Significantly enhanced activity and SO2 resistance of Zr-modified CeTiOx catalyst for low-temperature NH3-SCR by H2 reduction treatment

Abstract

The Zr-modified CeTiOx mixed oxide catalyst with good NH3-SCR activity and SO2 resistance was synthesized and reduced by H2. Performance test revealed that the obtained R-CZT-20/1 (Ce: Zr: Ti = 20: 1: 100) catalyst exhibited outstanding low-temperature activity after H2 reduction treatment, which achieved upon 98% NO conversion at 200–350 °C. Remarkably, it possessed excellent SO2 resistance as well as good reversibility, with the activity decreased from 100% to 96%. Meanwhile, R-CZT-20/1 possessed more surface acid sites and oxygen defects, which promoted the chemical adsorption and activation of NO and NH3 on the catalyst surface. XPS results confirmed that R-CZT-20/1 enriched Ce3+, accelerated the electron transfer between Ce3++ Ti4+ → Ce4++ Ti3+, and generated a large number of oxygen vacancies. Moreover, there is strong synergistic effect between Ce-Zr-Ti, which might be the reason for the excellent SO2 resistance. Among them, the presence of Zr facilitated the favorable process. In situ DRIFTS experiments indicated that the unreduced catalysts followed E-R and L-H mechanism at low and high temperatures, respectively, while R-CZT-20/1 obeyed only the L-H mechanism.