Estimation of CO(2) Separation Performances through CHA-Type Zeolite Membranes Using Molecular Simulation

Chabazite (CHA)-type zeolite membranes are a potential material for CO(2) separations because of their small pore aperture, large pore volume, and low aluminum content. In this study, the permeation and separation properties were evaluated using a molecular simulation technique with a focus on improving the CO(2) separation performance. The adsorption isotherms of CO(2) and CH(4) on CHA-type zeolite with Si/Al = 18.2 were predicted by grand canonical Monte Carlo, and the diffusivities in zeolite micropores were simulated by molecular dynamics. The CO(2) separation performance of the CHA-type zeolite membrane was estimated by a Maxwell–Stefan equation, accounting for mass transfer through the support tube. The results indicated that the permeances of CO(2) and CH(4) were influenced mainly by the porosity of the support, with the CO(2) permeance reduced due to preferential adsorption with increasing pressure drop. In contrast, it was important for estimation of the CH(4) permeance to predict the amounts of adsorbed CH(4). Using molecular simulation and the Maxwell–Stefan equation is shown to be a useful technique for estimating the permeation properties of zeolite membranes, although some problems such as predicting accurate adsorption terms remain.