Influence of calcination temperature on the performance of Pd-Mn/SiO2-Al2O3 catalysts for ozone decomposition

The catalytic decomposition of ozone was investigated over Pd-Mn/SiO2-Al2O3 catalysts in the ground air. The catalysts were prepared by incipient wetness impregnation method and characterized by powder X-ray diffraction (XRD), thermo gravimetric (TG) analysis, and N2 adsorption/desorption measurements (Brunauer-Emmet-Teller method). The influence of calcination temperature on the catalytic activities, and the lifetime test of the catalyst pretreated at 350 °C had been studied. XRD and TG results show that when calcined in the temperature range of 300-450 °C, manganese carbonate (MnCO3) is partly decomposed to MnOx (x = 1.6-2.0) species in the catalysts. However, when calcined at 500 °C, MnOx partly turns into Mn2O3 in the catalyst. The catalytic activity test indicates that the catalysts calcined at 300-400 °C exhibit the best performance for O3 decomposition, and the completely conversion temperature of ozone (T100) is in the region of 30-35 °C, which is lower than surface temperature of water tanks of running automobile. Under gas hour space velocity (GHSV) of 635,000 h−1 and reaction temperature of 40 °C, after lifetime test for 80 h, the catalyst calcined at 350 °C keeps 90% conversion, which indicates that they have excellent ability to resist deactivation. The catalysts calcined at 300-400 °C show great potential to be applied at lower temperature, especially in winter and at the stage of automobile engine cold start.