Non-thermal plasma-assisted NOx storage and reduction over cobalt-containing LNT catalysts

Abstract

Based on their high NO oxidation capacity (NOC) and NOx storage capacity (NSC), cobalt-containing LNT catalysts of the type Co/Ba/Al and Pd/Co/Ba/Al were tested under NOx storage-reduction (NSR) conditions, as well as in an H2-plasma assisted NSR process. For comparison purposes, a traditional Pt/Ba/Al catalyst was tested under the same conditions. The Co/Ba/Al catalyst exhibited similar catalytic properties to those of the Pt/Ba/Al catalyst when an H2-plasma was employed in the rich phase to assist reduction of the stored NOx. However, the NOx removal efficiency was greatly depressed by the presence of H2O and CO2 in the feed. Notably, the addition of Pd to the Co/Ba/Al sample greatly lessened the inhibiting effects of H2O and CO2 on plasma-assisted cycle-averaged NOx conversion, this being due to the excellent NOx storage performance of the Pd/Co/Ba/Al sample even in the presence of H2O and CO2. The results of the present study show that by combining the high NOx storage capacity of Pd/Co/Ba/Al in the lean phase with non-thermal plasma-assisted activation of the reductant in the rich phase, high NOx conversion can be obtained over a broad temperature window of 150–350°C.