Carbon dioxide reforming of methane to synthesis gas over Ni/La 2O 3 catalysts

Abstract

Carbon dioxide reforming of methane to synthesis gas was studied employing Ni/La 2O 3 catalysts. It was found that, in contrast to the performance of other nickel-based catalysts (e.g. Ni/Al 2O 3 and Ni/CaO) which exhibit continuous deactivation with time on stream, the rate over the Ni/La 2O 3 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 CO 2 pool, stored in the form of La 2O 2CO 3, is accumulating on the Ni/La 2O 3 catalyst, following exposure to the CH 4/CO 2 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/La 2O 3 catalyst, as compared to the Ni/Al 2O 3 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 La 2O 3 support or La species which are decorating the Ni crystallites is responsible for the unusual chemisorptive and catalytic behaviour observed over the Ni/La 2O 3 catalyst.