Abstract
One of the challenges in butanol production is its separation from aqueous acetone-butanol-ethanol (ABE) because of the azeotropic nature of the mixture and the high energy needed to recover the solvents from the dilute solution. Currently, pervaporation has been one of the most studied recovery approaches due to its selectivity when highly hydrophobic membranes are used, as well as the reduced energy demand involved in applying vacuum instead of conventional distillation. In this study, an ABE aqueous mixture was separated by pervaporation using pure and composite (mixed matrix and layered) PDMS + silicalite-1 membranes. For mixed matrix membranes, silicalite-1 crystals were dispersed in PDMS (20, 40, 60, and 80 wt%), then spin-coated using toluene as a solvent, and finally characterized by SEM-EDS, XRD, TGA, and FTIR. A total flux of 35.65 g/m2×h and a separation factor towards butanol of 22.60 was achieved with membranes prepared using 500 mg of (80 wt% + PDMS/mL of toluene) and 1,000 mg of silicalite-1 (80 wt% + PDMS/ mL of toluene), respectively. The high flux is related to the larger free volume in the polymer resulting from the incorporation of hydrophobic crystals of silicalite-1, thus improving the selectivity towards butanol. Also, the physicochemical properties of the membranes are paramount to high performance in the recovery of the ABE mixture, particularly the appropriate silicalite-1 loading.
Published Version
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