(583ay) Kinetics of Hydroformylation of Ethylene Using Homogeneous Hrh(CO)(PPh3)3 Catalyst

The hydroformylation reaction is a powerful method to functionalize C-C bonds for providing aldehyde and alcohol compounds, and is also an important industrial homogeneous 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 hydroformylation 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%. Under these typical hydroformylation conditions, the kinetic order of the mixed gas was found to be in positive fractional order about 0.65 and the activation energies was obtained about 55 kJ/mol at the range of temperature between 80 °C and 100 °C. The selectivity for propionaldehyde was low when the concentration of ethylene was high in the mixed gas, so the kinetic parameters below were evaluated under the low ethylene concentration. When the molar ratio of C₂H₄: CO: H₂was 1:1:10, the kinetic order of the mixed gas of C₂H₄ and CO was about 0.03, and when the molar ratio of C₂H₄: CO: H₂was 1:10:10, the kinetic order of C₂H₄ was about 0.62. From the analysis above, the kinetic orders of C₂H₄, CO and H₂ were 0.62, -0.6 and 0.63 respectively. Experimental data and observations provided relevant information for further engineering study on hydroformylation of ethylene and other low carbon olefins.