Quantitative Modeling and Analysis of Excess Molar Enthalpy in 2-Phenoxyethanol–Alcohol Systems

Abstract

As the gasoline industry seeks cleaner-burning and more efficient fuel formulations, glycol ethers and alcohols, due to their oxygenated functional groups, are gaining interest as additives. One promising candidate is 2-phenoxyethanol (2-PhE), a glycol ether known for its thermal stability and low volatility. In this work, we studied how 2-PhE mixes with various alcohols, 1-propanol, 1-butanol, 2-propanol, 2-butanol, methanol, and ethanol, by measuring the excess molar enthalpy (HmE) at a pair of 298.15 and 313.15 K and at 0.1 MPa. All binary mixtures analyzed showed mixing was endothermic, indicating weaker interactions between the different molecules. To evaluate the predictability of thermodynamic models for these types of mixtures, the Redlich–Kister equation was found to be the best for correlating the HmE. The NRTL and UNIQUAC provided reasonable agreement by incorporating molecular size and local interactions. The modified UNIFAC (Dortmund) model, based on group contributions, was less accurate, especially for mixtures where hydrogen-bonding and molecular structure play a big role. These findings highlight the challenges in modeling complex alcohol ether blends and underscore the need for better predictive tools in the development of next-generation gasoline additives.