Pd/SiC catalysts - Characterization and catalytic activity for the methane total oxidation

Silicon carbide, SiC, is a refractory material which shows a high thermal conductivity, Therefore, a better thermal stability of both the catalytic active phase and of the support for the SiC supported metallic catalysts can be expected for reactions occurring at high temperature and/or for highly exothermic reactions working with high turnover frequency, Various Pd based catalysts have been prepared by impregnation of a beta-SiC support with Pd(II) acetylacetonate [Pd(AcAc)(2)] and tested for the methane oxidation. The activity and thermal stability of the catalysts are depending on the process used for the Pd(AcAc)(2) decomposition on beta-SiC. When the Pd(AcAc)(2) complex is decomposed under Ar atmosphere at 400 degrees C the catalyst presents small metal particles homogeneous in size, But, they are strongly deactivated after ageing under an oxidizing mixture up to 800 degrees C. The samples obtained after decomposition under O-2 at 350 degrees C, further reduced 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 leads to large Pd particles. As for the precedent catalyst, they deactivate only moderately after reaction at 800 degrees C, (C) 1998 Academic Press.