Stabilization of supported Pd particles by the application of oxide coatings

The influence of an HfOx coating on the initial sintering rates of nearly monodisperse Pd model catalyst particles on silica was measured at well defined temperatures and residence times in the gas-phase.It was found that minute amounts of HfOx significantly retard the sintering of the Pd and at higher amounts the mean Pd size can even be maintained. Analysis of the Pd size distributions indicates an immobilization of the Pd particles and a growth by Ostwald ripening. The coated catalysts were extremely stable at reaction conditions and show only a negligible loss of activity in the hydrogenation of ethylene.

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► Novel experimental approach for stability investigations of supported catalysts.
► Synthesis of complex catalyst structures with high degree of process control.
► Stabilization of silica supported Pd by deposition of minute amounts of HfOx.
► Ostwald ripening could be identified as growth mechanism for immobilized Pd.
► Long-term stability on stream, minor loss of activity due to HfOx coating.