A process for the preparation of epoxycyclohexane

Abstract

The application discloses a method for preparing epoxycyclohexane, and comprises the following steps: using a titanium-silicon molecular sieve Ti-MWW with surface-loaded covalent organic framework material LZU-1 as a catalyst, namely, LZU-1@Ti-MWW, and catalyzing a cyclohexene epoxidation reaction to generate epoxycyclohexane in the presence of a solvent and an oxidant. The composite molecular sieve catalyst obtained by modifying the covalent organic framework material on the inorganic material titanium-silicon molecular sieve has good catalytic activity in the reaction of preparing epoxycyclohexane through cyclohexene epoxidation, and greatly improves the reaction conversion rate.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals, and specifically relates to a method for preparing cyclohexane oxide by catalyzing the reaction of cyclohexene with hydrogen peroxide using a composite molecular sieve as a catalyst. Background Technology

[0002] Epoxides are important intermediates in petrochemical, fine chemical, and pharmaceutical synthesis. Cyclohexane oxide is an important class of epoxides with highly reactive epoxy groups, which can be selectively ring-opened to transform into a series of other widely used compounds. These compounds are applied in the production of pesticides, plasticizers, and the synthesis of biodegradable monomers, showing promising market prospects. Traditional processes utilize the recovery of light oil waste to obtain cyclohexane oxide, but its production is limited by the yield of the main products cyclohexanone and cyclohexanol, and the product purity is low, severely restricting its development. Therefore, organic synthesis is currently the main source of cyclohexane oxide both domestically and internationally.

[0003] With the maturation of the process for preparing cyclohexene through the unsaturated hydrogenation of benzene, the process of preparing cyclohexane oxide using cyclohexene as a raw material through epoxidation has attracted widespread attention from researchers. Depending on the oxidant used, there are roughly the following preparation routes for synthesizing cyclohexane oxide both domestically and internationally: Organic peroxyacid method, commonly using peroxyformic acid or acetic acid as oxidants, but peroxyacids are unstable and easily decompose; Hypochlorous acid oxidation method, the first reported method in Japanese patents involving the addition of cyclohexene to HOCl followed by condensation to form a ring, but this method generates a large amount of wastewater and requires strong alkali treatment, causing significant environmental pollution; Molecular oxygen oxidation method, which requires the use of aldehydes as co-oxidants, is a relatively clean and environmentally friendly route, but has low yields and complex separation; Hydrogen peroxide oxidation method, which is inexpensive, environmentally friendly, and produces non-toxic, harmless, and pollution-free water as the oxidation product, aligning with the current trend of green chemistry, but using hydrogen peroxide as an oxidant usually requires the addition of a highly efficient catalyst to enhance its activity during the reaction.

[0004] The hydrogen peroxide oxidation method aligns with the current trend of green chemistry, and its application prospects are promising if a highly efficient catalyst can be developed. Current reports indicate that a novel catalytic oxidation system composed of titanium silicate molecular sieves and hydrogen peroxide overcomes the harsh conditions and environmental pollution associated with traditional processes, and exhibits good catalytic activity in the synthesis of propylene oxide. However, its application in the cyclohexene epoxidation system suffers from drawbacks such as low cyclohexene conversion and low yield of the target product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing cyclohexane oxide. This invention modifies an inorganic titanium-silicon molecular sieve with a covalent organic framework material to obtain a composite molecular sieve catalyst. This catalyst exhibits excellent catalytic activity in the epoxidation of cyclohexene to prepare cyclohexane oxide, significantly improving the reaction conversion rate.

[0006] The method for preparing cyclohexane oxide of the present invention includes the following steps: using a titanium-silicon molecular sieve Ti-MWW with a surface-supported covalent organic framework material LZU-1 as a catalyst, denoted as LZU-1@Ti-MWW, to catalyze the epoxidation reaction of cyclohexene to generate cyclohexane oxide in the presence of a solvent and an oxidant.

[0007] In the method of this invention, the catalyst, based on weight, comprises 0.8%–9.0% LZU-1 and 91.0%–99.2% Ti-MWW. The preparation method of the catalyst LZU-1@Ti-MWW in this invention includes the following steps: mixing titanium silicate molecular sieve Ti-MWW, mesitylene formaldehyde, p-phenylenediamine, and ethanol evenly, then adding an aqueous acetic acid solution, performing hydrothermal crystallization, followed by washing and drying to obtain the catalyst.

[0008] The mass ratio of the titanium-silicon molecular sieve Ti-MWW, mesitylene formaldehyde, p-phenylenediamine, and ethanol is 1:0.05~0.3:0.05~0.3:5~15.

[0009] The concentration of the acetic acid aqueous solution is 1 mol / L to 6 mol / L, and the amount added is 0.1 to 0.5 mL.

[0010] The hydrothermal crystallization treatment is generally carried out in a high-pressure reactor, with hydrothermal crystallization conditions of 100-150℃ and a reaction time of 2-5 days.

[0011] The washing process described is a conventional vacuum filtration washing process in the field of molecular sieves. For example, anhydrous ethanol can be used to wash 2 to 5 times until the filtrate is colorless.

[0012] The drying conditions are as follows: drying temperature is 60-100℃, and drying time is 4-6 hours.

[0013] In the method of the present invention, the oxidant is one or more of hydrogen peroxide solution and tert-butyl hydrogen peroxide solution, the oxidant mass concentration is 30% to 70%, and the amount used is 0.2 to 2.0 g H2O2 / g cyclohexene, preferably 1.0 to 1.5 g H2O2 / g cyclohexene.

[0014] In the method of the present invention, the solvent is one or more of methanol, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide, preferably acetonitrile.

[0015] In the method of this invention, the cyclohexene epoxidation reaction conditions are: reaction temperature 50-90℃, reaction time 2-6h.

[0016] In the method of the present invention, the amount of LZU-1@Ti-MWW used is 0.05 to 0.75 g / g cyclohexene, and the amount of catalyst used is preferably 0.1 to 0.3 g / g cyclohexene.

[0017] Compared with the prior art, the present invention has achieved the following beneficial effects: The present invention prepares a novel organic-inorganic composite catalytic material LZU-1@Ti-MWW by depositing covalent organic framework materials on the surface of titanium-silicon molecular sieves. The surface polarity of the titanium-silicon molecular sieve can be controlled by adjusting the amount of organic monomers added. The preparation method is simple and easy to operate. When this composite catalyst is used in the reaction process to prepare cyclohexane oxide, the conditions are mild, and its catalytic activity is improved compared with titanium-silicon molecular sieves without surface deposition. Higher raw material conversion rate is obtained at a lower reaction temperature. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the titanium-silicon molecular sieve Ti-MWW.

[0019] Figure 2 This is a scanning electron microscope image of the catalyst LZU-1@Ti-MWW from Example 1. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention.

[0021] Example 1

[0022] 16 mg of triphenylmethane, 16 mg of p-phenylenediamine, 0.2 g of Ti-MWW, and 2 mL of ethanol were placed in a 10 mL pressure-resistant tube. After thorough shaking and sonication, 0.2 mL of 3 mol / L acetic acid aqueous solution was added. The air in the upper layer of the solution was replaced with nitrogen, and the tube was placed in an oven at 120 °C for 3 days. The resulting solid powder was filtered, washed three times with anhydrous ethanol, dried at 100 °C for 6 hours, and calcined at 200 °C for 4 hours to obtain the LZU-1@Ti-MWW-1 catalyst.

[0023] Example 2

[0024] 32 mg of triphenylformaldehyde, 32 mg of p-phenylenediamine, 0.2 g of Ti-MWW, and 2 mL of ethanol were placed in a 10 mL pressure-resistant tube. After thorough shaking and sonication, 0.2 mL of 3 mol / L acetic acid aqueous solution was added. The air in the upper layer of the solution was replaced with nitrogen, and the tube was placed in an oven at 120 °C for 3 days. The resulting solid powder was filtered, washed three times with anhydrous ethanol, dried at 100 °C for 6 hours, and calcined at 200 °C for 4 hours to obtain the LZU-1@Ti-MWW-2 catalyst.

[0025] Example 3

[0026] 48 mg of triphenylformaldehyde, 48 mg of p-phenylenediamine, 0.2 g of Ti-MWW, and 2 mL of ethanol were placed in a 10 mL pressure-resistant tube. After thorough shaking and sonication, 0.2 mL of 3 mol / L acetic acid aqueous solution was added. The air in the upper layer of the solution was replaced with nitrogen, and the tube was placed in an oven at 120 °C for 3 days. The resulting solid powder was filtered, washed three times with anhydrous ethanol, dried at 100 °C for 6 hours, and calcined at 200 °C for 4 hours to obtain the LZU-1@Ti-MWW-3 catalyst.

[0027] Examples 1-3 show the synthesis of COF-deposited catalyst materials with different surface deposition amounts: LZU-1@Ti-MWW-1 catalyst with a COF deposition amount of 1.5 wt%, LZU-1@Ti-MWW-3 catalyst with a COF deposition amount of 4.3 wt%, and LZU-1@Ti-MWW-2 catalyst with a COF deposition amount of 2.9 wt%.

[0028] Example 4 evaluated the catalytic epoxidation performance of LZU-1@Ti-MWW-1, LZU-1@Ti-MWW-2, and LZU-1@Ti-MWW-3. The specific procedure was as follows: In a 50 mL flask, 10 mL of acetonitrile solvent, 3.2 g of cyclohexene (the reactant), and 4.5 g of a 30.0% hydrogen peroxide solution were added sequentially. Finally, 0.6 g of the composite catalyst was added. Under stirring, the reaction temperature was set to 65 °C, and the reaction time was 5 h. After the reaction was completed, the conversion rate, selectivity, and yield were analyzed by gas chromatography.

[0029] The catalytic performance results are summarized in Table 1. As can be seen from the table, the catalyst LZU-1@Ti-MWW-1 has higher catalytic activity and epoxide yield.

[0030] Table 1. Catalyst performance test results in Example 4

[0031] LZU-1@Ti-MWW-1 96.1 94.3 LZU-1@Ti-MWW-2 92.1 85.2 LZU-1@Ti-MWW-3 65.7 79.1

[0032] Example 5

[0033] In a 50 mL flask, 10 mL of acetonitrile solvent, 3.2 g of cyclohexene, and 3.6 g of 30.0% hydrogen peroxide solution were added sequentially. Finally, 0.6 g of LZU-1@Ti-MWW-1 composite catalyst was added. The reaction was carried out with stirring at 50 °C for 5 h. After the reaction was complete, gas chromatography analysis showed a cyclohexene conversion of 53.5% and a selectivity of 68.0%.

[0034] Example 6

[0035] In a 50 mL flask, 10 mL of methanol solvent, 3.2 g of cyclohexene, and 1.6 g of 70.0% tert-butyl hydrogen peroxide solution were added sequentially. Finally, 0.6 g of LZU-1@Ti-MWW-1 composite catalyst was added. The reaction was carried out with stirring at 80 °C for 5 h. After the reaction was complete, gas chromatography analysis showed a cyclohexene conversion of 85.1% and a selectivity of 82.3%.

[0036] Example 7

[0037] In a 50 mL flask, 10 mL of acetonitrile solvent, 3.2 g of cyclohexene, and 4.5 g of 50.0% hydrogen peroxide solution were added sequentially. Finally, 1.2 g of LZU-1@Ti-MWW-1 composite catalyst was added. The reaction was carried out with stirring at 90 °C for 2 hours. After the reaction was complete, gas chromatography analysis showed a cyclohexene conversion of 98.3% and a selectivity of 92.1%.

[0038] Comparative Example 1

[0039] In a 50 mL flask, 10 mL of acetonitrile solvent, 3.2 g of cyclohexene, and 4.5 g of 30.0% hydrogen peroxide solution were added sequentially. Finally, 0.6 g of Ti-MWW catalyst was added. The reaction was carried out with stirring at 80 °C for 5 h. After the reaction was complete, gas chromatography analysis showed a cyclohexene conversion of 64.0% and a cyclohexane oxide selectivity of 71.5%.

[0040] Comparative Example 2

[0041] In a 50 mL flask, 10 mL of acetonitrile solvent, 3.2 g of cyclohexene, and 3.6 g of a 30.0% hydrogen peroxide solution were added sequentially. Finally, 0.6 g of Ti-MWW catalyst was added. The reaction was carried out with stirring at 50 °C for 5 h. After the reaction was complete, gas chromatography analysis showed a cyclohexene conversion of 27.6% and a cyclohexane oxide selectivity of 63.1%.

[0042] By comparing LZU-1@Ti-MWW and Ti-MWW, it can be seen that the composite catalyst disclosed in this invention has high catalytic activity. Its application in the process of producing cyclohexene oxide from cyclohexene oxidation can improve the feed conversion rate and the selectivity of the target product.

Claims

1. A method for preparing cyclohexane oxide, characterized in that... The method includes the following: using a titanium-silicon molecular sieve Ti-MWW with a surface-supported covalent organic framework material LZU-1 as a catalyst, denoted as LZU-1@Ti-MWW, to catalyze the epoxidation reaction of cyclohexene to produce cyclohexane oxide in the presence of a solvent and an oxidant; the oxidant is a hydrogen peroxide solution; the oxidant mass concentration is 30%~70%, and the dosage is 0.2~1.0 g H2O2 / g cyclohexene; the dosage of LZU-1@Ti-MWW is 0.1~0.3 g / g cyclohexene; The catalysts, based on weight, have a COF deposition rate of 1.5%–2.9% and a Ti-MWW deposition rate of 97.1%–98.5%. The catalyst LZU-1@Ti-MWW was prepared by the following method: Ti-MWW titanium silicate molecular sieve, mestribenzaldehyde, p-phenylenediamine, and ethanol were mixed evenly, and then an aqueous acetic acid solution was added. The mixture was subjected to hydrothermal crystallization, and then washed and dried to obtain the catalyst. The cyclohexene epoxidation reaction conditions are: reaction temperature 50-65℃, reaction time 2-6h; The mass ratio of the titanium-silicon molecular sieve Ti-MWW, mesitylene formaldehyde, p-phenylenediamine, and ethanol is 1:0.05~0.3:0.05~0.3:5~15. The concentration of the acetic acid aqueous solution is 1 mol / L to 6 mol / L, and the amount added is 0.1 to 0.5 mL; The hydrothermal crystallization treatment is generally carried out in a high-pressure reactor, with hydrothermal crystallization conditions of 100~150℃ and a reaction time of 2~5 days.

2. The method according to claim 1, characterized in that: The drying conditions are as follows: drying temperature is 60~100℃, and drying time is 4~6 hours.

3. The method according to claim 1, characterized in that: The solvent is one or more of methanol, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide.

4. The method according to claim 3, characterized in that: The solvent is acetonitrile.

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