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ADSORPTION AND MEMBRANE SEPARATION MEASUREMENTS WITH MIXTURES OF ETHANOL, ACETIC ACID, AND WATER
Citation:
BOWEN, T. AND L. M. VANE. ADSORPTION AND MEMBRANE SEPARATION MEASUREMENTS WITH MIXTURES OF ETHANOL, ACETIC ACID, AND WATER. Presented at 16th Annual North American Membrane Society Meeting, Providence, RI, June 12 - 15, 2005.
Impact/Purpose:
To inform the public.
Description:
Biomass fermentation produces ethanol and other renewable biofuels. Pervaporation using hydrophobic membranes is potentially a cost-effective means of removing biofuels from fermentation broths for small- to medium-scale applications. Silicalite-filled polydimethylsiloxane (PDMS) membranes have effectively removed ethanol from aqueous binary mixtures. In addition, they offer the design flexibility and other advantages of polymer membranes with improved selectivity due to the adsorption properties of silicalite. Fermentation byproducts, including carboxylic acids, however, can get detrimental to zeolite-filled polymer membrane performance. Long-term pervaporation measurements with a silicite-filled PDMS membrane indicated that the ethanol/water separation factor gradually decreased over a 20-day period when acetic acid was present in the feed. The final separation factor was approximately 75% of the original separation factor, and the decrease was due to decreasing ethanol flux. The separation factor did not increase after removing acetic acid from the feed or flushing the membrane with a high ethanol concentration. To improve understanding of this behavior, adsorption isotherms of ethanol, acidic acid, and water adsorbed on silicalite-1 powder from liquid mixtures at room temperature have also been measured. Adsorption time dependence was investigated for some mixtures. The adsorbed amounts of each compound in the mixtures were determined using a recently developed method that accurately measures zeolite/liquid mixture density change and liquid concentration change upon adsorption.