(418f) Kinetics of Hydroformylation of Ethylene Using Homogeneous Rhodium-Phosphine Complexes

The hydroformylation reaction is a useful method to functionalize C-C bonds for providing aldehyde and alcohol compounds, and is also an important industrial catalytic process. In view of the importance, it is attracting continuous and increasing academic and industrial interest. Studies on the kinetics of hydroformylation of olefins not only are instructive for improvement of the catalytic system but also provide the basic information for design and scale-up of appropriate reactors.

In this research, the kinetics of hydroformylation of ethylene with triphenylphosphine modified rhodium catalyst was studied. The reaction was carried out batchwise in a flat-bottomed, magnetically stirred 150 mL steel autoclave equipped with a 120 mL teflon tube. Under the conditions of the Rh concentration of 0.0015mol/L, PPh₃/Rh=10, C₂H₄: CO: H₂ =1: 1: 1 (molar ratio), 2 Mpa and 100 °C, the selectivity for propionaldehyde was nearly 100%. The ethylene hydroformylation kinetics was studied as the function of the amount of catalyst and triphenylphosphine, partial pressure of ethylene, CO and H₂, and temperature. All these parameters were found to influence the rate of hydroformylation. On the range of conditions (catalyst, 1.024~2.2658 mmol·L^-1; PPh₃, 0.0058~0.3018 mmol·L^-1; P_H2, 0.26~1.27 MPa; P_CO, 0.11~1.22 MPa; P_C2H4, 0.18~1.13 MPa; T, 355.15~372.15 K), rates were observed to increase with the increase in the amount of the catalyst and triphenylphosphine; rates increased on increasing the C₂H₄ or H₂ pressure; rates increased on increasing the CO pressure up to certain values, and then decreased. The activation energy was found to be 61.52 kJ·mol^-1. A kinetic rate model based on the mechanism of hydroformylation of ethylene was found to fit with the experimental rate with ±5% deviation.