High performance of Mg-La mixed oxides supported Ni catalysts for dry reforming of methane: The effect of crystal structure

A series of mixed Mg-La oxide supports with various Mg2+/La3+ mole ratios were prepared via co-precipitation of Mg and La nitrates, and then impregnated to form 5 wt.% Ni catalysts. The as-prepared catalysts were evaluated in DRM reaction for 200 h and characterized by means of in situ DRIFTS, XRD, TEM, CO2-TPD, XPS, and TGA. It was found that the interaction of suitable amount of MgO with La2O3 stabilized cubic La2O3 species in catalysts, which has high basicity to adsorb CO2 forming monoclinic La2O2CO3 (Ia) species in DRM reaction. The introduction of MgO also created surface oxygen ions (i.e. O-). Both monoclinic La2O2CO3 (Ia) and surface oxygen species are able to oxidize and remove deposited carbon, keeping the Ni catalyst at high activity and stability. Low Mg2+/La3+ ratios generated hexagonal La2O3 and La2O2CO3 (II) in DRM reaction. The hexagonal La2O2CO3 (II) did not play significant role in carbon removal so that the catalysts deactivated fast.