Phase Behavior and Densities of Propylene + Hexane Binary Mixtures to 585 K and 70 MPa

In this study, we report phase behavior data for propylene + hexane mixtures at temperatures of 295 to 468 K and pressures to 5.5 MPa and high-pressure mixture density data at temperatures of 295 to 584 K and pressures to 70 MPa. Both the phase behavior and density data are simultaneously determined using a variable volume, high-pressure view cell that is coupled with a linear variable differential transformer. The phase behavior and mixture density data are modeled with the Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), modified Sanchez–Lacombe (MSL), and perturbed-chain statistical associating fluid theory (PC-SAFT) equations of state (EoS). The PC-SAFT and MSL EoS provide the best fit of the phase behavior data with a nonzero value of 0.028 for <i>k</i>_<i>ij</i>. Likewise, the PC-SAFT EoS provides the best fit of the high-pressure mixture density data, though the PC-SAFT equation slightly overpredicts the solution density and the calculated densities are relatively insensitive to changes in <i>k</i>_<i>ij</i> from zero to 0.028

Viscosity Measurements of Two Potential Deepwater Viscosity Standard Reference Fluids at High Temperature and High Pressure

This paper reports high-pressure viscosity measurements for Krytox GPL 102 lot K2391 and tris­(2-ethylhexyl) trimellitate (TOTM). These two viscous liquids have recently been suggested as potential deepwater viscosity standard (DVS) reference fluids for high temperature, high pressure viscosity studies associated with oil production from ultradeep formations beneath the deepwaters of the Gulf of Mexico. The measurements are performed using a windowed, variable-volume, rolling-ball viscometer at pressures between 7 and 242 MPa and temperatures between 314 and 527 K with an expanded uncertainty of 3% at a 95% confidence level. The viscosity results are correlated using an empirical temperature/pressure-dependent function and a modified Vogel–Fulcher–Tammann (VFT) Equation. The present viscosity data for TOTM and Krytox GPL 102 lot K2391 are in good agreement with the available reported data in the literature at lower temperatures and pressures. The viscosity values of TOTM and Krytox GPL 102 lot K2391 are 9.5 mPa·s and 25 mPa·s, respectively, at 473 K and 200 MPa, whereas the desired DVS viscosity value at this condition is 20 mPa·s. Although the viscosity of Krytox GPL 102 lot K2391 is closer to the targeted value, a comparison of the present viscosity results with data obtained for lot K1537 indicates a very large lot-to-lot variation of the viscosity for this polydisperse perfluoropolyether oil, which represents a significant deficiency for a DVS

Effect of Isomeric Structures of Branched Cyclic Hydrocarbons on Densities and Equation of State Predictions at Elevated Temperatures and Pressures

The <i>cis</i> and <i>trans</i> conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), <i>cis</i>-1,2-dimethylcyclohexane (<i>cis</i>-1,2), <i>cis</i>-1,4-dimethylcyclohexane (<i>cis</i>-1,4), and <i>trans</i>-1,4-dimethylcyclohexane (<i>trans</i>-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, <i>cis</i>-1,2 exhibits the largest densities and the smallest densities are exhibited by <i>trans</i>-1,4. The densities are modeled with the Peng–Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density

High-Temperature, High-Pressure Volumetric Properties of Propane, Squalane, and Their Mixtures: Measurement and PC-SAFT Modeling

This study reports the high-temperature, high-pressure density data for propane, squalane, and their binary mixtures for five compositions at temperatures to 520 K and pressures to 260 MPa. The density measurements are obtained with a floating-piston, variable-volume, high-pressure view cell. From the density data, the isothermal and isobaric excess molar volumes upon mixing are computed. For the mixture compositions studied here, the excess volume is mostly negative, showing a minimum at 0.6550 mole fraction of propane and becomes less negative as the propane concentration increases. The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) provides good representation for the experimental data. A mean absolute percent deviation (δ) of 1.4% is obtained with the PC-SAFT EoS when using propane and squalane pure component parameters fit to density data at high-temperature, high-pressure conditions