Seperation of aromatics by liquid-solid chromatography

Abstract

The separation characteristics of aromatics were investigated by the liquid - solid chromatography packed with silica gel, Lichroprep SI 100, as adsorbent. The chemical systems studied were m-cresol, quinoline and l-naphtol which are contained in the coal tar. In the adsorption equilibrium experiment, the isotherms of eight types for single component and five types for the binary component system were checked with the experimental data in order to select relevant adsorption isotherm. The isotherms determined for each system represented well to the experimental data over the experimental concentration ranges. For the binary systems, the competitive adsorption was quantitatively investigated with the competitive adsorption coefficient. The affinity of quinoline with respect to silica surface was larger than the other two components. Adsorption rates were studied in a finite batch adsorber. Experimental data were analyzed by Gluckauf``s model of the linear driving force approximation. The external film mass transfer was considered but the film resistances were very small as negligible, and hence the mass transfer into the solid phase was the rate controlling step in the system. To obtain the approximated analytical solution of the model equation, the equal area approximation method of the nonlinear isotherm was proposed with assumption that the internal mass transfer coefficient is constant. In the region where the slope of the constant time line is less than that of the operating line (region I) the original nonlinear isotherm was approximated as a quadratic form, and in the reverse case (region II) the isotherm was approximated as a linear from. The present experimental conditions were in region II, and the present approximated solution had a good agreement with the xperimental results. The internal mass transfer coefficient as a model parameter was determined by the superimposition of the approximated solution onto the experimental data. The internal mass trans...