Comparative Study of Carbon Dioxide Reforming of Methane to Synthesis Gas over Ni/La2O3and Conventional Nickel-Based Catalysts

Carbon dioxide reforming of methane to synthesis gas was studied by employing a Ni/La 2 O 3 catalyst as well as conventional nickel-based catalysts, i.e., Ni/γ-Al 2 O 3, Ni/CaO/γ-Al 2 O 3, and Ni/CaO. It is observed that, in contrast to conventional nickel-based catalysts, which exhibit continuous deactivation with time on stream, the rate of reaction over the Ni/La 2 O 3 catalyst increases during the initial 2−5 h and then tends to be essentially invariable with time on stream. X-ray photoelectron spectroscopy (XPS) studies show that the surface carbon on spent Ni/Al 2 O 3 catalyst is dominated by −C−C− species that eventually block the entire Ni surface, leading to total loss of activity. The surface carbon on the working Ni/La 2 O 3 catalyst is found to consist of −C−C− species and a large amount of oxidized carbon. Both XPS and secondary ion mass spectrometry results reveal that a large fraction of surface Ni on the working Ni/La 2 O 3 catalyst is not shielded by carbon deposition. FTIR studies reveal that the enhancement of the rate of reaction over the Ni/La 2 O 3 catalyst during the initial 2−5 h of reaction correlates well with increasing concentrations of La 2 O 2 CO 3 and formate species on the support, suggesting that these species may participate in the surface chemistry to produce synthesis gas. It is proposed that the interaction between nickel and lanthanum species creates a new type of synergetic sites at the Ni−La 2 O 3 interfacial area, which offer active and stable performance of carbon dioxide reforming of methane to synthesis gas over the stated catalyst.