A tungsten-containing TS-1 molecular sieve and its preparation method and application

Abstract

The present invention discloses a tungsten-containing TS-1 molecular sieve and a preparation method and application thereof. The preparation method comprises the following steps: step 1, mixing a silicon source, an alkali source, a tungsten source and water, adding cardanol polyoxyethylene ether sulfonate, heating, and forming a mixed gel B; step 2, adding a seed crystal to the mixed gel B, stirring, and obtaining a mixture C; step 3, crystallizing the mixture C to obtain a tungsten-containing TS-1 molecular sieve. The tungsten-containing TS-1 molecular sieve of the present invention is used for selective oxidation of olefins, and has a high conversion rate and a high selectivity for target products.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieves, and in particular to a tungsten-titanium-silicon molecular sieve and a preparation method and application thereof. Background Art

[0002] In order to cope with the global energy crisis, people are accelerating the development of new energy sources on the one hand, and striving to improve the utilization rate of fossil energy such as oil and coal on the other hand. In addition, obtaining high value-added downstream products through fine processing of raw materials is the goal pursued by people. Looking at the history of energy resource processing and utilization, it is not difficult to find that porous solid catalysts with molecular sieves as the main body play a pivotal role in this process.

[0003] Molecular sieve is made of TO 4 The three-dimensional framework crystalline silicate formed by tetrahedrons according to certain arrangement rules has the advantages of regular micropores, high crystallinity, and good (hydro)thermal stability. Titanium silicate molecular sieve is a type of heteroatom molecular sieve formed by replacing silicon or aluminum in the framework of zeolite molecular sieve with four-coordinated titanium atoms. Titanium silicate molecular sieve has the function of selective catalytic oxidation and is mainly used in the selective oxidation of hydrocarbons. It is a selective oxidation catalyst that is currently widely used in industry.

[0004] However, the titanium silicalite has a large number of silanol groups on its surface, which makes its structure hydrophilic. When it participates in an oxidation reaction system with hydrogen peroxide as the oxidant, the active sites are occupied by water molecules, and the accessibility between the reaction substrate and the active sites is reduced. In addition, the acidity of this type of molecular sieve is too strong, which causes the product epoxy compound to further hydrolyze and convert into a by-product diol, and the reaction selectivity decreases. To address these issues, existing methods include: using a metal impregnation post-treatment method to neutralize the acidity of titanium silicalite molecular sieves. This method only loads the metal on the molecular sieve, which is only a modification of the molecular sieve and does not enter the molecular sieve framework, which is prone to metal loss during high-temperature calcination; using fluorination post-treatment or surface silanization to adjust the surface hydrophilicity of the molecular sieve, but this method is costly and pollutes the environment; using organic amine templates to dope other transition metal elements of groups IV, V, and VI (such as Zr, V, Nb, Cr, Mo, and W) into the molecular sieve framework to regulate redox properties. In particular, the introduction of high-coordination heteroatoms greatly improves the redox efficiency on the one hand, and can neutralize silanol groups on the other hand, greatly improving the hydrophobicity of the structure. However, the method of introducing transition elements through organic templates is too costly.

[0005] The document "Molecular Sieve and Porous Material Chemistry" (Xu Ruren, Pang Wenqin, Yu Jihong. Science Press, 2004, 237-239) systematically studied the crystallization synthesis of M-ZSM-5 in a fluoride ion system, and believed that transition metal elements are unstable at high pH and are easily hydrolyzed to form hydroxide or oxide precipitation, making it difficult to form heteroatom zeolites with high transition metal content. However, in a fluoride ion system, these transition metal elements can form fluorine complexes, which is conducive to entering the molecular sieve framework.

[0006] Patent CN 109513458 A discloses adding a silicon source dropwise to an aqueous solution of a structure directing agent to form a clear solution A; adding an aqueous solution of a tungsten source or a tungsten source dropwise to solution A, and then hydrothermally crystallizing at 110°C to 150°C for 48h to 120h to obtain an MFI-type molecular sieve catalyst having a skeleton of tungsten atoms.

[0007] Patent CN 104437605A discloses that a certain proportion of deionized water, an alkali source, an organic template, a tungsten source, and a silicon source are stirred to form an initial gel, and a W-ZSM-5 molecular sieve is synthesized by hydrothermal crystallization. The X-ray diffraction pattern proves that W enters the molecular sieve framework to expand its unit cell and increase the unit cell volume.

[0008] Patent CN 113058643A discloses that a TS-1 molecular sieve precursor solution and a transition metal tungsten precursor solution are mixed under heating conditions to obtain a transition metal tungsten-modified TS-1 molecular sieve precursor solution, which is hydrothermally crystallized and then calcined to obtain a transition metal tungsten oxide-modified TS-1 molecular sieve; the transition metal tungsten oxide-modified TS-1 molecular sieve is placed in a rare earth element precursor solution, heated and stirred, and then allowed to stand for aging, separated, washed, dried, and calcined to obtain a rare earth element-modified transition metal oxide / TS-1 molecular sieve.

[0009] The above-mentioned prior art uses an organic template, which is relatively expensive and will increase the synthesis cost of zeolite. In addition, the hydrothermal method takes a long time to synthesize, and the gel is heated unevenly, making it difficult to rapidly nucleate.

[0010] Patent CN 104475149A uses microporous molecular sieve ZSM-5 or MCM-22 as a carrier, and uses ammonium tungstate as a precursor of tungsten oxide to load tungsten oxide on the outer surface of the microporous molecular sieve through an impregnation method. The content of tungsten oxide in the catalyst is 3% to 15% of the total mass of the catalyst. This method uses an impregnation method to load tungsten on the molecular sieve, which is only a modification of the molecular sieve. The tungsten species does not enter the molecular sieve framework, which is easy to cause tungsten sublimation loss during high-temperature calcination.

[0011] Patent CN110407695A discloses a method for preparing bio-based polyhydroxy fatty acid esters by rapid hydrolysis of epoxy fatty acid esters, which uses epoxy fatty acid methyl ester as a reaction raw material, silicon tungsten molecular sieve as a solid acid catalyst, and hydrogen peroxide as an oxidant. Under milder reaction conditions and shorter reaction times, a higher ring-opening conversion rate of epoxy fatty acid esters and a higher yield of product polyhydroxy fatty acid esters can be achieved. The preparation method of silicon tungsten molecular sieves described herein uses a dual template method, in which the mesoporous template agent is hexadecyltrimethylammonium bromide and the microporous template agent is tetramethylammonium hydroxide, which is expensive and will increase the synthesis cost of zeolite. In addition, the hydrothermal method has a long synthesis time, and the gel is heated unevenly, making it difficult to rapidly nucleate.

[0012] Therefore, there is still a need in the art to further study the TS-1 molecular sieve for selective oxidation of olefins. Summary of the invention

[0013] The main purpose of the present invention is to provide a tungsten-containing TS-1 molecular sieve and its preparation method and application, so as to solve the problems of high preparation cost of tungsten-containing TS-1 molecular sieve in the prior art, pollution to the environment, and difficulty for metal tungsten to enter the interior of the molecular sieve framework.

[0014] In order to achieve the above object, the present invention provides a method for preparing tungsten-containing TS-1 molecular sieve, comprising the following steps:

[0015] Step 1, mixing a silicon source, an alkali source, a tungsten source and water, adding cardanol polyoxyethylene ether sulfonate, and heating to form a mixed gel B;

[0016] Step 2, adding seed crystals to the mixed gel B and stirring to obtain a mixture C;

[0017] Step 3: crystallize the mixture C to obtain a tungsten-containing TS-1 molecular sieve.

[0018] The preparation method of tungsten-containing TS-1 molecular sieve described in the present invention, wherein step 1 is: mixing the silicon source, the alkali source and water to obtain solution A, hydrolyzing, then adding the tungsten source to the solution A, adding cardanol polyoxyethylene ether sulfonate, heating, and forming a mixed gel B; the cardanol polyoxyethylene ether sulfonate is cardanol polyoxyethylene ether sulfonate sodium, cardanol polyoxyethylene ether sulfonate magnesium or cardanol polyoxyethylene ether sulfonate ammonium.

[0019] The method for preparing the tungsten-containing TS-1 molecular sieve of the present invention further comprises: subjecting the tungsten-containing TS-1 molecular sieve obtained in step 3 to ammonium exchange treatment.

[0020] The preparation method of tungsten-containing TS-1 molecular sieve described in the present invention, wherein the silicon source is at least one of silica sol, tetraethyl silicate, methyl orthosilicate, and water glass, the alkali source is at least one of ethylamine and n-butylamine, and the tungsten source is at least one of ammonium metatungstate, ammonium tungstate, and sodium tungstate dihydrate.

[0021] The preparation method of the tungsten-containing TS-1 molecular sieve of the present invention, wherein the silicon source is SiO 2 The alkali source is Na 2 O, the tungsten source is WO 3 The molar ratio of the silicon source, the alkali source, the tungsten source and water is 1:2-10:0.01-0.05:4-10, and the molar ratio of the cardanol polyoxyethylene ether sulfonate and the silicon source is 0.01-0.06:1.

[0022] The method for preparing tungsten-containing TS-1 molecular sieve of the present invention comprises the following steps: the seed crystal is TS-1 molecular sieve, and the mass ratio of the added amount of the seed crystal to the mixed gel B is (1-5):100.

[0023] The preparation method of tungsten-containing TS-1 molecular sieve described in the present invention, wherein the temperature of the crystallization treatment in step 3 is 135°C to 170°C, the time is 1h to 3h, and the method of the crystallization treatment is microwave radiation heating; after the crystallization treatment, it also includes a drying step, the drying temperature is 100 to 120°C, and the drying time is 8 to 12h.

[0024] The preparation method of tungsten-containing TS-1 molecular sieve described in the present invention, wherein the hydrolysis time is 15 to 30 minutes, the heating temperature is 60°C to 90°C, the heating time is 15 to 60 minutes, and stirring is performed during the heating process at a stirring speed of 600 to 1000 rpm.

[0025] The preparation method of the tungsten-containing TS-1 molecular sieve of the present invention, wherein the synthesis of the cardanol polyoxyethylene ether sulfonate comprises:

[0026] Step a, using cardanol as a raw material and ethylene oxide to synthesize cardanol polyoxyethylene ether under alkaline conditions;

[0027] Step b, using cardanol polyoxyethylene ether as a raw material, adding tert-butanol base and anhydrous ethanol as a solvent, refluxing, then cooling the reaction system to room temperature, adding 1,3-propane sultone or 1,4-butane sultone dropwise, refluxing, cooling, and obtaining cardanol polyoxyethylene ether sulfonate.

[0028] In order to achieve the above object, the present invention also provides a tungsten-containing TS-1 molecular sieve obtained by the above-mentioned preparation method of the tungsten-containing TS-1 molecular sieve.

[0029] In order to achieve the above object, the present invention further provides the use of the above tungsten-containing TS-1 molecular sieve in the selective oxidation of olefins.

[0030] Beneficial effects of the present invention:

[0031] (1) The synthesis of the molecular sieve of the present invention adopts the seed method, does not use an organic template, has a low cost, and does not cause the problem of nitrogen oxides and carbon oxides polluting the environment due to the decomposition of the organic template.

[0032] (2) The present invention uses the bio-based raw material cardanol as a hydrophobic starting molecule to design and synthesize an environmentally friendly additive cardanol polyoxyethylene ether sulfonate. During the crystal nucleation and growth process, the solvent interface increases. A small amount of cardanol polyoxyethylene ether sulfonate can effectively reduce the surface tension of the solution, making it easier to nucleate from an energy perspective and form micelles in the gel. This effect increases the contact and interaction probability between silicon and tungsten, that is, by changing the thermodynamic properties of the sol, the crystallization rate is increased, thereby increasing the crystallinity of the sample, and successfully introducing tungsten into the molecular sieve framework, wherein the sodium sulfonate group can effectively neutralize the surface acidity of the molecular sieve. When the molecular sieve is used for the selective oxidation of olefins, the selectivity of the epoxidation reaction can be improved.

[0033] (3) The present invention adopts a seed crystal method in combination with microwave radiation heating to obtain a tungsten-containing TS-1 molecular sieve, and the synthesis time is short. The synthesized tungsten-containing TS-1 molecular sieve uses tungsten atoms to flexibly control the formation of silanols in the molecular sieve, increase the hydrophobicity of the molecular sieve surface, and prevent the formation of by-products such as alcohols and ketones. The molecular sieve of the present invention is used as a catalyst for the selective oxidation of olefins. Tungsten has more suitable acidity as an active center for catalyzing the selective oxidation reaction of olefins, and exhibits excellent catalytic effects in catalyzing the selective oxidation reaction of olefins, and the reaction conversion rate and the selectivity of the main product epoxide are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The XRD diagrams of the molecular sieves obtained in Comparative Example 1 and Example 5 of the present invention are shown below;

[0035] Figure 2 It is the Py-IR graph of the molecular sieves obtained in Comparative Example 1 and Example 5 of the present invention. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention is described in detail below. The following implementation modes are implemented on the premise of the technical scheme of the present invention, and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following implementation modes. The structures or experimental methods of specific conditions are not specified in the following implementation modes, and generally conventional conditions are followed.

[0037] In a first embodiment, the present invention provides a method for preparing a tungsten-containing TS-1 molecular sieve, comprising the following steps:

[0038] Step 1, mixing a silicon source, an alkali source, a tungsten source and water, adding cardanol polyoxyethylene ether sulfonate, and heating to form a mixed gel B;

[0039] Step 2, adding seed crystals to the mixed gel B and stirring to obtain a mixture C;

[0040] Step 3: crystallize the mixture C to obtain a tungsten-containing TS-1 molecular sieve.

[0041] The invention adds cardanol polyoxyethylene ether sulfonate in the process of molecular sieve crystallization, which can effectively reduce the interfacial tension of the solution in the process of crystal nucleation, making the nucleation process easier to carry out, and can form micelles in the gel, promote the contact and action probability between silicon and tungsten, and improve the crystallization rate by changing the thermodynamic properties of the gel, thereby improving the crystallinity of the molecular sieve, and also promoting tungsten to enter the molecular sieve framework; in addition, the sulfonate group part in the cardanol polyoxyethylene ether sulfonate can effectively neutralize the surface acidity of the molecular sieve, so that the molecular sieve has higher epoxidation reaction selectivity when used for olefin selective oxidation; the presence of polyether chains in the cardanol polyoxyethylene ether sulfonate also helps to form micelles, increases the contact and action probability between silicon and tungsten, and thus achieves the purpose of synthesizing the tungsten-containing TS-1 molecular sieve without adding a template agent.

[0042] The present invention does not specifically limit the silicon source, alkali source, and tungsten source, and the silicon source, alkali source, and tungsten source commonly used in the art can be used. In one embodiment, the silicon source of the present invention is at least one of silica sol, tetraethyl silicate, methyl orthosilicate, and water glass, the alkali source is at least one of ethylamine and n-butylamine, and the tungsten source is at least one of ammonium metatungstate, ammonium tungstate, and sodium tungstate dihydrate. In another embodiment, the cardanol polyoxyethylene ether sulfonate of the present invention is cardanol polyoxyethylene ether sodium sulfonate, cardanol polyoxyethylene ether magnesium sulfonate, or cardanol polyoxyethylene ether ammonium sulfonate.

[0043] In one embodiment, the silicon source is SiO 2 The alkali source is Na 2 O, tungsten source is WO 3 The molar ratio of silicon source, alkali source, tungsten source and water is 1:2-10:0.01-0.05:4-10, that is, the molar ratio of silicon source, alkali source, tungsten source and water is SiO 2 :2~10Na 2 O: 0.01~0.05WO 3 : 4~10H 2 O, the molar ratio of cardanol polyoxyethylene ether sulfonate to the silicon source is 0.01-0.06:1.

[0044] In one embodiment, the heating temperature in step 1 is 60° C. to 90° C., and the heating time is 15 to 60 minutes. Stirring operation can be performed during the heating process. The present invention does not specifically limit the stirring method. In another embodiment, the stirring speed is 600 to 1000 rpm.

[0045] The present invention does not particularly limit the source of cardanol polyoxyethylene ether sulfonate, and it can be a commercially available product. In one embodiment, the preparation method of cardanol polyoxyethylene ether sulfonate of the present invention comprises:

[0046] Step a, using cardanol as a raw material and ethylene oxide to synthesize cardanol polyoxyethylene ether under alkaline conditions;

[0047] Step b, using cardanol polyoxyethylene ether as a raw material, adding tert-butanol base and anhydrous ethanol as a solvent, refluxing, then cooling the reaction system to room temperature, adding 1,3-propane sultone or 1,4-butane sultone dropwise, refluxing, cooling, and obtaining cardanol polyoxyethylene ether sulfonate.

[0048] The tert-butanol base is, for example, sodium tert-butoxide, magnesium tert-butoxide, or tert-butanolamine.

[0049] In another embodiment, the preparation method of the cardanol polyoxyethylene ether sulfonate of the present invention is specifically as follows: cardanol is used as a raw material, and cardanol polyoxyethylene ether is synthesized with ethylene oxide under alkaline conditions, and cardanol polyoxyethylene ether (EON value: n≈5, 6, 10, 12, 18) is used as a raw material in a three-necked flask under argon protection, tert-butanol base is added, anhydrous ethanol is used as a solvent, and refluxed for 30 minutes. The reaction system is cooled to room temperature, 1,3-propane sultone or 1,4-butane sultone is slowly added dropwise, refluxed, cooled, and excess ethanol is removed by vacuum distillation, petroleum ether is added, and grinding is performed to obtain a white solid, centrifuged, and vacuum dried to obtain the final product, which is a white, easily deliquescent solid cardanol polyoxyethylene ether sulfonate.

[0050] Step 2 is to add seed crystals to the mixed gel B and stir to obtain a mixture C. The seed crystals are TS-1 molecular sieves. In one embodiment, the mass ratio of the added amount of the seed crystals to the mixed gel B is (1 to 5): 100. The present invention does not particularly limit the TS-1 molecular sieve used as the seed crystals. It can be a commercially available TS-1 molecular sieve seed crystal or a homemade TS-1 molecular sieve seed crystal. In another embodiment, the method for making homemade TS-1 molecular sieve seed crystals is as follows: silica sol is mixed with a tetrapropylammonium hydroxide (TPAOH) solution and a small amount of water, and stirred at 10°C to 40°C for 1 to 3 hours to evaporate excess water to obtain a molar composition of SiO 2 :0.042~0.1 TPAOH:2~10H 2The resulting mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and maintained at 150°C to 180°C for 3 to 5 days. After concentration and drying recovery, the product was calcined in air at 550°C for 6 hours to obtain TS-1 molecular sieve seed crystals.

[0051] The present invention also does not particularly limit the stirring method in step 2. In one embodiment, the stirring speed is 600-1000 rpm.

[0052] Step 3 is to crystallize the mixture C, for example, by placing it in a polytetrafluoroethylene device for crystallization. In one embodiment, the crystallization heating method is microwave radiation heating, which can improve the crystallization efficiency and shorten the molecular sieve synthesis time. In another embodiment, the crystallization temperature is 135°C to 170°C, and the time is 1h to 3h. After the crystallization is completed, the crystallized product is cooled to room temperature, and then centrifuged, washed, and dried in sequence to obtain the Na-type tungsten-containing TS-1 molecular sieve. Wherein, the drying temperature is 100 to 120°C, and the drying time is 8 to 12h.

[0053] In the second embodiment, the preparation method of the tungsten-containing TS-1 molecular sieve of the present invention, step 1 is: mixing a silicon source, an alkali source and water to obtain a solution A, hydrolyzing, and then adding the tungsten source to the solution A, adding cardanol polyoxyethylene ether sulfonate, heating, and forming a mixed gel B.

[0054] The remaining steps 2 and 3 are similar to those in the first embodiment and will not be described again.

[0055] The types and amounts of the silicon source, alkali source, and tungsten source have been described in detail in the first embodiment and will not be repeated here. In this embodiment, the silicon source, alkali source, and water are first mixed and hydrolyzed, and the hydrolysis time is, for example, 15 to 30 minutes. Then the tungsten source is added dropwise to the above solution A, and then the additive cardanol polyoxyethylene ether sulfonate is added and heated to form a mixed gel B. In one embodiment, the heating temperature is 60°C to 90°C, the heating time is 15 to 60 minutes, and stirring is performed during the heating process, and the stirring speed is 600 to 1000 rpm.

[0056] In a third embodiment, the method for preparing the tungsten-containing TS-1 molecular sieve of the present invention comprises:

[0057] Step 1, mixing a silicon source, an alkali source, a tungsten source and water, adding cardanol polyoxyethylene ether sulfonate, and heating to form a mixed gel B;

[0058] Step 2, adding seed crystals to the mixed gel B and stirring to obtain a mixture C;

[0059] Step 3, crystallizing the mixture C to obtain a tungsten-containing TS-1 molecular sieve;

[0060] Step 4, subjecting the tungsten-containing TS-1 molecular sieve obtained in step 3 to ammonium exchange treatment.

[0061] Among them, steps 1, 2, and 3 are similar to those of the first embodiment, and are not described again. This embodiment adds step 4, wherein the obtained Na-type tungsten-containing TS-1 molecular sieve is subjected to at least one ammonium exchange, and then filtered, washed, and dried to obtain the tungsten-containing TS-1 molecular sieve. In one embodiment, the solution for the ammonium exchange is a 1 mol / L ammonium nitrate solution.

[0062] In one specific embodiment, the preparation method of the tungsten-containing TS-1 molecular sieve of the present invention comprises the following steps:

[0063] (1) Mix the silicon source with the alkali source and H 2 O mixed to form solution A, hydrolyze for 15 to 30 minutes;

[0064] (2) adding the tungsten source dropwise into the above solution A, and then adding the additive cardanol polyoxyethylene ether sulfonate, stirring at 60° C. to 90° C. for 15 to 60 minutes to form a mixed gel B;

[0065] (3) adding the seed TS-1 molecular sieve to the mixed gel B and stirring evenly for 1 to 2 hours to obtain a mixture C;

[0066] (4) placing the mixture C in a temperature-controlled microwave radiation heating device with a polytetrafluoroethylene liner for crystallization, cooling to room temperature after crystallization, and then centrifugally filtering, washing, and drying in sequence to obtain a Na-type tungsten-containing TS-1 molecular sieve;

[0067] (5) The Na-type tungsten-containing TS-1 molecular sieve is subjected to multiple ammonium exchanges with a 1 mol / L ammonium nitrate solution, filtered, washed, and dried to obtain a tungsten-containing TS-1 molecular sieve.

[0068] Therefore, the present invention provides a tungsten-containing TS-1 molecular sieve, which mainly uses silica sol, tetraethyl silicate, tetramethyl silicate or water glass as silicon source, ammonium metatungstate, ammonium tungstate or sodium tungstate dihydrate as tungsten source, and does not use organic templates. The tungsten-containing TS-1 molecular sieve is obtained by using a seed crystal method combined with microwave radiation heating, wherein the addition of cardanol polyoxyethylene ether sulfonate during the crystallization process can reduce the surface interfacial tension of the solution during the crystallization process, promote the contact and action probability between silicon and tungsten, promote tungsten to enter the molecular sieve framework, and neutralize the surface acidity of the molecular sieve. In addition, the method of the present invention has low cost and short synthesis time.

[0069] The tungsten-containing TS-1 molecular sieve obtained by the method of the present invention has high crystallinity, low Si-OH content and improved hydrophobicity. The tungsten-containing TS-1 molecular sieve obtained by the method of the present invention is used for selective oxidation of olefins and has high conversion rate and cycloalkane selectivity.

[0070] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0071] Embodiment preparation method:

[0072] (1) Mix the silicon source with the alkali source and H 2 O mixed to form solution A, hydrolyzed;

[0073] (2) adding the tungsten source dropwise into the above solution A, and then adding the additive cardanol polyoxyethylene ether sulfonate, stirring at a constant speed for 15 to 60 minutes at 60° C. to 90° C. to form a mixed gel B;

[0074] (3) adding seed TS-1 molecular sieve to the mixed gel B, aging and stirring to obtain a mixture C;

[0075] (4) placing the mixture C in a temperature-controlled microwave radiation heating device with a polytetrafluoroethylene liner for crystallization, cooling to room temperature after crystallization, and then centrifugally filtering and washing in sequence to obtain a Na-type tungsten-containing TS-1 molecular sieve;

[0076] (5) The Na-type tungsten-containing TS-1 molecular sieve is subjected to multiple ammonium exchanges with a 1 mol / L ammonium nitrate solution, filtered, washed, and dried to obtain a tungsten-containing TS-1 molecular sieve.

[0077] The preparation method of TS-1 molecular sieve seed is as follows: silica sol is mixed with tetrapropylammonium hydroxide (TPAOH) solution and a small amount of water, and stirred at 10°C to 40°C for 1 to 3 hours to evaporate excess water to obtain a molar composition of SiO 2 :0.042~0.1 TPAOH:2~10H 2 The resulting mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and maintained at 150°C to 180°C for 3 to 5 days. After concentration and drying recovery, the product was calcined in air at 550°C for 6 hours to obtain TS-1 molecular sieve seed crystals.

[0078] In each example, tungsten-containing TS-1 molecular sieve was prepared according to the above method, with reference to the selection of specific raw materials and implementation process conditions in Table 1 below.

[0079] Table 1 Raw material selection and ratio of each example

[0080]

[0081]

[0082] Comparative Example 1 is commercial TS-1 molecular sieve, SiO 2 / TiO 2=50, purchased from Zibo Hengyi Chemical Technology Co., Ltd.;

[0083] Comparative Example 2 is the W-modified TS-1 raw powder disclosed in patent CN 113058643A, and the specific preparation process is as follows:

[0084] 1) Weigh 20g of tetraethyl orthosilicate (TEOS) and 1.31g of tetrabutyl titanate (TBOT) and gradually add them dropwise into 35ml of 10wt% tetrapropylammonium hydroxide aqueous solution, stir until colorless and transparent, then add 0.19g of ammonium metatungstate and 2g of Tween 20, continue stirring and heating to 80°C to remove alcohol for 3h to obtain W-modified TS-1 molecular sieve precursor solution.

[0085] 2) placing the precursor solution in a crystallization kettle and hydrothermally crystallizing it at 175° C. and autogenous pressure for 72 hours; the mixed solution after crystallization is centrifuged and washed, and dried at a constant temperature of 110° C. for 10 hours. The product is calcined at 575° C. in an air atmosphere for 6 hours to obtain W-modified TS-1 molecular sieve raw powder. 3)

[0087] Table 2 Crystallinity of molecular sieves obtained in Examples and Comparative Examples

[0088]

[0089] As shown in Table 2, the crystallinity of the tungsten-containing TS-1 molecular sieve synthesized in the embodiment of the present invention is higher than that of the tungsten-containing TS-1 molecular sieve synthesized in Comparative Example 1 and Comparative Example 2.

[0090] Table 3 Specific surface area and pore volume parameters of the molecular sieves obtained in Comparative Example 1 and Example 5 of the present invention

[0091]

[0092] Where: HF (level factor, V mico / V total and S ext / S BET The product of (x) is used to describe the interaction between the catalytic function of the micropores in the hierarchical zeolite molecular sieve and the diffusion advantage provided by the mesopores.

[0093] As shown in Table 3, the hierarchy factor HF of the molecular sieve obtained in Example 5 is greater than the HF of the molecular sieves obtained in Comparative Examples 1 and 2, which indicates that the introduction of W heteroatom into the tungsten-containing TS-1 molecular sieve prepared by the method of the present invention can improve the catalytic performance of the molecular sieve.

[0094] Figure 1 The XRD diagrams of the molecular sieves obtained in Comparative Example 1 and Example 5 of the present invention are shown below; Figure 2 It is the Py-IR graph of the molecular sieves obtained in Comparative Example 1 and Example 5 of the present invention.

[0095] Depend on Figure 1 As shown, the molecular sieves obtained in Comparative Example 1 and Example 5 show characteristic diffraction peaks of the MFI framework at 7.9°, 8.8°, 23.2°, 23.9° and 24.4°, and there are no impurity peaks, indicating that the molecular sieves obtained in Comparative Example 1 and Example 5 are both pure-phase MFI framework molecular sieves and have good crystallinity.

[0096] Depend on Figure 2 As shown, the commercial TS-1 molecular sieve of Comparative Example 1 and the tungsten-containing TS-1 molecular sieve sample prepared in Example 5 both have an absorption peak near 3740 cm-1, which is the vibration absorption peak of Si-OH at the end of the molecular sieve framework. However, the peak area in the commercial TS-1 molecular sieve sample is significantly higher than that of the W-TS-1 molecular sieve of Example 5, indicating that the hydroxyl group at the end of the W-TS-1 molecular sieve framework synthesized in Example 5 is significantly reduced and the hydrophobicity is improved, which can be explained that the W heteroatom introduced by the method of the present invention can enter the molecular sieve framework and change the hydrophobicity of the molecular sieve surface.

[0097] In order to verify the catalytic effect of the TS-1 molecular sieve obtained in the above examples and comparative examples, 500 mg of the molecular sieves of Example 5, Comparative Example 1 and Comparative Example 2 were taken and epoxidation reaction was tested in a 250 ml three-necked flask. In a 250 ml round-bottom flask with condensation reflux, 0.5 g of molecular sieve, 100 ml of solvent acetonitrile, 0.1 mol of cyclopentene, 0.1 mol of oxidant H 2 O 2 (30 wt % aqueous solution). Stir at 60° C. for 2 h. After the reaction is completed, filter the reaction solution and detect it by gas chromatography. The reaction test results are shown in Table 4.

[0098] Table 4 Cyclopentene epoxidation reaction results of Example 5, Comparative Example 1 and Comparative Example 2

[0099]

[0100] As shown in Table 4, the tungsten-containing TS-1 molecular sieve prepared in Example 5 of the present invention has significantly improved reaction conversion rate and product selectivity in the process of catalyzing cyclopentene oxidation to produce 1,2-epoxycyclopentane, compared with the molecular sieves of Comparative Example 1 and Comparative Example 2. Since cyclopentene can enter the micropores to participate in the reaction, the influence of the pore limitation on the catalytic reaction is no longer the main factor, and it mainly depends on the influence of the hydrophilicity of the molecular sieve. Figure 2 From the analysis, it can be seen that the hydroxyl groups at the ends of the skeleton of the tungsten-containing TS-1 molecular sieve prepared in Example 5 of the present invention are significantly reduced, the surface hydrophobicity is improved, and the reactant cyclopentene is easy to contact the active sites on the surface of the molecular sieve to undergo epoxidation reaction, so the reaction performance is excellent.

[0101] Therefore, the tungsten-containing TS-1 molecular sieve prepared by the method of the present invention has a good catalytic effect on the cyclopentene epoxidation reaction, has high selectivity and conversion rate, and can be widely used in the olefin epoxidation reaction.

[0102] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing tungsten-containing TS-1 molecular sieve, It is characterized in that The following steps are involved: Step 1, mixing a silicon source, an alkali source, a tungsten source and water, adding cardanol polyoxyethylene ether sulfonate, and heating to form a mixed gel B; Step 2, adding seed crystals to the mixed gel B and stirring to obtain a mixture C; Step 3, crystallizing the mixture C to obtain tungsten-containing TS-1 molecular sieve: Wherein, the silicon source is SiO 2 The alkali source is Na 2 O, the tungsten source is WO 3 The molar ratio of the silicon source, the alkali source, the tungsten source and water is 1:2-10:0.01-0.05:4-10, and the molar ratio of the cardanol polyoxyethylene ether sulfonate and the silicon source is 0.01-0.06:1; The seed crystal is TS-1 molecular sieve.

2. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that Step 1 is: mixing the silicon source, the alkali source and water to obtain solution A, hydrolyzing, then adding the tungsten source to the solution A, adding cardanol polyoxyethylene ether sulfonate, heating, and forming a mixed gel B; the cardanol polyoxyethylene ether sulfonate is cardanol polyoxyethylene ether sulfonate sodium, cardanol polyoxyethylene ether sulfonate magnesium or cardanol polyoxyethylene ether sulfonate ammonium.

3. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that Also includes: The tungsten-containing TS-1 molecular sieve obtained in step 3 is subjected to ammonium exchange treatment.

4. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that The silicon source is at least one of silica sol, tetraethyl silicate, methyl orthosilicate, and water glass; the alkali source is at least one of ethylamine and n-butylamine; and the tungsten source is at least one of ammonium metatungstate, ammonium tungstate, and sodium tungstate dihydrate.

5. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that The mass ratio of the added amount of the seed crystal to the mixed gel B is (1-5):

100.

6. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that The crystallization treatment temperature in step 3 is 135°C to 170°C, the time is 1h to 3h, and the crystallization treatment is carried out by microwave radiation heating; after the crystallization treatment, a drying step is also included, the drying temperature is 100 to 120°C, and the drying time is 8 to 12h.

7. The method for preparing the tungsten-containing TS-1 molecular sieve according to claim 2, It is characterized in that The hydrolysis time is 15 to 30 minutes, the heating temperature is 60° C. to 90° C., the heating time is 15 to 60 minutes, and stirring is performed during the heating process at a stirring speed of 600 to 1000 rpm.

8. The method for preparing tungsten-containing TS-1 molecular sieve according to claim 1, It is characterized in that The synthesis of the cardanol polyoxyethylene ether sulfonate comprises: Step a, using cardanol as a raw material and ethylene oxide to synthesize cardanol polyoxyethylene ether under alkaline conditions; Step b, using cardanol polyoxyethylene ether as a raw material, adding tert-butanol base and anhydrous ethanol as a solvent, reflux, then cooling the reaction system to room temperature, adding 1,3-propane sultone or 1,4-butane sultone dropwise, reflux, and cool to obtain cardanol polyoxyethylene ether sulfonate.

9. The tungsten-containing TS-1 molecular sieve obtained by the preparation method of the tungsten-containing TS-1 molecular sieve according to any one of claims 1 to 8.

Images