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

Many bioethanol plants in the U.S. have been running energy-intensive PSA processes for more than 10 years, and these systems will soon require adsorbent bed retrofitting. Energy-efficient separation technologies such as membrane methodology can play a critical role in the future of bioethanol dehydration. NaA zeolite membranes are highly effective for dehydration of bioethanol and many other organic solvents. However, the high production cost of NaA zeolite membranes is currently prohibitive, with around 80% of the cost driven by the porous ceramic or metallic supports. To address this high-cost issue, we are adopting commercially available, low-cost, flat-sheet metallic foams including Ni and stainless steel as the substrates for NaA zeolite membrane synthesis. During Phase II, NaA zeolite membranes with high ethanol dehydration performance were successfully prepared on the low-cost metallic porous supports. The H2O/EtOH separation factor of the membranes met the project target, while the total permeation flux doubled the Phase II target. The individual membrane size was successfully scaled up from 5.6 × 5.6 cm2 to 12.3 × 12.3 cm2, and then to 17.3 × 17.3 cm2. In addition, a membrane module with a novel plate and frame configuration was designed and fabricated to increase the volume specific permeation area (m2/m3) of membrane modules. The H2O/EtOH separation factor achieved in Phase II can be further enhanced by eliminating the non- selective defects that were observed, such as micro-cracks, pinholes, and delamination. These opportunities for further optimization will be pursued during Phase IIA. Specifically, we will improve the dehydration performance of NaA zeolite membranes by: (1) applying an intermediate ceramic layer between the NaA zeolite layer and the metallic porous support to address the thermal expansion coefficient mismatch of the materials, and (2) eliminating the non-selective defects using hydrophilic polymer materials. Successful completion of these items will result in higher performing NaA zeolite membranes that are more suitable for commercial application. The hydrophilic membranes and membrane modules developed in this project have widespread applications for dehydration of ethanol and many other different organic solvents in the chemical industry. Compared with traditional dehydration techniques, such as pressure swing adsorption and azeotropic and extractive distillations, this novel membrane technology has many advantages, such as low operation cost, high dehydration efficiency, and low environmental impact. In addition, the unique multilayered porous support and the plate & frame membrane module design that are being developed in this project can be transferred to many other different kinds of microporous inorganic membranes.