Activity-based approach to predict the effect of solvent composition on the reaction kinetics of hydroformylation

Solvent effects on the kinetics of a homogeneously catalyzed reaction were successfully predicted using a thermodynamically consistent, activity-based approach. The methodology was applied to the Rh/BIPHEPHOScatalyzed hydroformylation of 1-dodecene performed with equimolar CO/H2 mixtures in different compositions of a non-polar/polar solvent system, specifically decane/N,N-dimethylformamide. By employing thermodynamic activities in contrast to conventionally used concentrations, the study effectively decouples solvent effects from kinetic parameters. The PC-SAFT equation of state was used to calculate activity coefficients. Intrinsic, solvent-independent kinetic parameters were fitted to the experimental data of one specific decane/ DMF solvent composition, demonstrating for the activation energies quantitative agreement with the results of density functional theory (DFT) calculations. The analysis of the activity coefficients of the reactant 1-dodecene revealed a significant influence on both DMF content and temperature. In contrast, the activities of CO and H2 were confirmed to depend neither on pressure nor on the solvent. Results of quantum chemical calculations performed for the system considered revealed that the impact of solvent composition on activation energies was insignificant. Compared with experimental results, the proposed approach was proven to accurately predict the reaction kinetics over a wide range of decane/DMF solvent compositions. Thus, it minimizes the need for extensive experimental screening and provides an efficient method for optimizing solvent conditions in homogeneously catalyzed reactions.