Selective oxidation of soot over Cu doped ceria/ceria–zirconia catalysts

Copper doped ceria and ceria–zirconia mixed oxides were prepared using the citric acid sol–gel method. The temperature-programmed oxidation (TPO) results showed that the Cu modification helped to improve the activity and selectivity of ceria and ceria–zirconia for soot catalytic oxidation. The CO-TPR results showed that Cu–Ce had a better reducibility than pure ceria at low temperatures. After ageing at 800 °C for 20 h in flow air, CuO–CeO2 showed the maximum soot oxidation rate at 378 and 519 °C under tight and loose contact conditions, respectively, achieving a nearly 100% selectivity to CO2 production. This effect may be attributed to the existence of well dispersed copper oxide species strongly interacting with the ceria surface, which may decrease the activation energy of soot oxidation. A conceivable mechanism of this synergetic effect was proposed.