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Published on: July 2, 2020
Microscopic structure and interaction analysis for supercritical carbon dioxide-ethanol mixtures: a Monte Carlo
Wenhao Xu1, Jichu Yang, Yinyu Hu
1Department of Chemical Engineering, Tsinghua University, Beijing 100084, People's Republic of China.
The Journal of Physical Chemistry. B
|April 3, 2009
Summary
Supercritical carbon dioxide and ethanol mixtures show complex interactions. Ethanol-CO2 electron donor-acceptor bonds are more stable than hydrogen bonds, influencing mixture structures.
Area of Science:
- Physical Chemistry
- Chemical Engineering
- Materials Science
Background:
- Supercritical carbon dioxide (scCO2) is a tunable solvent with unique properties.
- Understanding scCO2-organic molecule interactions is crucial for separation and reaction processes.
- Ethanol (EtOH) is a common co-solvent whose interactions with scCO2 are not fully characterized.
Purpose of the Study:
- To investigate the microscopic structures and molecular interactions in scCO2-EtOH mixtures.
- To analyze EtOH-EtOH, EtOH-CO2 hydrogen bonding, and EtOH-CO2 electron donor-acceptor (EDA) bonding.
- To determine the effect of composition, temperature, and pressure on these interactions.
Main Methods:
- Configurational-bias Monte Carlo simulations in the isobaric-isothermal ensemble.
- Utilized the TraPPE-UA force field for molecular modeling.
- Calculated binary vapor-liquid coexisting curves at multiple temperatures.
Main Results:
- Simulations accurately predicted vapor-liquid coexisting curves, validating the model.
- Identified and compared EtOH-EtOH, EtOH-CO2 hydrogen bonding, and EtOH-CO2 EDA bonding.
- Observed a preference for EtOH-CO2 hydrogen-bonded tetramers and pentamers at higher EtOH concentrations.
- Found extensive EtOH-EtOH hydrogen-bonded networks and linear EtOH-CO2 aggregates (dimers and trimers).
- Determined that EtOH-CO2 EDA complexes are more stable than EtOH-CO2 hydrogen-bonded complexes.
Conclusions:
- The study provides a detailed molecular-level understanding of scCO2-EtOH mixtures.
- Competition between EtOH-EtOH and EtOH-CO2 interactions governs mixture behavior.
- EtOH-CO2 EDA interactions play a significant role in the structural organization of these mixtures.
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