Several organophilic membranes were utilized to selectively permeate ethanol, n-butanol, and t-butanol from dilute aqueous mixtures using pervaporation (PV). Poly[ 1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were utilized to investigate the effect of temperature, pressure, and start-up/transient time on the separation of aqueous ethanol mixtures. Results indicate optimal ethanol selectivity and flux at the lowest permeate-side pressure. Increased temperature significantly enhanced the productivity of PTMSP, but extended operation of the PTMSP membranes at high temperatures resulted in flux degradation. Two other hydrophobic membranes, poly(dimethy1 siloxane) (PDMS) and a poly(methoxy siloxane) (PMS) composite, were used to separate n-butanol and t-butanol from dilute aqueous mixtures. The effect of feed concentration on the flux and selectivity was investigated. Both membranes were found to be more permeable to n-butanol than r-butanol. The PDMS membrane was found to be more effective than the PMS membrane in terms of flux and selectivity. The effect of m e m b r x e thickness on water permeation and on organic selectivity was also studieu using the PDMS membrane.

The separation of ethanollwater mixtures by pervaporation with a poly(dimethy1 siloxane) membrane has been studied. The membrane exhibited ethanol selectivity during all process runs. Investigations focused on the effects of temperature and permeate-side pressure on membrane transport with dilute ethanol feed solutions. An increase in temperature increased the flux exponentially but had little effect on selectivity. As the permeate-side pressure was increased, the flux decreased. Selectivity did not change appreciably over the pressure range evaluated. Studies also analyzed the effect of feed concentration on flux and selectivity. Flux increased and selectivity decreased as the ethanol feed concentration increased. The permeate concentration profile is superior to a standard vapor-liquid equilibrium curve at low ethanol feed concentrations.