An Alumina-Supported Ni-La-Based Catalyst for Producing Synthetic Natural Gas

LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (gamma-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt% La-Ni/gamma-Al2O3 particles were prepared via solution combustion synthesis (SCS) and exhibited good catalytic activity, achieving a CO2 conversion of 75% with a high CH4 selectivity (98%) at 1 atm and 300 degrees C. Characteristics of the La-Ni/gamma-Al2O3 catalyst were identified at various stages of the catalytic process (as-prepared, activated, and post-reaction) and in-situ DRIFTS was used to probe the reaction mechanism. The as-prepared catalyst contained amorphous surface La-Ni spinels with particle sizes < 6 nm. The reduction process altered the catalyst make-up where, despite the reducing conditions, Ni2+-based particles with diameters between 4 and 20 nm decorated with LaOx moieties were produced. However, the post-reaction catalyst had particle sizes of 4-9 nm and comprised metallic Ni, with the LaOx decoration reverting to a form akin to the as-prepared catalyst. DRIFTS analysis indicated that formates and adsorbed CO species were present on the catalyst surface during the reaction, implying the reaction proceeded via a H-2-assisted and sequential CO2 dissociation to C and O. These were then rapidly hydrogenated into CH4 and H2O.