INFLUENCE OF WATER AND HYDROCARBON PROCESSED IN FEEDSTREAM ON THE 3-WAY BEHAVIOR OF PLATINUM-ALUMINA CATALYSTS

The influence of water and the nature of the hydrocarbon -methane, eth ylene, propene and 1-butene- processed in the feedstream on the three- way behaviour of a ceria-modified alumina supported platinum catalyst is investigated. Experiments were carried out with static feedstreams with air-to-fuel ratios between 14.13 and 15.17 as well as with oxidiz ing-reducing cycled feedstreams simulating the real automobile exhaust mixture. Conclusions are drawn on the importance of water-gas shift a nd steam reforming reactions and their relationship with inhibition se lf-poisoning effects of carbon monoxide and/or hydrocarbons. Compariso n of data of the prepared catalyst and those obtained at the same oper ational conditions with two commercial catalysts, with only platinum/a lumina and platinum-rhodium/ceria-alumina respectively, allows confirm ation of the effects of ceria and establishes the role of rhodium when added to the catalyst.