4-Hydroxybutanal → 1,4-Butanediol

The 4-hydroxybutanal which is produced as the high yield product of the invention hydroformylation process can be separated and recovered by conventional distillation procedures. It is highly preferred, however, to subject the hydroformylation product mixture to aqueous phase extraction. Surprisingly it was found that water is capable of extracting 4-hydroxybutanal from the product mixture substantially to the exclusion of the other product mixture components. In a commercial scale operation, an aqueous phase stream can be contacted countercurrently and continuously with reaction product effluent from the hydroformylation reaction zone. The resultant aqueous phase containing 4-hydroxybutanal is an excellent vehicle for subsequent processing procedures, such as hydrogenation of 4-hydroxybutanal with Raney nickel to produce valuable 1,4-butanediol.