Efficiently Catalytic Epoxidation Of Styrene With Air Over Cobalt-containing Molecular Sieves

The catalytic epoxidation of alkenes to produce epoxides is an important industrial reaction, since epoxides are key building blocks in organic synthesis, as well as commercially important intermediates used in the synthesis of chiral pharmaceuticals, pesticides, epoxy paints, agrochemicals, perfume materials and sweeteners. At present, most epoxides are still produced by the epoxidation of alkenes with traditional oxides, such as iodine acyl benzene, peroxide acid, organic peroxide, hypochlorite salt, etc. With the development of green chemistry, the epoxidation of olefins by using molecular oxygen or air as the oxidant has been more attractive and challenging.Firstly, mercaptopropyl-functionalized hybrid materials (HM) have been synthesized through dry-gel conversion (DGC) route. Then, a series of Co-HM catalysts are prepared through the coordination of mercaptopropyl groups (-(CH2)3-SH) with cobalt(II) ions and characterized by various techniques, including XRD, XPS, SEM, UV-Vis, FT-TR, and TG. Co-HM-50 presents the most excellent catalytic acivity and epoxide selectivity. Furthermore, the effects of reaction temperature, reaction time, type of solvents and oxidant on the epoxidation of styrene have been discussed systematically.Secondly, SAPO-5 molecular sieves have been synthesized by dry-gel conversion (DGC) and hydrothermal synthesis (HTS) methods. Then, various M-SAPO-5 catalysts have been prepared by transition-metal ion-exchange method (M= Fe3+、 Cr3+、Co2+、Ni2、Cu2+、Zn2+ and Mn2+), among which the Co-SAPO-5 (DGC) exhibits better activity for the epoxidation of styrene with air than the Co-SAPO-5 (HTS). Furthermore, the effects of Si/Al molar ratio, reaction temperature, reaction time, type of translation metal, solvent, and oxidant on the epoxidation of styrene have been discussed carefully.Finally, the microwave-assisted heating technology has been applied in the epoxidation of styrene with air. It is found that the reaction time has been shortened greatly. Furthermore, the deactivation of catalysts has been discussed.