The rhodium-catalyzed hydroformylation of 1-dodecene was investigated with a series of sulfonated water-soluble phosphine ligands at a pressure of 60 bar CO/H-2 and a temperature of 120 degreesC. Seven different groups of water-soluble phosphines were used for our investigations. We established an optimized ligand/rhodium ratio of 5 for the phosphines la, [Ph2P(CH2)(2)S(CH2)(2)SO3Na], and 1b, [Ph2P(CH2)(2)S(CH2)(3)SO3Na]. The utilized arylphosphino-thioether-alkylsulfonates formed with Rh(l) compounds highly active catalysts which could be recycled. The addition of detergents speeds up the hydroformylation reaction, but disturbs the phase separation (recycling). The best promotion effect and the smallest negative influence on phase separation gave polyoxyethylene-polyoxypropylene-polyoxyethylene triblock co-polymers. The ratio of 1-dodecene/rhodium could be increased up to 10.000 and we achieved turnover numbers (TONs) > 50.000 without any surfactant and TONs of about 65.000 in presence of the co-polymers owing to the recycling on the catalytic system. (C) 2003 Elsevier Science B.V. All rights reserved.