CHEMICAL-REACTIONS IN SUPERCRITICAL FLUIDS

Most homogeneous catalysts have higher selectivity but lower rates than heterogeneous catalysts in gas-phase reactions. An ideal catalyst would have the best of both worlds, high selectivity and high rates which may be possible with homogeneous catalysts in supercritical fluids rather than liquid solvents. These fluids are compressed gases heated past their critical point. Preliminary results have confirmed that increased rates and selectivities can be obtained because of several unusual properties of supercritical fluids: high solubility of reactant gases, rapid diffusion between phases, and possibly weaker solvation of the catalyst. This review will describe research on organic reactions and homogeneous catalysis in supercritical fluids, with emphasis on supercritical carbon dioxide and water as reaction media.