The Role of Zr in Zr Doped La-Mn Perovskite Oxides for Nh3‒Scr and So2/H2o Resistance

Abstract

La-Mn perovskite catalysts with Zr doped A-site La ions were prepared by sol-gel method, systematically characterized and evaluated for their NH3‒SCR activity and resistance to SO2 and/or H2O in the long-term and multi-cycles. We found that Zr-2 catalyst achieves a nearly 100% NOX conversion at 120~240 °C without SO2/H2O and nearly 100% NOX conversion and nearly 90% N2 selectivity in the long-term case with SO2/H2O at 200 °C. The introduction of Zr reduces the adsorption energy of the catalyst for O2, NO, and NH3 but increases the formation energies of oxygen vacancies. Zr doping increases specific surface area, enriches surface acid sites and optimizes redox performance. However, the coverage of sulfate changes the redox properties, reduces adsorbed oxygen species and increases surface acidic strength, causing a decrease of activity, but Zr doping accelerates the decomposition of (NH4)2SO4 at low temperature, thereby improving the SO2 resistance of the catalyst.

Keywords: catalyst, perovskite, SCR, Mn, Zr