Preparation of immobilized MnP-PGMA/SiO2 catalyst and its catalytic activity for ethylbenzene oxidation

Ploy(glycidyl methacrylate) (PGMA) was grafted on the surface of silica gel particles in a solution polymerization system, and PGMA/SiO2, was prepared. Subsequently, in meso-tetra (4-hydroxylphenyl) porphyrin (THPP) was bound on PGMA/SiO2, through the ring-opening reaction between the epoxy groups of the grafted PGMA and the hydroxyl groups of THPP, resulting in the HPP-PGMA/SiO2. Further, the coordination reaction between HPP-PGMA/SiO2 and MnCl2 was performed, and the immobilized MnP (manganoporphyrin)-PGMA/SiO2 was obtained. The MnP-PGMA/SiO2 catalyst was used in the oxidation of ethylbenzene with molecular oxygen as the oxidant, and the transform of ethylbenzene into acetophenone was realized. The effects of various factors, such as the catalyst amount and MnP-immobilizing density, on the supported MnP-PGMA/SiO2 catalyst were examined. The results showed that the supported MnP-PGMA/SiO2 catalyst can effectively activate molecular oxygen and obviously catalyze the oxidation of ethylbenzene to acetophenone. MnP-PGMA/SiO2 exhibited high catalytic activity and selectivity, and the yield of acetophenone reached 18 % under the conditions of p(O-2) = 0.1 MPa, T = 95 degrees C, and t = 12 h, but the content of a-methyl benzoic alcohol was very small. As a biosimulation catalyst, MnP in the supported catalyst had an optimum amount for the reaction, and the excess amount would inhibit, the catalyst activity. The supported MnP-PGMA/SiO2 catalyst with a smaller MnP-immobilizing density had higher catalytic activity, and the catalytic activity increased slowly when the catalyst was reused.