A method and application of synthesizing TS-1 using tetramethoxysilane as raw material

Abstract

The present invention discloses a method for synthesizing TS-1 using tetramethoxysilane as a raw material. Using tetramethoxysilane as a silicon source, tetrabutyl titanate as a titanium source, tetrapropylammonium hydroxide as a template, and isopropanol as a solvent, a hydrothermal method is used to synthesize titanium silicon molecular sieve TS-1 by two dealcoholizations. The present invention uses tetramethoxysilane to replace the ethyl orthosilicate in the traditional hydrothermal method, and the catalytic performance of the titanium silicon molecular sieve synthesized using ethyl orthosilicate as a raw material can still be achieved. However, since the market price of tetramethoxysilane is much lower than that of ethyl orthosilicate, this significantly reduces the production cost of the titanium silicon molecular sieve, so the synthesis of titanium silicon molecular sieve using tetramethoxysilane as a raw material has industrial significance for large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve material preparation, and relates to a method for synthesizing TS-1 by taking tetramethoxysilane as a raw material and an application of the method in an allyl chloride epoxidation reaction. Background Art

[0002] Titanium silicate molecular sieve TS-1 belongs to the orthorhombic system and has the same MFI topological structure as ZSM-5 molecular sieve. Due to the introduction of transition metal titanium, TS-1 has unique catalytic oxidation performance. TS-1 is widely used in catalytic oxidation reactions such as olefin epoxidation, hydroxylation of phenol and benzene, partial oxidation of alkanes, oxidation of alcohols, and oximation of ketones.

[0003] Titanium silicate molecular sieve is usually synthesized by hydrothermal method. At present, the synthesis system is mainly divided into two categories, one is the synthesis system with tetraethyl orthosilicate as silicon source and tetrapropylammonium hydroxide as template, and the other is the synthesis system with silica sol as silicon source and tetrapropylammonium bromide as template. The former has a high synthesis cost due to the high price of tetraethyl orthosilicate and tetrapropylammonium hydroxide, while the latter has a lower cost but poorer catalytic performance than the former. Therefore, how to reduce the synthesis cost of titanium silicate molecular sieve while ensuring better catalytic performance is of practical and industrial production significance.

[0004] Patent CN107500309B discloses a method for preparing titanium silicon molecular sieve, using tetraethyl orthosilicate as silicon source and tetrabutyl titanate as titanium source. The molecular sieve preparation process includes hydrolysis of silicon source and titanium source, dealcoholization, crystallization, filtration, roasting, modification and other steps. The final catalyst is used for and undergoes two dealcoholizations. After the silicon source is hydrolyzed, the titanium source is hydrolyzed. Cyclohexanone ammoxidation is performed to prepare cyclohexanone oxime.

[0005] Patent CN103641134B describes a method for preparing a titanium silicon molecular sieve with controllable grain size. Ethyl orthosilicate, tetrabutyl titanate, a template, an alkali source, an inorganic ammonium salt and a molecular sieve mother liquor are mixed in a molar ratio of SiO2:TiO2:template:alkali source:inorganic ammonium salt:H2O of 1:0.01-0.04:0.2-0.6:0.1-3.0:0-0.3:20-60, and crystallization is performed. The titanium silicon molecular sieve synthesized by this method has a small grain size, high crystallinity, high skeleton titanium content, strong hydrophobicity, and has high activity for selective oxidation reactions such as olefin epoxidation, aromatic hydrocarbon hydroxylation, and ketone ammoxidation.

[0006] Patent CN103214000B discloses a method for synthesizing titanium silicon molecular sieve TS-1, wherein the silicon source is first subjected to acid-catalyzed hydrolysis, and then the titanium source is simultaneously subjected to base-catalyzed hydrolysis, and the silicon source can be selected from one or a mixture of two or more of methyl orthosilicate, ethyl orthosilicate, and butyl orthosilicate. However, the specific process and application of synthesizing titanium silicon molecular sieve using methyl orthosilicate as a silicon source are not specifically described in the specific embodiments.

[0007] It can be seen that the synthesis of titanium silicon molecular sieve using tetramethoxysilane as a silicon source is not a conventional technical means. This may be due to the difference in the hydrolysis rate of tetramethoxysilane and ethyl orthosilicate. The hydrolysis rate of the former is very fast and difficult to control. However, compared with the prices of the two, the price of tetramethoxysilane is only about one-third of the price of ethyl orthosilicate, and to obtain the same silicon content, the amount of tetramethoxysilane used is three-quarters of the amount of ethyl orthosilicate used. Therefore, if tetramethoxysilane is used as a raw material to synthesize titanium silicon molecular sieve, the synthesis cost of molecular sieve can be greatly reduced. Summary of the invention

[0008] The invention provides a method for synthesizing TS-1 by using tetramethoxysilane as a raw material. The synthesized TS-1 has the same catalytic performance as TS-1 synthesized by using tetraethyl orthosilicate as a raw material. The method significantly reduces the synthesis cost of titanium silicon molecular sieve and has industrial significance.

[0009] In order to achieve the above purpose and effect, the following scheme is adopted:

[0010] A method for synthesizing TS-1 using tetramethoxysilane as a raw material, characterized in that tetramethoxysilane is used as a silicon source, tetrabutyl titanate is used as a titanium source, tetrapropylammonium hydroxide is used as a template, and isopropanol is used as a solvent, and a hydrothermal method is used to synthesize titanium silicon molecular sieve TS-1 by two dealcoholizations. The specific synthesis steps are as follows:

[0011] (1) Hydrolysis of tetramethoxysilane: At 20-30°C, add an aqueous solution of tetrapropylammonium hydroxide to tetramethoxysilane, control the temperature in the reactor to be below 40°C, and stir for 2-4 hours after the addition is complete.

[0012] (2) Primary dealcoholization: under negative pressure, the temperature in the kettle is controlled to be lower than 70°C by controlling the vacuum degree, and the alcohol is removed. A corresponding amount of deionized water is added to the kettle until the methanol content is 5-15%, and the temperature is lowered to below 40°C.

[0013] (3) Hydrolysis of tetrabutyl titanate: tetrabutyl titanate and isopropanol are mixed and then added dropwise to the mixture in (2). The temperature in the autoclave is controlled to be below 40° C. After the addition is completed, the mixture is stirred for 1 to 2 hours.

[0014] (4) Secondary dealcoholization: The mixture in (3) is heated to dealcoholize and add water, the dealcoholization temperature is 80-90°C, the secondary dealcoholization amount is 25-40% of the total feed amount, and the water addition amount is the same as the secondary dealcoholization amount.

[0015] (5) Heating crystallization: The mixture in (4) is placed in a stainless steel high-pressure reactor, crystallized at 160-180°C for 48-120h, cooled, filtered, washed, dried at 80-100°C, and calcined at 500-600°C to obtain titanium silicate molecular sieve TS-1.

[0016] Furthermore, in the synthesis method described above, the mass ratio of the feed amounts of the various materials is tetramethoxysilane: tetrabutyl titanate: isopropanol: tetrapropylammonium hydroxide: water = 1: 0.06-0.08: 0.3-0.7: 0.2-0.8: 0.5-3.

[0017] The present invention provides a titanium silicon molecular sieve synthesized by the above method.

[0018] The present invention provides application of the titanium silicon molecular sieve in the epoxidation reaction of allyl chloride.

[0019] Further, in the above technical solution, in the epoxidation reaction of allyl chloride, allyl chloride and H 2 O 2 The molar ratio is 2-5:1, and the mass ratio of methanol to hydrogen peroxide is 4-10:1.

[0020] Furthermore, in the above technical solution, in the epoxidation reaction of allyl chloride, the reaction temperature is 30-45°C, the reaction pressure is 0.2-1.0 MPa, and the mass space velocity of allyl chloride is 0.5-5 h -1 .

[0021] The present invention will be further described below with specific examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD spectrum of titanium silicalite molecular sieve CAT-1;

[0023] Figure 2 This is the SEM photo of titanium silicate molecular sieve CAT-1;

[0024] Figure 3 This is the XRD spectrum of titanium silicalite D-1;

[0025] Figure 4 This is the SEM photo of titanium silicate molecular sieve D-1;

[0026] Figure 5 This is the SEM photo of titanium silicate molecular sieve D-2. DETAILED DESCRIPTION

[0027] The present invention is further described in the following examples, but the present invention is not limited thereto.

[0028] The purity of the materials used in the examples is not less than 99%.

[0029] The titanium silicalite synthesized by the present invention is used in the fixed bed reaction of allyl chloride epoxidation. Inert quartz sand is added to both ends of the stainless steel jacket reaction tube, and 6g of titanium silicalite (20-40 mesh) is filled in the middle. The temperature of the reactor is maintained by a super constant temperature water bath. The reactants hydrogen peroxide, allyl chloride and solvent methanol are fed simultaneously, and product analysis is performed regularly. The reaction index is H 2 O 2 Conversion rate (X H2O2 ) and the epoxidation product selectivity (S ECH ). The reaction index is calculated as follows:

[0030] H 2 O 2 Conversion rate X = H 2 O 2 Mole / H 2 O 2 Total moles*100%;

[0031] Epichlorohydrin Selective S ECH = moles of epichlorohydrin generated by the reaction / H 2 O 2 Number of moles*100%.

[0032] The XRD characterization of the catalyst was measured by X-ray diffraction analyzer (PANalytical, X'Pert3 Powder).

[0033] The catalyst scanning electron microscopy (SEM) characterization was measured by scanning electron microscope (Hitachi, SU5000).

[0034] Example 1

[0035] At 25°C, add 800g of tetrapropylammonium hydroxide aqueous solution (mass fraction 25%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 3h after the addition is completed. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 330g, add 330g of deionized water, measure the methanol content in the kettle to be 9.5%, and cool to below 40°C. Mix 35g of tetrabutyl titanate and 250g of isopropanol evenly, add them to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is completed. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 550g, and 550g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-1.

[0036] The XRD spectrum and SEM photos of titanium silicate molecular sieve C-1 are attached. Figure 1 and attached Figure 2 .

[0037] Example 2

[0038] At 25°C, add 800g of tetrapropylammonium hydroxide aqueous solution (mass fraction 25%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 3h after the addition is completed. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 400g, add 400g of deionized water, measure the methanol content in the kettle to be 5.5%, and cool to below 40°C. Mix 35g of tetrabutyl titanate and 250g of isopropanol evenly, add them to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is completed. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 550g, and 550g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-2.

[0039] Example 3

[0040] At 25°C, add 800g of tetrapropylammonium hydroxide aqueous solution (mass fraction 25%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 3h after the addition is completed. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 290g, add 290g of deionized water, measure the methanol content in the kettle to be 12.1%, and cool to below 40°C. Mix 35g of tetrabutyl titanate and 250g of isopropanol evenly, add them to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is completed. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 550g, and 550g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-3.

[0041] Example 4

[0042] At 25°C, add 800g of tetrapropylammonium hydroxide aqueous solution (mass fraction 25%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 3h after the addition is completed. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 260g, add 260g of deionized water, measure the methanol content in the kettle to be 14.2%, and cool to below 40°C. Mix 35g of tetrabutyl titanate and 250g of isopropanol evenly, add them to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is completed. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 550g, and 550g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-4.

[0043] Example 5

[0044] At 25°C, add 1300g of tetrapropylammonium hydroxide aqueous solution (mass fraction 23%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 2h after the addition is complete. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 375g, add 375g of deionized water, measure the methanol content in the kettle to be 5.2%, and cool to below 40°C. Mix 40g of tetrabutyl titanate and 300g of isopropanol evenly, add dropwise to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is complete. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 650g, and 650g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-5.

[0045] Example 6

[0046] At 25°C, add 975g of tetrapropylammonium hydroxide aqueous solution (mass fraction 23%) to a glass kettle containing 500g of tetramethoxysilane, control the temperature in the kettle to be below 40°C, and stir for 2h after the addition is complete. Under negative pressure conditions, control the temperature in the kettle to be below 70°C by controlling the vacuum degree, dealcoholize 375g, add 375g of deionized water, measure the methanol content in the kettle to be 6.3%, and cool to below 40°C. Mix 30g of tetrabutyl titanate and 250g of isopropanol evenly, add them to the kettle, control the temperature in the kettle to be below 40°C, and stir for 1h after the addition is complete. Heat up for dealcoholization, the dealcoholization temperature is 80-90°C, the dealcoholization amount is 650g, and 650g of water is added. The obtained material was charged into a stainless steel high-pressure reactor, crystallized at 170°C for 96 hours, cooled, filtered, washed to neutrality, dried at 100°C, and calcined at 500°C for 6 hours to obtain a titanium silicalite molecular sieve, which was recorded as CAT-6.

[0047] Comparative Example 1

[0048] Put 684g of tetraethyl orthosilicate into the kettle, add 750g of 18% tetrapropylammonium hydroxide aqueous solution at 30℃, control the temperature in the kettle below 40℃, and stir for 3h after the addition is completed. Mix 35g of tetrabutyl titanate with 250g of isopropanol, add the mixed materials to the kettle, control the temperature in the kettle below 40℃, and stir for 1h after the addition is completed. Heat up, dealcoholate, the dealcoholate temperature is 80-90℃, the dealcoholate amount is 900g, and water is added 900g. The obtained material is loaded into a stainless steel high-pressure reactor, crystallized at 170℃ for 96h, cooled, filtered, washed to neutral, dried at 100℃, and roasted at 500℃ for 6h to obtain titanium silicon molecular sieve, recorded as D-1.

[0049] The XRD spectrum and SEM photos of titanium silicate molecular sieve D-1 are attached. Figure 3 and attached Figure 4 .

[0050] Comparative Example 2

[0051] Put 500g of tetramethoxysilane into the kettle, add 750g of 18% tetrapropylammonium hydroxide aqueous solution at 30℃, control the temperature in the kettle below 40℃, and stir for 3h after the addition is completed. Mix 35g of tetrabutyl titanate with 250g of isopropanol, add the mixed materials to the kettle, control the temperature in the kettle below 40℃, and stir for 1h after the addition is completed. Heat up, dealcoholate, dealcoholate temperature 80-90℃, dealcoholate amount 1350g, make up 897g of water. The obtained material is loaded into a stainless steel high-pressure reactor, crystallized at 170℃ for 96h, cooled, filtered, washed to neutral, dried at 100℃, calcined at 500℃ for 6h, and titanium silicon molecular sieve is obtained, recorded as D-2.

[0052] See the attached SEM photo of titanium silicate molecular sieve D-2 Figure 5 .

[0053] Application Examples

[0054] The epoxidation performance of allyl chloride was evaluated for the catalyst samples obtained in the comparative example and the example. The epoxidation reaction was carried out in a fixed bed reactor, 6 g (20-40 mesh) of catalyst was loaded into the middle section of a stainless steel jacketed reaction tube, the upper and lower ends of the reaction tube were filled with inert quartz sand, the reaction pressure was 0.5 MPa, the reaction temperature was maintained at 40°C in a constant temperature water bath, the raw materials allyl chloride, hydrogen peroxide, and solvent methanol were fed simultaneously, and the allyl chloride space velocity was 2 h -1 , allyl chloride and H 2 O 2 The molar ratio was 3, the mass ratio of methanol to hydrogen peroxide was 8, and samples were taken and analyzed after the reaction was carried out for 24 hours. The reaction results are shown in Table 1.

[0055] The performance evaluation results of the samples obtained in the comparative examples and embodiments are listed in Table 1.

[0056] It can be seen from the table below that the catalytic performance of the titanium silicate molecular sieve synthesized using tetramethoxysilane as raw material can reach the catalytic performance of the titanium silicate molecular sieve synthesized using ethyl orthosilicate as raw material.

[0057] Table 1 Catalytic performance evaluation results of each sample catalyst

[0058]

Claims

1. A method for synthesizing TS-1 using tetramethoxysilane as a raw material, characterized in that: Titanium silicon molecular sieve TS-1 was synthesized by hydrothermal method through two dealcoholizations using tetramethoxysilane as silicon source, tetrabutyl titanate as titanium source, tetrapropylammonium hydroxide as template, and isopropanol as solvent. The specific synthesis steps are as follows: (1) Hydrolysis of tetramethoxysilane: at 20-30°C, add an aqueous solution of tetrapropylammonium hydroxide to tetramethoxysilane, control the temperature in the reactor to be below 40°C, and stir for 2-4 hours after the addition is complete; (2) primary dealcoholization: under negative pressure, the temperature in the kettle is controlled to be lower than 70°C by controlling the vacuum degree, dealcoholization is performed, a corresponding weight of deionized water is added until the methanol content in the kettle is 5-15%, and the temperature is lowered to below 40°C; (3) Hydrolysis of tetrabutyl titanate: tetrabutyl titanate and isopropanol are mixed and then added dropwise to the mixture in (2), the temperature in the autoclave is controlled to be lower than 40° C. After the addition is completed, the mixture is stirred for 1 to 2 hours; (4) Secondary dealcoholization: The mixture in (3) is heated to remove alcohol and add water, the dealcoholization temperature is 80-90°C, the secondary dealcoholization amount is 25-40% of the total feed amount, and the water addition amount is the same as the secondary dealcoholization amount; (5) Heating crystallization: The mixture in (4) is placed in a stainless steel high-pressure reactor, crystallized at 160-180°C for 48-120h, cooled, filtered, washed, dried at 80-100°C, and calcined at 500-600°C to obtain titanium silicate molecular sieve TS-1.

2. A method for synthesizing TS-1 using tetramethoxysilane as a raw material according to claim 1, characterized in that: The mass ratio of the feeding amount of each material is tetramethoxysilane: tetrabutyl titanate: isopropanol: tetrapropylammonium hydroxide: water = 1: 0.06-0.08: 0.3-0.7: 0.2-0.8: 0.5-3.

3. Use of the titanium silicon molecular sieve synthesized by the method as claimed in claim 1 or 2 in the epoxidation reaction of allyl chloride.

4. The use according to claim 3, characterized in that: In the epoxidation reaction of allyl chloride, the molar ratio of allyl chloride to H2O2 is 2-5:1, and the mass ratio of methanol to hydrogen peroxide is 4-10:

1.

5. The application according to claim 4, characterized in that: In the epoxidation reaction of allyl chloride, the reaction temperature is 30-45°C, the reaction pressure is 0.2-1.0 MPa, and the mass space velocity of allyl chloride is 0.5-5 h -1 .

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