². 2 / g, preferably 350-500m2 / g; total pore volume is 0.2–0.4 cm³. 3 / g, preferably 0.25~0.35cm 3 / g;

[0084] In one specific embodiment, the titanium-silicon molecular sieve is selected from one or more of the following molecular sieves: MFI structure, MEL structure, MOR structure, BEA structure, MWW structure, IMF structure, CON structure, TUN structure, FAU structure, and EWT structure. Preferably, it is selected from one or more of the following molecular sieves: MFI structure, BEA structure, CON structure, and EWT structure. Different template agents result in different structures of the synthesized titanium-containing molecular sieves. For example, the titanium-containing molecular sieve is MFI type TS-1, and the template agent is one or more combinations of tetrapropylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium hydroxide, and organic amines; the titanium-containing molecular sieve is MEL type TS-2, and the template agent is one or more combinations of tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium hydroxide, and organic amines.

[0085] In this disclosure, the titanium-silicon molecular sieve can be used directly as a catalyst from raw molecular sieve powder, or it can be used after being shaped, such as by pressing into tablets, by rolling to prepare microspheres or small spheres of catalyst, by extrusion to prepare strip catalyst, by spray drying to prepare spherical catalyst, etc. Alternatively, the titanium-silicon molecular sieve can be used without being shaped, and can be added to the reaction of this disclosure simultaneously or sequentially with other catalysts, co-catalysts, and inert matrix supports.

[0086] According to this disclosure, the catalyst containing titanium-silicon molecular sieves preferably contains 20-100% by weight, more preferably 50-100% by weight, and even more preferably 80-100% by weight. In addition to titanium-silicon molecular sieves as the main catalyst, it may also contain binders, co-catalysts, pore expanders, inert matrix supports, etc., all of which are conventionally selected reagents in the art.

[0087] This disclosure provides a third aspect regarding the application of the titanium-silicon molecular sieve described in the second aspect of this disclosure in organic catalytic reactions.

[0088] In a preferred embodiment, the organic catalytic reaction is the epoxidation of 1-hexene to produce hexane oxide, which includes the following steps: contacting titanium silicate molecular sieves with 1-hexene and hydrogen peroxide to carry out the reaction.

[0089] Preferably, the reaction conditions include: the mass ratio of titanium silicate molecular sieve to hydrogen peroxide (pure substance) is 0.01 to 10:1, preferably 0.02 to 2:1; the molar ratio of hydrogen peroxide to 1-hexene is 0.5 to 2:1, preferably 1 to 1.2:1;

[0090] Optionally, the reaction temperature is 30–60°C, the reaction pressure is atmospheric pressure, and the reaction time is 1–10 h; preferably, the reaction temperature is 35–50°C, and the reaction time is 2–6 h.

[0091] Optionally, between reactions, the method further includes adding a solvent to the system, the solvent being a conventional organic solvent, such as acetonitrile, methanol, ethanol, etc.; preferably, the molar ratio of the organic solvent to 1-hexene is 10 to 100:1, more preferably 20 to 50:1.

[0092] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0093] The UV-Vis diffuse reflectance (UV-vis) spectra of the solid samples synthesized in the examples were measured using a Cary 300 UV spectrophotometer manufactured by Agilent Technologies. The test conditions were: room temperature, normal pressure, and the samples were tested after being compressed into pellets. The scanning range was 190–800 nm.

[0094] The chemical composition of the molecular sieve was determined by XRF analysis.

[0095] The specific surface area of ​​the molecular sieve was measured by nitrogen low-temperature adsorption-desorption method, and the micropore specific surface area was calculated by BET method; the pore volume and pore distribution were determined according to the method described in RIPP 151-90 in "Analytical Methods for Petrochemical Industry" (published by Science Press in September 1990, first edition) compiled by Yang Cuiding et al.

[0096] Unless otherwise specified, all raw materials used in the examples and comparative examples are analytical grade reagents.

[0097] Example 1

[0098] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and n-propanol was 1:4:30. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.02:0.2:25. The temperature was programmed and stirred to obtain a hydrolysate of silicon and titanium. The temperature programmed conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor. The hydrothermal crystallization conditions were as follows: the temperature was programmed to rise from room temperature to 170°C at a rate of 1°C / min, and then crystallized at a constant temperature under autogenous pressure at 170°C for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were drying at 110°C for 2 hours and calcination conditions were calcination at 550°C for 3 hours in an air atmosphere.

[0099] Example 2

[0100] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and n-propanol was 1:0.5:10. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.1:0.8:30. The temperature was programmed and stirred to obtain a hydrolysate of silicon and titanium. The temperature programmed conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0101] Example 3

[0102] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium tetrachloride and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium tetrachloride, 12-crown ether-4, and n-propanol was 1:3:8. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium bromide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.04:0.2:20. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0103] Example 4

[0104] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate to obtain a titanium-containing precursor solution without adding organic solvent. The molar ratio of titanium sulfate to 12-crown ether-4 was 1:2. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.1:0.3:15. The temperature was programmed and stirred to obtain a hydrolysate of silicon and titanium. The temperature programmed conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0105] Example 5

[0106] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and toluene to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and toluene was 1:4:40. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium bromide. The molar ratio of silicon source: source for synthesizing titanium source: template agent: water was 1:0.01:0.3:20. The temperature was programmed and stirred to obtain a hydrolysate of silicon and titanium. The temperature programmed conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0107] Example 6

[0108] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and dichloromethane to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and dichloromethane was 1:3:30. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetrabutyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium chloride. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.03:0.2:10. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0109] Example 7

[0110] Using 15-crown ether-5 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 15-crown ether-5, and n-propanol was 1:0.8:5. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium source: template agent: water was 1:0.1:0.05:15. The temperature was programmed and stirred to obtain a hydrolysate of silicon and titanium. The temperature programmed conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0111] Example 8

[0112] Using 15-crown ether-5 as a ligand compound, it was mixed uniformly with titanium tetrafluoride and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium tetrafluoride, 15-crown ether-5, and n-propanol was 1:2:25. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium source: template agent: water was 1:0.2:0.1:10. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0113] Example 9

[0114] Using 18-crown ether-6 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 18-crown ether-6, and n-propanol was 1:3:10. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetrabutyl silicate were mixed, and then mixed with an aqueous solution of tetrabutylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium source: template agent: water was 1:0.02:0.1:10. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0115] Example 10

[0116] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with tetrabutyl titanate and toluene to obtain a titanium-containing precursor solution. The molar ratio of tetrabutyl titanate, 12-crown ether-4, and toluene was 1:4:30. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.02:0.2:30. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0117] Example 11

[0118] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and n-butanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and n-butanol was 1:4:20. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium: template agent: water was 1:0.01:0.2:20. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 10°C every hour until the temperature reached 80°C and hydrolysis was completed for 1 hour. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 1°C / min, and the mixture was kept at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours and calcination conditions were 550°C for 3 hours in an air atmosphere.

[0119] Example 12

[0120] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and n-propanol was 1:4:30. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: source for synthesizing titanium source: template agent: water was 1:0.02:0.2:25. The temperature was increased by stirring under programmed temperature to obtain a hydrolysate of silicon and titanium. The programmed temperature conditions were: starting from 30°C, the temperature was increased by 20°C every hour until the temperature reached 90°C and hydrolysis was completed for 3 hours. The resulting mixture was hydrothermally crystallized in a reactor under the following conditions: temperature was increased from room temperature to 170°C at a rate of 0.5°C / min, and crystallized at 170°C under autogenous pressure for 48 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 120°C for 6 hours and the calcination conditions were 600°C for 5 hours in an air atmosphere.

[0121] Example 13

[0122] This embodiment refers to the preparation method in Example 2, but differs from Example 2 in that:

[0123] Using 12-crown ether-4 as a ligand compound, it was mixed uniformly with titanium sulfate and n-propanol to obtain a titanium-containing precursor solution. The molar ratio of titanium sulfate, 12-crown ether-4, and n-propanol was 1:8:30. This titanium precursor solution was used as the source for synthesizing titanium. The source for synthesizing titanium and tetraethyl silicate were mixed, and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source: synthesized titanium source: template agent: water was 1:0.7:1:25. The mixture was heated and stirred under programmed temperature to obtain a hydrolysate of silicon and titanium. The remaining process was the same as in Example 2 to prepare a titanium-silicon molecular sieve.

[0124] Example 14

[0125] This embodiment refers to the preparation method in Example 1, but differs from Example 1 in that:

[0126] The obtained silicon and titanium hydrolysate was subjected to a programmed temperature increase as follows: starting from 30°C, the temperature was increased by 30°C every hour until reaching 100°C for 0.5 hours, at which point hydrolysis was complete. The resulting mixture was then hydrothermally crystallized in a reactor under the following conditions: a programmed temperature increase from room temperature to 190°C at a rate of 1.7°C / min, followed by isothermal crystallization at 190°C under autogenous pressure for 5 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were 110°C for 2 hours, and the calcination conditions were 450°C for 10 hours in an air atmosphere.

[0127] Comparative Example 1

[0128] Using tetrabutyl titanate as the titanium source and tetraethyl silicate as the silicon source, the silicon and titanium sources were mixed and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source:titanium source:template agent:water was 1:0.02:0.2:25 (the same ratio as in Example 1). A hydrolysate of silicon and titanium was obtained by programmed temperature increase and stirring. The programmed temperature conditions were: starting hydrolysis at 30°C, increasing the temperature by 10°C every hour until reaching 80°C for 1 hour, at which point hydrolysis was complete. The resulting mixture was then hydrothermally crystallized in a reactor under the following conditions: a programmed temperature increase from room temperature to 170°C at a rate of 1°C / min, followed by isothermal crystallization at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were: drying at 110°C for 2 hours, and calcination conditions were: calcination at 550°C for 3 hours in an air atmosphere.

[0129] Comparative Example 2

[0130] Using tetrabutyl titanate as the titanium source and tetraethyl silicate as the silicon source, the silicon and titanium sources were mixed and then mixed with an aqueous solution of tetrapropylammonium hydroxide. The molar ratio of silicon source:titanium source:template agent:water was 1:0.1:0.8:30 (the same ratio as in Example 2). A hydrolysate of silicon and titanium was obtained by programmed temperature increase and stirring. The programmed temperature conditions were: starting hydrolysis at 30°C, increasing the temperature by 10°C every hour until reaching 80°C for 1 hour, at which point hydrolysis was complete. The resulting mixture was then hydrothermally crystallized in a reactor under the following conditions: a programmed temperature increase from room temperature to 170°C at a rate of 1°C / min, followed by isothermal crystallization at 170°C under autogenous pressure for 72 hours. After crystallization, the solid product was recovered, dried, and calcined to obtain titanium-containing molecular sieves. The drying conditions were: drying at 110°C for 2 hours, and calcination conditions were: calcination at 550°C for 3 hours in an air atmosphere.

[0131] The values ​​of X1 (skeleton titanium content), non-skeleton titanium content, silicon-titanium molar ratio, and molecular sieve structural characteristic parameters, calculated from the UV-Vis spectra of the molecular sieves prepared according to the above embodiments and comparative examples, are listed in Table 1 below.

[0132] Table 1

[0133]

[0134]

[0135] The ultraviolet-visible (UV-vis) spectra of the titanium-silicon molecular sieves obtained in Example 1 and Comparative Examples 1-2 are shown below. Figure 1 As shown by curves A, B, and C, from Figure 1 It can be seen that curves B and C have obvious peaks at 330 nm, while the peak of curve A of the titanium-silicon molecular sieve obtained in Example 1 is the least obvious at 330 nm. That is, the content of anatase titanium species in the titanium-silicon molecular sieve prepared in Example 1 is less than that in the titanium-silicon molecular sieves of Comparative Examples 1 and 2.

[0136] Furthermore, peak fitting was performed on curves A to C of the ultraviolet-visible (UV-vis) spectra of the titanium-silicon molecular sieves obtained in Example 1 and Comparative Examples 1-2, and the results are as follows: Figures 2-4 As shown, comparing the three figures reveals that... Figure 2 In the peak fitting results of the titanium-silicon molecular sieve of Example 1 shown in the figure, the peak area at 330 nm is the smallest, and the peak areas at 210 nm and 270 nm are higher, indicating that the titanium-silicon molecular sieve prepared by the method provided in this disclosure in Example 1 has a higher skeleton titanium content.

[0137] In addition, the XRD patterns of the titanium-silicon molecular sieves prepared in Example 1 and Comparative Examples 1-2 are as follows: Figure 5As shown, according to Figure 5 It can be seen that the titanium-silicon molecular sieves prepared in Example 1 and Comparative Examples 1-2 have an MFI molecular sieve structure.

[0138] According to the data in Table 1 above, we can see that:

[0139] Comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 2, Example 1 and Example 2 prepared titanium-silicon molecular sieves according to the method provided in this disclosure. During the preparation process, crown ether compounds were added as ligand compounds. The titanium-silicon molecular sieves prepared in Example 1 and Example 2 had higher X1 values, that is, higher skeleton titanium content and lower non-skeleton titanium content, which shows that the method provided in this disclosure can effectively reduce the generation of non-skeleton titanium.

[0140] Comparing Example 2 with Example 13, it can be seen that Example 2 prepared titanium-silicon molecular sieves according to the range of "molar ratio of titanium source: crown ether compound: solvent is 1:(0.5~5):(0~100); molar ratio of silicon source: titanium-containing precursor solution: organic base: water is (0.001~0.5):(0.001~0.8):(5~100)" provided in this disclosure. The titanium-silicon molecular sieve obtained in Example 2 has a higher framework titanium content and a lower non-framework titanium content.

[0141] Comparing Example 1 with Examples 2 and 4, it can be seen that Example 1 prepared titanium-silicon molecular sieves according to the preferred molar ratio of titanium source: crown ether compound: solvent and silicon source: titanium-containing precursor solution: organic base: water. The titanium-silicon molecular sieves obtained in Example 1 had a higher framework titanium content and a lower non-framework titanium content.

[0142] Comparing Example 1 with Example 14, it can be seen that Example 1 synthesizes titanium-silicon molecular sieves according to the preferred preparation process conditions provided in this disclosure, and the titanium-silicon molecular sieve obtained in Example 1 has a higher framework titanium content.

[0143] Test Example 1

[0144] This test example is used to illustrate the catalytic oxidation effect of the titanium-silicon molecular sieves prepared in the above examples and comparative examples in the reaction of 1-hexene epoxidation to epoxide.

[0145] Specific evaluation methods include:

[0146] (1) Initial reaction: The titanium-silicon molecular sieve, 1-hexene, and 30% (mass fraction) hydrogen peroxide aqueous solution prepared in the examples and comparative examples were added into a round-bottom flask. The mass ratio of titanium-containing molecular sieve to hydrogen peroxide (pure substance) was 0.3:1, the molar ratio of hydrogen peroxide (pure substance) to 1-hexene was 1.5:1, methanol was used as solvent, and the molar ratio of methanol to 1-hexene was 20:1. The above mixture was reacted in a water bath at 40°C for 8 hours. After the reaction was completed, samples were taken for analysis.

[0147] (2) Repeated reaction: The titanium silicon molecular sieve was reused in the same way as the first reaction experiment. A total of 10 reactions were carried out (including the first reaction), and the product obtained in the 10th experiment was sampled and analyzed.

[0148] The reaction products were analyzed by gas chromatography, and the results were quantified using the external standard method. The chromatographic conditions were as follows: Agilent-6890 chromatograph, HP-5 capillary column, injection volume 0.5 μL, injection port temperature 280℃. Column temperature was maintained at 100℃ for 2 min, then increased to 250℃ at a rate of 15℃ / min and held for 15 min. An FID detector was used, with a detector temperature of 280℃.

[0149] The hydrogen peroxide content was measured by indirect titration with sodium thiosulfate, and the hydrogen peroxide was measured as hydrogen peroxide.

[0150] The following indicators of the titanium-containing molecular sieve evaluation reaction were mainly examined in each embodiment and comparative example:

[0151] 1-Hexene conversion rate (%) = number of moles of 1-hexene consumed in the reaction / number of moles of 1-hexene in the feedstock before the reaction × 100%;

[0152] Selectivity of hexane oxide (%) = number of moles of hexane oxide in the product / number of moles of olefins consumed in the formation of main and by-products × 100%;

[0153] Effective utilization rate of hydrogen peroxide (%) = number of moles of hydrogen peroxide consumed in the formation of organic matter in the product / (number of moles of hydrogen peroxide in the raw material before reaction - number of moles of hydrogen peroxide in the product after reaction) × 100%.

[0154] The test results are listed in Table 2 below.

[0155] Table 2

[0156]

[0157] According to the data in Table 2 above:

[0158] Compared with Comparative Examples 1-2, the titanium-silicon molecular sieves prepared in Examples 1-13 according to the method provided in this disclosure, and the titanium-silicon molecular sieves obtained in Examples 1-14 all showed higher 1-hexene conversion, epoxide selectivity and hydrogen peroxide utilization in the first and tenth reactions of 1-hexene epoxidation to hexane, indicating that the titanium-silicon molecular sieves obtained in the examples of this disclosure have better catalytic performance and stability for repeated use;

[0159] Comparing Example 2 with Example 13, it can be seen that Example 2 prepared titanium-silicon molecular sieves according to the range of the molar ratio of titanium source: crown ether compound: solvent and the range of the molar ratio of silicon source: titanium-containing precursor solution: organic base: water provided in this disclosure. The titanium-silicon molecular sieves obtained in Example 2 have higher 1-hexene conversion, epoxide selectivity and hydrogen peroxide utilization in the epoxidation of 1-hexene to epoxide reaction, and the titanium-silicon molecular sieves have higher catalytic stability after ten repeated reactions.

[0160] Comparing Example 1 with Examples 2 and 4, it can be seen that Example 1 prepared titanium-silicon molecular sieves according to the preferred molar ratio of titanium source: crown ether compound: solvent and silicon source: titanium-containing precursor solution: organic base: water. The titanium-silicon molecular sieves prepared in Example 1 have better catalytic effect in the epoxidation of 1-hexene to epoxide, and can obtain higher 1-hexene conversion, epoxide selectivity and hydrogen peroxide utilization rate. Moreover, the catalytic stability of the titanium-silicon molecular sieves is better after repeating the reaction ten times.

[0161] Comparing Example 1 with Example 14, Example 1 synthesized titanium-silicon molecular sieves according to the preferred preparation process conditions provided in this disclosure. The titanium-silicon molecular sieves obtained in Example 1 had higher 1-hexene conversion, hexane selectivity and hydrogen peroxide utilization in the first and tenth reactions, and higher catalytic stability after repeating ten reactions.

[0162] Test Examples 2-4

[0163] These Test Examples 2-4 illustrate the application effect of the titanium-silicon molecular sieves provided in this disclosure in the epoxidation of 1-hexene to epoxide under different reaction conditions. A similar reaction method to Test Example 1 is used, except that the reaction conditions are adjusted (all reactions are performed only once):

[0164] Test Example 2: Titanium silicate molecular sieve, 1-hexene, and 30% (mass fraction) hydrogen peroxide solution were added to a round-bottom flask. The mass ratio of titanium silicate molecular sieve to hydrogen peroxide (pure substance) was 8:1, and the molar ratio of hydrogen peroxide (pure substance) to 1-hexene was 2:1. Methanol was used as the solvent, and the molar ratio of methanol to 1-hexene was 10:1. The mixture was reacted in a water bath at 40°C for 8 hours. After the reaction was completed, samples were taken for analysis.

[0165] Test Example 3: Titanium silicate molecular sieve, 1-hexene, and 30% (mass fraction) hydrogen peroxide solution were added to a round-bottom flask. The mass ratio of titanium silicate molecular sieve to hydrogen peroxide (pure substance) was 0.3:1, and the molar ratio of hydrogen peroxide (pure substance) to 1-hexene was 1.5:1. Methanol was used as the solvent, and the molar ratio of methanol to 1-hexene was 20:1. The mixture was reacted at 60°C and atmospheric pressure for 1 hour. The rest of the process was the same as in Test Example 1. After the reaction was completed, samples were taken for analysis.

[0166] Test Example 4: Titanium silicate molecular sieve, 1-hexene, and 30% (mass fraction) hydrogen peroxide solution were added to a round-bottom flask. The mass ratio of titanium silicate molecular sieve to hydrogen peroxide (pure substance) was 0.01:1, and the molar ratio of hydrogen peroxide (pure substance) to 1-hexene was 2.5:1. Methanol was used as the solvent, and the molar ratio of methanol to 1-hexene was 5:1. The mixture was reacted at 90°C and atmospheric pressure for 12 hours. The rest of the process was the same as in Test Example 1. After the reaction was completed, samples were taken for analysis.

[0167] The catalysts used in the reaction and the corresponding test results are listed in Table 3 below.

[0168] Table 3

[0169]

[0170] According to the data in Table 3 above:

[0171] Compared with Test Example 4, Test Examples 2-3 were carried out in accordance with the range of raw material addition ratios or reaction conditions provided in this disclosure. Under the same conditions of using titanium-silicon molecular sieves, Test Examples 2-3 showed higher 1-hexene conversion, 1-hexene selectivity, and hydrogen peroxide utilization rate in the reaction of 1-hexene epoxidation to hexane.

[0172] Compared with Test Example 1 (data for Test Example 1 is from Table 2), Test Examples 2-3, under the same conditions of using titanium silicate molecular sieves, showed that Test Example 1, with optimized raw material addition ratio or reaction conditions, achieved higher 1-hexene conversion, hexane selectivity, and hydrogen peroxide utilization rate.

[0173] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0174] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0175] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing titanium-silicon molecular sieves, characterized in that, Includes the following steps: (1) Mix the titanium source, crown ether compound and optional solvent to obtain a titanium-containing precursor solution; (2) The titanium-containing precursor solution, silicon source and template agent are contacted and hydrolyzed to obtain a hydrolyzed mixture; (3) The hydrolyzed mixture is subjected to hydrothermal crystallization, drying and calcination.

2. The method according to claim 1, characterized in that, In step (1), the crown ether compound is selected from one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, dicyclohexano-18-crown ether-6 and dibenzo-18-crown ether-6; preferably selected from one or more of 12-crown ether-4, 15-crown ether-5 and 18-crown ether-6.

3. The method according to claim 1, characterized in that, The titanium source is selected from one or more of inorganic titanium sources and organic titanium sources. Optionally, the inorganic titanium source is selected from one or more of titanium tetrafluoride, titanium tetrachloride, titanium tetrabromide, titanium trichloride, and titanium sulfate; the organic titanium source is selected from one or more of tetramethyl titanate, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate. Preferably, the titanium source is an inorganic titanium source, more preferably titanium sulfate.

4. The method according to claim 1, characterized in that, The silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol; preferably, it is selected from at least one of silicone grease, solid silica gel, and fumed silica. Optionally, the silicone grease is selected from one or more compounds with the structure shown in formula (1): R a 、R b 、R c and R d Each is independently selected from alkyl groups having 1 to 4 carbon atoms, wherein the alkyl group is branched or straight-chain alkyl; preferably, the R a 、R b 、R c and R d Each of the following is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; more preferably, the organosilicon grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silyl ester; even more preferably, it is selected from one or more of tetramethyl silicate, tetraethyl silicate, and dimethyl diethyl silyl ester.

5. The method according to claim 1, characterized in that, The template agent is selected from one or more of organic quaternary ammonium salts and organic bases; Optionally, the organic quaternary ammonium salt is selected from one or more of tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium bromide; Optionally, the organic base is selected from one or more of organic quaternary ammonium bases and organic amines; preferably, the organic quaternary ammonium base is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the organic amine is selected from one or more of ethylamine, n-butylamine, butanediamine, hexamethylenediamine, monoethanolamine, diethanolamine, triethanolamine, theanine, toluidine, and p-phenylenediamine. Optionally, the solvent is selected from one or more of polar protic solvents and aprotic solvents; preferably, the polar protic solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol; the aprotic solvent is selected from one or more of dichloromethane, dichloroethane, allyl chloride, methylchloropropene, 1-chlorobutane, acetonitrile, N,N-dimethylformamide, toluene, acetone, propylene glycol methyl ether and dimethyl sulfoxide; preferably, the solvent is selected from one or more of polar protic solvents, more preferably n-propanol.

6. The method according to claim 1, characterized in that, In step (1), the molar ratio of titanium source: crown ether compound: solvent is 1:(0.5-5):(0-100), preferably 1:(1-4):(5-50).

7. The method according to claim 1, characterized in that, In step (2), the molar ratio of silicon source: titanium-containing precursor solution: organic base: water is (0.001~0.5):(0.001~0.8):(5~100), preferably 1:(0.01~0.4):(0.01~0.5):(5~50), wherein the silicon source is calculated as SiO2 and the titanium-containing precursor solution is calculated as TiO2.

8. The method according to claim 1, characterized in that, In step (2), the conditions for the hydrolysis treatment include: first heating to 60-100°C at a first heating rate, and then hydrolyzing at a constant temperature for 0.5-10 hours; preferably, first heating to 70-90°C at a first heating rate, and then hydrolyzing at a constant temperature for 1-5 hours. Optionally, the first heating rate is 5 to 30°C / h, preferably 10 to 20°C / h.

9. The method according to claim 1, characterized in that, In step (3), the conditions for the hydrothermal crystallization treatment include: First, the temperature is increased to 80–200°C at a second heating rate, and then crystallized at a constant temperature for 2–360 hours; preferably, the temperature is increased to 120–180°C at a second heating rate, and then crystallized at a constant temperature for 10–240 hours. Optionally, the second heating rate is 0.3 to 1.7 °C / min, preferably 0.5 to 1.4 °C / min.

10. The method according to claim 1, characterized in that, In step (3), the drying conditions include: a drying temperature of 80-120°C and a drying time of 2-30 hours; preferably, the drying temperature is 90-110°C and the drying time is 5-10 hours. Optionally, the calcination conditions include: a calcination temperature of 450–650°C and a calcination time of 1–10 h; preferably, the calcination temperature is 480–620°C and the calcination time is 2–6 h.

11. The titanium-silicon molecular sieve prepared by the method according to any one of claims 1 to 10.

12. The application of the titanium-silicon molecular sieve as described in claim 11 in organic catalytic reactions.

13. The application according to claim 12, characterized in that, The organic catalytic reaction includes the epoxidation of 1-hexene to produce hexane oxide; Optionally, the epoxidation reaction of 1-hexene to produce hexane includes: reacting the titanium-silicon molecular sieve with 1-hexene and hydrogen peroxide. Preferably, the conditions for the epoxidation reaction of 1-hexene to hexane oxide include: a mass ratio of titanium silicate molecular sieve to hydrogen peroxide of 0.01 to 10:1, preferably 0.02 to 2:1; and a molar ratio of hydrogen peroxide to 1-hexene of 0.5 to 2:1, preferably 1 to 1.2:

1. Optionally, the reaction temperature is 30–60°C and the reaction time is 1–10 h; preferably, the reaction temperature is 35–50°C and the reaction time is 2–6 h.

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