Abstract
The transient and steady pervaporation of 1-butanol–water mixtures through a poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membrane was studied to observe and elucidate the diffusion phenomena in this high-performing organophilic glassy polymer. Pervaporation was studied in a continuous sequence of experiments under conditions appropriate for the separation of bio-butanol from fermentation broths: feed concentrations of 1.5, 3.0 and 4.5 w/w % of 1-butanol in nutrient-containing (yeast extract) water, temperatures of 37, 50 and 63 °C, and a time period of 80 days. In addition, concentration polarization was assessed. As expected, the total flux and individual component permeabilities declined discernibly over the study period, while the separation factor (average β = 82) and selectivity towards 1-butanol (average α = 2.6) remained practically independent of the process conditions tested. Based on measurements of pervaporation transients, for which a new apparatus and model were developed, we found that the diffusivity of 1-butanol in PTMSP decreased over time due to aging and was comparable to that observed using microgravimetry in pure vapor in 1-butanol. Hence, despite the gradual loss of free volume of the aging polymer, the PTMSP membrane showed high and practically independent selectivity towards 1-butanol. Additionally, a new technique for the measurement and evaluation of pervaporation transients using Fourier transform infrared spectroscopy (FTIR) analysis of permeate was proposed and validated.
Highlights
After more than 100 years of history in industrial acetone–butanol–ethanol (ABE) fermentation, patented by Chaim Azriel Weizmann in 1915, 1-butanol is again considered a promising biofuel [1].1-butanol is a valuable solvent, energy carrier and chemical feedstock that is extensively used in various industries [1,2,3]
We propose a new type of apparatus for the measurement of pervaporation transients
Pervaporation was studied in a continuous sequence of experiments under certain conditions, including those relevant to the separation of bio-butanol from fermentation broths
Summary
1-butanol is a valuable solvent, energy carrier and chemical feedstock that is extensively used in various industries [1,2,3] This compound has been considered to be a useful partial replacement for automotive fossil fuels as it has a higher energy content, can be blended with gasoline to high concentrations and has a lower vapor pressure than ethanol, which is the far more commonly used renewable oxygenated blend with gasoline [2,4,5,6,7]. 1-butanol can be produced from renewable feedstocks by clostridial ABE fermentation [8,9,10,11], and separated from the medium by pervaporation. Experiments were performed to test its influence on pervaporation membranes
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