Pd/SiC Catalysts: Characterization and Catalytic Activity for the Methane Total Oxidation

Abstract

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 β-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)2decomposition on β-SiC. When the Pd(AcAc)2complex is decomposed under Ar atmosphere at 400°C the catalyst presents small metal particles homogeneous in size. But, they are strongly deactivated after ageing under an oxidizing mixture up to 800°C. The samples obtained after decomposition under O2at 350°C, further reduced under H2, present larger particles and some formation of palladium silicide Pd2Si. They are first less active, but they show only a slight deactivation after ageing under an oxidizing mixture up to 800°C. The direct decomposition of the catalytic precursor under H2leads to large Pd particles. As for the precedent catalyst, they deactivate only moderately after reaction at 800°C.