A model is presented for the supercritical reaction-extraction of a solid component from a bed of porous particles through which the solvent flows. Accounted for are reaction at an intraparticle position, pore diffusion, interphase mass and heat transfer, and flow in a differential reactor. The behavior of the bed is dynamic since both temperature and concentration of extractable solid vary with time.
The model is compared with experimental data for the extraction with toluene of kerogen from a bed of Colorado shale particles. Curves of effluent bitumen concentration vs. time were measured and fitted with predicted curves to evaluate three parameters: preexponential factor and activation energy for the conversion of insoluble kerogen to soluble bitumen, and the diffusivity of toluene at the critical point. The predicted curves agreed well with the experimental results and gave reasonable values for the parameters. Rates of reaction-extraction as well as extraction curves exhibited a sharp dip as the reactor was heated through the critical temperature.