Titanium silicalite molecular sieve, preparation method thereof and propylene epoxidation reaction method
By employing a step-by-step molding and steam aging method, combined with silica binder, the mechanical strength and catalytic activity of titanium silica molecular sieves are enhanced, solving the problems of low catalyst strength and activity loss in existing technologies, and achieving a highly efficient propylene epoxidation reaction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-10-22
- Publication Date
- 2026-04-24
AI Technical Summary
Existing titanium-silicon molecular sieve catalysts suffer from problems such as severe loss of catalytic activity, complex molding process, and low mechanical strength, making it difficult to meet the needs of industrial applications.
A step-by-step molding method is adopted, which combines pre-forming and molding treatment with water vapor aging. Silica rich in silanols is used as a binder to form an interfacial adhesive structure based on covalent bonds, thereby improving mechanical strength and uniformity.
The prepared titanium-silicon molecular sieve has high mechanical strength and suitable pore structure, which improves the efficiency of mass transfer process, catalytic activity and target product selectivity. It is suitable for propylene epoxidation reaction and has good industrialization prospects.
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Abstract
Description
Technical Field
[0001] This disclosure relates to the field of titanium-silicon molecular sieve preparation, specifically to a titanium-silicon molecular sieve, a method for its preparation, and a method for propylene epoxidation reaction. Background Technology
[0002] Titanium silicate molecular sieves are novel catalytic oxidation materials with multi-level and regular channels, ultra-high specific surface area, and high catalytic activity and selectivity. They are widely used as heterogeneous solid catalysts in catalytic oxidation reactions such as phenyl amination, cyclohexane oxidation, propane epoxidation, and phenol hydroxylation, which are beneficial for improving the feed conversion rate and target product selectivity of these reactions. The original crystals of titanium silicate molecular sieves are relatively small, typically ranging from 100 to 500 nm in diameter. To facilitate catalyst separation and recovery during industrial use, these small crystals are usually shaped. Shaping also improves the mechanical strength of the catalyst, reduces pressure drop caused by fluid flow, prevents channeling, and achieves uniform fluid flow, thereby maximizing catalytic efficiency.
[0003] To fully utilize the catalytic efficiency of molecular sieves and ensure their high catalytic performance and stability, the molded molecular sieve catalyst particles are typically spherical and possess characteristics such as high specific surface area, uniform and controllable shape, narrow particle size distribution, and high mechanical strength. However, current methods for preparing titanium-silicon molecular sieve catalysts generally suffer from drawbacks such as severe loss of catalytic activity, complex molding processes, and low catalyst mechanical strength. Summary of the Invention
[0004] The purpose of this disclosure is to provide a titanium-silicon molecular sieve, a method for its preparation, and a method for propylene epoxidation reaction.
[0005] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps: S1. Mix the titanium-silicon molecular sieve raw powder, the first binder, water and optional first additive and pre-form them to obtain titanium-silicon molecular sieve microspheres; S2. The titanium-silicon molecular sieve microspheres, the second primary binder, water, optional secondary binder and optional second auxiliary agent are mixed and molded to obtain the titanium-silicon molecular sieve precursor; S3. The titanium-silicon molecular sieve precursor is aged with water vapor to obtain a titanium-silicon molecular sieve pre-product. S4. The titanium-silicon molecular sieve pre-product is subjected to calcination treatment. The second primary binder includes silica.
[0006] Optionally, the first adhesive includes one or more of silicone adhesives, preferably including silica sol and / or water glass; The second adhesive includes one or more of silicone adhesives, preferably including silica sol and / or water glass; The first adjuvant and the second adjuvant respectively include one or more of Span-20, Span-40, Span-60, Span-65, Span-80, Span-85, Tween-20, Tween-21, Tween-40, Tween-60, Tween-61, Tween-80, Tween-81 and Tween-85.
[0007] Optionally, step S1 includes: mixing the titanium-silicon molecular sieve raw powder with a first solution containing the first binder and optionally the first auxiliary agent and performing the pre-forming to obtain the titanium-silicon molecular sieve microspheres; In the first solution, the content of the first binder is 0.1~20% by weight, and the content of the first additive is 0~8% by weight. The weight ratio of the first solution to the titanium-silicon molecular sieve raw powder is 0.1~15.
[0008] Optionally, step S2 includes: mixing the titanium-silicon molecular sieve microspheres with a second solution containing the second primary binder, optionally the second binder, and optionally the second auxiliary agent, and performing the molding process to obtain the titanium-silicon molecular sieve precursor; In the second solution, the content of the second primary binder is 0.1-10% by weight, the content of the secondary binder is 0-10% by weight, and the content of the second auxiliary agent is 0-8% by weight. The weight ratio of the second solution to the titanium-silicon molecular sieve microspheres is 0.1 to 0.7.
[0009] Optionally, the average particle size of the titanium-silicon molecular sieve microspheres is 20~80μm.
[0010] Optionally, the preforming and the forming process can be one or more of the following methods: sugar coating machine forming, granulation machine forming, and spray drying forming.
[0011] Optionally, the preforming method is spray drying molding, with an outlet air temperature of 70~400℃.
[0012] Optionally, in step S3, the conditions for water vapor aging include: a temperature of 60~500℃, a time of 0.5~144h, a pressure of 0~3MPa, and a water vapor humidity of 50~100%.
[0013] Optionally, in step S4, the calcination conditions include: a temperature of 300~600℃ and a time of 2~24h; The roasting atmosphere includes an air atmosphere or a mixed atmosphere containing oxygen, wherein the oxygen content in the mixed atmosphere is 1 to 50% by volume.
[0014] The second aspect of this disclosure provides a titanium-silicon molecular sieve prepared using the method described in the first aspect of this disclosure.
[0015] The third aspect of this disclosure provides a method for propylene epoxidation, the method comprising: contacting propylene, hydrogen peroxide, and the titanium-silicon molecular sieve described in the second aspect of this disclosure to carry out the epoxidation reaction.
[0016] The method disclosed herein, employing the above technical solution, prepares titanium-silicon molecular sieves through stepwise molding and subsequent steam aging. The method first pre-forms molecular sieve microspheres, then adds silica-rich silane black as a binder during the molding process to enhance the interfacial bonding effect during molecular sieve microsphere molding, improving uniformity and mechanical properties. After molding, steam aging further enhances the interfacial bonding effect and improves the mechanical strength of the finished molecular sieve. The prepared titanium-silicon molecular sieve possesses an intracrystalline porous structure, improving mass transfer, and exhibits high mechanical strength and a suitable pore size range. This method features simple process steps, a short flow rate, mild reaction conditions, and no organic solvents, effectively improving the production efficiency of titanium-silicon molecular sieves. Furthermore, it avoids the discharge of acidic or alkaline wastewater by eliminating the use of acids and alkalis. The prepared titanium-silicon molecular sieve exhibits good catalytic activity in propylene epoxidation reactions, achieving high feed conversion rates and target product selectivity, demonstrating promising industrialization prospects.
[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation
[0018] 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.
[0019] The first aspect of this disclosure provides a method for preparing titanium-silicon molecular sieves, the method comprising the following steps: S1. Mix the titanium-silicon molecular sieve raw powder, the first binder, water and optional first additive and pre-form them to obtain titanium-silicon molecular sieve microspheres; S2. The titanium-silicon molecular sieve microspheres, the second primary binder, water, optional secondary binder and optional second auxiliary agent are mixed and molded to obtain the titanium-silicon molecular sieve precursor; S3. The titanium-silicon molecular sieve precursor is aged with water vapor to obtain a titanium-silicon molecular sieve pre-product. S4. The titanium-silicon molecular sieve pre-product is subjected to calcination treatment. The second primary binder includes silica.
[0020] This disclosure discloses a stepwise molding and steam aging method for preparing titanium-silicon molecular sieves. First, molecular sieve microspheres are pre-formed. Then, silica rich in silanol groups is added as a binder during the molding process to enhance the interfacial bonding effect during the molecular sieve microsphere formation, improving uniformity and mechanical properties. After molding, the bonding interface of the titanium-silicon molecular sieve is treated with steam to form a covalent bond-based adhesive structure at the interface, significantly improving the mechanical strength of the titanium-silicon molecular sieve. The method disclosed herein is simple, has a short process flow, mild reaction conditions, and does not use organic solvents, effectively improving the production efficiency of titanium-silicon molecular sieves. The prepared titanium-silicon molecular sieve has an intracrystalline porous structure, which improves the mass transfer process, and also exhibits high mechanical strength.
[0021] According to one embodiment of this disclosure, the preparation method of titanium-silicon molecular sieve raw powder is conventional in the art, for example, it is synthesized by hydrothermal method using titanium ester, silicon ester and organic template agent.
[0022] According to one embodiment of this disclosure, the first binder includes one or more of the following silicone binders, preferably including silica sol and / or water glass. When the first binder includes silica sol and water glass, the ratio of the two is not limited. The second binder includes one or more of the following silicone binders, preferably including silica sol and / or water glass. When the second binder includes silica sol and water glass, the ratio of the two is not limited. The first additive and the second additive respectively include one or more of Span-20, Span-40, Span-60, Span-65, Span-80, Span-85, Tween-20, Tween-21, Tween-40, Tween-60, Tween-61, Tween-80, Tween-81, and Tween-85.
[0023] According to one embodiment of this disclosure, step S1 includes: mixing the titanium-silicon molecular sieve raw powder with a first solution containing the first binder and an optional first additive, and performing the pre-forming process to obtain the titanium-silicon molecular sieve microspheres; in the first solution, the content of the first binder is 0.1~20% by weight, preferably 0.1~15% by weight, including but not limited to 0.1% by weight, 3% by weight, 4% by weight, 5% by weight, 10% by weight, 13% by weight, 15% by weight, and 20% by weight, and the content of the first binder is based on the weight of SiO2; The content of the first additive is 0-8% by weight, preferably 0-4% by weight, including but not limited to 0% by weight, 1% by weight, 2% by weight, 2.5% by weight, 3% by weight, 4% by weight, 5% by weight, and 8% by weight; the weight ratio of the first solution to the titanium-silicon molecular sieve raw powder is 0.1-15, preferably 0.2-10, including but not limited to 0.1, 0.2, 0.5, 0.6, 0.8, 1, 3, 5, 5.5, 8, 10, and 15; the mixing can be carried out under stirring conditions, and the method for preparing the first solution is conventional in the art. Mixing under solution conditions can promote the contact between the titanium-silicon molecular sieve raw powder and the first binder and optional first additive, improve the mixing uniformity, and facilitate the formation of titanium-silicon molecular sieve microspheres.
[0024] According to one embodiment of this disclosure, step S2 includes: mixing the titanium-silicon molecular sieve microspheres with a second solution containing the second primary binder, an optional second binder, and an optional second auxiliary agent, and performing the molding process to obtain the titanium-silicon molecular sieve precursor; in the second solution, the content of the second primary binder is 0.1-10% by weight, preferably 0.5-5% by weight, including but not limited to 0.1% by weight, 3% by weight, 4% by weight, 5% by weight, and 10% by weight; the content of the second binder is 0-10% by weight, preferably 0.5-6% by weight, including but not limited to 0% by weight, 3% by weight, 4% by weight, 5% by weight, and 10% by weight, the content of the second primary binder and the second binder being based on the weight of SiO2; the content of the second auxiliary agent is 0-8% by weight, preferably 0-4% by weight; the weight ratio of the second solution to the titanium-silicon molecular sieve microspheres is 0.1-0.7, preferably 0.2-0.6, including but not limited to 0.1, 0.2, 0.5, 0.6, and 0.7; the mixing can be carried out under stirring conditions, and the method for preparing the second solution is conventional in the art. Mixing under solution conditions can promote the contact between the titanium-silicon molecular sieve microspheres and the second primary binder, the secondary binder, and the optional second auxiliary agent, thereby improving the mixing uniformity and the degree of contact. This is beneficial for leveraging the binding effect of silica and further enhancing the mechanical strength of the titanium-silicon molecular sieve.
[0025] To control the size of molecular sieve particles and improve their uniformity and strength, according to one embodiment of this disclosure, the average particle size of the titanium-silicon molecular sieve microspheres is 20~80μm.
[0026] In order to improve the regularity of the shaped catalyst, according to one embodiment of the present disclosure, a first auxiliary agent is added in step S1 and a second auxiliary agent is added in step S2.
[0027] According to one embodiment of this disclosure, the preforming and the forming process respectively include one or more of sugar coating machine forming, granulation machine forming and spray drying forming, and the specific methods are conventional in the art.
[0028] According to one embodiment of this disclosure, the preforming method is spray drying molding, and the outlet air temperature is 70~400℃.
[0029] According to one embodiment of this disclosure, the method further includes: calcining the pre-formed solid product obtained in step S1 at 200~600℃ for 2~6h to obtain titanium silicon molecular sieve microspheres; the calcination atmosphere includes an air atmosphere or a mixed atmosphere containing oxygen, wherein the oxygen content in the mixed atmosphere is 1~50% by volume, and the mixed atmosphere can be, for example, a mixed atmosphere of oxygen and nitrogen and / or argon, and the calcination treatment method is conventional in the art; and then the obtained calcined product is subjected to step S2.
[0030] According to one embodiment of this disclosure, in step S3, the conditions for water vapor aging include: a temperature of 60~500℃, preferably 60~200℃; a time of 0.5~144h, preferably 0.5~20h; a pressure of 0~3MPa, preferably 0~1MPa; and a water vapor humidity of 50~100%, preferably 50~80%, where "water vapor humidity" refers to relative humidity, i.e., the ratio of the actual pressure of the water vapor to the saturated vapor pressure of water at the same temperature. The above embodiment is conducive to the formation of silicon-oxygen bonds, optimizes the physicochemical environment of the interface, forms a covalent bond-based adhesive structure at the interface, and achieves a significant improvement in the mechanical strength of the titanium-silicon molecular sieve.
[0031] According to one embodiment of this disclosure, in step S4, the calcination conditions include: a temperature of 300~600℃, a time of 2~24h, and a calcination atmosphere including an air atmosphere or a mixed atmosphere containing oxygen, wherein the oxygen content in the mixed atmosphere is 1~50% by volume, and the mixed atmosphere can be, for example, a mixed atmosphere of oxygen and nitrogen and / or argon. The calcination method is conventional in the art. Using the above calcination conditions can remove residual organic matter in the catalyst and improve its mechanical strength and structural stability.
[0032] According to one embodiment of this disclosure, the method further includes: sieving the product obtained in step S4 to obtain a titanium-silicon molecular sieve with a particle size that meets the requirements, for example, a particle size of 1.0~1.4 mm.
[0033] The second aspect of this disclosure provides a titanium-silicon molecular sieve prepared using the method described in the first aspect of this disclosure.
[0034] According to one embodiment of this disclosure, the titanium-silicon molecular sieve has an average particle size of 1.0~1.4 mm and a specific surface area of 360~460 m². 2 / g, with a strength of 8~35N / particle; the titanium-silicon molecular sieve disclosed in this invention has the advantages of uniform size and shape and high mechanical strength, making it suitable for industrial production. When used in the propylene epoxidation reaction, it can achieve good catalytic performance.
[0035] According to one embodiment of this disclosure, the titanium-silicon molecular sieve has a spherical or near-spherical shape.
[0036] The third aspect of this disclosure provides a method for propylene epoxidation, the method comprising: contacting propylene, hydrogen peroxide, and the titanium-silicon molecular sieve described in the second aspect of this disclosure to carry out the epoxidation reaction.
[0037] According to one embodiment of this disclosure, the epoxidation reaction is carried out in a fixed-bed reactor, such as a tubular fixed-bed reactor, under the following conditions: a temperature of 20-60°C, a pressure of 0-3 MPa, a feed molar ratio of propylene to hydrogen peroxide of (0.5-3):1, and a feed mass hourly space velocity (WHSV) of 0.01-10 h⁻¹ for the hydrogen peroxide. -1 The epoxidation reaction is carried out in the presence of a solvent, including methanol, and the molar ratio of the solvent to the propylene feed is (2~20):1.
[0038] The present invention will be described in detail below through embodiments, but is not limited to the following embodiments.
[0039] Unless otherwise specified, the instruments, reagents, and materials used in the following examples are all conventional instruments, reagents, and materials that are already available in the prior art and can be purchased through legitimate commercial channels.
[0040] Method for testing average particle size: Particle size analyzer.
[0041] Test method for particle size range: laser particle size analyzer.
[0042] Test methods for pore volume and specific surface area: N2 adsorption-desorption analysis.
[0043] Strength testing method: particle strength tester.
[0044] The preparation method of the titanium-silicon molecular sieve raw powder used in the examples and comparative examples is hydrothermal synthesis. The titanium-silicon molecular sieve raw powder used in the examples and comparative examples is the same.
[0045] Example 1 Titanium-silicon molecular sieve A1 was prepared using the following steps: (1) Dissolve 3 kg of silica sol and 2 kg of Tween-20 in 50 L of water at 40 ℃ and stir evenly to prepare the first solution. Add 10 kg of titanium silicon molecular sieve raw material powder and stir to mix. Perform pulping operation, spray dry to form, and obtain titanium silicon molecular sieve microspheres with an average particle size of 63 μm at an air outlet temperature of 120 ℃. In the first solution, the content of silica sol, calculated as SiO2, is 2% by weight, the content of Tween-20 is 3.6% by weight, and the weight ratio of the first solution to the titanium-silicon molecular sieve raw powder is 5.5. (2) The titanium silicon molecular sieve microspheres prepared in step (1) are added to a second solution containing 0.3 kg of silica and 0.05 kg of Tween-80, stirred and mixed, and the resulting mixture is molded in a sugar coating machine to obtain a spherical titanium silicon molecular sieve precursor. In the second solution, the content of silica by weight is 6% by weight of SiO2, the content of Tween-80 is 1% by weight, and the weight ratio of the second solution to the titanium-silicon molecular sieve microspheres is 0.5. (3) The titanium-silicon molecular sieve precursor prepared in step (2) is subjected to water vapor aging at a pressure of 0.05 MPa, a temperature of 80 °C, a water vapor humidity of 60%, and a time of 2 h to obtain the titanium-silicon molecular sieve pre-product. (4) The titanium silicon molecular sieve preproduct prepared in step (3) is calcined at 500°C for 4 h. The calcination atmosphere is a mixture of oxygen and nitrogen with an oxygen content of 20% by volume. The calcined titanium silicon molecular sieve is sieved to obtain spherical titanium silicon molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicon molecular sieve A1. The parameters are listed in Table 1.
[0046] Example 2 Titanium silicate molecular sieve A2 was prepared using the method of Example 1. The difference is that in step (2), the amount of silica used was 0.2 kg, the amount of silica sol was 0.1 kg, the content of silica in the second solution was 4% by weight based on SiO2, the content of silica sol based on SiO2 was 0.8% by weight, the content of Tween-80 was 1% by weight, and the weight ratio of the second solution to the titanium silicate molecular sieve microspheres was 0.5. The titanium silicate molecular sieve obtained by calcination was sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicate molecular sieve A2. The parameters are listed in Table 1.
[0047] Example 3 Titanium silicate molecular sieve A3 was prepared using the method of Example 1. The difference is that in step (2), the amount of silica used was 0.1 kg, the amount of silica sol was 0.2 kg, the content of silica in the second solution was 2% by weight based on the weight of SiO2, the content of silica sol based on the weight of SiO2 was 1.6% by weight, the content of Tween-80 was 1% by weight, and the weight ratio of the second solution to the titanium silicate molecular sieve microspheres was 0.5. The titanium silicate molecular sieve obtained by calcination was sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicate molecular sieve A3. The parameters are listed in Table 1.
[0048] Example 4 Titanium silicate molecular sieve A4 was prepared using the method of Example 1. The difference is that in step (2), the amount of silica used is 0.2 kg, the amount of water glass used is 0.1 kg, the content of silica in the second solution is 4% by weight based on SiO2, the content of water glass based on SiO2 is 0.8% by weight, the content of Tween-80 is 1% by weight, and the weight ratio of the second solution to the titanium silicate molecular sieve microspheres is 0.5. The titanium silicate molecular sieve obtained by calcination is sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicate molecular sieve A4. The parameters are listed in Table 1.
[0049] Example 5 Titanium silicate molecular sieve A5 was prepared using the method of Example 1. The difference is that in step (2), the amount of silica used is 0.5 kg, the content of silica in the second solution is 10% by weight based on the weight of SiO2, the content of Tween-80 is 1% by weight, and the weight ratio of the second solution to the titanium silicate molecular sieve microspheres is 0.5. The titanium silicate molecular sieve obtained by calcination is sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicate molecular sieve A5. The parameters are listed in Table 1.
[0050] Example 6 Titanium silicate molecular sieve A6 was prepared using the method of Example 1. The difference is that in step (2), the amount of silica used is 0.2 kg, the content of silica in the second solution is 4 wt% based on the weight of SiO2, the content of Tween-80 is 1 wt%, and the weight ratio of the second solution to the titanium silicate molecular sieve microspheres is 0.5. The titanium silicate molecular sieve obtained by calcination is sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.0~1.4 mm, which is titanium silicate molecular sieve A6. The parameters are listed in Table 1.
[0051] Example 7 Titanium silicate molecular sieve A6 was prepared using the method of Example 1. The difference is that in step (1), the content of silica sol (calculated as SiO2) in the first solution is 3% by weight, the content of Tween-20 is 3% by weight, and the weight ratio of the first solution to the titanium silicate molecular sieve powder is 4. The titanium silicate molecular sieve obtained by calcination is sieved to obtain spherical titanium silicate molecular sieves with a particle size of 1.0~1.4mm, which is titanium silicate molecular sieve A7. The parameters are listed in Table 1.
[0052] Example 8 Titanium silicate molecular sieve A8 was prepared using the method of Example 1, except that in step (3), the aging time was 6 hours, the temperature was 60°C, the pressure was 0.1 MPa, and the water vapor humidity was 50%. In step (4), the calcination time is 6 hours and the temperature is 600℃. The calcined titanium silicon molecular sieve is sieved to obtain spherical titanium silicon molecular sieves with a particle size of 1.1~1.3mm, which is titanium silicon molecular sieve A8. The parameters are listed in Table 1.
[0053] Comparative Example 1 (1) Dissolve 0.4 kg of silica sol and 0.2 kg of Tween-20 in 5 L of water at 40 °C and stir evenly to prepare the first solution. Add 10 kg of titanium silicon molecular sieve raw material powder and stir to mix. Perform pulping operation, spray dry to form, and obtain titanium silicon molecular sieve microspheres at 150 °C with an average particle size of 39 μm. (2) The titanium-silicon molecular sieve microspheres prepared in step (1) are added to a second solution containing 0.05 kg Tween-80, stirred and mixed, and the resulting mixture is molded in a sugar coating machine to obtain spherical titanium-silicon molecular sieve precursors; (3) The titanium-silicon molecular sieve precursor prepared in step (2) is aged with water vapor at a pressure of 0.05 MPa, a temperature of 100 °C, a water vapor humidity of 50%, and a time of 1 h to obtain the titanium-silicon molecular sieve pre-product. (4) The titanium silicon molecular sieve preproduct prepared in step (3) is calcined at 450°C for 4 hours. The calcination atmosphere is a mixture of oxygen and nitrogen with an oxygen content of 20% by volume. The calcined titanium silicon molecular sieve is sieved to obtain spherical titanium silicon molecular sieves with a particle size of 1.1~1.3 mm, which is titanium silicon molecular sieve D1. The parameters are listed in Table 1.
[0054] Comparative Example 2 (1) 10 kg of titanium-silicon molecular sieve raw material powder and a solution containing 1.2 kg of silica sol and 0.1 kg of Tween-80 were molded in a sugar coating machine to obtain spherical titanium-silicon molecular sieve precursor; (2) The titanium-silicon molecular sieve precursor prepared in step (1) is aged with water vapor at a pressure of 0.1 MPa, a temperature of 100 °C, a water vapor humidity of 20%, and a time of 1 h to obtain the titanium-silicon molecular sieve pre-product. (3) The titanium silicon molecular sieve preproduct prepared in step (2) is calcined at 450°C for 4 hours. The calcination atmosphere is a mixture of oxygen and nitrogen with an oxygen content of 20% by volume. The calcined titanium silicon molecular sieve is sieved to obtain spherical titanium silicon molecular sieves with a particle size of 1.0~1.4 mm, which is titanium silicon molecular sieve D2. The parameters are listed in Table 1.
[0055] Test case The titanium-silicon molecular sieve catalysts A1-A8 and D1-D2 prepared in the examples and comparative examples were fixed in a reactor. Propylene and hydrogen peroxide underwent an epoxidation reaction in a tubular fixed-bed reactor. The catalyst loading was 10 mL, and the reactor pressure was 0.4 MPa, maintained by nitrogen. Propylene, aqueous hydrogen peroxide solution, and methanol were fed into the reactor by three metering pumps. The epoxidation reaction of propylene and hydrogen peroxide was carried out at a reaction tube temperature of 45 °C, a reaction pressure of 0.4 MPa, a propylene to hydrogen peroxide feed molar ratio of 2:1, a methanol to propylene feed molar ratio of 5:1, and a hydrogen peroxide feed mass hourly space velocity of 0.14 h⁻¹. -1 The reaction was carried out under the specified conditions, and the results are listed in Table 1.
[0056] The H2O2 content in the reactor feed and discharge was determined by indirect iodometric titration, and the content of propylene oxide and byproducts in the reactor discharge was determined by gas chromatography.
[0057] The conversion rate of H2O2 is calculated according to the following formula:
[0058] The selectivity of propylene oxide is calculated using the following formula: .
[0059] Table 1
[0060] Based on the above data, it can be seen that the titanium-silicon molecular sieve prepared by the method disclosed herein has less specific surface area loss, high particle strength, and suitable pore volume. When applied to the propylene epoxidation reaction, it can achieve high propylene oxide selectivity and effectively reduce the production cost of propylene oxide.
[0061] 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.
[0062] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.
[0063] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.
Claims
1. A method for preparing titanium-silicon molecular sieves, characterized in that, The method includes the following steps: S1. Mix the titanium-silicon molecular sieve raw powder, the first binder, water and optional first additive and pre-form them to obtain titanium-silicon molecular sieve microspheres; S2. The titanium-silicon molecular sieve microspheres, the second primary binder, water, optional secondary binder and optional second auxiliary agent are mixed and molded to obtain the titanium-silicon molecular sieve precursor; S3. The titanium-silicon molecular sieve precursor is aged with water vapor to obtain a titanium-silicon molecular sieve pre-product. S4. The titanium-silicon molecular sieve pre-product is subjected to calcination treatment. The second primary binder includes silica.
2. The method according to claim 1, wherein, The first adhesive includes one or more of silicone adhesives, preferably including silica sol and / or water glass; The second adhesive includes one or more of silicone adhesives, preferably including silica sol and / or water glass; The first adjuvant and the second adjuvant respectively include one or more of Span-20, Span-40, Span-60, Span-65, Span-80, Span-85, Tween-20, Tween-21, Tween-40, Tween-60, Tween-61, Tween-80, Tween-81 and Tween-85.
3. The method according to claim 1, wherein, Step S1 includes: mixing the titanium-silicon molecular sieve raw powder with a first solution containing the first binder and optionally the first auxiliary agent and performing the pre-forming to obtain the titanium-silicon molecular sieve microspheres; In the first solution, the content of the first binder is 0.1~20% by weight, and the content of the first additive is 0~8% by weight. The weight ratio of the first solution to the titanium-silicon molecular sieve raw powder is 0.1~15.
4. The method according to claim 1, wherein, Step S2 includes: mixing the titanium-silicon molecular sieve microspheres with a second solution containing the second primary binder, an optional second binder, and an optional second auxiliary agent, and performing the molding process to obtain the titanium-silicon molecular sieve precursor; In the second solution, the content of the second primary binder is 0.1-10% by weight, the content of the secondary binder is 0-10% by weight, and the content of the second auxiliary agent is 0-8% by weight. The weight ratio of the second solution to the titanium-silicon molecular sieve microspheres is 0.1 to 0.
7.
5. The method according to claim 1, wherein, The average particle size of the titanium-silicon molecular sieve microspheres is 20~80μm.
6. The method according to claim 1, wherein, The preforming and the forming process respectively include one or more of sugar coating machine forming, granulator forming and spray drying forming.
7. The method according to claim 1, wherein, The preforming method is spray drying molding, and the outlet air temperature is 70~400℃.
8. The method according to claim 1, wherein, In step S3, the conditions for water vapor aging include: temperature of 60~500℃, time of 0.5~144h, pressure of 0~3MPa, and water vapor humidity of 50~100%.
9. The method according to claim 1, wherein, In step S4, the calcination conditions include: a temperature of 300~600℃ and a time of 2~24h; The roasting atmosphere includes an air atmosphere or a mixed atmosphere containing oxygen, wherein the oxygen content in the mixed atmosphere is 1 to 50% by volume.
10. Titanium silicate molecular sieve prepared by the method according to any one of claims 1 to 9.
11. The titanium-silicon molecular sieve according to claim 10, wherein, The titanium-silicon molecular sieve has a particle size of 1.0~1.4mm and a specific surface area of 360~460m². 2 / g, strength is 8~35N / piece.
12. A method for propylene epoxidation, characterized in that, The method includes contacting propylene, hydrogen peroxide, and the titanium-silicon molecular sieve of claim 10 or 11 to carry out the epoxidation reaction.