Theoretical investigation into the effect of water on the N2O decomposition reaction over the Cu-ZSM-5 catalyst

摘要

Copper exchanged zeolites are admirable catalysts for the direct decomposition reaction of harmful N2O gas. However, the inhibition of the decomposition reaction in the presence of water vapor greatly limits their application. The present study discloses the mechanism for N2O decomposition over dicopper active sites [Cu⋯Cu]2+ positioned at the opposite sides of the 10-membered ring in Cu-ZSM-5 by employing QM/MM calculations. The theoretical findings demonstrate the formation of [Cu–O–Cu]2+ and [Cu–O2–Cu]2+ moieties during the decomposition of the first and second N2O over dicopper active centers. Further, we have investigated the effect of water on the reaction steps, the possible intermediates, and the energetics of the direct decomposition of N2O. The barrier for the dissociation step of O–N2 involved in the water incorporating mechanism is significantly higher than the same reaction in the absence of water. The intermediate species [Cu–(OH)–Cu (OH)]2+ formed in the water incorporating pathway plays a crucial role in the inhibitory process of N2O decomposition. The present study contributes to the understanding of the mechanism of various complex reactions involving N2O and provides insights into the influence of water on other fields of heterogeneous catalysis.