| Abstract
| - The pervaporation transport of methanol through an amorphous microporous methylated silica membranewas studied experimentally and analyzed through modeling within a Maxwell−Stefan (MS) framework. Theexperimental conditions cover a temperature range of 60−155 °C and absolute pressures up to 16 bar. Exertinghigher absolute pressures on the liquid feed-side of the membrane did not lead to enhanced fluxes, confirmingthat (i) the selective layer of the 56.8 cm2 membrane was a closed layer and defect-free, and (ii) the chemicalpotential gradient of the permeating component is an appropriate driving force to describe the transport throughthe microporous membrane. Both the adsorption isotherm and the heat of adsorption (−ΔHi,ads) weredetermined, and a two-site Langmuir isotherm adequately correlated the heterogeneous adsorption behaviorof methanol in amorphous silica. Different levels of detail were adopted for modeling the diffusion transportthrough the selective layer, after having accounted for the resistance of the different support layers. Twomodels based on the MS approach described best the data: one model had a constant diffusivity and theother model had a loading-dependent diffusivity. The latter is equivalent to the classical pervaporation model,where the flux is proportional to the fugacity difference over the membrane and an exponential temperaturedependency of the permeance. The presented derivation eliminates the inconsistencies of earlier interpretationsgiven in the literature. Although there is a slight preference for the latter, easy-to-use model, no further statisticaldiscrimination could be made based on the data.
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