Influence of Pr and Ce in dry methane reforming catalysts produced from La1−xAxNiO3−δ perovskites Original Research Article

La1−xAxNiO3−δ (A = Pr, Ce) perovskites were synthesized by the auto-combustion method and evaluated as catalyst precursors in the dry reforming of methane. After reduction of the perovskites the average diameter of Ni° on the catalysts LaNiO3, La0.9Ce0.1NiO3 and La0.9Pr0.1NiO3−δ were: 15 nm, 9 nm and 6 nm, respectively. Catalysts obtained by the reduction of the perovskites had the highest catalytic activity under drastic reaction conditions (10 mg of catalyst and a mixture of CH4/CO2 without dilution gas) compared to unreduced catalysts. The highest catalytic activity was obtained with the catalyst which was produced from the La0.90Pr0.1NiO3−δ perovskite. CH4 and CO2 conversions and the H2/CO molar ratio were 49%, 55% and 0.81, respectively. No carbon deposits were detected after 100 h of reaction. The high resistance to deactivation is related to the lower Ni° particle size as well as to the redox chemistry of praseodymium oxide Pr2O3, which may become re-oxidized by CO2 during the reforming reaction to produce PrO2 and CO. Subsequently, the PrO2 may react with carbon residues regenerating again the reduced Pr2O3 oxide and gasifying the carbon deposits. A trend to decrease the amount of carbon deposits with increasing the Ce or Pr doping level was observed. The catalysts were characterized by TPR, TGA, TEM, ICP-AES and in situ XRD.