Preparation of apatite-type-silicate-supported precious metal catalysts for selective catalytic reduction of NOx

Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La9.33Si6O26 and La8.33ASi6O25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La9.33Si6O26 catalyst exhibited high activity for oxidation of C3H6, comparable to Pd/Al2O3 catalyst, although the specific surface area of La9.33Si6O26 was lower than that of Al2O3. In addition, Pt/La9.33Si6O26 catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al2O3 catalyst. Substitution of Ba2+ for La3+ of La9.33Si6O26 led to increased catalytic activity at low temperature.