Manganese-containing hollow TS-1: Description of the catalytic sites and surface properties for solvent-free oxidation of ethylbenzene

Abstract

Hollow MnOx/TS-1 catalyst was prepared by dissolution-recrystallization and impregnation method, and its catalytic activity was evaluated in aerobic oxidation of ethylbenzene under solvent-free conditions. Tetrahedral Ti4+ and MnOx species homogeneous dispersed on the hollow TS-1 surface and strong favourable synergic interactions between them occurred, which supported by the comprehensive analysis of XRD, N2 physical adsorption, TEM, FTIR, UV–vis, XPS and Raman spectroscopy. The virtue of such synergic effect was reflected in a catalytic efficiency enhancement of valuable ketone and alcohol products (TOF=137h−1): MnOx/TS-1 catalyst showed about 2.2 times higher activity compared to MnOx/Silicalite-1 references. Furthermore, the Mn species content and calcination temperature of the MnOx/TS-1 catalyst presented significant effects of lower-nuclearity Mn species on the structural, chemical, and catalytic properties. Based on the theoretical calculations, the reaction mechanism was proposed where the cleavage of the longer methylene CH bond (1.0935Å) of ethylbenzene and OO bond (1.5267Å) of alkyl hydroperoxide over the OTiOMn sites is a key step to yield radical continuously for recycle.