What is the state of aggregation of ethanol molecules in ethanol–supercritical carbon dioxide mixtures? An FTIR investigation in the full molar fraction range

• The near infrared spectra of ethanol–CO2 mixtures in the full molar fraction range.
• Investigation in the temperature range 40–200 °C at two pressures P = 15 and 20 MPa.
• Analysis of the free OH peak to determine the evolution of the degree of hydrogen bonding.
• Degree of hydrogen bonding of ethanol molecules in ethanol–CO2 mixtures.

The evolution of the degree of hydrogen bonding of ethanol molecules in scCO2–ethanol mixtures for different molar fraction (from 0.5 to 100% in ethanol) in the temperature range 40–200 °C and at two different constant pressures P = 15 and 20 MPa is reported in this paper. For a given pressure, we observe a strong dependence of the degree of hydrogen bonding as a function of temperature and ethanol molar fraction. We emphasize that a detailed knowledge of the degree of hydrogen bonding of ethanol molecules in these binary systems is important for the understanding and the further development of the supercritical fluid technology.

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