Equilibrium and kinetics properties of p-dichlorobenzene and toluene on silica gel in dense CO 2 by chromatography analysis

Abstract

The adsorption equilibrium constant and kinetics properties for p-dichlorobenzene and toluene on silica gel adsorbent in the subcritical and supercritical CO 2 have been measured by an impulse chromatography technique. The experiments were performed at temperatures of 298.15, 208.15, 318.15 K and pressures of 75–178 bar. A series fit method was applied to treat the chromatography peak. The adsorption equilibrium constant increased with temperature and decreased with pressure under the experimental conditions. The fluid density is found to be the main controlling factor determining the adsorption equilibrium constant. The dependence of the kinetics properties, dispersion coefficient and intraparticle effective diffusivity, on temperature and pressure has been investigated. The pore diffusion is the main diffusion mechanism within the pore medium. The partial molar volume (PMV) and partial molar enthalpy (PME) for p-dichlorobenzene in supercritical CO 2 have also been evaluated from the adsorption equilibrium constants obtained in this work. Very large and negative values for the two partial molar properties were obtained near the critical point of CO 2.