Measurements and predictions of densities and viscosities in CO₂ + hydrocarbon mixtures at high pressures and temperatures: CO₂ + n-pentane and CO₂ + n-hexane blends

This work reports new experimental data on densities and viscosities of (CO₂ + n-pentane) and (CO₂ + n-hexane) mixtures at high pressures and temperatures. The densities were measured by a vibrating-tube densimeter with an expanded uncertainty (k = 2) smaller than 1.8 kg·m⁻³ at six isotherms (from 273.15 K to 373.15 K), twelve pressures starting at 5 MPa up to 100 MPa, and at six CO₂ molar compositions (from 0 to 0.6). The viscosities were measured by a vibrating-wire viscometer with the corresponding relative expanded uncertainty (k = 2) smaller than 0.016 at five isotherms (from 273.15 K to 373.15 K), twelve pressures (from 5 MPa up to 100 MPa), and at two CO₂ molar compositions (0.1 and 0.3). The densities were fitted by the semiempirical Tammann-Tait equation for density data and the Vogel-Fulcher-Tammann (VFT) equation for viscosity data, respectively. The Groupe Européen de Recherches Gazières (GERG-2008) equation of state was also applied for modelling the densities. Over-all robustness and reliability of the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT) and its critical point-based modification (CP-PC-SAFT) were examined. Accuracies of the Modified Yarranton-Satyro (MYS) coupled with CP-PC-SAFT and the NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP 10) in predicting the viscosities were evaluated.