Method for preparing styrene oxide through epoxidation of styrene

Abstract

The invention provides a method for preparing styrene oxide through epoxidation of styrene, which is characterized in that H2O2 is used as an oxidant, and a core-shell catalyst is used to realize high conversion rate of styrene and high selectivity of styrene oxide; according to the core-shell catalyst, a high-activity nano composite metal oxide or a noble metal simple substance serves as a core, a layer of TS-1 molecular sieve grows on the outer layer, and the high-activity nano composite metal oxide comprises MgO and Co3O4. The method is applied to styrene epoxidation reaction, has the advantages of high catalyst activity, good product selectivity and the like, and is simple in catalyst preparation and process flow and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, specifically to a method for preparing epoxide phenylene oxide by epoxidation of styrene. Background Technology

[0002] Phenylacetylene oxide is an important organic intermediate, mainly used in the production of organic fragrances, pharmaceuticals, and organic synthesis. Due to its high market price and the continuous growth in market demand in recent years, research on its synthesis is of great significance.

[0003] Existing production methods include the halohydrin method and the direct peroxyacid oxidation method. The halohydrin method uses halide oxides as the oxygen source. Styrene reacts with hypohalous acids to produce halophenylethanol, and then a strong base is used to remove one molecule of halohydrogen to produce crude epoxide phenylethane. This process is mature and has a high yield, but it suffers from problems such as generating large amounts of halogen wastewater and corroding equipment. The direct peroxyacid oxidation method uses alkyl hydrogen peroxide or peroxyacid to react with olefins. The hydrogen from the peroxy group can selectively add to the olefin double chain to generate peroxides. The reaction conditions are relatively mild, but these reactions are prone to various side reactions, and the resulting byproducts increase the difficulty of separation and purification. Currently, the main synthesis process for epoxide phenylethane is the halohydrin method, which typically uses styrene and sodium bromide as raw materials, hydrogen peroxide as the oxidant, and proceeds to saponification under alkaline conditions after bromohydration and oil phase separation in an acidic environment. This process is simple to operate and low in cost, but it generates large amounts of high-salt wastewater.

[0004] Patent CN101972665B discloses a supported catalyst prepared by adsorbing cobalt ions using an amino-functionalized molecular sieve. Using N,N-dimethylformamide or N,N-dimethylacetamide as a solvent, epoxide styrene is prepared under oxygen or air oxidation, achieving a styrene conversion ≥82% and an epoxide styrene selectivity ≤62%. Due to the use of mesoporous molecular sieve SBA-15 as a support, the internal pores have abundant specific surface area, resulting in high catalyst activity. However, air oxidation readily generates a large number of free radicals, initiating styrene polymerization, thus leading to lower selectivity. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing epoxide-based phenylene oxide by epoxidation of styrene. This method utilizes a core-shell composite material as a catalyst and H₂O₂ as an oxidant, achieving high styrene conversion and high selectivity for epoxide-based phenylene oxide. The process is simple, and the catalyst preparation method is straightforward, offering advantages such as high activity, high selectivity, and the ability to be regenerated multiple times.

[0006] The technical solution of the present invention is as follows: A method for preparing epoxide by epoxidation of styrene includes adding a solvent, styrene, and a core-shell catalyst into a reaction vessel. After reaching the reaction temperature, hydrogen peroxide is added dropwise to obtain epoxide. The core-shell catalyst uses a highly active nano-composite metal oxide or noble metal element as the core, with a TS-1 molecular sieve with precise sieving function grown on its outer layer. The solvent is a mixture of dimethylformamide and acetonitrile. The composite metal oxide includes MgO and Co3O4.

[0007] The highly active nanocomposite metal oxide has a spinel structure.

[0008] The molar ratio of dimethylformamide to acetonitrile is 0.2-3.5:1, preferably 0.6-2.5:1.

[0009] The precious metal includes Ag nanoparticles.

[0010] The shell layer TS-1 has a titanium-to-silicon ratio of SiO2:TiO2 = 1:0.01-0.08, preferably SiO2:TiO2 = 1:0.02-0.04.

[0011] The mass ratio of composite metal oxides or noble metal elements to TS-1 molecular sieves is 1:5-20.

[0012] The molar ratio of active oxygen to styrene in hydrogen peroxide is 0.5-5:1, the hydrogen peroxide droplet acceleration rate is 0.2-1 g / min, and the addition is completed within 60-90 minutes.

[0013] The molar ratio of the solvent to styrene is 1-5:1.

[0014] The catalyst dosage is 0.5-5 g, preferably 1-3.5 g.

[0015] The reaction temperature is 50-100 ℃, preferably 60-70 ℃.

[0016] The preparation method of core-shell catalysts with composite metal oxide cores specifically includes the following steps: Preparation of S1 composite metal oxide core layer: Cobalt salt, magnesium salt and urea were dissolved in deionized water and placed in a reaction vessel with polytetrafluoroethylene lining and reacted at 80-150 ℃ for 4-8 h. After washing with deionized water and ethanol alternately, the mixture was dried and calcined to obtain nano MgCo2O4 spheres, which were then surface modified using CTAB. Preparation of S2 shell TS-1 gel: Tetrapropylammonium hydroxide was mixed with deionized water and stirred vigorously. Then tetraethyl orthosilicate was added, which was denoted as solution A. Tetrabutyl titanate was diluted with anhydrous ethanol to prepare solution B. Solution A and solution B were mixed and stirred vigorously at 60-70 °C to form a gel. The gel was aged at room temperature for 6-12 h to obtain TS-1 gel. Preparation of S3 core-shell catalyst: CTAB-modified nano-MgCo2O4 spheres were uniformly dispersed in TS-1 gel, crystallized at 120-240 °C for 48-72 h, washed until neutral, and dried and calcined to obtain the core-shell catalyst.

[0017] The cobalt salt, magnesium salt, or noble metal salt includes nitrates, carbonates, or chlorides.

[0018] The preparation method of core-shell catalysts with noble metal elements as the core is referred to Dai Qiaoling, Sun Jiaxin, Jia Yanzi, et al. Research progress on preparation and application of silica-coated core-shell catalysts [J]. Petroleum Refining and Chemical Industry, 2024, 55(3):148-153.

[0019] Compared with the prior art, the present invention has the following advantages: This invention uses H2O2 as an oxidant, avoiding the production safety and pollution problems caused by using peroxyacids as oxidants. Using a core-shell composite material as a catalyst, the highly active nano-composite metal oxide or noble metal elemental core layer has numerous effective active sites, which can improve reaction activity; the TS-1 molecular sieve shell can inhibit the formation of the large-volume isomer phenylacetaldehyde, improving product selectivity. Detailed Implementation

[0020] The hydrogen peroxide used in the examples has a mass concentration of 30%.

[0021] Example 1 Catalyst preparation: 2.9 g cobalt nitrate, 1.28 g magnesium nitrate, and 3.0 g urea were dissolved in deionized water and placed in a polytetrafluoroethylene-lined reactor. The mixture was reacted at 100 °C for 6 h, followed by alternating washing with deionized water and ethanol. The mixture was then filtered, dried at 100 °C for 4 h, and calcined at 400 °C for 3 h to obtain black nano-MgC with a spinel structure. O2 MgCo₂O₄ spheres were added to 0.1% wt CTAB and sonicated for 30 minutes to modify their surface. With SiO₂ / TiO₂ ratio of 30 (based on titanium and silicon oxides), 80 g of tetrapropylammonium hydroxide was mixed with deionized water and stirred vigorously before adding tetraethyl orthosilicate, denoted as solution A. Tetrabutyl titanate was diluted with anhydrous ethanol to prepare solution B. Solution A and solution B were mixed, and the mixture was stirred vigorously at 65 °C to evaporate the ethanol and a small amount of water to form a gel. The gel was aged at room temperature for 8 h to obtain TS-1 gel. Nano-MgCo₂O₄ spheres were uniformly dispersed in TS-1 gel and sonicated for 1 h, crystallized at 180 °C for 48 h, washed until neutral, dried at 100 °C for 4 h, and calcined at 550 °C for 4 h to obtain the core-shell catalyst.

[0022] Example 2 Styrene:dimethylformamide:acetonitrile in a molar ratio of 0.5:1.25:1 and 3 g of core-shell catalyst were added to a three-necked flask. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained products were analyzed by gas chromatography. The results are shown in Table 1.

[0023] Table 1 Epoxidation Performance of Core-Shell Catalysts - 1 Example 3 Styrene:dimethylformamide:acetonitrile in a molar ratio of 0.5:1.5:1 and 3 g of core-shell catalyst were added to a three-necked flask. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 2.

[0024] Table 2 Epoxidation Performance of Core-Shell Catalysts - 2 Example 4 Styrene:dimethylformamide:acetonitrile in a molar ratio of 0.5:2:1 and 3 g of core-shell catalyst were added to a three-necked flask. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 3.

[0025] Table 3 Epoxidation Performance of Core-Shell Catalysts - 3 Comparative Example 1 Styrene:dimethylformamide:acetonitrile in a molar ratio of 0.5:1.5:1 and 3 g of TS-1 catalyst (the TS-1 gel described in Example 1 was dried at 100°C for 4 h and calcined at 550°C for 4 h) were added to a three-necked flask. When the reaction temperature reached 70°C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 4.

[0026] Table 4 Epoxidation Performance of TS-1 Comparative Example 2 Styrene:dimethylformamide:acetonitrile were mixed in a molar ratio of 0.5:1.5:1 with 3 g of the nano-MgC obtained in Example 1. O2 O4 sphere catalyst was added to a three-necked flask. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide was added. Samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 5.

[0027] Table 5 Nano MgC O2 O4 sphere catalyst epoxidation performance Comparative Example 3 Styrene:dimethylformamide:acetonitrile in a molar ratio of 0.5:1.5:1 and 3 g of the nano-Co3O4@TS-1 spherical catalyst obtained in Example 1 (without the addition of magnesium nitrate) were added to a three-necked flask. When the reaction temperature reached 70°C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in the hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained product was analyzed using gas chromatography, and the results are shown in Table 6.

[0028] Table 6. Epoxidation performance of nano-Co3O4@TS-1 catalyst Comparative Example 4 Styrene:ethanol:acetonitrile in a molar ratio of 0.5:1.5:1 and 3g of core-shell catalyst were added to a three-necked flask. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was completed, and samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 7.

[0029] Table 7 Epoxidation performance of core-shell catalysts in different solvents - 1 Comparative Example 5 Styrene:acetonitrile was added to a three-necked flask at a molar ratio of 0.5:1 and 3 g of core-shell catalyst. When the reaction temperature reached 70 °C, hydrogen peroxide was slowly added dropwise. The molar ratio of active oxygen in hydrogen peroxide to styrene was 1.1:1. The hydrogen peroxide was added dropwise over 65 minutes. Timing was started after the hydrogen peroxide addition was complete, and samples were taken for analysis every two hours. The obtained products were analyzed using gas chromatography. The results are shown in Table 8.

[0030] Table 8. Epoxidation performance of core-shell catalysts in different solvents - 2 C% Styrene S% Epoxyphenylene oxide S% Phenylacetaldehyde 2h 40.10% 67.09% 19.91% 4h 42.22% 49.60% 28.54%

Claims

1. A method for preparing epoxide phenylene oxide by epoxidation of styrene, characterized in that: The process involves adding a solvent, styrene, and a core-shell catalyst into a reaction vessel, and then adding hydrogen peroxide dropwise after the reaction temperature is reached to obtain epoxide phenyl ethane. The core-shell catalyst has a highly active nano-composite metal oxide or noble metal element as the core and TS-1 molecular sieve as the shell. The solvent is a mixture of dimethylformamide and acetonitrile. The composite metal oxide includes MgO and Co3O4.

2. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The composite metal oxide has a spinel structure.

3. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The molar ratio of dimethylformamide to acetonitrile is 0.2-3.5:

1.

4. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The titanium-silicon ratio of the TS-1 molecular sieve shell is SiO2:TiO2 = 1:0.01-0.

08.

5. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The mass ratio of the composite metal oxide or noble metal element to the TS-1 molecular sieve is 1:5-20.

6. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The molar ratio of active oxygen to styrene in hydrogen peroxide is 0.5-5:1, the hydrogen peroxide droplet acceleration rate is 0.2-1 g / min, and the addition is completed within 60-90 minutes.

7. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The molar ratio of the solvent to styrene is 1-5:

1.

8. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The amount of core-shell catalyst used is 0.5-5 g.

9. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The reaction temperature is 50-100 ℃.

10. The method for preparing epoxide by epoxidation of styrene as described in claim 1, characterized in that: The preparation method of the core-shell catalyst with composite metal oxide as the core specifically includes the following steps: Preparation of S1 composite metal oxide core layer: Cobalt salt, magnesium salt and urea were dissolved in deionized water and placed in a reaction vessel with polytetrafluoroethylene lining and reacted at 80-150 ℃ for 4-8 h. After washing with deionized water and ethanol alternately, the mixture was dried and calcined to obtain nano MgCo2O4 spheres, which were then surface modified using CTAB. Preparation of S2 shell TS-1 gel: Tetrapropylammonium hydroxide was mixed with deionized water and stirred vigorously. Then tetraethyl orthosilicate was added and labeled as solution A. Tetrabutyl titanate was diluted with anhydrous ethanol to prepare solution B. Solution A and solution B were mixed and stirred vigorously at 60-70℃ to form a gel. The gel was aged at room temperature for 6-12 h to obtain TS-1 gel. Preparation of S3 core-shell catalyst: CTAB-modified nano-MgCo2O4 spheres were uniformly dispersed in TS-1 gel, crystallized at 120-240 °C for 48-72 h, washed until neutral, and dried and calcined to obtain the core-shell catalyst.

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