Hydrodechlorination of CCl4 over carbon-supported palladium–gold catalysts prepared by the reverse “water-in-oil” microemulsion method

Abstract Two series of carbon-supported Pd–Au catalysts were prepared by the reverse “water-in-oil, W/O” method, characterized by various techniques and investigated in the reaction of tetrachloromethane with hydrogen at 423 K. The synthesized nanoparticles were reasonably monodispersed having an average diameter of 4–6 nm (Pd/C and Pd–Au/C) and 9 nm (Au/C). Monometallic palladium catalysts quickly deactivated during the hydrodehalogenation of CCl 4 . Palladium–gold catalysts with molar ratio Pd:Au = 90:10 and 85:15 were stable and much more active than the monometallic palladium and Au-richer Pd–Au catalysts. The selectivity toward chlorine-free hydrocarbons (especially for C 2+ hydrocarbons) was increased upon introducing small amounts of gold to palladium. Simultaneously, for the most active Pd–Au catalysts, the selectivity for undesired dimers C 2 H x Cl y , which are considered as coke precursors, was much lower than for monometallic Pd catalysts. Reasons for synergistic effects are discussed. During CCl 4 hydrodechlorination the Pd/C and Pd–Au/C catalysts were subjected to bulk carbiding.