Chemical reactivity indices as a tool for understanding the support-effect in supported metal oxide catalysts

The oxidation of methanol to formaldehyde on supported vanadium oxides is investigated with chemical reactivity indices. Starting from a simple model for isolated vanadium oxides supported on SiO2, Al2O3, TiO2, and ZrO2, a detailed investigation of the reaction mechanism for methanol oxidation on these catalysts is presented. Our results follow current insights into the reaction mechanism and provide a new interesting way for rationalizing the support-effect on the basis of the concept of bond ionicity as probed by computed electrostatic potential based atomic charges for the vanadium and oxygen atoms. The origin of this rationalization is further investigated by visualizing the density of the determining vanadium−oxygen−support structure for the different supports