Application of Zeolite Membranes to Dehydrate a Bio-Ethanol Solution Produced by High-Temperature Fermentation

Abstract

The combination of high-temperature fermentation and membrane separation has the potential to realize a simple on-site process to produce concentrated bioethanol. The performance of dehydration membranes in separating bioethanol was investigated in this study. Three types of zeolite membranes, LTA, MFI, and MOR, were synthesized. Their dehydration ability was compared using a bioethanol solution produced by high-temperature fermentation followed by vacuum distillation. The LTA zeolite membranes deformed and became amorphous while treating the distillate. On the contrary, no significant changes were observed in the MFI and MOR zeolite membranes analyzed by X-ray diffraction after treating the distillate. However, the flux declined when the membranes were in contact with the distillate (pH = 3.8). Neutralizing the distillate to pH 6.6 with sodium hydroxide did not prevent the flux decline. Even though flux decreased by about 20–30%, the MOR membrane showed quite high water-selectivity, with a water concentration of over 99.9% in the permeate, suggesting the feasibility of its application to concentrate bioethanol.

Investigating the Physical and Operational Characteristics of Manufacturing Processes for MFI-Type Zeolite Membranes for Ethanol/Water Separation via Principal Component Analysis

“…Efforts over the last few decades focused on decreasing the thickness of zeolite membranes to increase their permeability while maintaining selectivity. In addition, attempting to decrease the thickness of zeolite membranes would make their use more economically viable [3]. This involved synthesizing smaller and thinner zeolite seeds, from the micrometer to the nanometer size, or even ultrathin zeolite sheets, which are then coated and assembled on porous supports to form thin membranes [4][5][6].…”

“…Membrane technology has presented promising findings in this matter. Following this strategy, zeolite membranes offer an interesting option for ethanol separation and purification [3][4][5].…”

“…In biodiesel production, MFI (Mobil No. 5) zeolite membranes act as an effective catalyst in the transesterification reaction, converting triglycerides into biodiesel [3][4][5]. Their unique structure and acidity enhance the reaction efficiency.…”

“…Additionally, MFI zeolite membranes play a role in biomass conversion, facilitating biomass pyrolysis, cracking, and hydrodeoxygenation, resulting in the production of valuable biofuels and chemicals. Their shape and catalytic properties improve the yield and selectivity of the desired products [3][4][5].…”