**Abstract**

Pd/composites are catalysts in which the catalytically active metal phase is located in a small layer on the support surface. The metal distribution obtained on these supports corresponds to a structure commonly known as "egg-shell". This distribution is optimal for reactions that have heat or mass transfer resistances. The small thickness of the metal layer is mainly attributed to the use of support pellets of mixed organic–inorganic composition, the special interaction between the hydrophobic–hydrophillic support surface and the metal species (Pd or Pt) present in the impregnating aqueous solution. Pd/composite catalysts are active and selective for the reactions of selective hydrogenation of styrene, 1-heptyne, 3-hexyne and 2,3-butanone, and enantioselective hydrogenation of ethyl pyruvate. These reactions are of interest in both academic and industrial aspects.

**Keywords:** composite catalyst, inorganic–organic supports, selective hydrogenation, improved mechanical resistance, egg-shell catalysts
