Process for the hydroformylation of olefinically unsaturated compounds in a non-aqueous ionic solvent

A process comprising reacting under hydroformylation conditions at least one olefinically unsaturated compound in the liquid phase in a reaction section, with carbon monoxide and hydrogen in the presence of at least one polar phase comprising:

• a non-aqueous ionic liquid which is liquid at the reaction temperature and at least partly miscible with the reaction products, the ionic liquid comprising at least one salt of general formula Q+A−, in which Q+ represents a quaternary ammonium and/or a quaternary phosphonium and A− represents an anion;
• and at least one catalyst comprising at least one compound or one complex of a transition metal of groups 8, 9 and 10 of the periodic table, optionally co-ordinated with at least one ligand containing at least one atom of phosphorus, arsenic, antimony or nitrogen,
• said process further comprising withdrawing from the reaction section the resultant reaction medium, adding to the resultant reaction medium at least one organic solvent which serves to improve separation by demixing of the crude reaction products from the polar phase, and recycling separated polar phase to the reaction section for re-use.