Redox Activity and NO Storage Capacity of MnOx−ZrO2 with Enhanced Thermal Stability at Elevated Temperatures

Abstract

MnOx−ZrO2 mixed oxides are very active catalysts for oxidation or combustion applications due to their excellent redox activity. Recently, they have also shown promising results for NO storage in emission control. Despite the versatile applications, a systematic study on the redox activity and NO storage capacity of MnOx−ZrO2 with their thermal stability at high temperatures is still missing. In this paper the evolution of these properties in the temperature range 500−900 °C is reported. It was found that there is a dramatic deterioration in redox activity and NO storage capacity when the calcination temperature increases to 900 °C, which is attributed to the loss of thermal stability at this high temperature. On the other hand, doping with La can hinder the sintering of MnOx−ZrO2 particles and therefore increase the surface area of the mixed oxides calcined at 900 °C. Correspondingly, La-doped MnOx−ZrO2 mixed oxides show much improved redox activity and NO storage capacity even after 900 °C heat treatment.