Synergy Effects of Cobalt Oxides on Ni/Co-Embedded Al2O3 for Hydrogen-Rich Syngas Production by Steam Reforming of Propane

The synergetic effects of Co oxides on the Ni/CoAl (NCA) catalysts were observed at an optimal molar ratio of Al/Co = 2 (NCA(2)) due to the partial formations of thermally stable spinel CoAl2O4 phases for the steam reforming of propane (SRP). The optimal content of the spinel CoAl2O4 phases on the NCA(2) was responsible for the formation of the relatively active oxophilic metallic Co nanoparticles with a smaller amount of less active NiAl2O4 on the surfaces by preserving the relative amount of metallic Co of 68% and 52% in the reduced and used catalysts, which enhanced the catalytic activity and stability with the largest specific rate of 1.37 C3H8/(Ni + Co)h(-1) among the tested NCA catalysts. The larger or smaller amounts of Co metal on the less active NCA mainly caused the preferential formation of larger aggregated Ni nanoparticles similar to 16 nm in size due to their weaker interactions, or induced the smaller formations of active metal phases by selectively forming the spinel NiAl2O4 phases with similar to 60% in the NCA(4), resulting in a fast deactivation.