Mass transport enhancement in modified supercritical fluid

In this paper, the supercritical-fluid extraction. (SCFE) of a packed bed o f beta-naphthol-impregnated porous pellets was studied. An increasing numbe r of industrial SCFE processes involve the extraction of a solute retained within a porous matrix, usually in the form of seeds or irregular grains. T he interest in high-pressure extraction is due to certain advantages of den se gases and near-critical solvents over conventional liquid solvents. In t his study, modified carbon dioxide was the fluid studied. The effects of te mperature, pressure, fluid velocity, particle size, and gravity were experi mentally studied using carbon dioxide, pure or mixed with varying amounts o f toluene (6%, and 10%). For the solute, beta-naphthol, the solubilities in SC carbon dioxide mixtures (from 0 to 10% toluene) were available from sep arate experiments. The dispersed plug-flow model was used to describe the n onideal flow. Fitting the experimental data with the model solution allowed the measurements of the fluid-to-particle mass transfer coefficient, the i ntraparticle diffusivity, and the axial dispersion coefficient (the latter in terms of the axial Peclet number). The influence of cosolvent concentrat ion on the three transport parameters, which were not available so far, is presented.