Hydroformylation of ethylene compounds, involves separating reacted content into product fraction, and catalyst fraction whose portion(s) is returned to reaction zone with monodentate phosphine ligand

Ethylene compounds are reacted with carbon monoxide, hydrogen and catalyst system in a reaction zone (R). The reacted content from the zone (R) is separated into a fraction enriched in product (F1) and a fraction enriched in catalyst system (F2), and the F2 is worked-up, and portion(s) of F2 is returned to the zone (R), in absence of CO, H and in presence of monodentate phosphine ligand. Ethylene compounds are reacted with carbon monoxide, hydrogen, and catalyst system which comprises metal(s) of transition group VIII and bidentate phosphine ligand(s) in reaction zone. An output taken from the reaction zone is separated into fraction enriched in product (F1) and fraction enriched in catalyst system (F2). The F2 is subjected to work-up, and portion(s) of the F2 is returned to reaction zone. The taking of output from the reaction zone, separating the output, subjecting fraction (F2) to work-up and returning F2 to reaction zone are performed with monodentate phosphine ligand(s) and in absence of CO and H. An independent claim is also included for stabilization of hydroformylation catalyst system, by using catalyst system having metal of transition group VIII, bidentate and monodentate phosphine ligands. Die vorliegende Erfindung betrifft ein Verfahren zur Hydroformylierung ethylenisch ungesättigter Verbindungen, wobei man als Hydroformylierungskatalysator wenigstens einen Komplex oder eine Verbindung eines Metalls der VIII. Nebengruppe mit wenigstens einem zweizähnigen Phosphinliganden einsetzt, wobei wenigstens einer der auf die Hydroformylierungsreaktion folgenden Reaktionsschritte im Wesentlichen in Abwesenheit von Kohlenmonoxid und Wasserstoff und in Gegenwart wenigstens eines einzähnigen Phosphinliganden durchgeführt wird.