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

ABSTRACT

The catalytic decomposition of ozone was investigated over Pd-Mn/SiO(2)-Al(2)O(3) 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 N(2) 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 degrees C had been studied. XRD and TG results show that when calcined in the temperature range of 300-450 degrees C, manganese carbonate (MnCO(3)) is partly decomposed to MnOx (x=1.6-2.0) species in the catalysts. However, when calcined at 500 degrees C, MnOx partly turns into Mn(2)O(3) in the catalyst. The catalytic activity test indicates that the catalysts calcined at 300-400 degrees C exhibit the best performance for O(3) decomposition, and the completely conversion temperature of ozone (T(100)) is in the region of 30-35 degrees C, which is lower than surface temperature of water tanks of running automobile. Under gas hour space velocity (GHSV) of 635,000h(-1) and reaction temperature of 40 degrees C, after lifetime test for 80 h, the catalyst calcined at 350 degrees C keeps 90% conversion, which indicates that they have excellent ability to resist deactivation. The catalysts calcined at 300-400 degrees C show great potential to be applied at lower temperature, especially in winter and at the stage of automobile engine cold start.