A Density Functional Theory Study of C-H Bond Activation of Methane on a Bridge Site of M-O Clusters (M = Au, Ag, Fe and Cu)

Abstract

C-H bond activation of methane on a bridge site M-O-M- of ZSM-5 (M = Au, Ag, Fe and Cu) clusters has been performed by means of Density Functional Theory (DFT) calculations with the utilization of [Si6Al2O9H14(M-O-M](2+) (where M = Au, Ag, Fe and Cu) cluster models representing ZSM-5 surfaces. According to the activation barrier data based on TS calculations. The following activity order of clusters with respect to their activation barriers could be classified: Ag approximate to Au > Cu Fe for Metal-O-Metal-ZSM-5 clusters. Activation barriers for C-H bond activation of methane on Au-O-Au- and Ag-O-Ag-ZSM-5 clusters are calculated as 4.83 and 4.79 kcal/mol, respectively. These values are lower than the activation barrier values for C-H bond activation on Cu-O-Cu-ZSM-5 and Fe-O-Fe-ZSM-5 which are 9.69 and 26.30 kcal/mol, respectively. Activation process is exothermic on Au-O-Au-, Cu-O-Cu-, and Fe-O-Fe-ZSM-5 clusters whereas it is endothermic on Ag-O-Ag-ZSM-5 cluster. (C) 2010 Elsevier Inc. All rights reserved.