OXYGEN STORAGE CAPACITY OF ALUMINA-SUPPORTED RH/CEO2 CATALYST

In the present work, Rh/CeO2/Al2O3 catalysts were prepared by two different methods. One is a subsequent impregnation of alumina with an aqueous solution containing Ce ions and then with that containing Rh ions. The other method is a mixing of CeO2/Al2O3 with Rh/Al2O3 so that the Rh: CeO2 ratio is same as the ratio in the impregnated catalyst. The intimate contacts between rhodium and cerium oxide particles are much more expected in the former catalyst. In order to estimate the Oxygen Storage Capacity (OSC) values the catalysts were completely oxidized by injection of oxygen pulses, followed by cyclic pulses of oxygen and hydrogen until the consumptions of both gases on the catalyst were constant. The OSC of cerium oxide in the Rh/CeO2/Al2O3 catalyst was found to be greater than that of the physically mixed catalyst, indicating that the intimate contacts between rhodium and cerium oxide particles dispersed on alumina play an important role for the OSC of cerium oxide in the catalyst. Because of these intimate contacts, hydrogen and oxygen activated on the surface of rhodium particles are easy to spill over the neighboured cerium oxide particles to react with lattice oxygens and oxygen vacancies in the ceria crystallites. Thus, the intimate contacts between rhodium and cerium oxide particles are essential for the enhanced OSC of cerium oxide. © 1990, The Chemical Society of Japan. All rights reserved.