Hydroformylation process for preparation of aldehydes and alcohols

A hydroformylation process which comprises hydroformylating an olefinic compound selected from the group consisting of dimers, trimers and tetramers of propylene, butene or isobutylene, by reacting said olefinic compound with water gas at a temperature of from 50.degree. to 170.degree. C. under water gas partial pressure of from 20 to 500 kg/cm.sup.2 in a catalyst solution containing rhodium, an oxide of an organic trivalent phosphorus compound present in an amount such that the phosphrous concentration is at least 10 atoms per atom of rhodium, and high boiling by-products produced by side reactions, to form a hydroformylation product composed mainly of an aldehyde having a carbon atom number greater by one than the starting olefinic compound;

• adding an organic trivalent phosphrous compound to the reaction mixture, followed by distillation to separate a distillate containing the hydroformylation product from a high-boiling residue containing rhodium;
• oxidizing the high-boiling residue at the same time or as subsequent to the distillation, to convert the organic trivalent phosphorus compound to its oxide;
• and recycling the oxidized residue to the hydroformylation reaction zone.