(443f) Recovery of Butanol From ABE Mixture Using Pervaporation Hollow Fiber Contained-Liquid Membrane

Pervaporation
is an energy-efficient and cost effective  process that can be used in the
recovery of  volatile organic compounds
(VOCs) from fermentation broth. Pervaporation is
considered to be the best among various methods for the recovery of butanol.  A new
technology in pervaporation was demonstrated by using  hollow fiber
contained-liquid membrane which can achieve high selectivity, increased rate of
permeate flux and high recovery of butanol. Mixture
of acetone, butanol and ethanol (ABE) in the ratio of
3:6:1 was used in the pervaporation experiments. The pervaporation module with polypropylene hollow fibers
coated with nanofluorosilicone was  purchased from Applied Membrane
Technology, Inc. (AMT, Minnetonka, MN).  The performance of the pervaporation  module was  investigated at high butanol
feed concentration. Two glass tubes were used to simultaneously collect
permeate using a vacuum pump operated  at 29.9 inches of water (Figure 1).
Over the high butanol feed concentration
 range  (~30 to 120 g/L) the butanol
mass flux was shown to increase proportionally (60 to 592 g/m²-h)
with an increase in the feed concentration (Figure 2). The values of ABE
selectivity in water for butanol feed concentration
of 30, 50, 85  and 120 g/L varied from
28, 17, 47, and 12, respectively. The pervaporation
permeate collected formed two layers ? organic and aqueous  ?which was ~ 50 %wt butanol.
The recovery of butanol from the mixture was
dependent on the initial feed concentration. The recovery of butanol in 120 g/L ABE mixture was ~61 %wt, which
represented the highest yield of butanol. The
permeate mixture obtained was ~50 %wt  butanol. An increase in butanol
feed concentration increased both the butanol and
water fluxes, however, the increase in butanol flux
was more pronounced than water flux, resulting in higher butanol
recovery. The membrane selectivity initially increased and then
started to decrease when the butanol concentration
was as high as 85 g/L. These results are especially important for potential
application of  hollow
fiber pervaporation membrane
 in
integrated process for butanol  extraction from fermentation.

Figure
1. Schematic diagram of hollow fiber              Figure
2. Effect of butanol feed concentration in

               pervaporation membrane                                             permeate mass flux