Selective hydrogenation of methyl oleate into unsaturated alcohols in the presence of cobalt-tin supported over zinc oxide catalysts

The hydrogenation of methyl oleate (methyl-9-octadecenoate) into oleyl alco hol (methyl-9-octadecen-1-ol) was studied in the presence of a bimetallic C oSn supported over a zinc oxide catalyst in a stainless steel batch reactor at 270 degreesC and 8.0 MPa. Zinc oxide can activate the carbonyl group an d also the hydrogen by a possible heterolytic and homolytic dissociation of dihydrogen. The selectivity to unsaturated alcohol (oleyl alcohol) was sig nificantly enhanced by adding tin to cobalt. The activity and the selectivi ty to unsaturated alcohols was maximum for an atomic Sn/Co ratio of 1, as f or the CoSn alumina sol-gel catalyst. For all CoSn catalysts, the selectivi ty to unsaturated alcohols goes through a maximum for a surface Sn/Co ratio close to 2, the active species being a mixed Me-0-(SnOx)(2), where the oxi dation of tin is close to 0. The reduction of CoSn solids with sodium boroh ydride increased the activity of the catalyst. (C) 2001 Academic Press.