Two series of 2 wt.% active carbon (Sibunit)-supported Pd-Ni catalysts were prepared using chloride and nitrate precursors. They were characterized by CO chemisorption, temperature programmed palladium hydride decomposition and XRD, and investigated in the hydrodechlorination of 1,2-dichloroethane in the gas phase at a relatively low reaction temperature (230oC). All catalysts showed rather moderate metal dispersion (below 10%). They appeared very stable during a 20 h testing. Ni-rich bimetallic samples exhibited the highest selectivities towards ethylene (desired reaction product). Small amounts of added palladium, the metal which is known for its high activity in hydrogenation, resulting in a massive production of ethane. The results showed a smooth correlation between turnover frequency towards ethylene and Pd-Ni phase composition, irrespective of the type of metal precursor used in catalyst preparation. The 2 wt.% Ni/C catalyst prepared from chloride precursor showed some nonnegligible selectivity toward vinyl chloride monomer, the selectivity which gradually increased in time on stream. All other catalysts did not show such a propensity.
The overall results indicate that palladium segregates to the surface of Pd-Ni, shaping the overall catalytic behavior of bimetallic Pd-Ni catalysts. The temperature programmed hydrogenation of deposits left after reaction show only the presence of surface carbon, without considerable amounts of chlorine.