The effect of Cu-loading on different reactions involved in NH3-SCR over Cu-BEA catalysts

Abstract

In this study, we investigate the effect of varying copper loading in Cu-BEA on different reactions involved in the SCR mechanism. The catalysts were characterized by BET, ICP-AES, and UV-Vis. Enlarged ammonia storage was observed when increasing the copper loading mainly owing to loosely bonded NH3, but for over-exchanged samples, a new high-temperature shoulder was also observed. The N2O production significantly grew with increasing copper loading. In addition, the reaction rates of NO oxidation and NH3 oxidation per Cu site were higher on the high-loaded copper samples compared to those with lower loading. However, the opposite results were found for NH3 SCR, but differences were small for this reaction. Ammonium nitrate formation and decomposition were examined during a variety of temperature-programmed desorption (TPD) experiments, and three regions related to the presence of acid sites and low- versus high-loaded copper sites were observed. When dosing NO2 before NH3, ammonium nitrate species were formed but in lower amounts than if NH3 and NO2 were dosed simultaneously