Zeolite physical mixing restores the high temperature NH3-SCR of CeO2: The crucial role of NOx activation

The occurrence of NH3 over-oxidation represents one intractable challenge for the effective application of NH3-SCR technology. Herein, a rational NOx activation strategy was innovatively proposed to counteract NH3 over oxidation during high temperature NH3-SCR. As a proof of concept, the hybrid catalyst of CeO2-ZSM-5 was explored. It was shown that the activity of CeO2 in NH3-SCR was profoundly improved via physically mixing with ZSM-5, achieving more than 85 % NO at 500 degrees C, in sharp contrast to the negative NO conversion present for pristine CeO2. Comprehensive characterizations from NH3-TPD, NO-TPD and in situ DRIFTS verified the negligible modification of NH3 oxidation but significant alteration of surface NOx. Due to the facile NOx activation, the reaction of NH3 + NOx overwhelms that of NH3 + O2, leading to the obtainment of excellent high temperature NH3-SCR performance. The novel strategy reported here is expected to provide valuable guidance for designing NH3-SCR catalysts with superior high temperature performance.