Total oxidation of methane over Pd catalysts supported on silicon nitrideInfluence of support nature

Abstract

Abstract Non-oxide refractory materials such as silicon nitride showing high thermal stability and thermal conductivity can be used as catalytic supports. Silicon nitride with different specific area and crystallinity: amorphous silicon nitride (SiN-am), amorphous silicon nitride annealed at 1450 °C (120 min) under nitrogen flow (SiN-annl) and α-Si 3 N 4 were chosen as supports for Pd catalysts. Commercial amorphous silicon nitride contains a small amount of crystalline phase with α/β Si 3 N 4 ratio of 2.3. Annealing of the amorphous silicon nitride leads to changes in the phase composition, as well as in the morphology of the powder. An increase of the amount of crystalline phases up to 80% with α/β Si 3 N 4 ratio of 6.6 was obtained after annealing. Palladium catalysts were prepared by impregnation of Pd(II) acetylacetonate in toluene solution of silicon nitride powder and were tested in the methane total oxidation reaction. A strong influence of the phase composition and the crystalline state of supports on the catalytic properties of Pd catalysts was found. The activity of Pd catalysts deposited on the amorphous Si 3 N 4 is very poor. It increases with the α-Si 3 N 4 content of the support.