THE EFFECT OF IRIDIUM AGGLOMERATION ON THE PERFORMANCE OF PLATINUM-IRIDIUM BIMETALLIC CATALYSTS - MODEL-COMPOUND AND NAPHTHA REFORMING STUDIES

Alumina supported platinum-iridium bimetallic catalysts were partially-agglomerated by calcining samples under oxygen for various times at elevated temperatures. Calcination conditions were chosen so as to agglomerate selectively the iridium component into large IrO//2 crystallites. Upon reduction, the partially-agglomerated catalysts contain two distinct types of metal particles, one consisting of highly dispersed platinum or platinum rich clusters and the second consisting of large iridium or iridium rich crystallites. The extent of agglomeration was established by hydrogen and carbon monoxide chemisorption measurements.