Preparation and characterization of spherical silica–porphyrin catalysts obtained by the sol–gel methodology

Abstract

This work describes the synthesis of a first-generation iron porphyrin catalyst entrapped in a silica matrix by the sol–gel route, leading to spherical particles. The catalyst was synthesized by the method of Stober, through hydrolysis and condensation of the alkoxysilane TEOS in a mixture of alcohol, water and ammonia, in the presence of the iron porphyrin Fe(TPP)Cl. The relation between particle morphology and catalytic activity of the different Fe(TPP)–SiO 2, obtained using different H 2O/silane molar ratios and ammonia concentrations in the xerogel syntheses, was studied. The obtained catalysts were characterized by UV–vis spectroscopy, NMR 29Si, thermogravimetric analysis and transmission electron microscopy. Their ability to catalyze ( Z)-cyclooctene epoxidation and cyclohexane oxidation was tested using iodosylbenzene as oxygen donor; the oxidation products were analyzed by gas chromatography and the catalysts obtained in a form of particles spherical and monodispersed showed to be a promising catalytic system for selective oxidation.