Soot oxidation on a catalytic NOx trap:: Beneficial effect of the Ba-K interaction on the sulfated Ba,K/CeO2 catalyst

The Ba,K/CeO:, catalyst is active both for NOx trapping and soot combustion. In this work we report a Ba- K interaction that prevents K sulfation when NO, is present, thus preserving the activity of K towards soot combustion during the working period of the trap. This effect is originated in the K2SO4(s) + Ba(NO3)(2)(s) -> 2KNO(3)(s) + BaSO4(s) reaction, which is thermodynamically favored. In the absence of NOx the soot combustion reaction is strongly depressed by SO2 whereas when NOx is present both the sulfated and the non-sulfated catalysts present similar TPO patterns. (c) 2006 Elsevier B.V. All rights reserved.