Evaporation of ethanol blended fuel is complex because ethanol forms azeotropes with light hydrocarbons and has a high heat of vaporization due to hydrogen bonding. We present an evaporative model that leverages FTIR and NMR spectroscopies to quantify hydrogen bonding. While the spectroscopic approaches are not new, they are complicated by the challenges involved with quantifying the associating clusters. Issues persist in curve fitting IR for evaluating the spectra because absorbances are highly concentration and temperature dependent. More importantly, the significant variation in the IR molar extinction coefficient across the broad hydroxyl band has been ignored in most studies and thus hindered accurate quantification of association. Drawing on insights obtained from MD and quantum chemical calculations, we have developed a method for scaling experimental FTIR spectra such that the entire hydroxyl region can be quantified with Beer’s law. The scaling facilitates meaningful extraction of model-relevant thermodynamic association constants. The association constants are subsequently used in a phase equilibria model to study effects of cooperative bonding on the evaporation process.

Spectroscopic characterization of hydrogen bonding of ethanol in hydrocarbons for applied evaporative modeling

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.