GAS MEMBRANE EXTRACTION OF ETHANOL BY GLYCOLS - EXPERIMENTS AND MODELING

The removal of ethanol from fermentation broth by gas membrane extraction was analysed. Aqueous solutions of glycols were used as extractants. The extractant and the broth were separated by a microporous hydrophobic membrane which was not wetted by the broth or the extractant. Ethanol and water vapors passed across the membrane by diffusion through the stagnant air entrapped within the pores. Since the glycols alter the liquid-vapor equilibrium of the ethanol-water mixtures by reducing the ethanol content in the vapor phase with respect to the binary system, ethanol vapors preferentially diffused through the stagnant gas layer. 1,3-Butanediol, ethylene, diethylene, triethylene and tetraethylene glycols were tested as extractants. A detailed model including all the transport phenomena involved in the process was developed and compared with the experimental results.