A method for preparing a titanium silicalite molecular sieve catalyst

Abstract

The application relates to the technical field of catalyst preparation, and particularly discloses a titanium-silicon molecular sieve catalyst preparation method, which comprises the following process steps: a, aging reaction: uniformly mixing raw materials, and performing aging reaction to obtain a silicon-titanium mixed solution; b, crystallization reaction: heating the silicon-titanium mixed solution to perform crystallization reaction, discharging tripropylamine gas and butanol after the reaction is completed, and obtaining a silicon-titanium sol solution; c, membrane separation: separating the silicon-titanium sol solution to obtain a clear liquid and a concentrated liquid; d, spray drying: mixing the concentrated liquid and auxiliary materials, and performing spray drying to obtain titanium-silicon molecular sieve catalyst powder; and e, calcination: calcining the titanium-silicon molecular sieve catalyst powder to obtain titanium-silicon molecular sieve catalyst products. The titanium-silicon molecular sieve catalyst preparation process has the advantages of low production cost, good stability, high safety and the like, and the titanium-silicon molecular sieve catalyst has high catalytic efficiency and good stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a preparation method of titanium-silicon molecular sieve catalyst. BACKGROUND

[0002] The increasingly severe energy and environmental problems have put forward higher requirements for the development of green chemistry, and high-performance catalysts play a decisive role in improving the activity, selectivity of chemical reactions and reducing the operation and energy consumption of chemical reactions.

[0003] Titanium-silicon molecular sieve is a three-dimensional pore structure composed of two sets of ten-membered ring pores and one set of nine-membered ring pores, the first set of ten-membered ring pores is composed of ten-membered rings composed of four coordination atoms; the second set of ten-membered ring pores is also composed of ten-membered rings composed of four coordination atoms, and is perpendicular to the first set of pores; the nine-membered ring pores are interlaced with the two sets of ten-membered ring pores and are composed of nine-membered rings composed of four coordination atoms. The titanium-silicon molecular sieve has a molar composition of TiO2:SiO2=0.001:0.2, and the molecular sieve can be used as a catalyst for catalytic oxidation. Due to the action of the framework titanium atom, TS-1 molecular sieve can be applied to the fields of olefin epoxidation and cyclohexanone ammoxidation, alcohol oxidation catalyst, saturated hydrocarbon oxidation and aromatic hydrocarbon (phenol and benzene) hydroxylation. The clean reaction using titanium-silicon molecular sieve as catalyst has many advantages such as environmental friendliness, safety, low cost of raw materials, low equipment investment, etc., and has become one of the most advanced and fastest industrialized clean production processes in the world.

[0004] The preparation process of titanium-silicon molecular sieve catalyst mainly includes hydrolysis of ethyl silicate and tetrabutyl titanate into gel, crystallization, separation and drying and calcination processes. CN102614911 discloses a method for one-step molding of titanium-silicon molecular sieve. In an isopropanol solvent containing tetraethyl orthosilicate as a silicon source and tetrabutyl titanate as a titanium source, a hydrolysis reaction is carried out with tetrapropylammonium hydroxide as a template agent. The obtained raw material liquid is prepared into a gel by alcohol removal, and the obtained gel is crystallized to obtain a crystallization liquid containing a titanium-silicon molecular sieve precursor. A matrix material, a binder, a peptizing agent and a pore-expanding agent are directly added to the crystallization liquid for beating, and the obtained slurry is spray-formed and calcined to obtain a titanium-silicon molecular sieve catalyst. In this patent, the matrix material, the binder, the peptizing agent and the pore-expanding agent are directly added to the crystallization liquid for beating, and then spray drying and calcination are carried out. In the preparation of titanium-silicon molecular sieve catalyst, the raw materials used include ethyl silicate and tetrabutyl titanate, isopropanol, a template agent, and auxiliary materials such as a matrix material, a binder, a peptizing agent and a pore-expanding agent used in spray drying, and the production cost is high. In order to further reduce the production cost, improve the economic benefit of enterprises, improve the market competitiveness, and not reduce the product quality, it is necessary to further study the preparation method of titanium-silicon molecular sieve catalyst. SUMMARY

[0005] To address the issue of high production costs in existing methods for preparing titanium-silicon molecular sieve catalysts, this invention provides a method for preparing titanium-silicon molecular sieve catalysts.

[0006] To achieve the above-mentioned objectives, the embodiments of the present invention employ the following technical solutions:

[0007] A method for preparing a titanium-silicon molecular sieve catalyst includes the following process steps:

[0008] a. Aging reaction

[0009] Silica sol, tetrabutyl titanate, water, template agent, and hydrogen peroxide are mixed evenly in an aging reactor and subjected to an aging reaction to obtain a silicon-titanium mixed solution.

[0010] The molar ratio of the added raw materials silica sol, tetrabutyl titanate, water, template agent, and hydrogen peroxide is 1:(0.01-0.06):(2-25):(0.01-0.5):(0.1-1);

[0011] The template agent is an organic quaternary ammonium salt and an organic base, preferably tetrapropylammonium hydroxide;

[0012] The reaction temperature is controlled between 50-90℃;

[0013] The aging reaction time is 0.5-2 hours.

[0014] During the reaction, the reaction solution is stirred at a speed of 20-110 rpm.

[0015] Additionally, a silsesquioxane quaternary ammonium salt structure directing agent can be added, and its reaction mechanism is as follows:

[0016] The silsesquioxane quaternary ammonium salt structure directing agent is obtained by amino addition reaction of tetraallylammonium bromide, acrylate-cage-shaped polysilsesquioxane, and 1,1'-diaminoferrocene.

[0017] The amount of the silsesquioxane quaternary ammonium salt structure directing agent added is 0.1-8% of the total amount of the template agent, and is further optimized to 1-4% of the total amount of the template agent;

[0018] The preparation method of the silsesquioxane quaternary ammonium salt structure directing agent is as follows:

[0019] In a closed stirring reaction kettle, the air is replaced with nitrogen, then 10-20 parts of tetraallyl ammonium bromide, 0.1-2.5 parts of acrylic cage polysilsesquioxane, 16-25 parts of 1,1'-diaminoferrocene, 100-200 parts of DMF, 3-8 parts of organic base are added, stirred at 60-70℃ for 60-100 minutes, and then the DMF is removed by distillation to obtain a silsesquioxane quaternary ammonium salt structure directing agent.

[0020] The organic base is selected from one or more of the following: dimethylamine, triethylamine, N-methyl-n-propylamine, N-methyl-isopropylamine, N-methyl-ethylamine.

[0021] b. Crystallization reaction

[0022] The silicon-titanium mixed solution obtained in step a is fed into a high-pressure crystallization reactor, and the temperature is raised to 140-210℃ for crystallization reaction. After the reaction is completed, 1h is used to discharge the tripropylamine gas generated during the crystallization reaction and the butanol generated during the aging reaction to obtain a silicon-titanium sol solution;

[0023] The maximum pressure during the crystallization reaction is 0.9-1.8 MPa.

[0024] The crystallization reaction time is 24-72h.

[0025] During the crystallization reaction, the reaction solution is stirred at a stirring speed of 10-90 rpm.

[0026] The temperature rising rate during the crystallization reaction is 5-35℃ / h.

[0027] The solid content of the silicon-titanium sol is 4-16%.

[0028] c. Membrane separation

[0029] The silicon-titanium sol solution obtained in step b is separated using a membrane separation system. When concentrated to a certain concentration multiple, pure water is continuously added to wash the titanium-silicon molecular sieve catalyst to obtain a clear liquid and a concentrated liquid.

[0030] The membrane in the membrane separation system is a ceramic membrane or a metal membrane, and the filtration precision of the membrane is 30nm-0.5μm.

[0031] The temperature during membrane filtration is 30-70℃, and the pressure is 0.25-0.65 MPa.

[0032] During membrane filtration, water washing is used to remove small molecular impurities in the silicon-titanium sol solution. The water washing mass is 20-45% of the mass of the silicon-titanium sol solution.

[0033] The concentration multiple is 1.5-2.5.

[0034] The solid content of the concentrated solution is 10-40%.

[0035] d. spray drying

[0036] The concentrated solution obtained in step c is mixed with the auxiliary material, and spray drying is performed to separate water discharge and obtain titanium silicalite catalyst powder at the same time;

[0037] The hot air or nitrogen gas used in the spray drying is at 270-380 DEG C.

[0038] The auxiliary material is a titanium silicate sol solution with a solid content of 5-25%.

[0039] The mass ratio of the concentrated solution to the auxiliary material is 1:(0.1-0.45).

[0040] e. calcination

[0041] The titanium silicalite catalyst powder obtained in step d is calcined at 400-900 DEG C to further remove impurities in the titanium silicalite catalyst powder to obtain a titanium silicalite catalyst product.

[0042] Compared with the prior art, the method for preparing a titanium silicalite catalyst has the following advantages:

[0043] (1) In the present application, the use of silica sol instead of ethyl silicate can greatly reduce the production cost.

[0044] (2) In the present application, the use of isopropyl alcohol is avoided, the production cost is saved, the problem of high difficulty in subsequent separation of isopropyl alcohol and butanol in the prior art is completely solved, and the energy consumption is reduced.

[0045] (3) The use of titanium silicate sol solution as an auxiliary material for spray drying avoids the use of auxiliary materials such as matrix material, binder, glue solvent and hole expanding agent, and further reduces the production cost.

[0046] (4) In the present application, the membrane separation technology is used for concentration and dehydration, which reduces the energy consumption compared with the existing evaporation dehydration technology, and at the same time, the impurities in the titanium silicate sol solution can be removed during the membrane separation, and the product quality is improved.

[0047] (5) Ammonium bromide containing ammonium bromide and polysilsesquioxane can be used for the synthesis of titanium silicalite molecular sieve, which can increase the particle size of titanium silicalite molecular sieve, thereby improving its catalytic performance and selectivity. Polysilsesquioxane is an organic silicon compound with a cage structure, which can be combined with the surface of titanium silicalite molecular sieve through hydrogen bonding and π-π interaction, etc. to promote the aggregation and growth of titanium silicalite molecular sieve, thereby increasing its particle size. Ammonium bromide containing ammonium bromide and polysilsesquioxane can increase the particle size of titanium silicalite molecular sieve by promoting its aggregation and growth, thereby improving its catalytic performance and selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is the process flow chart of the preparation method of the titanium silicalite molecular sieve catalyst provided by the embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0050] Example 1

[0051] A preparation method of a titanium silicalite molecular sieve catalyst, comprising the following process steps:

[0052] a, aging reaction

[0053] Silica sol, tetrabutyl titanate, water, tetrapropylammonium hydroxide, hydrogen peroxide were mixed uniformly in a molar ratio of 1:0.03:5:0.2:0.4 in an aging reactor, and an aging reaction was carried out at 60°C to obtain a silicon-titanium mixed solution, the reaction time was 30 minutes, and the stirring speed was 30 rpm.

[0054] Among them, the reaction kettle is added with a silsesquioxane quaternary ammonium salt structure directing agent before the raw materials are mixed, and the amount of the silsesquioxane quaternary ammonium salt structure directing agent is 1% of the total amount of the template;

[0055] The preparation method of the silsesquioxane quaternary ammonium salt structure directing agent is as follows:

[0056] In a sealed stirring reaction kettle, the air was replaced with nitrogen, then 10g of tetraallyl ammonium bromide, 0.5g of acrylic cage polysilsesquioxane, 16g of 1,1'-diaminoferrocene, 10g of DMF, and 3g of organic base were added, and stirred at 60°C for 60 minutes. Distill the DMF to obtain the silsesquioxane quaternary ammonium salt structure directing agent.

[0057] The organic base is selected from triethylamine.

[0058] b, crystallization reaction

[0059] The silicon-titanium mixed solution obtained in step a is fed into a high-pressure crystallization reactor, and the temperature is increased to 190℃ at a rate of 10℃ / h to perform the crystallization reaction. During the crystallization reaction, the solution is stirred at a stirring speed of 15 rpm. After 35 h of reaction, the pressure in the crystallization reactor reaches 1.1 MPa. The tripropylamine gas generated during the crystallization reaction and the butanol generated during the aging reaction are discharged in 1 h. A silicon-titanium sol solution with a solid content of 7% is obtained.

[0060] c. Membrane separation

[0061] The silicon-titanium sol solution with a solid content of 7% obtained in step b is separated by using a ceramic membrane separation system with a filtration precision of 30 nm. During the separation, the temperature is 30℃ and the pressure is 0.35 MPa. When the concentration multiple is 2.5, 20% of the mass of the silicon-titanium sol solution of purified water is added to wash and remove the impurities in the silicon-titanium sol solution to obtain a clear liquid and a concentrated solution with a solid content of 20%.

[0062] d. Spray drying

[0063] The concentrated solution with a solid content of 20% obtained in step c and the silicon-titanium sol solution with a solid content of 10% are mixed. The mass ratio of the concentrated solution to the silicon-titanium sol solution is 1:0.2. Hot air at 300℃ is used for spray drying to separate and discharge water, and a titanium silicalite catalyst powder is obtained.

[0064] e. Calcination

[0065] The titanium silicalite catalyst powder obtained in step d is calcined at 550℃ to further remove the impurities in the titanium silicalite catalyst powder to obtain a titanium silicalite catalyst product.

[0066] Example 2

[0067] A method for preparing a titanium silicalite catalyst, comprising the following process steps:

[0068] a. Aging reaction

[0069] A silicon sol, tetrabutyl titanate, water, tetrapropylammonium hydroxide, and hydrogen peroxide are mixed uniformly in an aging reactor at a molar ratio of 1:0.05:20:0.4:1. An aging reaction is performed at 80℃ to obtain a silicon-titanium mixed solution. The reaction time is 2 h. The solution is stirred at a stirring speed of 110 rpm during the reaction.

[0070] Before the raw materials are mixed, a silsesquioxane quaternary ammonium salt structure directing agent is added to the reactor. The amount of the silsesquioxane quaternary ammonium salt structure directing agent added is 4% of the total amount of the template.

[0071] The preparation method of the silsesquioxane quaternary ammonium salt structure directing agent is as follows:

[0072] In a closed stirring reaction kettle, air is replaced with nitrogen, then 15 g of tetraallyl ammonium bromide, 1.5 g of acrylic cage polysilsesquioxane, 20 g of 1,1'-diaminoferrocene, 150 g of DMF, 5 g of organic base are added, stirred at 65℃ for 80 minutes, and then DMF is removed by distillation to obtain a silsesquioxane quaternary ammonium salt structure directing agent.

[0073] The organic base is selected from N-methyl-n-propylamine.

[0074] b. Crystallization reaction

[0075] The silicon-titanium mixed solution obtained in step a is fed into a high-pressure crystallization reactor, and the temperature is raised to 160℃ at a rate of 20℃ / h for crystallization reaction. During the crystallization reaction, the solution is stirred at a stirring speed of 60 rpm. After 71 h of reaction, the pressure in the crystallization reactor reaches 1.5 MPa. The tripropylamine gas generated during the crystallization reaction and the butanol generated during the aging reaction are discharged in 1 h to obtain a silicon-titanium sol solution with a solid content of 11%.

[0076] c. Membrane separation

[0077] The silicon-titanium sol solution with a solid content of 11% obtained in step b is separated by a ceramic membrane separation system with a filtration precision of 200 nm. During the separation, the temperature is 50℃ and the pressure is 0.40 MPa. When the concentration multiple is 2, 25% of the mass of the silicon-titanium sol solution of pure water is added to wash and remove impurities in the silicon-titanium sol solution to obtain a clear liquid and a concentrated liquid with a solid content of 25%.

[0078] d. Spray drying

[0079] The concentrated liquid with a solid content of 25% obtained in step c and the silicon-titanium sol solution with a solid content of 15% are mixed, and the mass ratio of the concentrated liquid to the silicon-titanium sol solution is 1:0.25. Hot air at 340℃ is used for spray drying to separate and discharge water, and at the same time, a titanium silicalite catalyst powder is obtained.

[0080] e. Calcination

[0081] The titanium silicalite catalyst powder obtained in step d is calcined at 700℃ to further remove impurities in the titanium silicalite catalyst powder to obtain a titanium silicalite catalyst product.

[0082] Example 3

[0083] A method for preparing a titanium silicalite catalyst, comprising the following process steps:

[0084] a. Aging reaction

[0085] Silica sol, tetrabutyl titanate, water, tetrapropyl ammonium hydroxide, hydrogen peroxide were mixed in a molar ratio of 1:0.03:13:0.3:0.5 in a aging reactor, and aging reaction was carried out at 70°C to obtain a silicon-titanium mixed solution, the reaction time was 1h, and the stirring speed was 50rpm.

[0086] The silsesquioxane quaternary ammonium salt structure directing agent was added into the reactor before mixing the raw materials, and the amount of the silsesquioxane quaternary ammonium salt structure directing agent was 6% of the total amount of the template.

[0087] The preparation method of the silsesquioxane quaternary ammonium salt structure directing agent is as follows:

[0088] In a closed stirring reactor, the air was replaced with nitrogen, then 20g of tetraallyl ammonium bromide, 2.5g of acrylic cage polysilsesquioxane, 25g of 1,1'-diaminoferrocene, 200g of DMF, and 8g of organic base were added, and stirring was carried out at 70°C for 100 minutes, and then DMF was removed by distillation to obtain the silsesquioxane quaternary ammonium salt structure directing agent.

[0089] The organic base is selected from one or more mixtures of N-methyl ethylamine.

[0090] b. Crystallization reaction

[0091] The silicon-titanium mixed solution obtained in step a was sent to a high-pressure crystallization reactor, and the temperature was raised to 175°C at a rate of 15°C / h for crystallization reaction. During the crystallization reaction, stirring was carried out at a stirring speed of 30rpm, and after 55h, the pressure in the crystallization reactor reached 1.3MPa. The generated tripropylamine gas during the crystallization reaction and the generated butanol during the aging reaction were discharged in 1h to obtain a silicon-titanium sol solution with a solid content of 9%.

[0092] c. Membrane separation

[0093] The silicon-titanium sol solution with a solid content of 9% obtained in step b was separated by a metal membrane separation system with a filtration precision of 500nm. During the separation, the temperature was 70°C, the pressure was 0.45MPa, the concentration multiple was 2.3, and 24% of pure water was added to wash and remove impurities in the silicon-titanium sol solution to obtain a clear liquid and a concentrated liquid with a solid content of 23%.

[0094] d. Spray drying

[0095] The concentrated liquid with a solid content of 23% obtained in step c and the silicon-titanium sol solution with a solid content of 12% were mixed, and the mass ratio of the concentrated liquid to the silicon-titanium sol solution was 1:0.22. Hot nitrogen gas at 330°C was used for spray drying, water was separated and discharged, and a titanium-silicon molecular sieve catalyst powder was obtained.

[0096] e. Calcination

[0097] The titanium silicalite catalyst powder obtained in step d is calcined at 600°C to further remove impurities in the titanium silicalite catalyst powder to obtain a titanium silicalite catalyst product.

[0098] Comparative Example 1

[0099] A method for preparing a titanium silicalite catalyst includes the following process steps:

[0100] a. Aging reaction

[0101] Ethyl silicate, tetrabutyl titanate, water, tetrapropyl ammonium hydroxide, and hydrogen peroxide are mixed in a molar ratio of 1:0.08:25:0.1:0.1 in an aging reactor, and an aging reaction is performed at 50°C to obtain a silicon-titanium mixed solution, with a reaction time of 3h and a stirring speed of 130rpm.

[0102] b. Crystallization reaction

[0103] The silicon-titanium mixed solution obtained in step a is fed into a high-pressure crystallization reactor, and a crystallization reaction is performed at a temperature increasing rate of 30°C / h to 200°C, with a stirring speed of 15rpm during the reaction, and after 55h, the pressure in the crystallization reactor reaches 1.8MPa, and the generated tripropylamine gas during the crystallization reaction and butanol generated during the aging reaction are discharged for 1.5h to obtain a silicon-titanium sol solution with a solid content of 12%.

[0104] c. Membrane separation

[0105] The silicon-titanium sol solution with a solid content of 9% obtained in step b is separated by a ceramic membrane separation system with a filtration precision of 30nm, with a temperature of 30°C and a pressure of 0.35MPa, and when the concentration multiple is 2.1, 30% of the silicon-titanium sol solution is added with purified water to wash and remove impurities in the silicon-titanium sol solution to obtain a clear liquid and a concentrated liquid with a solid content of 25%.

[0106] d. Spray drying

[0107] The concentrated liquid with a solid content of 25% obtained in step c is mixed with a base material, a binder, a peptizing agent, and a pore-expanding agent to obtain a slurry with a solid content of 30%, and the slurry is spray dried by hot nitrogen gas at 350°C to separate and discharge water, and a titanium silicalite catalyst powder is obtained.

[0108] e. Calcination

[0109] The titanium silicalite catalyst powder obtained in step d is calcined at 500°C to further remove impurities in the titanium silicalite catalyst powder to obtain a titanium silicalite catalyst product.

[0110] The specific surface area, pore volume, conversion and selectivity of the catalytic reaction of the titanium silicalite catalysts obtained in Examples 1-3 and Comparative Example 1 for the aminooxylation of cyclohexanone were measured, and the production costs were compared. The results of the measurements and the comparison of the raw material costs are shown in Table 1.

[0111] Table 1

[0112]

[0113] The above description is merely preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A process for the preparation of a titanium silicalite molecular sieve catalyst characterized by: The process comprises the following steps: a. aging reaction: uniformly mix silica sol, tetrabutyl titanate, water, template agent, hydrogen peroxide in an aging reactor, and then carry out aging reaction to obtain a silica-titanium mixed solution; b. crystallization reaction: feed the silica-titanium mixed solution obtained in step a into a high-pressure crystallization reactor, and then carry out crystallization reaction by heating, and then discharge tripropylamine gas and butanol after the reaction is completed to obtain a silica-titanium sol solution; c. membrane separation: separate the silica-titanium sol solution obtained in step b by using a membrane separation system to obtain a clear liquid and a concentrated liquid; d. spray drying: mix the concentrated liquid obtained in step c and auxiliary materials, and then carry out spray drying to separate and discharge water, and then obtain a titanium-silicon molecular sieve catalyst powder; e. calcination: carry out calcination on the titanium-silicon molecular sieve catalyst powder obtained in step d to further remove impurities in the titanium-silicon molecular sieve catalyst powder to obtain a titanium-silicon molecular sieve catalyst product; In step a, the aging reaction is carried out by adding a silsesquioxane quaternary ammonium salt structure directing agent in an amount of 0.1-8% of the total amount of the template agent. The preparation method of the silesquioxane quaternary ammonium salt structure directing agent is as follows: In a closed stirring reactor, replace air with nitrogen, and then add 10-20 parts of tetraallyl ammonium bromide, 0.1-2.5 parts of acrylic cage-shaped poly-silsesquioxane, 16-25 parts of 1,1'-diamino ferrocene, 100-200 parts of DMF, 3-8 parts of an organic base, and then stir at 60-70℃ for 60-100 minutes, and then distill off the DMF to obtain the silesquioxane quaternary ammonium salt structure directing agent.

2. The method of making a titanium silicalite molecular sieve catalyst according to Claim 1 wherein: In step a, the molar ratio of the raw materials silica sol, tetrabutyl titanate, water, template agent, and hydrogen peroxide is 1:(0.01-0.06):(2-25):(0.01-0.5):(0.1-1); The template agent is tetrapropyl ammonium hydroxide; The reaction temperature is controlled at 50-90℃; The aging reaction time is 0.5-2h; The reaction liquid is stirred during the reaction, and the stirring speed is 20-110rpm.

3. The method of making a titanium silicalite molecular sieve catalyst according to Claim 1 wherein: In step b, the crystallization reaction temperature is 140-210℃; The maximum pressure during the crystallization reaction is 0.9-1.8MPa; The crystallization reaction time is 24-72h; The reaction liquid is stirred during the crystallization reaction, and the stirring speed is 10-90rpm; The temperature rising rate during the crystallization reaction is 5-35℃ / h; The solid content of the silica-titanium sol is 4-16%.

4. The method of making a titanium silicalite molecular sieve catalyst according to Claim 1 wherein: In step c, the membrane in the membrane separation system is a ceramic membrane or a metal membrane, and the filtration precision of the membrane is 30nm-0.5μm; The temperature during the membrane separation is 30-70℃, and the pressure is 0.25-0.65MPa; During the membrane separation, water is added to wash the silica-titanium sol solution to remove small molecular impurities; The mass of the water is 20-45% of the mass of the silica-titanium sol solution; The concentration multiple is 1.5-2.5; The solid content of the concentrated liquid is 10-40%.

5. The method of making a titanium silicalite molecular sieve catalyst of claim 1 wherein: In step d, hot air or nitrogen at 270-380℃ is used during the spray drying; The auxiliary material is a silica-titanium sol solution with a solid content of 5-25%; The mass ratio of the concentrated solution to the adjuvant is 1:(0.1-0.45).

6. The method of making a titanium silicalite molecular sieve catalyst of claim 1 wherein: In step e, the calcination temperature is 400-900 DEG C.

7. The method of making a titanium silicalite molecular sieve catalyst of claim 1 wherein: In step a, the addition amount of the silsesquioxane quaternary ammonium salt structure directing agent is optimized to be 0.5-4.5% of the total amount of the template agent.

8. The method of making a titanium silicalite molecular sieve catalyst of claim 1 wherein: In step a, the organic base is selected from one or more mixtures of dimethylamine, triethylamine, N-methyl-n-propylamine, N-methyl-isopropylamine, N-methyl-ethylamine.

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