FTIR study of the adsorption and transformation of allylbenzene over oxide catalysts

Abstract

The interaction of allylbenzene with oxide catalyst surfaces having different surface characters, such as acidic (alumina, titania, silica–alumina, tungsta–alumina and sulfated titania), basic (magnesium oxide) and redox character (vanadia–titania and magnesium chromite), and with slightly reducible transition–metal oxides (zirconium and zinc oxides) has been investigated by FTIR spectroscopy. For acidic catalysts, polymerization (sulfated titania) and the formation of 1-phenyl-2-propoxide by the addition of an OH over the vinylic bond have been observed. For ZnO, TiO₂ and vanadia-titania the features of a species identified as a π-allylbenzyl have been observed. For redox surfaces this intermediate converts rapidly to an oxidized species resulting in benzylic C—C bond breaking. For MgO and ZrO₂ no reaction has been found. The mechanism of C—H activation over these surfaces is briefly discussed.