Comparative Study of the Effect of Defects on Selective Adsorption of Butanol from Butanol/Water Binary Vapor Mixtures in Silicalite-1 Films

Amirfarrokh Farzaneh, Robert F. DeJaco, Lindsay Ohlin, Allan Holmgren, J. Ilja Siepmann, Mattias Grahn

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

A promising route for sustainable 1-butanol (butanol) production is ABE (acetone, butanol, ethanol) fermentation. However, recovery of the products is challenging because of the low concentrations obtained in the aqueous solution, thus hampering large-scale production of biobutanol. Membrane and adsorbent-based technologies using hydrophobic zeolites are interesting alternatives to traditional separation techniques (e.g., distillation) for energy-efficient separation of butanol from aqueous mixtures. To maximize the butanol over water selectivity of the material, it is important to reduce the number of hydrophilic adsorption sites. This can, for instance, be achieved by reducing the density of lattice defect sites where polar silanol groups are found. The density of silanol defects can be reduced by preparing the zeolite at neutral pH instead of using traditional synthesis solutions with high pH. In this work, binary adsorption of butanol and water in two silicalite-1 films was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy under equal experimental conditions. One of the films was prepared in fluoride medium, whereas the other one was prepared at high pH using traditional synthesis conditions. The amounts of water and butanol adsorbed from binary vapor mixtures of varying composition were determined at 35 and 50 °C, and the corresponding adsorption selectivities were also obtained. Both samples showed very high selectivities (100-23000) toward butanol under the conditions studied. The sample having low density of defects, in general, showed ca. a factor 10 times higher butanol selectivity than the sample having a higher density of defects at the same experimental conditions. This difference was due to a much lower adsorption of water in the sample with low density of internal defects. Analysis of molecular simulation trajectories provides insights on the local selectivities in the zeolite channel network and at the film surface.

Original languageEnglish (US)
Pages (from-to)8420-8427
Number of pages8
JournalLangmuir
Volume33
Issue number34
DOIs
StatePublished - Aug 29 2017

Bibliographical note

Funding Information:
The authors at Luleå University of Technology acknowledge the Swedish Research Council (VR, under Grant 2011-4060) for financially supporting this work. We acknowledge the Foundation in memory of J. C. and Seth M. Kempe for funding a Bruker IFS 66v/S FTIR spectrometer at LTU. The molecular simulation work was supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE-SC0001004. R.F.D. and J.I.S. thank the Minnesota Supercomputing Institute for part of the computer resources used in this work.

Publisher Copyright:
© 2017 American Chemical Society.

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