Abstract

The effect of partial substitution of La by Ca and Sr in the catalytic activity of lanthanum cobaltite (LaCoO3) was studied. Two series of La1-xCaxCoO3 and La1-xSrxCoO3 (x = 0, 0.2, and 0.4) reduced perovskites were prepared, characterized and evaluated in the succinic acid conversion at 200 degrees C and 6 MPa. The characterization results showed a larger Ca substitution in the La1-xCaxCoO3 series, whereas carbonates as segregated phases up to x = 0.2 of Sr were obtained in the La1-xSrxCoO3 series. In the Sr substituted perovskites, the oxidation of Co3+ to Co4+ neutralizes the electronic instability, whereas in the Ca substituted perovskites the presence of Ca2+ generates oxygen vacancies. The succinic acid conversion forms mainly succinic anhydride and 2-hydroxy-tetrahydrofuran by dehydration and hydrogenation processes. The highest initial rate of the reduced LaCoO3 was attributed to the smallest Co crystal size with no segregated phases, compared to substituted catalysts.