Selective hydrogenation of alkynes to alkenes in the presence of a phosphorus compound and an organic sulphur compound

A process for hydrogenating an alkyne selectively to an alkene which comprises subjecting the alkyne to hydrogenation conditions in the presence of a hydrogenation catalyst which is palladium supported on a carrier and in the presence of an additive mixture comprised of an additive AP and an additive AS, wherein

• (a) the additive AP is an organic phosphorus compound having no sulphur atoms which is selected from the group consisting of triphenylphosphine, 1,2-bis(diphenylphosphino) ethane and 1,3-bis(diphenylphosphino) propane;
• and
• (b) the additive AS which is 2,2′-(ethane-1,2-diylbis(sulfanediyl)) bis(ethan-1-ol) of the formula:
• wherein
• the alkyne comprises at least one carbon-carbon triple bond, and wherein
• the at least carbon-carbon triple bond is selectively hydrogenated to a respective carbon-carbon double bond to form the alkene.