Influence of change in the unit cell parameters on permeation properties of AEI-type zeolite membrane

Abstract The permeability and separation ability of zeolite membranes correspond to the micropore volume and channel diameter of zeolites, respectively. Since the AEI-type zeolite possess a large pore volume (0.28 mL g −1 ) and small channel diameter (0.38 nm), they can potentially be used as membrane materials. In this study, a polycrystalline AEI-type zeolite layer was formed on a porous support tube by means of secondary growth, and the physicochemical properties of the membrane were characterized using SEM, EDX, XRD, and TG-DTA. Furthermore, the dehydration performance of the membrane was determined by pervaporation for an equimolar mixture of water and ethanol at 313 K. It was determined that the water/ethanol flux ratio was 10,000 before structure-directing agent (SDA) removal, although defect-free membranes could not be obtained. Zeolite micropores were formed by air calcination at temperatures above 523 K. However, the SDA could not be removed completely at temperatures between 523 and 673 K. Moreover, the separation performance of the calcined membrane decreased due to the change in the unit cell parameters owing to SDA removal. These results suggest that the expansion and/or distortion of the unit cell after the SDA removal creates larger defects at the grain boundaries of the crystals.