Direct oxidation of methanol to formaldehyde by N₂O on [Fe]¹⁺ and [FeO]¹⁺ sites in Fe–ZSM-5 zeolite: A density functional theory study

Density functional theory (DFT) calculations were carried out in a study of the mechanism of direct oxidation of methanol to formaldehyde by N₂O over an extra-framework species in ZSM-5 zeolite represented by a [(SiH₃)₄AlO₄(Fe) or (FeO)] cluster models. The major difference between these two sites is that in the case of the [Fe]¹⁺ site, a reaction is present that leads to the formation of the thermodynamically highly stable grafted OH and methoxy (OCH₃) species. Moreover, the vibrational frequencies for grafted species on the surface match well with the experimental values. The theoretical calculations achieved in this study obviously show that [Fe–O]¹⁺ site in Fe–ZSM-5 catalyst has a significant role on the catalytic oxidation of methanol to formaldehyde by N₂O.