Low temperature DPF regeneration by delafossite catalysts

Several Li-Cr delafossite catalysts (LiCrO(2), LiCr(0.9)O(2), LiCr(0.8)O(2), LiCr(0.7)O(2), Li(0.9)CrO(2), Li(0.8)CrO(2) and Li(0.7)CrO(2)) were prepared via a highly exothermic and self-sustaining reaction, the so-called solution combustion synthesis (SCS) method, and characterized by means of XRD, BET, FESEM-EDS, H(2)-temperature programmed reduction (TPR) and XPS analyses, as catalysts for the combustion of soot, a major pollutant emitted by diesel engines. These catalysts already showed appreciable activity at 350 degrees C towards the catalytic combustion of soot even under loose contact conditions. The best prepared catalyst (LiCr(0.9)O(2)) could ignite soot combustion well below 350 degrees C, which is inside the range of temperatures reached at the exhaust line of a diesel engine. The correlation between the activity order and the capability to provide surface adsorbed oxygen (O(-)) by the prepared delafossite catalysts, enabled by a shift of the chromium from a high valence to a low valence state, is pointed out as a peculiar feature of these catalysts. An in situ SCS method was tailored to the preparation of a LiCr(0.9)O(2)-catalyzed trap based on a SiC wall-flow monolith. Engine bench tests on these catalytic traps (trap loading and regeneration by induced temperature increase) showed that the presence of the catalyst enabled both a more complete regeneration and a one-third fold reduction of the regeneration time compared to the case of a bare, non-catalytic trap. The catalyzed trap was finally characterized in terms of soot emissions during both the loading and the regeneration phase. (C) 2010 Elsevier B.V. All rights reserved.