In this paper, the supercritical-fluid extraction (SCFE) of a packed bed of β-naphthol-impregnated porous pellets was studied. An increasing number of industrial SCFE processes involve the extraction of a solute retained within a porous matrix, usually in the form of seeds or irregular grains. The interest in high-pressure extraction is due to certain advantages of dense gases and near-critical solvents over conventional liquid solvents. In this study, modified carbon dioxide was the fluid studied. The effects of temperature, pressure, fluid velocity, particle size, and gravity were experimentally studied using carbon dioxide, pure or mixed with varying amounts of toluene (6%, and 10%). For the solute, β-naphthol, the solubilities in SC carbon dioxide mixtures (from 0 to 10% toluene) were available from separate experiments. The dispersed plug-flow model was used to describe the nonideal flow. Fitting the experimental data with the model solution allowed the measurements of the fluid-to-particle mass transfer coefficient, the intraparticle diffusivity, and the axial dispersion coefficient (the latter in terms of the axial Peclet number). The influence of cosolvent concentration on the three transport parameters, which were not available so far, is presented.

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Solubility of solids was modeled in modified supercritical

High initial conversions for the cyclododecatriene (CDT) hydrogenation in a slurry reactor at 433 K and 1.2 MPa were obtained from a supercritical (sc) CO 2 -cleaned 0.5% Pd/Al 2 O 3 catalyst. A recovered intermediate selectivity was achieved by the sc CO 2 -cleaned catalyst at the higher CDT conversion values, suggesting an effective cleaning of Pd sites and a possible reconstruction of the residual coke layers onto the surface caused by the solvent nature of sc CO 2 . SEM pictures show that the cleanup of the used catalyst with sc CO 2 removes most of the coke and oily materials from the surface. Pd SEM X-ray microanalysis evidenced a decrease of the Pd dispersion on the surface of the used-activated catalyst. Coke was also characterized using elemental analysis and TGA in air, indicating that about 80 wt % of the deactivating materials were efficiently removed from the surface by sc CO 2 . The formation of the oligomerized and stabilized residual coke (remaining 20%) should be presumably avoided if the catalytic hydrogenation had taken place at sc (in situ) conditions where oligomerization times are minimized. The SCF conditions are then highly challenging at the catalytic hydrogenation of polyunsaturated hydrocarbons.