CHEMICAL MODIFICATION OF CATALYST SUPPORT FOR ENHANCEMENT OF TRANSIENT CATALYTIC ACTIVITY - NITRIC-OXIDE REDUCTION BY CARBON-MONOXIDE OVER RHODIUM

A commercial ceria powder was chemically modified by doping with gadolinia in order to improve its oxygen storage/transport characteristics. The catalytic activity of Rh impregnated on this modified ceria support was measured and compared with those impregnated on conventional ceria or alumina support, using a packed-bed reactor and an isotopic reactant (13CO) for the NO + CO reaction under both cycled- and steady-feed conditions. Results of transient pulse experiments indicated that the oxygen uptakes of both ceria and modified ceria are an order of magnitude greater than that of alumina. This work has demonstrated that the chemical modification of the ceria support can significantly enhance the catalytic activity of Rh for the NO + CO reaction under cycled feedstream conditions at high temperatures above 500°C. This enhancement of catalytic activity of Rh supported on the modified ceria is discussed in light of the oxygen storage and transport characteristics of the modified support. © 1991.