Preparation of MFI zeolite membranes on coarse macropore stainless steel hollow fibers for the recovery of bioalcohols

Abstract

Hydrophobic MFI zeolite membranes are considered suitable for the recovery of bioalcohols (bioethanol and biobutanol) from fermentation broths. Stainless steel (SS) hollow fibers (HF) are more appropriate Al-free supports for MFI membranes due to their high mechanical strength and easily-sealing property as compared to other Al-free HF such as silica or yttria-stabilized zirconia HF. High-quality MFI membranes on coarse macropore SS HF were fabricated via secondary growth with a simple dip-coating seeding method. The synthesis conditions (composition, time, temperature) were systematically investigated in this study. Considering the separation performance and time saving demand, the membranes synthesized at 175 °C for 6 h exhibited the optimal ethanol or butanol permselectivity with a flux of 1.68 kg (m² h)⁻¹ and a separation factor of 65 for 5 wt% ethanol/water pervaporation (PV) at 80 °C, and with a flux of 218 g (m² h)⁻¹ and a separation factor of 207 for 1.5 wt% butanol/water PV at 80 °C. The separation performance for ethanol or butanol permselectivity was comparable to that reported in the literature. The MFI membranes together with the intrinsic advantages of SS HF displayed promising prospects in the field of bioethanol or biobutanol recovery.