Experiments of propane and propene steam reforming have been performed over a Pd–Cu/γ-Al2O3 catalyst and over a Ni/NiAl2O4 catalyst. Over the palladium-based catalyst, the steam reforming of propene is faster and more selective than steam reforming of propane. Over the Pd catalyst, the steam reforming of propane is likely inhibited by site poisoning. In contrast, over Ni-based catalyst the reforming of propane and propene have similar reaction rates and product selectivity. This suggests a different mechanisms for the two catalysts. The well-known ability of Pd centers to adsorb olefins and catalyze their transformation suggests that over this catalyst π-bonding or di-σ-bonding of the olefin may be a key feature allowing its transformation.