Abstract. High-energy ball milling has been employed to convert a microcrystalline, stoichiometric (S/Mo = 2), catalytically completely inactive MoS2 (prepared by high-temperature decomposition of ammonium tetrathiomolybdate, ATM) into an active catalyst, the activity profile of which was studied with test reactions (ethylene hydrogenation, H2/D2 scrambling, cis–trans isomerization of cis…