HOMOGENEOUS CATALYSIS IN SUPERCRITICAL FLUIDS

Supercritical fluids (SCFs), compounds heated and pressurized beyond t he critical point, have many unusual properties. Homogeneous molecular catalysts, which have far greater control over selectivity than heter ogeneous solid catalysts, are now being tested in SCFs, and early resu lts show that high rates, improved selectivity, and elimination of mas s-transfer problems can be achieved. As industry moves away from toxic or environmentally damaging solvents, supercritical carbon dioxide ma y be an ideal replacement medium for nonpolar or weakly polar chemical processes. More than simply substitutes for nonpolar solvents, SCFs c an radically change the observed chemistry. Supercritical carbon dioxi de is also an excellent medium for its own fixation, as demonstrated b y studies of its hydrogenation.