Preparation and NO reduction property of apatite-type ALa9Si6O26 (A = Li, Na, K) supported Pt catalyst
Journal of the Ceramic Society of Japan
Apatite-type ALa 9 Si 6 O 26 (A = Li, Na, K) were prepared by solid state reaction method. The hexagonal unit cell volumes of ALa 9 Si 6 O 26 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 ALa 9 Si 6 O 26 were less than 1 m 2 /g. X-ray photoelectron spectroscopy measurement showed that Pt species on as-prepared catalysts were highly oxidized. Reduction temperature of
... tion temperature of Pt oxides on the catalyst for temperature-programmed reduction by H 2 was decreased by substitution of alkali metal ion at La site in the apatitetype silicate. For C 3 H 6 NOO 2 reaction, Pt/NaLa 9 Si 6 O 26 catalyst exhibited a maximum NO conversion of 42%, the highest among Pt/ALa 9 Si 6 O 26 catalysts. The temperature for maximum NO conversion over Pt/NaLa 9 Si 6 O 26 catalyst was lower than that over Pt/£-Al 2 O 3 catalyst under the same reaction condition. The temperature of 50% C 3 H 6 conversion for C 3 H 6 O 2 reaction over Pt/ALa 9 Si 6 O 26 catalysts increased in the sequence of A = K < A = Na < A = Li. In addition, C 3 H 6 oxidation activity was suppressed by presence of CO 2 and NO on the catalyst. These results suggest that the basic sites on the apatite-type support affect the catalytic activities of Pt/ALa 9 Si 6 O 26 catalysts for C 3 H 6 NOO 2 and C 3 H 6 O 2 reaction.