An atomistic explanation of the ethanol–water azeotrope

Carravetta, Vincenzo; Gomes, Aline Cristine; Marinho, Ricardo R. T.; Öhrwall, Gunnar; Ågren, Hans; Björneholm, Olle; Brito, A. Naves de

doi:10.1039/d2cp03145k

Cited by 7 publications

(19 citation statements)

References 51 publications

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“…In this situation, any water molecule left is trapped in the ethanol chains and the formation of four H-bonds is not an option anymore. The MD calculations in ref indicate that at high ethanol molar concentrations, the shorter ethanol chains are more numerous in the surface region. Moreover, the relatively short chains have higher water content, especially above the azeotrope region.…”

Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 97%

“…Here, we augmented this description with results from MD simulations. 4 On a macroscopic scale, surface tension and partial vapor pressure measurements complement the overall picture. The VSFG signal measured with two polarization combinations depends on the second-order susceptibility, which is a Cartesian tensor.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

“…We notice that in region IV an azeotrope is formed. 4 In the azeotrope, the composition of the vapor phase and the liquid phase is the same, for lower ethanol percentage mixtures, the vapor contains more ethanol than the liquid, and for higher ethanol percentage mixtures, the vapor contains more water than the liquid. Above ethanol 85 M%, the cMJ-PES signal from the C 1s photoelectron first ceases to increase with the ethanol bulk concentration and then increases again.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

“…Chem. Phys.2022 cMJ-PES and theory are combined to describe the atomic surface of an ethanol–water mixture. A connection between this surface composition and the partial vapor pressure is established explaining the azeotropic behavior in liquid mixtures.…”

Section: Key Referencesmentioning

confidence: 99%

“…However, at these concentrations the microstructures, i.e., the hydrogen bond networks, may change a lot with increasing alcohol content. The bar customer will not recognize this, but it is nevertheless an interesting result of recent research as reviewed in this Account. − …”

Section: Introductionmentioning

confidence: 99%

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Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

et al. 2022

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Metrics & MoreArticle Recommendations CONSPECTUS: By combining results and analysis from cylindrical microjet photoelectron spectroscopy (cMJ-PES) and theoretical simulations, we unravel the microscopic properties of ethanol−water solutions with respect to structure and intermolecular bonding patterns following the full concentration scale from 0 to 100% ethanol content.In particular, we highlight the salient differences between bulk and surface. Like for the pure water and alcohol constituents, alcohol−water mixtures have attracted much interest in applications of X-ray spectroscopies owing to their potential of combining electronic and geometric structure probing. The water mixtures of the two simplest alcohols, methanol and ethanol, have generated particular attention due to their delicate hydrogen bonding networks that underlie their structural and thermodynamic properties. Macroscopically ethanol−water seems to mix very well, however microscopically this is not true. The aberrant thermodynamics of water−alcohol mixtures have been suggested to be caused by energy differences of hydrogen bonding between water−water, alcohol− alcohol and alcohol−water molecules. These networks may perturb the local character of the interaction between X-rays and matter, calling for analysis that go beyond the normally applied local selection and building block rules and that can combine the effects of light−matter, intra-and intermolecular interactions. However, despite decades of ongoing research there are still controversies of the precise nature of hydrogen bonding networks that underlie the mixing of these simple molecules. Our combined analysis indicates that at low concentration ethanol molecules form a film at the surface since ethanol at the surface can expose its hydrophobic part to the vacuum retaining its two (or three) possible hydrogen bonds, while water at the surface cannot retain all its four possible hydrogen bonds. Thus, ethanol at the surface becomes energetically favorable. Ethanol molecules show a tilting angle variation of the C−C axis with respect to the surface normal as large as 60°at very low concentration. In bulk, around ca. ten %, the ethanol oxygen atoms tend to make a third acceptor hydrogen bond to water molecules. At ca. 20 %, there is a U-shaped change in the CH 3 to CH 2 OH binding energy (BE) shift indicating the presence of ring-like agglomerates called clathrate structures. At the surface, between 5 and 25%, ethanol forms a closely packed layer with the smallest C−C tilting angle variation down to ∼20°. Above 25% and below the azeotrope at the surface, ethanol shows an increase in the tilting angle variation, while at very high ethanol concentrations water tends to move to the surface so giving a microscopic explanation of the azeotrope effect. This migration is connected to the presence of longer (shorter) ethanol chains in the bulk (surface). A brief comparison with discussions and predictions from other spectroscopic techniques is also given. We emphasize the execution of an integrated a...

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Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 97%

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

Section: Key Referencesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

et al. 2022

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Process simulation–based scenario analysis of scaled-up bioethanol production from water hyacinth

Abeysuriya

Sethunga²,

Rathnayake³

2023

Biomass Conv. Bioref.

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Water hyacinth (WH) is an aquatic weed with an experimentally proven potential as a feedstock for bioethanol production. Unlike other bioethanol feedstocks, water hyacinth has no requirement for land use and resource consumption for cultivation. This study evaluates scaled-up bioethanol production process routes, modelled using the Aspen Plus process simulator to analyse the process performance of water hyacinth as a bioethanol feedstock. Four process scenarios are developed by combining two different feedstock pretreatment methods (i.e., alkali pretreatment and diluted acid pretreatment) and bioethanol dehydration techniques (i.e., azeotropic distillation and extractive distillation). Mass and energy flows of the four scenarios are comparatively analysed. Results show that the alkali pretreatment method provides a higher bioethanol yield (i.e., 254 L/tonne-WH) compared with the dilute acid pretreatment method (i.e., 210 L/tonne-WH). In addition, the process route combining alkali pretreatment and extractive dehydration techniques indicates the least process energy consumption of 45,310 MJ/m 3 of bioethanol. The process energy flow analysis evaluates two energy sustainability indicators, i.e., net energy gain and renewability factor, with further interpretation of variation effects of the key process parameters through a sensitivity analysis. The feasible ways of utilising water hyacinth as a fuel-grade bioethanol feedstock for industrial-scale production are discussed. Graphical Abstract Supplementary Information The online version contains supplementary material available at 10.1007/s13399-023-03891-w.

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Vapor-liquid phase equilibria behavior prediction of binary mixtures using machine learning

Sun,

Zhao,

Sun

et al. 2023

Chemical Engineering Science

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An atomistic explanation of the ethanol–water azeotrope

Abstract: Ethanol and water form an azeotropic mixture at an ethanol molecular percentage of ∼ 91% (∼ 96% by volume), which prohibits ethanol from being further purified via distillation. Aqueous solutions...

Cited by 7 publications

References 51 publications

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

Process simulation–based scenario analysis of scaled-up bioethanol production from water hyacinth

Vapor-liquid phase equilibria behavior prediction of binary mixtures using machine learning

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