(627f) Computationally Investigating Zeolite Nanosheets As Pervaporation Membranes for Ethanol Extraction and the Role of Membrane Surfaces

Changlong Zou¹ and Li-Chiang Lin¹*

¹William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA

Discovering more energy-efficient and cost-effective approaches for anhydrous ethanol extraction from dilute biomass fermentation broth is of utmost importance due to the increasing demand for a green alternative to the fossil fuels. For this, pervaporation, driven by the vapor pressure difference, using siliceous zeolite membranes may hold a great promise owing to their hydrophobic nature. As reported in the literature, zeolite membranes can offer outstanding separation factors (i.e., selective toward ethanol over water). However, their corresponding membrane flux is still relatively slow. Zeolite nanosheets, emerging ultrathin-film materials that are synthesized with a thickness of a few nanometers, may overcome this limitation because of their intrinsically short diffusion paths. To date, the potential of zeolite nanosheets as pervaporation membranes for ethanol extraction remains unknown. In this study, by employing molecular dynamics techniques, we studied the separation performance of zeolite nanosheets for ethanol extraction. The total flux of zeolite nanosheets was found to be orders of magnitudes higher than those zeolite membranes reported in the literature, while a high separation factor can be still achieved. Further, we have also explored the role of nanosheet surfaces at an atomic level, and the hydrophilicity of the membrane surface was identified to impact the overall separation factor significantly. Our results suggest that strategically functionalizing the surface of nanosheets and/or selecting structural topologies to maximize the ethanol concentration at the entrance region of pore/channels are the key toward the design of highly selective zeolite nanosheets membranes. Moreover, the multilayer effects of nanosheets on the separation performance were also studied. Although the existence of multiple layers was found, as expected, to decrease the overall flux, multilayer structures can accordingly increase the selectivity of ethanol and therefore offer an additional design variable to improve the separation factor. Overall, this work has demonstrated the enormous potential of zeolite nanosheets as pervaporation membranes. We believe that the insights obtained here can help guide the future design and discovery of the zeolite nanosheet membranes for ethanol/water pervaporation separation and potentially for other organics separation applications.