Metal Complexes Of Schiff Base Immobilized On Mesoporous Carbon Material: Synthesis, Characterization And Catalytic Properties In Styrsne Epoxidartion

The catalytic oxidation of alkenes to epoxides is an important industrial reaction, since epoxides are key building blocks in the manufacture of fine chemicals and pharmaceuticals. However, the method of producing the epoxide is found to consuming a large amount of energy, by-products, corroding the equipment, and most of all it is the serious pollution of environment. Therefore, exploring an environmental method of the epoxidation of alkene with green oxidant and highly efficient and stable catalyst is especially important for scientists.According to whether the catalyst and reactant are in the same phase, the catalyst is divided into two types: homogeneous catalyst and heterogeneous catalyst. Homogeneous catalysts have the value of existence, namely having more uniform distribution of active center in the liquid phase, and the catalyst has a good catalytic performance. It is a pity that these homogeneous catalysts can’t be separated easily from the liquid phase and are also difficult to be recycled. Moreover, they have the drawbacks of the corrosion of equipment and the serious pollution of the environment.Traditional heterogeneous catalyst is not well distributed on the solid surface, and they may have many different kinds of active centers and the loss of active centers, so it is difficult to control the composition and structure of the active center. And in the actual reaction, the mass transfer is hindered by the support. Therefore, the catalytic activity of the most heterogeneous catalysts is not better than homogeneous catalysts. However, catalysts which combine the advantages of homogeneous catalyst and heterogeneous catalyst are required in the rapid development of chemical and petrochemical industry. Generally, it is an effective way that immobilizing Schiff base complexes of transition metals onto the support with good mass transfer. Ordered mesoporous carbon materials are widely used as a perfect support for its good mass transfer recently.This paper is mainly reported the synthesis of heterogeneous Schiff base complexes with different transition metals immobilized on the ordered nanostructured carbon CMK-3 for the aerobic styrene oxidation. The main contents and the results are as follows:1 、 Different transition metal(Cu(II), Co(II), Fe(III)) Schiff complexes immobilized onto two-dimensional mesoporous carbon CMK-3 for the epoxidation of styreneTwo-dimensional ordered mesoporous carbon materials CMK-3 was oxidized and functionalized with amino by nitric acid and aminopropyltriethoxysilane, respectively. And then different metal(Cu(II), Co(II), Fe(III) and VO(II) Schiff base complexes were supported on the CMK-3-O. The catalytic activity of the catalysts for the epoxidation of styrene with air as oxidant was studied. The results showed that these catalysts had good catalytic performance. Among these prepared catalysts, the conversion of styrene is as high as 94.1%, the selectivity of epoxide(73.9%) with the catalyst Co-Sal-CMK-3. This may be due to the interaction between bivalent cobalt and support is stronger than others. In addition, the catalytic activity of these catalysts with tert-butyl hydroperoxide as oxidant is also explored in this section, the results showed that the catalyst Cu-Sal-CMK-3 is best with the high conversion of styrene(99.5%) and the good selectivity of epoxy ethane(92.8%). Compared with other transition metal complexes supported on different solid materials, it showed the advantages of CMK-3.2、VO(II), Cu(II) and Co(II) acetylacetonate complexes immobilized on amino-functionalized mesoporous carbon CMK-3 and its catalytic performance in styrene epoxidationHomogeneous metal complexes [VO(acac)2], [Cu(acac)2] and [Co(acac)2] was immobilized on amino-functionalized CMK-3-O, namely M-NH2-CMK-3. These catalysts were applied in the epoxidation of styrene under the condition of air as oxidant, 80 o C of reaction temperature, 8 h of reaction time. Catalytic results showed that the VO-NH2-CMK-3 had the best catalytic activity. The conversion of styrene and the selectivity of epoxide were 94.6% and 70.5% respectively. More importantly,the heterogeneous catalysts VO-NH2-CMK-3 had higher catalytic activity than homogeneous complexes VO(acac)2 a lot under the same conditions. This may be due to the isolated active center by the support, thus it increased the amount of activity center equivalently. At the same time, the use of the tert-butyl hydroperoxide as oxidant with different catalytic activity of metal complexes was explored in this chapter. The results showed that the highest catalytic activity with 99.6% conversion of styrene was catalyzed by Cu-NH2-CMK-3, but from the view of environment protection and energy saving, air as oxidant was available and applicable, considering various factors VO-NH2-CMK-3 was the target catalyst. And combined with ICP VO-NH2-CMK-3 was stable and it could be reused three times without significant loss of activity and could be regarded as the heterogeneous catalysts.