A multicomponent transport model for dehydration of organic vapors by zeolite membranes

Abstract

The permeation of gases and vapors through zeolite membranes is usually described by the adsorption–diffusion model, which is similar to the solution–diffusion model for polymeric membranes. According to this type of model, a permeating component first adsorbs into zeolite micropores and then diffuses through the zeolite pores due to its chemical potential gradient. However, multicomponent transport is complicated by the need to account for coupling effects, and these effects should be considered in any rigorous transport model. A general multicomponent transport model was developed herein based on the Maxwell–Stefan approach to describe dehydration of organic vapors by zeolite membranes. Separation of an ethanol–water vapor mixture by a silicalite membrane was selected to demonstrate the application of the method. The mixture adsorption behavior was expressed in terms of the extended Langmuir model, and concentration dependent diffusivity of each component was recovered from permeation as well as adsorption data from the literature. The permeability and selectivity values predicted by the multicomponent transport model conformed to the experimental data. The results indicated that the kinetic coupling has a very minor contribution in transport and can be easily ignored, while the equilibrium coupling has a major role to transport through the silicalite membrane.