Density functional study of NOx reduction in zeolite cage

A density functional method was applied to investigate the electronic structures of Cu ion adsorbed ZSM-5 zeolite and the interactions of NO molecules with zeolite. Two types of models were considered, the pentameric cluster model and the 5-membered ring cluster model. In the former, the Cu ion was bound to the two O atoms with larger stabilization energy (52 kcal/mol) than the single O atom. For the 5-membered ring model, a much smaller stabilization energy (38 kcal/mol) was calculated. The deNOx reaction mechanism was simulated as the reactions between two NO molecules or between NO and HNO (or NOH) molecules. The former did not produce N2 and O2 smoothly due to the activation barrier, whereas the latter is found to lead to N2O and OH more easily.