Abstract
La 1− x A x NiO 3− 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 LaNiO 3, La 0.9Ce 0.1NiO 3 and La 0.9Pr 0.1NiO 3− 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 CH 4/CO 2 without dilution gas) compared to unreduced catalysts. The highest catalytic activity was obtained with the catalyst which was produced from the La 0.90Pr 0.1NiO 3− δ perovskite. CH 4 and CO 2 conversions and the H 2/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 Pr 2O 3, which may become re-oxidized by CO 2 during the reforming reaction to produce PrO 2 and CO. Subsequently, the PrO 2 may react with carbon residues regenerating again the reduced Pr 2O 3 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.
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