EFFECT OF PERIODIC OPERATION OVER PT CATALYSTS IN SIMULATED OXIDIZINGEXHAUST-GAS

The effect of periodic operation over Pt and Pt/Ba catalysts supported on gamma-alumina under oxidizing conditions was investigated using si mulated automotive exhaust gas from lean-bum combustion. The conversio n of hydrocarbons and NOx was measured in cycled feedstream and steady feedstream under oxidizing conditions. The activities of the catalyst s were improved in the cycled feedstream between oxidizing and reducin g atmospheres under average oxidizing conditions. In particular, the N Ox reduction on the Pt/Bt catalyst was higher than that on the Pt cata lyst in the cycling operation. From the mass spectral analysis in stre ams of NO-O-2-C3H6 and NO-O-2-H-2 (balance He) gas, it was found that NO was oxidized and stored on the Pt/Ba catalyst under oxidizing condi tions, and that the stored NOx on the catalyst was subsequently reduce d to N-2 under reducing conditions. (C) 1998 Elsevier Science B.V.