Synergy Effects of Cobalt Oxides on Ni/Co-Embedded Al 2 O 3 for Hydrogen-Rich Syngas Production by Steam Reforming of Propane

摘要

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 CoAl 2 O 4 phases for the steam reforming of propane (SRP). The optimal content of the spinel CoAl 2 O 4 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 NiAl 2 O 4 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 C 3 H 8 /(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 ~16 nm in size due to their weaker interactions, or induced the smaller formations of active metal phases by selectively forming the spinel NiAl 2 O 4 phases with ~60% in the NCA(4), resulting in a fast deactivation.