ARTICLE pubs.acs.org/IECR
Preparation of Robust, Thin Zeolite Membrane Sheet for Molecular Separation Wei Liu,* Jian Zhang, Nathan Canfield, and L. Saraf Pacific Northwest National Laboratory, Richland, Washington 99352, United States ABSTRACT: This paper reports a feasibility study on the preparation of zeolite membrane films on a thin, porous metal support sheet (50 μm thick). Zeolite sodium A (NaA) and silicalite zeolite frameworks are chosen to represent syntheses of respective hydrophilic-type and hydrophobic-type zeolite membranes on this new support. It is found that a dense, continuous intergrown zeolite crystal layer at a thickness less than 3 μm can be directly deposited on such a support by using direct and secondary growth techniques. The resulting membrane shows excellent adhesion on the metal sheet. Molecular-sieving functions of the prepared membranes are characterized with ethanol/water separation, CO2 separation, and air dehumidification. The results show great potential to make flexible metal-foil-like zeolite membranes for a range of energy conversion and environmental applications.
1. INTRODUCTION Zeolite membranes have drawn worldwide interest since the mid-1990s, due to their unique molecular-sieving functions that allow selective separation of individual molecules based on slight differences in the shape, size, and/or polarity under continuous operation. Ultimately, the zeolite membrane entails development of membrane reactors to integrate catalytic reactions with separation into one vessel. Various separation process concepts in energy conversion and environmental areas have been studied in the literature, as reflected in a few recent review articles.14 However, significant industrial applications of the zeolite membrane are not yet prevalent. One major challenge is fabricating zeolite membranes of high surface area packing density at a cost competitive with existing separation means.4 Most studies around zeolite membranes involve using support structures in a tubular form (1030 mm diameter) or in a disk form (0.5 3 mm thick). The support is typically made of porous ceramics or sintered metals. Those inorganic membranes are viewed to be of much higher costs per unit membrane area than polymeric membranes. Pure zeolite membranes have not been prepared on inexpensive polymeric supports yet, which may be due to inherent differences in the two kinds of materials. For large-scale industrial separation processes, high membrane area packing density is critical to reduction of engineering and installation costs. Synthesis of zeolite membranes does not require exotic or precious materials. The membrane cost is mostly due to the support. Recently, deposition of zeolite membranes on smallchannel (
