Manufacture of predominantly straight-chain aldehydes

In an improved process for the manufacture of predominantly straight-chain aldehydes by hydroformylation of olefinically unsaturated compounds of 2 to 20 carbon atoms with carbon monoxide and hydrogen in which, in a first stage;

• aqueous cobalt salt solutions are treated with carbon monoxide and hydrogen at a temperature of 50.degree. to 200.degree.C and a pressure of 100 to 400 atmospheres in the presence of active charcoal, zeolites or basic ion exchangers which are charged with cobalt carbonyl, in a second stage cobalt carbonyl-hydride is extracted from the resultant reaction mixture at a temperature of 20.degree. to 180.degree.C and a pressure of 1 to 400 atmospheres by means of olefinically unsaturated compounds which are water-insoluble and liquid under the conditions used, the aqueous phase is separated from said liquid olefinically unsaturated compounds containing extracted cobalt carbonyl-hydride, and latter liquid is transferred to a third stage and in this stage, after introducing olefinically unsaturated compounds if the latter have only been used partially for the extraction, the hydroformylation is carried out at a temperature of 70.degree. to 170.degree.C and under a pressure of 100 to 400 atmospheres, the improvement comprising carrying out the extraction in the second stage as a cocurrent extraction while maintaining turbulent flow of said aqueous phase and said liquid olefinically unsaturated compounds during said cocurrent extraction.