NOx and diesel soot abatement over catalytic traps based on mixed transition metal oxides

Nanostructured perovskite-type oxides catalysts La1-xAxNi1-yByO3 (where A = Na, K, Rb and B = Cu; x = 0, 0.2 and y = 0, 0.05, 0.1), prepared by the solution combustion synthesis method and characterized by BET, XRD, FESEM, and catalytic activity tests in microreactors, proved to be effective in the simultaneous removal of soot and NO, the two prevalent pollutants in diesel exhaust gases in the temperature range 350–450 °C. The best compromise between soot and nitrogen oxide abatement was shown by La0.8K0.2Ni0.9Cu0.1O3 catalyst which displayed the higher catalytic activity towards carbon combustion and the highest NO conversion activity (CO2 peak temperature = 368°C; max NO conversion = 92% at 400°C). An in situ SCS method was tailored to the preparation of a La0.8K0.2Ni0.9Cu0.1O3-catalyzed trap based on a SiC wall-flow monolith. 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 2fold reduction of the regeneration time compared to the case of a non-catalytic trap, with consequent saving of post-injected fuel. Moreover, during the regeneration phase the presence of the catalyst enabled a NO conversion of about 45%.