Theoretical study of N2O decomposition mechanism over binuclear Cu-ZSM-5 zeolites

The mechanism of N2O decomposition over binuclear Cu-ZSM-5 zeolites is investigated using densityfunctional theory (DFT). It is found that the activation energy of two N2O molecules dissociation are47.19 and 63.89 kcal/mol, and the desorption energy of O2from Cu2O2is 14.70 kcal/mol. The DFT resultsshow that the N O splitting step of N2O molecule controls the whole catalytic cycle, and the binuclearCu-ZSM-5 has not suffered from O2inhibition. Moreover, some experimental work reports O2inhibitionis not observed at high Cu loading, which is in agreement with the present calculation. These findingssuggest that the catalytic behavior of binuclear Cu-ZSM-5 is different from that of mononuclear. Further-more, the kinetic analysis confirms the rate-limiting step in the binuclear Cu-ZSM-5 system is the N2Odissociation step, and the rate constant indicates that high temperature could accelerate the N2O disso-ciation. These results could allow us to understand the structure of the active sites and reveal the activesites controlling catalytic activity. The DFT calculation results combined with the kinetic study wouldprovide us a comprehensive understanding on the NOxdecomposition mechanism over the Cu-ZSM-5zeolites. © 2014 Elsevier B.V.