Promotional effect of alkaline earth over Ni-La_2O_3 catalyst for CO_2 reforming of CH_4: Role of surface oxygen species on H_2 production and carbon suppression

摘要

Alkaline earth elements (Mg, Ca and Sr) on Ni-La_2O)_3 catalyst have been investigated as promoters for syngas production from dry CO_2 reforming of methane (DRM). The catalysis results of DRM performance at 600 ℃ show that the Sr-doped Ni-La_2O_3 catalyst not only yields the highest CH_4 and CO_2 conversions (~78% and ~60%) and highest H_2 production (～42% by vol.) but also has the lowest carbon deposition over the catalyst surface. The XPS, O_2-TPD, H_2-TPR and FTIR results show that the excellent performance over the Sr-doped Ni-La_2O_3 catalyst is attributed to the presence of a high amount of lattice oxygen surface species which promotes C-H activation in DRM reaction, resulting in high H_2 production. Moreover, these surface oxygen species on the Ni-SDL catalyst can adsorb CO_2 molecules to form bidentate carbonate species, which can then react with the surface carbon species formed during DRM, resulting in higher CO_2 conversion and lower carbon formation.