Hydroformylation of <i>n</i> -Hexene Catalyzed by Unmodified Cobalt Carbonyl under Mild Conditions

The hydroformylation of n-hexene was studied using unmodified Co2(CO)8 under mild conditions (<80 bar, 393 K) to provide guidance for optimizing reaction conditions and catalysts for the hydroformylation of plastic pyrolysis oils. A quantitative kinetic framework was developed, incorporating both isomerization and hydroformylation pathways, to resolve the kinetic and mechanistic contributions of individual steps to aldehyde formation rates and product distribution. Experimental data from thermodynamically equilibrated hexenes (Model 1) and pure n-hexene (Model 2) were used to regress kinetic constants and validate the mechanistic model. The degree of rate control and selectivity control analyses identified kinetically relevant steps that govern the formation of linear aldehydes. Hydrogen pressure was found to accelerate hydrogenolysis and enhance linear selectivity, while CO pressure exerted compensating effects by both promoting carbonylation and binding reactive intermediates. These findings provide a quantitative mechanistic foundation for tuning regioselectivity and isomerization with unmodified cobalt catalysts, thereby offering guiding principles for the selective transformation of waste plastic-derived alkenes into functionalized products via catalytic processes.