Clean chemistry in supercritical fluids

Abstract

Publisher Summary Supercritical fluids—particularly supercritical CO2 (scCO2)—are attractive solvents for cleaner chemical synthesis. The optimization of chemical reactions in supercritical fluids is more complicated than in conventional solvents, because the high compressibility of the fluids means that solvent density is an additional degree of freedom in the optimization process. The chapter describes the combination of spectroscopy with chemistry so that processes as varied as analytical separations and chemical reactions can be monitored and optimized in real time. The chapter illustrates the approach using three examples—(1) polymerization in scCO2, (2) hydrogen and hydrogenation, and (3) miniature flow reactors for synthetic chemistry. Polymerization is one area where the introduction of supercritical fluids is especially appealing. Supercritical fluids offer both environmental acceptability and the potential of extra control of the process. This potential arises from the gas-like nature of the fluids that allows pressure to be used as an additional parameter in the tuning of chemical reactions. The chapter describes the use of vibrational spectroscopy to monitor the progress of polymerization reactions in situ.