Adsorption of Water and Butanol in Silicalite-1 Film Studied with in Situ Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy

Abstract

Biobutanol produced by, e.g., acetone-butanol-ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35-120 °C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 °C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.

Colloidal Defect-Free Silicalite-1 Single Crystals: Preparation, Structure Characterization, Adsorption, and Separation Properties for Alcohol/Water Mixtures

“…28 In the procedure, the contribution from OH stretching vibration from adsorbed n-butanol was subtracted from the total signal using single component adsorption spectra of butanol. The butanol/water adsorption selectivities (α BuOH/water described in eq 1 obtained from the spectra were 165 and 14, for the SCTPAF and SCTPAOH samples, respectively.…”

“…Band intensities have previously been calibrated against volumetric adsorption isotherms enabling the adsorbed concentrations to be extracted from infrared spectra. 28 Adsorption selectivity is determined as…”

Zeolite MFI adsorbent for recovery of butanol from ABE fermentation broths produced from an inexpensive black liquor-derived hydrolyzate

“…Recent research shows that the butanol/water adsorption selectivity of a MFI adsorbent may be further increased by decreasing the density of structural defects, in the form of silanol groups, present in the framework [25,26]. These defects are formed during conventional zeolite synthesis at high pH.…”

“…from model solutions and very little attention was given to recovery from real fermentation broths. Most studies have been performed on adsorption from liquid phase; however, recently, it was shown that high silica MFI zeolite showed very high butanol selectivity from vapor phase as reported by our group previously [25,26]. As zeolite MFI is a stable material and strightforward to synthesize in its hydrophobic (high Si/Al ratio) form at relatively low cost, it is one of the most studied materials for recovering butanol from dilute aqueous solutions.…”

Quest for sustainable bio-production and recovery of butanol as a promising solution to fossil fuel

“…Silicalite, a polymorph of silica with a structure analogous to the zeolites, is a compound with a very high SiO 2 /Al 2 O 3 ratio, a parameter which indicates the hydrophobicity level of the material's surface. Farzaneh et al (2015) demonstrated its suitability to separate butanol from the vapour obtained in an ABE fermentation gasstripping process (85:15 v H2O /v Bu-OH ), as silicalite-1 was butanol-selective with an adsorption selectivity of 107 at 35°C [228]. Silicalite-1, the pure silica analogue of the zeolite ZSM-5, has been stated as the most promising adsorbent for biobutanol recovery regarding its high adsorption capacity and selectivity, high stability and desorption ease by heating at 200°C [161].…”