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Keywords:

  • adsorption;
  • ethanol;
  • diffusion separation;
  • IR spectroscopy;
  • membranes;
  • zeolites

Abstract

The adsorption, separation, and diffusion properties of intergrown silicalite-1 membrane on a pre-seeded porous stainless-steel-net support in ethanol/water mixtures are evaluated. The permeation of ethanol and water as vapors and liquids on the silicalite-1 membrane is investigated. Operando IR spectroscopy combined with mass spectrometry is used to study directly the silicalite-1 membrane supported on the stainless-steel-net in mixtures of ethanol/water with different mass ratios (ethanol/water=0, 5, 25, 50, 75, and 100). It was found that the diffusion coefficients for ethanol and water in the mixture (ethanol/water=50:50) are 0.81×10−10 and 2.2×10−10 cm2 s−1, respectively. The silicalite-1 membrane shows higher ethanol selectivity with an increase of the ethanol content in the reaction mixture. Furthermore, when using the membrane the high selectivity of 19.6 and 39 for the mixtures containing 5 wt % and 50 wt % ethanol is combined with a high flux, which is 11.5 kg m−2 h−1 and 17.1 kg m−2 h−1, respectively. The silicalite-1 membrane with high reproducibility resists cracking and possesses high mechanical stability. In addition, the stainless-steel-net support possesses very high porosity thus leading to an improved permeation flux, and also it is transparent and suitable for quantitative characterization by operando IR spectroscopy. The good performance of the supported silicalite-1 membrane (high separation factor and high flux for ethanol over water) makes it interesting for use in extracting ethanol from aqueous bioethanol system.