CONTROL OF METAL RADIAL PROFILES IN ALUMINA SUPPORTS BY CARBON-DIOXIDE

The competitive effect of carbon dioxide adsorption on the radial profiles of H2PtCl6, H2IrCl6 and HReO4 in gamma-Al2O3 supports was studied. Classically, adsorption of the metal-containing anions proceeds rapidly resulting in shallow penetration of the metal into the support, the egg shell catalyst. Various additives, such as carboxylic and mineral acids, have been employed in a slow process to promote uniform metal profiles. It was found that rapid preadsorption of carbon dioxide onto the alumina promotes the desirable uniform metal distribution. Furthermore, the effect of carbon dioxide preadsorption is maintained even after calcination at elevated temperatures.