A detailed study of the hydrochlorination of acetylene using supported gold and gold-based bimetallic catalysts is described and discussed. Carbon-sup ported Au-Pd catalysts were studied in detail, because Au and Pd can form a continuous solid solution across all alloy compositions. The addition of <= 5 at% Pd to Au increased the initial activity but with a significant loss of selectivity. In addition, all Au-Pd/C catalysts deactivated rapidly due to coke deposition. Pt-Au catalysts behaved in a similar manner. In contrast, Au-catalysts doped with It and Rh demonstrated enhanced activity with little change in selectivity. The addition of Ru had no significant effect. The observations are rationalized in terms (i) of the relative solubilities of the second metal in Au, which were explored by detailed STEM-XEDS analysis, and (ii) the dehydrochlorination and oligomerization activity of the dopant metal. These results confirm that the most active known catalyst for the hyd rochlori nation of acetylene for long-term use is undoped Au, and that the activity of the catalyst correlates with the standard electrode potential. (c) 2008 Elsevier Inc. All rights reserved.