Carbon dioxide reforming of methane to synthesis gas over Ni/La2O3 catalysts

Carbon dioxide reforming of methane to synthesis gas was studied employing Ni/La2O3 catalysts. It was found that, in contrast to the performance of other nickel-based catalysts (e.g. Ni/Al2O3 and Ni/CaO) which exhibit continuous deactivation with time on stream, the rate over the Ni/La2O3 catalyst increases during the initial 2-5 h of reaction and then tends to be essentially invariable with time on stream, displaying very good stability, X-ray diffraction (XRD) studies reveal that a large CO2 pool, stored in the form of La2O2CO3, is accumulating on the Ni/La2O3 catalyst, following exposure to the CH4/CO2 mixture at reaction conditions. Results of H-2- and CO-temperature-programmed desorption reveal that the H-Ni bond is weakened and CO disproportionation is unfavoured on the Ni/La2O3 catalyst, as compared to the Ni/Al2O3 catalyst. Comparison of H-2 and CO uptake and Ni dispersion by XRD shows that H-2 and CO uptakes are significantly suppressed, by ca. 3-10 times, suggesting that a large portion of the Ni surface is blocked by lanthanum species. It is proposed that the interaction between Ni crystallites and La2O3 support or La species which are decorating the Ni crystallites is responsible for the unusual chemisorptive and catalytic behaviour observed over the Ni/La2O3 catalyst.