Preparation method and application of titanium silicalite molecular sieve catalyst

Abstract

The invention discloses a preparation method of a titanium silicalite molecular sieve catalyst, the catalyst adopts 1, 4-cyclohexane dimethylamine as a template agent, the prepared titanium silicalite molecular sieve is good in crystal form, high in strength and not easy to break, and the problem of slow filtration of the catalyst in the production process is well solved. Meanwhile, the invention also discloses an application method of the catalyst in preparation of benzenediol by oxidizing phenol with hydrogen peroxide, a polar compound is used as a solvent, the phenol conversion rate in the oxidation reaction can reach more than 20%, the total selectivity of hydroquinone and catechol can reach more than 90%, and the output ratio of hydroquinone to catechol can reach more than 8: 1. In addition, the catalyst can be continuously used for more than 20 times under working conditions, and is especially suitable for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic oxidation, and specifically relates to a method for preparing a titanium silicon molecular sieve and an application of the method in preparing hydroquinone by hydroxylation of phenol. Background Art

[0002] Hydroquinone and catechol are important isomers of catechol. Hydroquinone is widely used in the fields of inhibitors, rubber industry antioxidants, special engineering plastics, food antioxidants, dye intermediates, photosensitive materials, pesticide intermediates and pharmaceutical intermediates. Especially with the development and growth of acrylic acid and its special esters in recent years, the demand for hydroquinone has increased year by year, and its price has also risen accordingly. The selling price of hydroquinone is about more than twice that of catechol.

[0003] Because the titanium silicate catalytic system is environmentally friendly, the preparation process is simple, and it is suitable for industrialization, there are many studies on titanium silicate in China, but few can be applied to the hydroxylation of phenol to prepare hydroquinone. U.S. Patent US4410501 first reported the TS-1 titanium silicate synthesized with tetraethyl silicate as silicon source, tetrabutyl titanate as titanium source, and tetrapropylammonium hydroxide as template. This catalyst can be well used in the industry of preparing hydroquinone by hydroxylation of phenol with hydrogen peroxide, but there are problems such as low selectivity of the catalyst for hydroquinone, difficulty in filtering, easy wear of the catalyst after long-term use, and decreased selectivity.

[0004] This application was developed based on this. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing titanium silicalite and its application in the hydroxylation of phenol to prepare hydroquinone. This application successfully synthesized a titanium silicalite catalyst that can be well applied to the hydroxylation of phenol to prepare hydroquinone by improving the template and preparation process on the basis of hydrothermal synthesis of titanium silicalite. At the same time, the present invention discloses the application method of the catalyst in the oxidation of phenol to prepare hydroquinone by hydrogen peroxide. With polar compounds as solvents, the phenol conversion rate in the oxidation reaction can reach more than 20%, the total selectivity of hydroquinone and catechol can reach more than 90%, and the output ratio of hydroquinone and catechol can reach more than 8:1. In addition, the catalyst can be continuously applied more than 20 times under working conditions, which is particularly suitable for industrial application.

[0006] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a titanium silicon molecular sieve catalyst, wherein tetraethyl silicate (TEOS) is used as a silicon source, tetraethyl titanate (TEOT) is used as a titanium source, and 1,4-cyclohexanedimethylamine is used as a template agent to prepare the titanium silicon molecular sieve catalyst; The amount of the template added is 10-50% of the total mass of the silicon source and the titanium source, preferably 15-35%.

[0007] Specifically, in the obtained titanium silicon molecular sieve catalyst, the molar ratio of Si atoms to Ti atoms can be 25-30:1, that is, n(Si):n(Ti)=25-30.

[0008] As a preferred method, the preparation method of the titanium silicon molecular sieve catalyst is prepared by hydrothermal synthesis, which specifically comprises the following steps: Step 1: prepare tetraethyl titanate TEOT and part of tetraethyl silicate TEOS into a mixed solution A; prepare the template into an aqueous solution B of a certain concentration; Step 2: Place part of aqueous solution B in a container, heat it to 30-100°C (preferably 40-70°C) in a water bath while stirring, add mixed solution A dropwise while stirring, and keep warm for 2-4 hours after the addition is complete to obtain a uniform transparent solution; Step 3: transfer the homogeneous transparent solution obtained in step 2 into a hydrothermal synthesis reactor, perform hydrothermal reaction at 150-250° C. for 0.1-10 h, and cool down to obtain a gel solution; Step 4: Add the remaining amount of aqueous solution B and the remaining amount of tetraethyl silicate TEOS (as a binder) to the gel solution obtained in step 3 under stirring, mix well, heat to 30-120° C. (preferably 50-80° C.) and keep warm for 1-2 hours to obtain a gel solution after bonding; Step 5: spray drying the gel solution obtained in step 4 to obtain a powdered catalyst precursor; Step 6: calcine the powdered catalyst precursor obtained in step 5 at 350-750° C. for 2-10 hours, and cool it down naturally to obtain the catalyst.

[0009] Furthermore, in the mixed solution A in step 1, the mass ratio of tetraethyl silicate to tetraethyl titanate can be 1:(0.045-0.055); and the concentration of the aqueous solution B can be 10-20%.

[0010] Furthermore, the hydrothermal reaction temperature in step three is preferably 180-220° C., and the hydrothermal reaction time is preferably 1-5 h.

[0011] During the preparation process of the above-mentioned titanium silicon molecular sieve catalyst, the template and tetraethyl silicate can be added twice, the first time to participate in the preparation of the hydrothermal crystal form, preferably adding about 85% of the total amount, and the second time as a binder, preferably adding about 15% of the total amount; in step one, 80-90% (preferably 85%) of the total amount of tetraethyl silicate can be added to prepare a mixed solution A, and in step two, 80-90% (preferably 85%) of the total amount of aqueous solution B can be placed in a container.

[0012] The present invention provides a titanium silicon molecular sieve catalyst prepared by the above-mentioned preparation method. The catalyst uses 1,4-cyclohexanedimethylamine as a template agent, and the prepared titanium silicon molecular sieve has a good crystal form and high strength, is not easy to break, and well solves the problem of slow catalyst filtration in the production process. At the same time, the present invention discloses an application method of the catalyst in the oxidation of phenol to prepare hydroquinone by hydrogen peroxide, using a binary polar mixture as a solvent. In the oxidation reaction, the total selectivity of hydroquinone and catechol can reach more than 90%, and the output ratio of hydroquinone and catechol can reach more than 8:1. In addition, the catalyst can be continuously applied more than 20 times under working conditions, and is particularly suitable for industrial application.

[0013] The present invention also provides the use of the titanium silicon molecular sieve catalyst in reaction processes such as phenol hydroxylation, olefin epoxidation, cyclohexanone ammoxidation, saturated hydrocarbon oxidation, aromatic hydrocarbon hydroxylation and pyridine oxidation, and is particularly suitable for the project of preparing diphenol by phenol hydroxylation.

[0014] Further, in the above application, the titanium silicon molecular sieve catalyst is used to catalyze the oxidation of phenol to produce diphenol by hydrogen peroxide, specifically: According to the feed ratio of phenol: 2 O 2 : Catalyst: solvent = 62:10.5:7:70-80. First, add phenol, catalyst and solvent into the reaction kettle in proportion, heat to 70-80°C with stirring, then add hydrogen peroxide dropwise for 120 minutes. After the addition is completed, continue to keep the temperature for 120 minutes, cool down, filter, and take samples for analysis.

[0015] Furthermore, the solvent used includes but is not limited to one or more of water, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol (C2-C5 diols), 1,4-dioxane, 1,3-dioxolane, etc.; the solvent is preferably a mixture of 1,4-dioxane and water, and the proportion of water in the mixed solvent is 10-80%, preferably 20-50%. 2 O 2 The concentration of hydrogen peroxide can be 10-50%, preferably 20-40%, and most preferably 35%.

[0016] Furthermore, the present invention provides a catalyst regeneration process and a catalyst application method. The catalyst application is specifically as follows: the filtered catalyst is washed with a solvent, 1 / 3 is washed with water and then transferred to a rotary kiln, heated to 550°C for 300 minutes and roasted for 5 hours, and then naturally cooled to room temperature after roasting, combined with the unroasted catalyst and applied, and 3% of the total catalyst is supplemented with new catalyst.

[0017] The invention discloses a method for preparing a titanium silicon molecular sieve catalyst. The catalyst uses 1,4-cyclohexanedimethylamine as a template agent. The prepared titanium silicon molecular sieve has good crystal form and high strength, is not easy to break, and well solves the problem of slow catalyst filtration in the production process. The catalyst uses tetraethyl silicate (TEOS) as a silicon source, tetraethyl titanate (TEOT) as a titanium source, and uses 1,4-cyclohexanedimethylamine as a template agent. The obtained catalyst n (Si): n (Ti) = 25-30, and the amount of the template agent added is 10-50% of the total mass of the silicon source and the titanium source, preferably 15-25%; the template agent 1,4-cyclohexanedimethylamine and tetraethyl silicate are added twice, the first time to participate in the preparation of the hydrothermal crystal form, and the second time as a binder, and the mass ratios of the two additions are preferably 85% and 15% respectively.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1) The present invention uses 1,4-cyclohexanedimethylamine as a template agent, and the synthesized molecular sieve has good crystal form, high strength, and is not easy to break, so it can be used multiple times; 2) The titanium silicon molecular sieve catalyst of the present invention is applied to the project of preparing hydroquinone by hydroxylation of phenol. With polar organic solvent as reaction solvent, the phenol conversion rate can reach more than 20%, the total selectivity of hydroquinone and catechol can reach more than 90%, and the output ratio of hydroquinone and catechol can reach more than 8:1, which has better economic benefits; 3) The titanium silicate molecular sieve catalyst of the present invention can be continuously applied for more than 20 times under working conditions, and the catalyst particle size is basically unchanged, which is particularly suitable for industrial application. DETAILED DESCRIPTION

[0019] In order to make the technical purpose, technical scheme and beneficial effects of the present invention clearer, the technical scheme of the present invention is further described below in conjunction with specific embodiments. However, the embodiments are intended to explain the present invention and cannot be understood as limiting the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0020] The raw materials and analytical reagents used in the present invention are all common commercially available products that can be directly purchased on the market.

[0021] Room temperature refers to 25±5°C. Unless otherwise specified, all percentages used refer to mass percentages.

[0022] Catalyst Preparation Example 1: The preparation method of the titanium silicon molecular sieve catalyst is prepared by hydrothermal synthesis, and specifically comprises the following steps: 1. Take 23.80g of TEOS (purity 99.7%) and 1.19g of TEOT (TiO2 8.8g of 1,4-cyclohexanedimethylamine (1,4-BAC, purity 99.0%) was used to prepare a 14wt% aqueous solution B with 54.1g of pure water. The aqueous solution B was placed in a three-necked flask, kept warm at 60℃ in a water bath, and the mixed solution A was added dropwise under magnetic stirring for 70min. After the addition was completed, the reaction was continued for 3h to obtain a uniform transparent solution.

[0023] 2. Transfer the above homogeneous transparent solution into a hydrothermal synthesis reactor, close the reactor, start heating, start stirring, set the temperature to 200°C, raise the temperature to 200°C in 80 minutes, keep warm for 2 hours, stop heating, and cool naturally under stirring. After depressurization, open the reactor to obtain a gel solution.

[0024] 3. Add the gel solution obtained by the above crystallization into a three-necked flask and start stirring. Add 11.1g of 14wt% 1,4-BAC solution and 4.2g of TEOS into the three-necked flask, mix well, heat to 70°C and keep warm for 90min to obtain the bonded gel solution.

[0025] 4. The obtained gel solution after bonding was spray dried, the spray dryer was set at an inlet temperature of 300°C, the material was slowly fed, and the material was collected. The obtained material was transferred to a rotary kiln, first heated from room temperature to 350°C for 75 minutes and kept warm for 1 hour, then continued to heat to 550°C for 200 minutes and kept warm for 5 hours, and cooled naturally to obtain the catalyst. In the obtained titanium silicon molecular sieve catalyst, the molar ratio of n (Si) to n (Ti) is 28:1.

[0026] Catalyst Preparation Example 2: The difference from Example 1 is that the amount of template used is reduced to 90% of that in Example 1.

[0027] Catalyst Preparation Example 3: The difference from Example 1 is that the amount of template is increased to 110% of that in Example 1.

[0028] The catalyst prepared above was subjected to relevant catalytic application tests.

[0029] Catalytic test case According to the mass ratio of phenol: 35% hydrogen peroxide: catalyst: solvent = 62:30:7:75, phenol, catalyst and solvent were first added to the reactor in proportion, heated to 75°C under stirring, and then hydrogen peroxide was added dropwise for 120 minutes. After the addition was completed, the reaction was continued at room temperature for 120 minutes, the temperature was lowered, filtered, and sampled for analysis. The filtrate was detected by liquid phase external standard method; the detection conditions were: Agilent liquid chromatograph LC1100, reverse C 18Chromatographic column: OSD-35um, 4.6×250mm; mobile phase: methanol: water = 40:60 (volume ratio); flow rate: 1.0ml / min; optimal detection wavelength: λ=277nm; column oven temperature: 25℃; detection time: 20min; injection volume: 2μL.

[0030] Catalyst application: After the filtered catalyst is washed with solvent, 1 / 3 is washed with water and transferred to a rotary kiln. The temperature is raised to 550°C for 300 minutes and then calcined for 5 hours. After calcination, it naturally cools to room temperature and is combined with the uncalcined catalyst for application, and 3% of the total catalyst is supplemented with new catalyst.

[0031] Water, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol (C2-C5 diols), 1,4-dioxane, 1,3-dioxolane, etc. were used as solvents for evaluation. The results of phenol conversion rate, to-ortho ratio and total selectivity are summarized in the following table.

[0032] Phenol conversion rate = (phenol feed amount - total amount of reaction liquid * liquid phase external standard content) / phenol feed amount * 100%; P-to-ortho ratio = hydroquinone liquid phase external standard content / catechol liquid phase external standard content; Total selectivity = total amount of reaction liquid * (external standard content of hydroquinone liquid phase + external standard content of catechol liquid phase) / (total amount of reaction liquid * phenol conversion rate / molar amount of phenol * molar amount of catechol) * 100%.

[0033] Summary: Example 1 obtained better test results under the conditions of 30% water + 70% 1,4-dioxane mixed solvent, with a phenol conversion rate of 22.7%, a selectivity of 96.5%, and an ortho-to-dipamine ratio of more than 8:1.

[0034] The catalyst obtained in Example 1 was tested with mixed solvents in different proportions, and the results are summarized in the following table.

[0035] Summary: The mixed solvent system of water + 1,4-dioxane containing 20-30% water showed good selectivity.

[0036] Taking the catalyst obtained in Example 1 as an example, 30% water + 70% 1,4-dioxane was used as a mixed solvent for catalyst recycling: After the filtered catalyst was washed with 3 times the amount of the mixed solvent, 1 / 3 of it was taken, washed with 1 time the amount of pure water, transferred to a rotary kiln, heated to 550 °C in 300 min and calcined for 5 h. After the calcination was completed, it was naturally cooled to room temperature, then merged with 2 / 3 of the catalyst obtained by filtration and recycled together, and 3% of the new catalyst was added to supplement the catalyst dosage in the first kettle. The recycling results are shown in the following table.

[0037] Summary: The catalyst obtained in Example 1 was recycled under the recycling conditions, the conversion rate remained above 20%, the selectivity remained above 91.7%, and good reaction activity was still maintained after 20 recycles. The ortho ratio increased during the continuous recycling process.

Claims

1. A method for preparing a titanium silicon molecular sieve catalyst, characterized in that: A titanium silicate molecular sieve catalyst was prepared by using tetraethyl silicate as a silicon source, tetraethyl titanate as a titanium source and 1,4-cyclohexanedimethylamine as a template agent. The added amount of the template agent is 10-50% of the total mass of the silicon source and the titanium source.

2. The method for preparing titanium silicon molecular sieve according to claim 1, characterized in that: In the obtained titanium silicon molecular sieve catalyst, the molar ratio of Si atoms to Ti atoms is 25-30:

1.

3. The method for preparing the titanium silicon molecular sieve catalyst according to claim 1, characterized in that: The steps include: Step 1: prepare tetraethyl titanate and part of tetraethyl silicate into a mixed solution A; prepare the template into an aqueous solution B of a certain concentration; Step 2: Place part of aqueous solution B in a container, heat it to 30-100°C in a water bath while stirring, add mixed solution A dropwise while stirring, and keep warm for 2-4 hours after the addition is complete to obtain a uniform transparent solution; Step 3: transfer the homogeneous transparent solution obtained in step 2 into a hydrothermal synthesis reactor, perform hydrothermal reaction at 150-250° C. for 0.1-10 h, and cool down to obtain a gel solution; Step 4: Add the remaining amount of aqueous solution B and the remaining amount of tetraethyl silicate to the gel solution obtained in step 3 under stirring, mix well, heat to 30-120° C. and keep warm for 1-2 hours to obtain a gel solution after bonding; Step 5: spray drying the gel solution obtained in step 4 to obtain a powdered catalyst precursor; Step 6: calcine the powdered catalyst precursor obtained in step 5 at 350-750° C. for 2-10 hours, and cool it down naturally to obtain the catalyst.

4. The method for preparing the titanium silicon molecular sieve catalyst according to claim 3, characterized in that: In the mixed solution A of step 1, the mass ratio of tetraethyl silicate to tetraethyl titanate is 1:(0.045-0.055); the concentration of aqueous solution B is 10-20%.

5. The method for preparing the titanium silicon molecular sieve catalyst according to claim 3, characterized in that: The hydrothermal reaction temperature of step 3 is 180-220° C., and the hydrothermal reaction time is 1-5 h.

6. The method for preparing the titanium silicon molecular sieve catalyst according to claim 3, characterized in that: The template and tetraethyl silicate are added twice, the first time for participating in the preparation of hydrothermal crystals, and the second time as a binder; in step one, 80-90% of tetraethyl silicate is added to prepare a mixed solution A, and in step two, 80-90% of aqueous solution B is placed in a container.

7. A titanium silicon molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the titanium silicon molecular sieve catalyst according to claim 7 in phenol hydroxylation, olefin epoxidation, cyclohexanone ammoxidation, saturated hydrocarbon oxidation, aromatic hydrocarbon hydroxylation and pyridine oxidation.

9. The use according to claim 8, characterized in that The titanium silicon molecular sieve catalyst is used to catalyze the oxidation of phenol to produce hydroquinone by hydrogen peroxide, specifically: According to the feed ratio of phenol: H2O2: catalyst: solvent = 62:10.5:7:70-80, phenol, catalyst and solvent are first added into the reaction kettle in proportion, heated to 70-80°C under stirring, and then hydrogen peroxide is added dropwise. After the addition is completed, the reaction is continued by keeping the temperature for 120 minutes, cooling, filtering, and sampling for analysis.

10. The use according to claim 9, characterized in that The solvent used is one or more of water, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,4-dioxane and 1,3-dioxolane; H2O2 is selected in the form of hydrogen peroxide with a concentration of 10 to 50%.

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