Abstract: This invention relates to a method of stabilizing a metal-organophosphorus ligand complex catalyst against deactivation in a process which comprises reacting one or more reactants in the presence of a metal-organophosphorus ligand complex catalyst and optionally free organophosphorus ligand to produce a reaction product fluid comprising one or more products, and in which at least a portion of said process is conducted under separation conditions sufficient to effect at least some deactivation of the metal-organophosphorus ligand complex catalyst, which method comprises conducting the portion of said process that occurs under separation conditions in the presence of one or more alkadienes sufficient to prevent and/or lessen deactivation of the metal-organophosphorus ligand complex catalyst.