Sorption of ethanol and water in bi-dispersed pellets formed by compaction of a hydrophobic crystalline molecular sieve, silicalite, was examined. The difficulties inherent in the measurement and interpretation of mixed liquid adsorption equilibria were discussed and the individual adsorption isotherms for {ethanol-water}/silicalite crystals presented. The adsorbed ethanol exhibited a density similar to but smaller than that of liquid ethanol. The adsorbed water was as much as four times lighter than liquid water. Diffusion of ethanol in the silicalite micropores was quite well described by a constant diffusivity of 5 x 10−14m2/s. The intracrystalline diffusivity of water was higher than that of ethanol at low loadings but was markedly reduced as saturation approached. A sensitivity analysis based on a detailed theoretical model yields the characteristic time constants of 3.3s for external boundary layer mass transfer, 83.9s for diffusion through the liquid filled macropores of the pellets and 0.03s for diffusion in the micropores of the embedded crystals. The intraparticle transport was therefore firmly controlled by the macropore diffusion and could be described in terms of a pore diffusion model with the embedded crystals assumed in point wise local equilibrium with the macro pore fluid.

Sorptive Separation of Ethanol-Water Mixtures with a Bi-Dispersed Hydrophobic Molecular Sieve, Silicalite: Determination of the Controlling Mass Transfer Mechanism. F.A.Farhadpour, A.Bono: Chemical Engineering and Processing, 1996, 35[2], 141-55