PD SIC CATALYSTS - CHARACTERIZATION AND CATALYTIC ACTIVITY FOR THE METHANE TOTAL OXIDATION/

Silicon carbide, SiC, is a refractory material which shows a high ther mal conductivity, Therefore, a better thermal stability of both the ca talytic active phase and of tile support for the SiC supported metalli c catalysts can be expected for reactions occurring at high temperatur e and/or for highly exothermic reactions working with high turnover fr equency, Various Pd based catalysts have been prepared by impregnation of a beta-SiC support with Pd(II) acetylacetonate [Pd(AcAc)(2)] and t ested for the methane oxidation. The activity and thermal stability of the catalysts are depending on the process used for the Pd(AcAc)(2) d ecomposition on beta-SiC. When the Pd(AcAc)(2) complex is decomposed u nder Ar atmosphere at 400 degrees C the catalyst presents small metal particles homogeneous in size, But, they are strongly deactivated afte r ageing under an oxidizing mixture up to 800 degrees C. The samples o btained after decomposition under O-2 at 350 degrees C, further reduce d under H-2, present larger particles and some formation of palladium silicide Pd2Si. They are first less active, but they show only slight deactivation after ageing under an oxidizing mixture up to 800 degrees C. The direct decomposition of the catalytic precursor under H-2 lead s to large Pd particles. As for the precedent catalyst, they deactivat e only moderately after reaction at 800 degrees C, (C) 1998 Academic P ress.