A STUDY ON THE ADSORPTION CHARACTERISTICS OF ACETONE AND BENZENE IN SUPERCRITICAL CARBON-DIOXIDE MEASURED BY CHROMATOGRAPHY AND IR SPECTROSCOPY

Chromatographic and FTIR techniques were applied to a study of the abs orption characteristics of acetone and benzene on a silica gel (SG800) in supercritical CO2 at 313.2 and 333.2 K. The chromatographic isothe rms for acetone and benzene have a maximum at a pressure lower than th e critical pressure of CO2, and then decrease with increasing pressure . When the temperature increases, the adsorption isotherms decrease in the low-pressure region, and increase in the high-pressure region, pr oviding a crossover at a relatively high pressure. The elution curves of acetone showed tailing, even at high pressures, while those of benz ene showed quasi-Gaussian curves at high pressures. The tailing curves for acetone indicate the existence of heterogeneous sites; evidence o f hydrogen-bonding formation with surface silanol groups has been prov ided by IR spectroscopy.