Continuous process for hydroformylating olefins with 6 to 20 carbon atoms

A continuous process for the hydroformylation of olefins having from 6 to 20 carbon atoms, in which

• a) an appliance is provided, which optionally comprises a catalyst formation zone, and comprises at least one reaction zone, an extraction zone, conveying means for conveying the output from the reaction zone to the extraction zone and recirculation means for recirculating an aqueous cobalt(II) salt solution emanating from the extraction zone back to the catalyst formation zone or the reaction zone, the recirculation zone means being thermally insulated and/or provided with heating means such that the aqueous cobalt(II) salt solution conveyed therein is maintained at a temperature of from 60 to 95° C.,
• b) the aqueous cobalt(II) salt solution having a concentration of from 1.1 to 1.7% by weight, calculated as cobalt, and a pH in the range from 2 to 4, is brought into intimate contact with hydrogen and carbon monoxide in the catalyst formation zone or the reaction zone, to form a hydroformylation-active cobalt catalyst,
• c) the aqueous phase comprising the cobalt catalyst is brought into intimate contact with the olefins and, if desired, an organic solvent and also hydrogen and carbon monoxide in the reaction zone where the cobalt catalyst is extracted into the organic phase and the olefins are hydroformylated,
• d) The output from the reaction zone is conveyed to the extraction zone and treated with oxygen in the presence of acidic aqueous cobalt(II) salt solution, and the cobalt catalyst being decomposed to form cobalt (II) salts and these being back extracted into the aqueous phase and the phases are subsequently separated,
• e) the aqueous cobalt(II) salt solution is recirculated in unchanged form to step b).