Palladium complex-based catalysts stabilized on mesostructured silica: reactivity in methane combustion

Novel catalysts were successfully obtained using hybrid composite silica-based mesoporous materials MCM-41 type LUS and Pd(II) complexes. The metal site localization was controlled using two different synthetic routes, namely in situ functionalization and post-grafting synthesis (ex situ synthesis). These materials were characterized by XRD, FT-IR, EPR, N-2 physisorption, TEM, SEM and H-2 chemisorption. The catalytic performance was investigated on methane combustion reaction under CH4/O-2/He (1/4/95 vol%) continuous flow at temperature below 450 A degrees C. It has been proved that the palladium complex is embedded inside the mesostructured walls for the materials synthesized by the in situ method; while it is grafted at the wall surface for the one resulted from ex situ path. The latter material performed the best catalytic activity at temperatures below 450 A degrees C thanks to a better dispersion of smallest PdO nanoparticles that optimizes the accessibility of the reactants to the actives sites in the mesoporous channels.