Experimental Measurement and Modeling of High-Pressure Liquid Densities of Isobutanol and 2-Butanol Up to 200 MPa

This study presents an investigation into the liquid density of isobutanol and 2-butanol at selected temperatures from 303.15 K to 383.15 K and pressures up to 200 MPa using a variable-volume high-pressure system. The apparatus was validated with n -decane, and the measured densities agreed with literature values within 0.2 %. The expanded relative uncertainty of density was estimated to be 0.27 % with a coverage factor of k  = 2. The experimental data were correlated with the Tammann–Tait equation, yielding average absolute deviations below 0.05 % for both butanol isomers. The isothermal compressibility and isobaric thermal expansivity were derived from the fitted correlations to characterize the pressure and temperature dependence of the volumetric properties. In addition, the pure-component parameters for the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state were optimized using the 2B association scheme. The optimized PC-SAFT model reproduced the measured densities with average absolute deviations lower than 0.2 %. The results expand the available high-pressure density database for these two butanol isomers and may be useful for thermodynamic modeling and engineering calculations within the investigated temperature and pressure ranges.