Styrene hydroformylation in supercritical carbon dioxide: Rate and selectivity control

Supercritical fluids have the unique characteristic of density-tuned physic ochemical properties that can affect reaction rates and selectivities. We h ave studied homogeneously catalyzed styrene hydroformylation in supercritic al carbon dioxide (scCO(2)) and have shown that the reaction rate and the r egioselectivity can be varied by changes in pressure at constant temperatur e. This rate and selectivity change is explained in terms of the transition state theory. We have determined the partial molar volumes of the reaction products based on the Peng-Robinson equation of state for an infinite-dilu tion solution model, a real solution model, and a real solution model with regressed interaction coefficients. Then, the estimated partial molar volum es were used to predict the experimentally observed selectivity behavior. T hrough these simulations, an understanding of the reaction rate and selecti vity control by adjustment of the pressure was developed.