Influence of calcination temperature on the performance of Pd–Mn/SiO 2–Al 2O 3 catalysts for ozone decomposition

Abstract

The catalytic decomposition of ozone was investigated over Pd–Mn/SiO 2–Al 2O 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 °C had been studied. XRD and TG results show that when calcined in the temperature range of 300–450 °C, manganese carbonate (MnCO 3) is partly decomposed to MnO x ( x = 1.6–2.0) species in the catalysts. However, when calcined at 500 °C, MnO x partly turns into Mn 2O 3 in the catalyst. The catalytic activity test indicates that the catalysts calcined at 300–400 °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 °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.