Abstract: This invention relates to a process for producing one or more products in a staged reactor having more than one reactive stage which process comprises reacting in said staged reactor one or more reactants with carbon monoxide in the presence of a metal-organophosphorus ligand complex catalyst and optionally free organophosphorus ligand to produce said one or more products, wherein said metal-organophosphorus ligand complex catalyst does not undergo substantial deactivation in the presence of solely carbon monoxide and/or effects a change in normal product selectivity of less than 0.2 percent of normal product per 1 pound per square inch of carbon monoxide partial pressure and/or effects a change in reaction rate of less than 2 percent per 1 pound per square inch of carbon monoxide partial pressure.