This study examined the effect of bimetallic catalyst preparation techniques and subsequent pre-treatments on alumina-supported Pt/Sn, Ir/Sn and Pt/Ir catalyst behavior for propane hydrogenolysis. Comparisons were made of conventional co-impregnated catalysts and "composite" catalysts, i.e. pellets in which a porous binder connected separately impregnated/calcined powders. The pre-treatments studied included sintering, Cl-2-induced redispersion, and pre-sulfiding with H2S. Relative to platinum, iridium was confirmed to be much more active for hydrogenolysis and more sensitive to pre-sulfiding. Propane hydrogenolysis over Ir/Al2O3 appeared to be structure-sensitive, probably due to an ensemble effect. Results indicated alloy cluster formation for co-impregnated Pt/Ir, but the effect of tin in Pt/Sn and Ir/Sn was too weak to allow a firm conclusion regarding alloy cluster formation. (C) 2003 Elsevier B.V. All rights reserved.