Recovery of alcohol fuels using selective membranes by pervaporation

The environment and concerns over the limited supply of economical oil have generated a renewed interest in development of technologies that use renewable resources for energy production. The acetone butanol ethanol (ABE) fermentation is one such fermentation that shows promise of industrial revitalization. However, ABE recovery by distillation from dilute fermentation broth makes the process uneconomic. Pervaporation, a technique to remove ABE selectively, has the potential to be more economical than distillation. Silicone/silicalite composite pervaporation membrane was made to remove ABE from model solutions and fermentation broths. Selectivity, flux and membrane stability of the pervaporation membrane were superior than those reported in the literature. At a retentate butanol concentration of 8-10 g/L butanol selectivity of 95-145 was achieved. At low butanol concentrations ($\u3c$1 g/L) butanol selectivity of 209 was achieved. However, flux through the pervaporation membrane was decreased by 34% when fermentation broth was used for 120 h. Butanol flux was predicted using a mathematical model. In addition, 2,3-butanediol recovery process was developed using a polytetrafluoroethylene (PTFE) membrane. The membrane, which retained butanediol, passed water at a flux rate of 14 kg/m$\sp2$.h at 55$\sp\circ$C. The PTFE membrane fouled with fermentation media and fermentation broth