Elucidating the role of La3+/Sm3+ in the carbon paths of dry reforming of methane over Ni/Ce-La(Sm)-Cu-O using transient kinetics and isotopic techniques

Abstract

The different effects of the presence of La3+ and Sm3+ heteroatoms in the 5 wt% Ni/45Ce-45(Sm or La)-10Cu-O catalytic system on the carbon deposition and removal reaction paths in the dry reforming of methane (DRM) at 750 °C were investigated using transient kinetic and isotopic experiments. The relative initial rates of carbon oxidation by lattice oxygen of support and that by oxygen derived from CO2 dissociation under DRM reaction conditions were quantified. Ni nanoparticles (23-nm) supported on La 3+-doped ceria exhibited at least 3 times higher initial rates of carbon oxidation to CO by lattice oxygen, and ~ 13 times lower rates of carbon accumulation than Ni (18-nm) supported on Sm3+-doped ceria. The concentration and mobility of labile surface oxygen at the Ni-support interface region seems to correlate with carbon accumulation. Ni/Ce-La(or Sm)-–10Cu-O formed NiCu alloy nanoparticles, partly responsible for lowering carbon deposition and increasing carbon oxidation rates to CO.