WATER SOLUBILITY MEASUREMENTS IN SUPERCRITICAL FLUIDS AND HIGH-PRESSURE LIQUIDS USING NEAR-INFRARED SPECTROSCOPY

A small amount of water added to a supercritical fluid can greatly inc rease the solubility of polar species in nonpolar fluids. These modifi ed supercritical solutions significantly expand the use of the fluids in separations and reactions. In order to successfully utilize these s ystems, information on the miscibility or solubility of water in the f luid is required. Often solubility data are not available for water in a supercritical fluid under a given set of temperature and pressure c onditions, and a costly set of equipment must be assembled in order to make these measurements. A relatively fast and inexpensive technique to measure water solubilities using a simple long path length optical cell in an FT-IR spectrometer is described. This technique is also app licable to common and newly developed refrigerants where water solubil ities are often unknown at temperatures much above ambient. In this pa per, water solubility data in carbon dioxide and two types of refriger ants (chlorodifluoromethane, R22; 1,1,1,2-tetrafluoroethane, R134a) ar e presented for temperatures from approximately 40 to 110 degrees C an d pressures from approximately 10 to 344.8 bar.