Copper Catalysts for Soot Oxidation: Alumina versus Perovskite Supports

Copper catalysts prepared using four supports (Mg- and Sr- modified Al2O3 and MgTiO3 and SrTiO3 perovskites) have been tested for soot oxidation by O-2 and NOx/O-2. Among the catalysts studied, Cu/SrTiO3 is the most active for soot oxidation by NOx/O-2 and the support affects positively copper activity. With this catalyst, and under the experimental conditions used, the soot combustion by NOx/O-2 presents a considerable rate from 500 degrees C (100 degrees C below the uncatalysed reaction). The Cu/SrTiO3 catalyst is also the most effective for NO, chemisorption around 425 degrees C. The best activity of Cu/SrTiO3 can be attributed to the improved redox properties of copper originated by Cu-support interactions. This seems to be related to the presence of weakly bound oxygen on this sample. The copper species present in the catalyst Cu/SrTiO3 can be reduced more easily than those in other supports, and for this reason, this catalyst seems to be the most effective to convert NO into NO2, which explains its highest activity for soot oxidation.