Zeolite - A Membrane for Solvent Dehydration: An Overview and Review of Results, pp. 523-554
Authors: (Marc Pera-Titus, Joan Llorens - Chemical Engineering Department, Univ. of Barcelona, Spain)
Abstract: This paper provides an overview and review (114 references) of own results in the field of supported zeolite NaA membranes for solvent dehydration by pervaporation. One of the main characteristics of Al-rich zeolite membranes, such as those based on zeolite A and FAU frameworks, is their high ability to shrink due to mismatch between thermal expansion coefficients of the support and the zeolite material in the presence of thermal gradients. This is why for this kind of membranes, rather than forming very thin layers, the synthesis of thick and well-intergrown layers by hydrothermal treatment using convenient techniques is highly recommended. In this study, three of these techniques have been surveyed in detail: (1) synthesis under the influence of a centrifugal force field, (2) semi-continuous synthesis, and (3) synthesis in a continuous flow system. These techniques have been compared one another in terms of pure N2 permeance and pervaporation performance (total flux and selectivity) towards dehydration of short- and long-chain primary alcohol/water binary mixtures for a collection of as-synthesized zeolite NaA membranes. The intercrystalline porosity in the zeolite layers ascribed to macro- and mesodefects has been measured using an original technique relying on the evolution of the total pervaporated flux with the feed pressure.