Development of polybenzoxazine membranes on alpha-Al2O3 support for ethanol-water separation via pervaporation technique

Abstract

Bioethanol is one of the candidates to replace fossil fuels. Currently, one way to reduce the use of fossil fuels is to utilize a mixture of gasoline with ethanol (gasohol). Bioethanol is an alcohol produced from agricultural feeds tocks by fermentation process. Traditionally, distillation was used to increase the purity of bioethanol. However, distillation presents some concerns in regards to environment, health, cost, and azeotropic mixture. Membrane technique is one of the attractive processes for separation. Polybenzoxazine (PBZ) membrane was evaluated for ethanol-water separation. Highly crosslink α -AI2O3 supporting PBZ membranes were successfully synthesized from bisphenol-A (BPA), formaldehyde, and two different types of multifunctionalamines: diethylenetriamine (deta), and tetraethylenepentamine (tepa). The developed membranes have a thin crosslinked polymeric selective layer over a porous ceramic support to increase mechanical strength of the membrane. Pervaporation technique was done to find separation performance under recycle-continuous mode of ethanol-water separation. It was found that the optimum poly(BA-deta) and poly(BA-tepa) concentration for the preparation of the the α -AI2O3 supporting PBZ membranes was 40 wt.% and 25 wt.%, respectively. The dipping cycles of poly(BA-deta) and poly(BA-tepa) was found to be 2, the membranes thickness was 12.40 and 12.34 µm, giving the total permeation flux of 17.77 and 25.90 g/m2h, respectively. The separation factor of both membranes was higher than 10,000. The synthesized membranes had excellent separation ability at both low and high ethanol concentration (10-90%) in pervaporation process.