Towards practical application of lanthanum chromite catalysts for diesel particulate combustion

The effect of specific aging protocols (thermal treatment at 400 °C for 96 h and 650 °C for 24 h) in the presence of potentially deactivating species present in diesel exhaust gases (SO2 and water), was studied on some promising catalysts (LaCrO3, La0.9CrO3, La0.9Na0.1CrO3, La0.9Rb0.1CrO3, La0.8Cr0.9Li0.1O3) for diesel particulate combustion. The catalytic activity was almost completely retained. The catalyst La0.8Cr0.9Li0.1O3 was found to allow the best compromise between satisfactory catalytic activity and stability. This catalyst was then deposited on a SiC wall-flow trap, submitted to the same aging treatments and then tested in a diesel engine bench showing satisfactory stability. Engine bench tests on this catalytic trap (trap loading and regeneration inducing a temperature increase by the catalytic combustion of suitably post-injected fuel) showed that the presence of the catalyst in the wall-flow trap enabled both a more complete regeneration and a significant reduction of the regeneration time compared to that of a non-catalytic trap, with a consequent saving of post-injected fuel.