Abstract
Pervaporation of binary ethanol/water solutions of 5–10 wt.% ethanol was studied experimentally through a thin supported high-silica MFI zeolite membrane of hydrophobic character in the temperature range of 30–70 °C. The fluxes obtained were very high, 2–14 kg m -2 h -1 with ethanol/water separation factors of 4–7. The loss of effective driving force was significant in the supporting layers, which limited the membrane performance. The correlation between the experimental data and three different semi-empirical mass-transfer models was examined. The correlation was good especially when the driving force for mass-transfer was determined based solely on bulk feed, or the bulk feed and permeate conditions together. Somewhat lower correlation was observed when the driving force was corrected with the effect of support resistance. This was most likely due to the inaccuracies of the used mass transfer parameters in the support. The investigated semi-empirical models can be applied for initial stage process design purposes.
Highlights
As energy issues have become increasingly important, there has been a growing interest towards separation processes with low energy consumption, such as pervaporation
Selective removal of ethanol straight from the fermentation broths by integrating pervaporation into fermentation would increase the productivity of fermentors and decrease the separation costs
Rubbery polymers have been recognized as potential materials for organophilic pervaporation applications, the most common being polydimethylsiloxane PDMS, often referred to as silicone rubber
Summary
As energy issues have become increasingly important, there has been a growing interest towards separation processes with low energy consumption, such as pervaporation. Various membrane materials have been studied in the recovery of organic compounds from water-containing streams by pervaporation. Rubbery polymers have been recognized as potential materials for organophilic pervaporation applications, the most common being polydimethylsiloxane PDMS, often referred to as silicone rubber. The reported ethanol-water separation factors using PDMS membranes vary between 4 and 11 [2,3,4]. The reported total fluxes, are typically relatively low, mostly below 1 kg m-2 h-1 [3,5,6,7,8]. The ethanol-water separation factor using such membranes has been increased, up to as high as 59, with the total flux remaining mostly below 1 kg m-2 h-1 [12]
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