Perovskites as catalysts precursors:: synthesis and characterization

Perovskites type oxides La1-xCaxRu1-xNixO3 were synthesized by the citrate sol-gel method. Characterization was carried out underlying the modification of metal catalysts by promoters by total or partial substitution of A- and B-site cations. The influence of Ru partial substitution by Ni in the LaRuO3 structure and of La by Ca on LaRu0.8Ni0.2O3 was also investigated in the dry and combine reforming of methane. All perovskites series, showed a well-defined perovskite structure with surface areas between 2 and 17 m(2)/g. After reduction Ru(Ni) crystallites size in the order of 10-15 nm were produced. An oxygen deficiency was shown by most perovskites. Substitution of La by Ca of smaller ionic radium decreases the stability of the perovskites and lowers their reduction temperature. Among the calcium series, La0.8Ca0.2Ru0.8Ni0.2O3, proved to be the most active precursor catalyst with the highest selectivity to syngas. Correlation between the effect of partial or total substitution of La by Ca as A-site cation of the precursor perovskite. the catalytic activity and stability of in situ formed Ru(Ni) particles was established. (C) 2004 Elsevier B.V. All rights reserved.