Fabrication of High-quality NaA Zeolite Membranes with a Novel Plate & Frame Configuration for Molecular-scale Mixture Separations

Bioethanol has come into widespread use as fuel additives worldwide, especially in the U.S. and Brazil, aiming to mitigate CO2 emissions by up to 70% and sustain the carbon-neutral ecosystem. Generally, bioethanol in various fermentation broths has a maximum concentration of 6-8 wt.%. Hence, concentration of bioethanol from dilute streams poses a grand challenge from the standpoint of energy efficiency. In bioethanol dehydration processes, the conventional distillation process is adopted, followed by energy-intensive pressure swing adsorption (PSA) dehydration process. Many bioethanol plants in the U.S. ran the PSA process more than 10 years ago, and will require adsorbent bed retrofitting in next several years. Energy-efficient membrane separation technologies are considered a highly cost-competitive alternative to PSA process for bioethanol concentration & purification. However, in order for these membrane technologies to become incorporated into real-world applications, focused R&D needs to be conducted in order to increase the technical feasibility and to lower the cost of implementation. In Phase I, nGimat had already made great progress in generating high-separation-performance NaA zeolite membranes on cheap porous supports. It is anticipated that the production cost of these membranes be at least 50% lower than zeolite membranes available nowadays, and play a critical role in reaching the cost objective of $0.02-0.09/L of bioethanol. Development of such low-cost NaA zeolite membranes will require distinct innovations in substrate pretreatment, gel formulation, and membrane module design to outperform the current state-of-the-art zeolite membranes. During Phase I, nGimat (1) pretreated zeolite/metal support composites in a low-cost way; and (2) prepared NaA zeolite membranes with superior separation performance. It is calculated that our newly designed zeolite membranes have a rather high membrane surface area to volume ratio, promising a high packing density in a membrane module. Overall, key improvements pursued in this effort were reflected by overcoming prohibitively high production cost of these membranes, and a significant energy saving of about 20-40%, as compared to conventional separation technologies such as distillation + PSA, is expected. Phase II of this SBIR effort will be concentrated on further optimization and scale-up production of the best-performing NaA zeolite membranes to meet the demand of energy efficiency.