Development of polybenzoxazine (PBZ) membranes for ethanol/water separation

Abstract

Fermentation is an attractive process for producing feedstock chemicals from renewable biomass. However, the low concentration of the fermentative products creates cost-intensive product separation. The separation of the alcohol from dilute aqueous solutions by distillations is unfavorable since the energy consumption required for purification exceeds the energy content of the alcohol recovered. In order to make the fermentation process economically attractive, a more efficient alcohol recovery process is preferred. The pervaporation (PV) technique is, especially, attractive for applications such as separation of close-boiling-point liquids or azeotropes, e.g. ethanol/water mixture, which cannot be separated by the standard distillation process; and dense membranes are usually used for the PV. In this study, polybenzoxazine (PBZ) membranes, are successfully synthesized from bisphenol-A, formaldehyde, and diamine, are effectively used in the PV system for the ethanol/water (88:12 wt%) separation. Poly(BA-hda) membrane shows the best service time. The average of the permeate flux is found around 0.008-0.01 kg/m²hr and the separation factor is increased to higher than 10,000 with the separation time. The PBZ membranes are characterized by ATR-IR and 1H-NMR to confirm the chemical composition.