Structural and kinetic studies of carbon methanation catalysis by small platinum particles

The methanation reaction has been studied for Pt samples supported on graphite and amorphous carbon. Gas chromatography and thermogravimetry were used to study the catalytic activity, and topographic refracted electron images and weak multi-beam images were used to determine the surface topography of both the particles and the support. STEM micro-diffraction techniques were applied for determining the crystal structure of the Pt particles after the reaction. Deactivation of the catalyst has also been studied at 1000 °C. The activation energy for the reaction has been determined over the temperature range 800-1000 °C. The main reaction exhibited zero order kinetics while the deactivation process was first order. The results show that reaction takes place at the Pt/support interface and that the main role of the catalyst is to reduce the activation energy for C-C bond breakage. The reaction is always associated with either pitting or channelling through the support surface. A reaction mechanism which explains most of the experimental findings is proposed.