The durability of a supported noble metal hydrodechlorination catalyst can be improved by (1) treating the supported catalyst, which comprises support and catalytic noble metal, with a non-elemental halide compound, which is not a mineral acid (such as an alkali metal halide, an ammonium halide, an alkaline earth metal halide, and/or a halogenated hydrocarbon); and (2) then using the treated catalyst in a hydrodechlorination reaction. Suitable treatment compounds include ammonium chloride, lithium chloride, or a chlorinated hydrocarbon. The treated catalyst is a novel composition of matter comprising at least one platinum group metal supported by an oxidic support wherein the metal, which is in the zero valent state, predominantly resides adjacent the surface of the support and is predominantly visible under a microscope having a resolution of about 5 .ANG..