Improved light-off performance by using transient gas compositions in the catalytic treatment of car exhausts

The influence of transient changes in the exhaust gas composition on the lo w-temperature activity of a Pt/CoOx/Al2O3, catalyst and a commercial three- way catalyst has been studied. Periodic O-2 and CO pulses caused well-contr olled perturbations in the composition of a synthetic car exhaust which was found to affect the overall performance of both catalysts. The presence of transients shifted the conversion starts of CO and propene as well as thei r light-off temperatures towards lower temperatures. The improved performan ce is suggested to origin from the combined effect of rich (CO) and lean (O -2) pulses that cause perturbations in the adsorbate composition on the act ive sites at temperatures below light off. (C) 1999 Elsevier Science Ltd. A ll rights reserved.