Experimental density measurements of bis(2-ethylhexyl) phthalate at elevated temperatures and pressures

Experimental high-temperature, high-pressure (HTHP) density data for bis(2-ethylhexyl) phthalate (DEHP) are reported in this study. DEHP is a popular choice as a reference fluid for viscosity calibrations in the HTHP region. However, reliable HTHP density values are needed for accurate viscosity calculations for certain viscometers (e. g. rolling ball). HTHP densities are determined at T = (373, 424, 476, 492, and 524) K and P to 270 MPa using a variable-volume, high-pressure view cell. The experimental density data are satisfactorily correlated by the modified Tait equation with a mean absolute percent deviation (delta) of 0.15. The experimental data are modeled with the Peng-Robinson (PREoS), volume-translated PREoS (VT-PREoS), and perturbed chain statistical associating fluid theory (PC-SAFT EoS) models. The required parameters for the two PREoS and the PC-SAFT EoS models are determined using group contribution methods. The PC-SAFT EoS performs the best of the three models with a delta of 2.12. The PC-SAFT EoS is also fit to the experimental data to obtain a new set of pure component parameters that yield a d of 0.20 for these HTHP conditions. (C) 2013 Elsevier Ltd. All rights reserved.