(218d) High-Pressure Hydroformylation Reaction Equilibria

Hydroformylation converts an olefin into an aldehyde via reaction with CO and H₂ (syngas). The reaction is performed in suitable solvents/solvent mixtures to ensure the intense contact of the hydrophobic olefin and the hydrophilic catalyst. On the one hand, the solvents also determine the syngas solubility in the reaction mixture and on the other hand have an influence on the reaction equilibria and reaction kinetics.

This work investigated the influence of solvent composition in DMF/decane solvent mixtures on gas solubilities as well as on reaction equilibria of the hydroformylation of dodecene to tridecanal.

The syngas solubilities in the reaction mixtures at varying solvent compositions were calculated using the thermodynamic model PC-SAFT. The same model was also used to determine the activity coefficients of reactants (dodecene, CO, and H₂) and product (tridecanal) in the different solvent systems. For a given ratio of the DMF/decane solvent mixture, equilibrium concentrations of dodecene and tridecanal were measured after sampling form a high-pressure reactor by means of gas chromatography and nuclear magnetic resonance spectroscopy. These values together with the syngas solubilities and reagent/product activity coefficients obtained from PC-SAFT were used to determine the thermodynamic equilibrium constant K_f and therewith the standard Gibbs energy of the dodecene hydroformylation reaction. The latter was found in very good agreement with the value obtained from quantum-chemical calculations.

Applying the so-obtained K_f and accounting for the solvent influence on the reagent/product activity coefficients, the equilibrium concentrations for varying solvent compositions could be predicted in almost quantitative agreement with the experimental data.