Reducing emissions is a key goal in developing sustainable fuels. Higher alcohols like 1-heptanol play an important key due to their excellent fuel properties, such as high energy content and good combustion behavior, making them promising candidates as renewable fuel additives. This study focuses on the investigation of heat- related behavior of five binary systems composed of glycol ethers with 1-heptanol: diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monophenyl ether, and ethylene glycol monobutyl ether. Experimental data were carried out for key thermal and physical properties, including excess molar enthalpy (HE m), density (ρ), speed of sound (u), and refractive index (nD), across the temperature range 293.15–323.15 K at 0.1 MPa. From these primary data, secondary thermophysical properties, namely excess molar volume (VE), isentropic compressibility (ks), and refractive index deviation (ΔnD), were derived to better characterize non-ideal mixing behavior. Peng–Robinson and PC-SAFT EOS were using to modeled the density data, while empirical polynomial expressions were applied to fit composition-dependent trends in ρ, u, nD, and ks as dependent on fraction. VE and ΔnD were fitted using the Redlich-Kister equation. The HE m was analyzed using both empirical method and heat-related models, including UNIQUAC, NRTL, and the predictive DM-UNIFAC model. All systems exhibited positive HE m values, indicating endothermic mixing processes. These findings offer valuable insight into the interaction mechanisms between 1-heptanol and glycol ethers, supporting their evaluation for use in environmentally friendly fuel formulations.
