Chapter 8 - Transport Mechanism and Modeling of Microporous Zeolite Membranes

Abstract

Zeolites are the most extensively studied crystalline microporous materials for membrane separation processes. In the development and design of equipment involving microporous zeolite membranes, the proper description of diffusion and transport mechanisms are of vital importance. However, this subject still needs more clarification. This chapter addresses the diffusion mechanisms of gases through zeolite membranes, such as molecular sieving, surface diffusion, and configurational diffusion, along with the activated transport that can occur as a facilitator of gas permeation in the case of each of these mechanisms. Also, the effect of temperature as an affecting parameter on the permeance of gases was studied. Subsequently, modeling of various diffusion mechanisms in microporous zeolite membranes was performed using the Maxwell-Stefan (MS) approach. To accomplish this, the Fickian coefficient introduced for the mentioned mechanisms was converted to an MS coefficient using Darken equation. Then, analytical solutions were presented for this model in both cases of weak and strong confinement.