Effect of B-site cation on the catalytic activity of La1-xCaxBO3 (B = Fe, Ni) perovskite-type oxides for toluene combustion

BACKGROUND: The effect of the B cation on the surface properties and catalytic activity in the total combustion of toluene over La1-xCaxBO3 (B = Fe, Ni) perovskite-type oxides was studied. RESULT: For the La1-xCaxFeO3 series, the perovskite structure was maintained in the range of substitution studied. A completely different behaviour was observed for the La1-xCaxNiO3 series. A Brownmillerite-type structure (La2Ni2O5) with a large degree of phase segregation as well dispersed mixed oxides was observed upon the substitution of La for Ca. In the Fe series, the catalytic activity in the total combustion of toluene showed that the insertion of calcium ions into the perovskite lattice resulted in higher activity relative to the unsubstituted LaFeO3 perovskite. In contrast, for the Ni series, substitution results in solids with lower activity than the pure LaNiO3 perovskite. CONCLUSION: For the Fe series, higher activity and stability are attributed to a synergy between Fe4+/Fe3+ and the oxygen vacancies generated by the calcium substitution. For the Ni counterpart, the structural modification leads to a lower activity of substituted solids compared with the pure LaNiO3 perovskite, indicating that Ni3+ ions are the active sites for toluene oxidation. (C) 2011 Society of Chemical Industry