Density functional study of the interaction of Cu + ion-exchanged zeolites with H 2O and SO 2 molecules

Abstract

In the present work, we report theoretical calculations of the interaction of H 2O, SO 2, O 2, NO 2 and NO with copper-exchanged zeolite (Cu-ZSM5). Calculations were carried out using ab initio density functional theory (DFT). The DF calculations show that the adsorption energies of NO 2 and NO are larger than the corresponding adsorption energies of water and oxygen. Therefore, neither water nor O 2 can easily displace the adsorbed NO x s. On the contrary, water can displace adsorbed O 2 over the Cu, which indicates that the water could blocks some reaction channels of the catalytic cycle. It was also found, that the adsorption of SO 2 is not strong but can obstructs completely the active site for the reduction of the NO x due to the formation of a CuSO 4 specie. The topological analysis of the molecular charge density shows that the O 2 and SO 2 molecules are activated after the adsorption over the Cu, whereas H 2O is not activated.