Mixed-matrix membranes containing inorganically surface-modified 5A zeolite for enhanced CO2/CH4 separation

Abstract

LTA zeolite with highly roughened surfaces were prepared in an aqueous phase by the ion-exchange induced growth of Mg(OH)(2) nanostructures on the zeolite surfaces. The morphology of LTA crystals was tuned by the systematic modification of reaction parameters such as the pH of the reaction medium and the amount of magnesium loaded in the substrates. After converting surface-modified LTA to 5A, which has been known as a good candidate for selective CO2 uptake and transport, by replacing extra framework cations remaining in LTA with Ca2+, a series of mixed-matrix membrane incorporating Matrimid and 5A was fabricated. Owing to improved zeolite/polymer adhesion property along with the selective transport of CO2 by the fillers, mixed-matrix membranes containing surface modified 5A showed enhanced CO2/CH4 separation properties, which were measured by a binary mixture permeation testing. In light of that, a dramatic increase in CO2 permeability (ca. 120%) was observed for Matrimid (R)/20 wt% 5A membrane which also showed an improved CO2/CH4 selectivity. In contrast, untreated 5A decreased CO2/CH4 selectivity of Matrimid membrane due to defects formed at zeolite/polymer interfaces. (C) 2016 Elsevier Inc. All rights reserved.