Cluster Model DFT Study of the Intermediates of Benzene to Phenol Oxidation by N2O on FeZSM-5 Zeolites Citation for published version (APA): Cluster model DFT study of the intermediates of benzene to phenol oxidation by N 2 O on FeZSM-5 zeolites

An Fe(II) ion at an -cation exchange position of ZSM-5 zeolite (Fe/Z) was taken as a model for the active site in the nitrous oxide decomposition and in the selective oxidation of phenol with nitrous oxide. The oxygen deposited by decomposition of N 2 O is commonly referred to as -oxygen (OFe/Z). Cluster model DFT calculations show that the interaction of the OFe/Z center with benzene resulted easily in arene oxide formation. The results indicate a rather low activation energy for this step. Possible transformations of the adsorbed arene oxide are considered and the experimental evidence for the absence of the kinetic H/D isotope effect in phenol formation is discussed. It is concluded that the rate-limiting step for the in situ oxidation of benzene to phenol is the desorption of the product

CO and NO Adsorptions on Different Iron Sites of Fe-ZSM-5 Clusters: A Density Functional Theory Study

Density functional theory (DFT) calculations were carried out. in a study of CO and NO adsorptions on different iron site of Fe-ZSM-5. The adsorption energies and distances were similar for CO adsorption on, both small and large cluster calculations. The adsorption energies (Delta E) and enthalpies (Delta H) found for NO adsorption on [FeO](1+)-ZSM-5 and [Fe(OH)(2)](1+)-ZSM-5 clusters were in line with the previous theoretical values. Some additional energy was required for NO and CO adsorptions on [FeO](2+) -ZSM-5 (NO adsorption only), [FeOH](2+)-ZSM-5, and [Fe(OH)(2)](2+)-ZSM-5 clusters because of their positive Delta G values. The scaled vibrational frequencies for adsorbed CO and NO molecules on Fe2+,ZSM-5 cluster were computed as 1870 and 2149 cm(-1), respectively. These values are in good agreement with the experimental values for the Fe2+-CO and Fe2+-NO bands (1882 and 2140 cm(-1), respectively). Moreover, the calculated vibrational frequency (1897 cm(-1)) for NO adsorption on the [HO-FeOFe-OH](2+)-ZSM-5 cluster matches well with the experimental value (1892 cm(-1))

A DFT Study of Direct Oxidation of Benzene to Phenol by N 2

Density functional theory (DFT) calculations were carried out in a study of the mechanism of benzene oxidation by N2O to phenol over an extra framework dimeric [FeOFe]2+ species in ZSM-5 zeolite represented by a [Si6Al2O9H14(Fe(µ-O)Fe)] cluster model. The catalytic reactivity of such a binuclear species is compared with that of mononuclear Fe2+ and (FeO)+ sites in ZSM-5 investigated in our earlier works at the same level of theory (J. Phys. Chem. C2009, 113, 15307; 2010, 114, 12580). The activation energies for the elementary reaction step involved in the benzene hydroxylation over the binuclear and the mononuclear iron sites are comparable. The major difference in the catalytic behavior of the systems considered is related to the ability of Fe3+-containing sites to promote side reactions leading to the active site deactivation. Regeneration of the active site via the phenol desorption is much less favorable than its dissociation resulting in the formation of very stable grafted phenolate species on both the [Fe(µ-O)Fe]2+ and (FeO)+ sites. In the case of Fe2+ sites such an alternative reaction path does not exist resulting in their stable catalytic performance. Benzene hydroxylation and phenol formation over the binuclear (Fe(µ-O)Fe)2+ sites in ZSM-5 are promoted in the presence of water. These computational findings are consistent with the experimental observations and allow their rationalization at the molecular level