A prospective study on the application of thermally rearranged acetate-containing polyimide membranes in dehydration of biofuels via pervaporation

Abstract

Dehydration of biofuels (bioalcohols) derived from fermented products via distillation process is always energy intensive and often limited by the formation of azeotropic mixtures between alcohols and water. We have explored the feasibility of thermally rearranged polybenzoxazole (PBO) membranes in dehydration of biofuels via pervaporation process. The polyimide based precursor was synthesized by polycondensation of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 3,3′-dihydroxybenzidine diamine (HAB) and cast into dense membranes. The resultant polyimide membranes were then subjected to thermal rearrangement reaction to initiate the solid-state chemical reconstruction into PBO. The effects of heating temperature and duration on pervaporation performance were systematically investigated. In general, the thermally rearranged PBO membranes showed an impressive enhancement in permeation flux with reasonable separation performance as compared to its polyimide precursor. In addition, the pervaporation performance was found to be greatly affected by the thermal rearrangement temperature as compared to the dwell duration. Furthermore, the stability of the thermally rearranged PBO membrane has been proven by continuously monitoring the pervaporation performance at 80°C for 250h. The long-term data revealed that there was no significant changes in separation performance that signifies the feasibility of the thermally rearranged PBO membrane in the separation and purification of biofuels via pervaporation process in biorefineries.