Sorption and modeling for pervaporation of ethanol/water solutions. Phase 2. (Final research effort report). Final report 16 Nov 87-15 Feb 90

Ethanol is an important commodity chemical that has a number of industrial and commercial uses. One of the potential applications is as fuel blend for automobiles. Based on the desire for better air quality, the president of the United States has recently initiated a drive for using ethanol as a fuel additive for automobiles in the 1990's. The purpose of the study was to advance pervaporation technology to permit energy-efficient separation of ethanol/water mixtures. One polymer, polytrimethyl 1-propyne (PTMSP), exhibited the highest selectivity (14.1) with intermediate ethanol permeation flux (V(sub w) = 0.184 kg/sq m h) compared with the many different apolar polymer materials that were cast and tested for their ability to separate ethanol and water using the pervaporation process. Another polymer, polyvinylidene difluoride (PVDF), exhibited reverse behavior with an intermediate selectivity (3.5) and a high flux (V(sub w) = 1.135 kg/sq m h). An unusual membrane with a high selectivity (12.5) and flux (0.425 kg/sq m h) was obtained by combining these two polymers into a composite membrane, PTMSP-PVDF. An economic analysis of a dual pervaporation plant gave a final operating cost of $0.45/gal of 99.9 percent ethanol using the performance of the PTMSP-PVDF membrane.