Selective liquid-phase hydrogenation of .alpha.,.beta.-unsaturated carbonyl compounds

A process for the selective liquid-phase hydrogenation of .alpha.,.beta.-unsaturated carbonyl compounds of the formula (I) ##STR7## wherein R.sub.1 is hydrogen or an olefinically unsaturated hydrocarbyl group, and R.sub.2, R.sub.3 and R.sub.4, independently of one another, are hydrogen or a C.sub.1 -C.sub.4 --alkyl group, to saturated carbonyl compounds of the formula (II) ##STR8## comprising:

• hydrogenating said .alpha.,.beta.-unsaturated carbonyl compound in the presence of a pulverulent palladium and/or rhodium catalyst and in the presence of an organic base under liquid phase conditions in a packed bubble column reactor with hydrogen fed into the reactor at a superficial velocity of 0.5 to 15 cm/s and circulating of the liquid phase containing product at a superficial velocity of 100 to 500 m.sup.3 /m.sup.2.h with recycling of the product and circulating hydrogen gas within the reactor.