催化双氧水氧化甲苯合成苯甲醛的研究
发布时间：2018-11-01 11:43
【摘要】：苯甲醛是一种重要的化工原料,也是一种重要的有机合成中间体,普遍用于香料、塑料合成和染料行业中。传统的合成苯甲醛方法是甲苯卤代水解法,该工艺是通过甲苯甲苯氯代反应、皂化反应,制得苯甲醛。该方法不仅污染环境且苯甲醛的收率低下,产品中含有卤素离子,使其应用受到限制。因此,寻求一种高效、清洁的苯甲醛合成路线具有十分重要的意义。本文通过可控合成,制备一系列对甲苯选择氧化合成苯甲醛具有高活性和高选择性的催化剂,探讨催化剂结构与性能的关系,为甲苯选择氧化合成苯甲醛新技术的开发,提供基础数据与关键技术。本研究通过可控固相合成,制备了Mo O_3-Mo V_2O_8催化剂和Mo O_3-Fe_2(Mo O_4)_3-Mo V_2O_8催化剂,并引入Fe_3O_4磁核,制备了Mo O_3-Mo V_2O_8@Fe_3O_4磁性催化剂。考虑石墨型氮化碳g-C_3N_4材料的特殊空间结构和电子分布特性,组装了Mo V_2O_8/g-C_3N_4催化剂。采用双氧水为氧化剂,甲苯选择性氧化反应为探针反应,对上述催化剂的活性与苯甲醛的选择性进行了评价。采用XPS、SEM、TG-DSC、XRD、TPR等系列现代分析表征方法,对催化剂结构进行了深入分析,并关联催化剂的催化性能,揭示催化剂的构效关系,为选择氧化反应催化剂的设计与组装提供重要的基础数据。研究表明,当钒钼比为1:1时,通过溶胶凝胶法制备的前驱物在550℃下的高温固相反应,制备出Mo O_3-Mo V_2O_8催化剂。该催化剂在80℃下催化甲苯氧化反应中,当反应8小时,甲苯转化率为36.0%,苯甲醛选择性为53.2%。为了进一步提高催化剂的性能,通过掺杂Co、Cr、Ce、La和Fe对Mo O_3-Mo V_2O_8催化剂进行了改性研究。研究表明,Co、Cr、Ce、La和Fe对催化剂都有改性作用,其中以Fe对催化剂的改性较大,当原子比V:Mo:Fe=6:7:1时,甲苯转化率为40.3%,苯甲醛选择性为84.5%。XRD分析表明,催化剂中存在Fe_2(Mo O_4)_3物相,XPS分析表明,铁的掺入,使得催化剂中钼物种的电子云密度增加,提高了催化剂的活性。为了便于快速回收液相反应中的催化剂粉体,引入了磁性材料Fe_3O_4,并以此为核,在Fe_3O_4表面自组装Mo O_3-Mo V_2O_8催化剂壳层,组装成具有核壳结构的Mo O_3-Mo V_2O_8@Fe_3O_4磁性催化剂。研究表明,在Fe_3O_4表面散乱分布的钒钼复合氧化物,在550℃下可自组装为Mo O_3-Mo V_2O_8晶相。甲苯在该催化剂上的转化率为36.6%,苯甲醛的选择性为79.8%。反应后,通过附加外部磁场,催化剂可快速聚集回收。基于石墨型氮化碳g-C_3N_4特殊的空间结构和在催化中呈现的优异催化性能,通过高温固相反应,在g-C_3N_4表面自组装了Mo V_2O_8催化剂,考察了制备过程对Mo V_2O_8/g-C_3N_4催化剂结构与性能的影响。研究表明,甲苯在该催化剂上的甲苯转化率和苯甲醛选择性分别为43.5%和72%,苯甲醛收率可达31.3%。
[Abstract]:Benzaldehyde is an important chemical raw material and an important intermediate of organic synthesis. It is widely used in perfume, plastics synthesis and dye industry. The traditional method of synthesizing benzaldehyde is the hydrolysis of toluene halogenation. The process is to produce benzaldehyde by chlorination of toluene and saponification. The method not only pollutes the environment, but also has a low yield of benzaldehyde and halogen ions in the product, so its application is limited. Therefore, it is of great significance to seek an efficient and clean synthetic route for benzaldehyde. In this paper, a series of catalysts with high activity and selectivity for the selective oxidation of toluene to benzaldehyde were prepared by controllable synthesis. The relationship between the structure and the performance of the catalyst was discussed, and the new technology of selective oxidation of toluene to benzaldehyde was developed. Provide basic data and key technologies. In this study, Mo O_3-Mo V_2O_8 catalyst and Mo O_3-Fe_2 (Mo Oste4) _ 3-Mo V_2O_8 catalyst were prepared by controllable solid-state synthesis, and Fe_3O_4 magnetic nuclei were introduced. Mo O_3-Mo V_2O_8@Fe_3O_4 magnetic catalyst was prepared. Considering the special space structure and electron distribution of graphite type carbon nitride (g-C_3N_4), the Mo V_2O_8/g-C_3N_4 catalyst was assembled. The activity of the catalyst and the selectivity of benzaldehyde were evaluated by hydrogen peroxide as oxidant and toluene selective oxidation as probe reaction. A series of modern analysis and characterization methods, such as XPS,SEM,TG-DSC,XRD,TPR and so on, were used to analyze the structure of the catalyst, and related the catalytic performance of the catalyst to reveal the structure-activity relationship of the catalyst. It provides important basic data for the design and assembly of catalyst for selective oxidation reaction. The results show that when the vanadium molybdenum ratio is 1:1, the Mo O_3-Mo V_2O_8 catalyst is prepared by solid state reaction of the precursor prepared by sol-gel method at 550 鈩，
本文编号：2303822
[Abstract]:Benzaldehyde is an important chemical raw material and an important intermediate of organic synthesis. It is widely used in perfume, plastics synthesis and dye industry. The traditional method of synthesizing benzaldehyde is the hydrolysis of toluene halogenation. The process is to produce benzaldehyde by chlorination of toluene and saponification. The method not only pollutes the environment, but also has a low yield of benzaldehyde and halogen ions in the product, so its application is limited. Therefore, it is of great significance to seek an efficient and clean synthetic route for benzaldehyde. In this paper, a series of catalysts with high activity and selectivity for the selective oxidation of toluene to benzaldehyde were prepared by controllable synthesis. The relationship between the structure and the performance of the catalyst was discussed, and the new technology of selective oxidation of toluene to benzaldehyde was developed. Provide basic data and key technologies. In this study, Mo O_3-Mo V_2O_8 catalyst and Mo O_3-Fe_2 (Mo Oste4) _ 3-Mo V_2O_8 catalyst were prepared by controllable solid-state synthesis, and Fe_3O_4 magnetic nuclei were introduced. Mo O_3-Mo V_2O_8@Fe_3O_4 magnetic catalyst was prepared. Considering the special space structure and electron distribution of graphite type carbon nitride (g-C_3N_4), the Mo V_2O_8/g-C_3N_4 catalyst was assembled. The activity of the catalyst and the selectivity of benzaldehyde were evaluated by hydrogen peroxide as oxidant and toluene selective oxidation as probe reaction. A series of modern analysis and characterization methods, such as XPS,SEM,TG-DSC,XRD,TPR and so on, were used to analyze the structure of the catalyst, and related the catalytic performance of the catalyst to reveal the structure-activity relationship of the catalyst. It provides important basic data for the design and assembly of catalyst for selective oxidation reaction. The results show that when the vanadium molybdenum ratio is 1:1, the Mo O_3-Mo V_2O_8 catalyst is prepared by solid state reaction of the precursor prepared by sol-gel method at 550 鈩，
本文编号：2303822
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