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DEHYDRATION OF LOW WATER CONTENT ETHANOL
Citation:
NAMBOODIRI, V. AND L. M. VANE. DEHYDRATION OF LOW WATER CONTENT ETHANOL. Presented at No. American Membrane Society Annual Meeting, Providence, RI, June 11 - 15, 2005.
Impact/Purpose:
To inform the public.
Description:
Pervaporation has emerged as an economically viable alternative technology for the dehydration of organic solvents, removal of organic compounds from water and organic/organic separations. Development of a membrane system with suitable flux and selectivity characteristics plays a critical role in achieving practical utility for this purpose. The present study is focused on the development of high performance polymeric membranes for the dehydration of low water content ethanol <2 wt% water) via pervaporation. Polymer membranes for dehydration generally perform poorly, exhibiting low flux at low water content due to reduced swelling. The novel membrane system to be described here consists of a mixture of hydrophilic polymers that provides high water fluxes and selectivity for water relative to the organic solvent. By blending various grades of poly(vinyl alcohol) with poly(allyl amine) hydrochloride, higher water fluxes were obtained for the low water content feeds than for typical polymeric pervaporation dehydration membranes. For example, a 20 micron thick blended selective layer supported on a porous PVDF backing delivered a water flux of 0.06 kg/m2hr(800 GPU*)and a water/ethanol separation factor of 900 for an ethanol feed liquid containing 2.0 wt% water at 70 deg C. Varying the amount of the polymer components enabled fine tuning of the dehydration performance. The effects of polymer molecular weights, type, and relative composition of each polymer, on membrane stability and performance is compared for the dehydration of ethanol on a pervaporation bench scale unit. The effects of various other parameters such as duration of membrane curing, feed temperature and feed water content will also be described.