Extraction of butanol from ABE solution by MFI zeolite membranes

Pervaporation is considered as a promising technique for biobutanol extraction from fermentation solution. In this work, hydrophobic MFI zeolite membranes were adopted to enrich butanol from low-concentration aqueous solution. The membranes were prepared by secondary growth method on Al-free hollow fibers. The membrane performance was evaluated by pervaporation separation of ABE solution and 5 wt% binary aqueous solutions containing ethanol, acetone, butanol. The effect of operation temperature (from 40 °C to 80 °C) on flux, separation factor as well as the membrane stabilities was investigated. Increasing temperature could improve the permeation of organics, but influence the stability of MFI zeolite membrane. Compared with organic solvent such as acetone, butanol and ethanol, the stability of MFI zeolite membrane is easily influenced by water, especially at high temperature. Water tends to attack the silicon defects in MFI zeolite membrane, leading to the decrease of crystallinity and the degradation of separation performance. A low operation temperature is favorable to keep the stability of zeolite membrane and the coupling of membrane separation and fermentation process. At 40 °C, the MFI zeolite membrane showed long-term stability for selective removal of butanol from ABE solution with the total flux of 0.12 kg·m⁻²·h⁻¹ and the separation factor of 14 for 120 h. Our results indicated that the integration of pervaporation using MFI zeolite membrane with an ABE fermentation could be a promising process to product bio-butanol efficiently.