Determination of Volumetric Properties Using Refractive Index Measurements for Nonpolar Hydrocarbons and Crude Oils

Abstract

A novel method to evaluate volumetric properties, namely the thermal expansivity (α P ) and the isothermal compressibility (κ T ) for nonpolar hydrocarbon systems using refractive index measurements, is presented in this work. New expressions for α P and κ T are derived from the Lorentz–Lorenz equation and the One-Third rule, respectively. A further simplified expression for α P is proposed requiring only refractive index data and molecular weight for calculation. Densities and refractive indices of 12 pure nonpolar hydrocarbons, 6 hydrocarbon mixtures, and 3 crude oils are measured at temperatures from 283.15 K up to 343.15 K and at 0.1 MPa. The measured refractive indices are used to calculate α P for a wide range of temperatures using the proposed method, and the measured densities are used to calculate α P for comparison. Reported densities and refractive indices of benzene at 298.15 K and at pressures up to 90 MPa are used for κ T evaluations with the proposed method. Values of α P and κ T calculated from refractive index measurements are in good agreement with experimental data and those determined from densities. This work aims to establish the foundation for experimental methods to determine volumetric properties of nonpolar hydrocarbon systems based on refractive index measurements. A high temperature and high pressure refractometer is expected to have multiple advantages over conventional techniques for density measurements, which include but are not limited to smaller amounts of sample needed, simpler calibration, faster measurement, and cells that are corrosion-resistant (i.e., sapphire glass).

PC-SAFT Parameter Correlations from Simple Measurements at Ambient Conditions for Predictive Modeling of Nonpolar Hydrocarbons

“…Experimental density data are available for various pure hydrocarbons at temperatures in the range of 283−343 K and ambient pressure. 37 Experimental data for the derivative properties of n-heptane, n-dodecane, benzene, and toluene are taken from NIST REFPROP. 38 A summary of the pure component experimental data used in this section is shown in Table 3.…”

“…Parity plots for density modeling of pure components using PC-SAFT parametrized by ASV correlations. Experimental data are at 1 bar and 283–343 K taken from Wang et al …”

“…Predictions of density as a function of temperature at 1 bar using PC-SAFT for (a) binary and (b) ternary/quinary mixtures treated as lumped solvents parametrized by Assareh et al correlations. Markers represent experimental data. ,, Solid lines represent PC-SAFT predictions.…”

Aromatic Ring Index (ARI): A Characterization Factor for Nonpolar Hydrocarbons from Molecular Weight and Refractive Index

“…The behavior of the newly developed ARI for well-defined mixtures is studied in this section. Three binary and three ternary hydrocarbon mixtures are studied with mixture data taken from the work of Wang et al The properties of the six mixtures are shown in Table . The reader is referred to ref for more information about the experimental procedure and properties of the hydrocarbons used.…”

“…Properties of Binary and Ternary Mixtures Used for This Investigation. The Calculated ARI Is Based on the Hydrocarbon Mixtures Being Treated as Lumped Solvents 23. …”