2013 Volume 121 Issue 1410 Pages 169-175
Apatite-type ALa9Si6O26 (A = Li, Na, K) were prepared by solid state reaction method. The hexagonal unit cell volumes of ALa9Si6O26 increased with increasing ionic radii of alkali metal ions, indicating that the alkali metal ions were incorporated into the apatite-type lattice. The specific surface areas of ALa9Si6O26 were less than 1 m2/g. X-ray photoelectron spectroscopy measurement showed that Pt species on as-prepared catalysts were highly oxidized. Reduction temperature of Pt oxides on the catalyst for temperature-programmed reduction by H2 was decreased by substitution of alkali metal ion at La site in the apatite-type silicate. For C3H6–NO–O2 reaction, Pt/NaLa9Si6O26 catalyst exhibited a maximum NO conversion of 42%, the highest among Pt/ALa9Si6O26 catalysts. The temperature for maximum NO conversion over Pt/NaLa9Si6O26 catalyst was lower than that over Pt/γ-Al2O3 catalyst under the same reaction condition. The temperature of 50% C3H6 conversion for C3H6–O2 reaction over Pt/ALa9Si6O26 catalysts increased in the sequence of A = K < A = Na < A = Li. In addition, C3H6 oxidation activity was suppressed by presence of CO2 and NO on the catalyst. These results suggest that the basic sites on the apatite-type support affect the catalytic activities of Pt/ALa9Si6O26 catalysts for C3H6–NO–O2 and C3H6–O2 reaction.
Journal of the Ceramic Association, Japan
Journal of the Ceramic Association, Japan
