Theoretical Investigation of the Selective Oxidation of Methanol to Formaldehyde on Vanadium Oxide Species Supported on Silica: Umbrella Model

The mechanisms of the selective oxidation of methanol to Formaldehyde facilitated by monomeric vanadium oxide species oil silica Support are Studied theoretically. The active sites Lire modeled by clusters With umbrella structures: O=V(OH)(2)-O-Si(OH)(3) (hydrated VO4) and O=V(O-O)-O-Si(OH)(3) (dehydrated VO4). The possible reaction pathways are Studied by density functional theory, and the reaction kinetics is Studied using statistical mechanics and absolute rate theory. The reaction mechanisms and catalytic cycles are proposed: the hydrated VO4 species reacts with methanol to produce formaldehyde and the dehydrated VO4 species; the dehydrated VO4 species has high reactivity toward methanol to recycle the hydrated VO4. Hydrogen transfer is the rate-limiting step. The Umbrella models of the active sites are found to be capable of giving a reliable description of the mechanisms of the methanol oxidation reaction, which supports the possibility of the existence of VO4 species With Umbrella Structure Oil the catalyst surface.