DFT Study of Direct Methanol Oxidation to Formaldehyde by N2O on the [Fe](2+)-ZSM-5 Zeolite Cluster
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The mechanistic pathways of direct oxidation of methanol to formaldehyde by N2O were theoretically investigated by means of density functional theory (DFT) over an extra framework species in ZSM-5 zeolite represented by a [Si6Al2O9H14](2-)[Fe](2+) cluster model. The catalytic reactivity of these species is compared with that of mononuclear Fe1+ and (FeO)(1+) sites in ZSM-5 investigated in our earlier work at the same level of theory (J. Catal. 2011, 282, 191). The formation of the grafted species including methoxy on the [Fe](2+) site was calculated to be thermodynamically more stable than on the [FeO](1+) site and less stable than on the [Fe](1+) site. The order of activation barrier values of a critical step, proton transfer from grafted methoxy to form formaldehyde and water, on these sites is as follows: [Fe](1+) > [Fe](2+) >> [FeO](1+). The calculated vibrational frequencies for grafted species on the iron site on the surface are in good agreement with the experimental values.