Abstract
The adsorption of aromatics and alkanes in MFI zeolites is usually characterized by a characteristic S-shaped isotherm (formally type VI) caused by the presence of different potential sorption sites (i.e., channel intersections and interiors) and by an intricate panel of sorbate−sorbate interactions. Herein we show that this behavior can be conveniently modeled through a thermodynamic formulation alternative to the classical dual-site Langmuir isotherm linking the integral free energy of adsorption relative to saturation, Ψ/RT, expressed as a Kiselev integral, with the variable Z = 1/−ln(Π), Π being the relative pressure. The model is defined by a set of parameters providing direct information about the evolution of the energy heterogeneity of the solid upon adsorption, including the phase transition zone. Unlike the Dubinin−Astakhov and Dubinin−Radushkevich isotherms, lacking thermodynamic consistency at low pressures, the present formulation converges to Henry’s law at low pressures. Moreover, the prese...
Published Version
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