(584c) Zeolite LTA Membrane for Pervaporation Separation of Water-Ethanol Mixture

Microporous membranes (molecular sieves) are an important and energy efficient method to separate molecules based on size and shape. In bioethanol process plants, the need for a high throughput, robust dehydration method has led to many studies on zeolite membranes. Zeolite membranes combine excellent specificity with continuous operation, in addition to impressive chemical stability. Furthermore, high thermal stability of these inorganic materials allows for quick and facile methods in removal of most fouling material. In this study, zeolite NaA (LTA) films are synthesized on porous planar substrates to fabricate a separation module for energy efficient water-ethanol separation. Direct growth shows thick, non-uniform zeolite layers with the presence of impurities and undesired zeotypes. However, secondary growth, utilizing NaA nanocrystals and a dipcoat-seed wiping method, results in zeolite layers of low thickness and increased uniformity. Zeolite surface morphology is shown to vary spatially along the axial direction of the hydrothermal reactor and is also strongly affected by orientation of the substrate during membrane synthesis. Zeolite film thickness and uniformity are correlated to separation performance with the aid of analysis tools such as scanning electron microscopy, electron dispersive X-ray spectroscopy, and X-ray diffraction.