The hydrogenation of methyl oleate (methyl cis-9-octadecenoate) to oleyl alcohol (methyl cis-9-octadecen-1-ol) was studied in the presence of a bimetallic CoSn supported over zinc oxide catalyst in a stainless steel batch reactor at 270 degrees C and 8.0 MPa of hydrogen. The active species in the reduction of methyl oleate into unsaturated alcohols was CoSn2. In order to increase the amount of these active species the nature of the precursor salts was studied. These results have shown that the carbonyl cobalt precursor is the optimum salt for the hydrogenation of methyl oleate into unsaturated alcohol since the selectivity to unsaturated alcohol reached 55% at 80% of conversion. Moreover, the selectivity is governed by the reduction of the heavy esters (oleyl oleate and oleyl stearate) formed, which can occur in the presence of small Co-Sn-2 particles, well dispersed on the catalyst surface and with a high surface content. (C) 2012 Elsevier B.V. All rights reserved.