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

The Ba,K/CeO2 catalyst is active both for NOx trapping and soot combustion. In this work we report a Ba–K interaction that prevents K sulfation when NOx 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) → 2KNO3(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.