Adsorbent screening for biobutanol separation by adsorption: kinetics, isotherms and competitive effect of other compoun
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Adsorbent screening for biobutanol separation by adsorption: kinetics, isotherms and competitive effect of other compounds N. Abdehagh • F. H. Tezel • J. Thibault
Received: 15 April 2013 / Accepted: 6 August 2013 / Published online: 18 August 2013 Ó Springer Science+Business Media New York 2013
Abstract Butanol, considered as one of the best renewable alternatives for gasoline, has attracted significant attention in recent years. However, biobutanol production via fermentation is plagued by the low final product concentration due to product inhibition. It is possible to enhance productivity by selectively removing biobutanol from the fermentation broth. Adsorption is one of the most promising and energy-efficient techniques for butanol separation and recovery. In the present study, different adsorbents were tested by performing kinetic and equilibrium experiments to find the best adsorbent for butanol separation. Activated carbon (AC) F-400 showed the fastest adsorption rate and the highest adsorption capacity amongst ACs and zeolites tested. AC F-400 also showed the highest affinity toward butanol and to a lesser extent for butyric acid whereas its adsorption capacity for the other main components present in acetone–butanol–ethanol fermentation broths was very low. In addition, the butanol adsorption capacity was not affected by the presence of ethanol, glucose and xylose while the presence of acetone led to a slight decrease in adsorption capacity at low butanol concentrations. On the other hand, the presence of acids (acetic acid and butyric acid) showed a significant effect on the butanol adsorption capacity over a wide range of butanol concentration and this effect was more pronounced for butyric acid. Keywords Butanol adsorption Adsorbent screening Activated carbon Zeolites Kinetic and equilibrium experiments N. Abdehagh F. H. Tezel J. Thibault (&) Chemical and Biological Engineering Department, University of Ottawa, 161 Louis Paster St., Ottawa, ON K1N 6N5, Canada e-mail: [email protected]
List of symbols a Equation constant (Eq. 2) b Langmuir constant, L/g C Butanol concentration at time t, g/L C0 Initial butanol concentration, g/L Ce Equilibrium butanol concentration in solution, g/L k Pseudo-second order Lagergren’s rate constant, g/g min Mads The amount of adsorbent used, g n Freundlich constant, (dimensionless) q Butanol adsorption capacity at time t, g/g qe Butanol adsorption capacity at equilibrium state, g/g qs Maximum butanol adsorption capacity, g/g t Time, min Abbreviations ABE Acetone–butanol–ethanol AC Activated carbon NHOC Net heat of combustion MWCNT Multi-walled carbon nano tube
1 Introduction Depletion of oil resources combined with the continuous rising of oil prices, political instability in oil-producing countries and environmental challenges are some of the reasons that have motivated significant interest for producing alternative biofuels from renewable and sustainable resources. Amongst these fermentation-derived fuels, butanol bioproduction is currently attractin
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