(481g) Bubble Pressure, Enthalpy of Mixing and Excess Volume Measurement and Prediction for n-Alkane + Aromatic and Naphthenic Hydrocarbon Binary Mixtures

Experimental phase behavior data are scarce for long chain n-alkane + aromatic and naphthenic mixtures. In two recent works [1, 2] we showed that commonly used cubic equations of state systematically predict both qualitatively and quantitatively incorrect phase behavior unless negative binary interaction parameter (k_ij) values are used. We also showed that the PC-SAFT equation of state accurately computes the phase behavior, with binary interaction parameters set to zero, and therefore can be used to estimate k_ij values for cubic equations of state in the absence of experimental phase equilibrium data. However, the investigation was restricted to the correctness of phase behavior type [3], bubble pressures and critical points for a limited number of mixtures for which data were available at the time of publication. In this follow up study, a more extensive set of high-precision bubble-pressure, excess volume and enthalpy of mixing measurements are presented for representative binary mixtures of n-alkanes + aromatic and naphthenic compounds. The selected mixtures comprise binaries of n-alkanes, from n-C₁₆ to C₃₆, combined with alkyl-benzene, alkyl-naphthtalene, and their naphthenic analogues such as alkyl-cyclohexane. The experimental data are compared with predicted and regressed outcomes obtained using the Peng-Robinson, Soave-Redlich-Kwong and the PC-SAFT equations of state where interaction parameter values are regressed from bubble pressure data. Outcomes are evaluated. Expected applications of this work include improved phase behavior model accuracy applicable to hydrocarbon production, transport and refining environments, and improved corresponding state based transport property prediction, particularly for viscosity, that require accurate phase behaviors and phase compositions as inputs.

[1] S. Ahitan, M. A. Satyro, J. M. Shaw, "Systematic Misprediction of n-Alkane + Aromatic and Naphthenic Hydrocarbon Phase Behavior Using Common Equation of State", J. Chem. Eng. Data 2015. DOI:10.1021/acs.jced.5b00539

[2] S. Ahitan, J. M. Shaw, â??Quantitative Comparison Between Predicted and Experimental Binary n-Alkane + Benzene Phase Behaviors Using Cubic and PC-SAFT EOSâ?, Submitted to Fluid Phase Equilibria 2016.

[3] P. H. van Konynenburg, R. L. Scott, â??Critical lines and phase-equilibria in binary van der Waals mixturesâ?, Philos. Trans. R. Soc., A1980, 298, 495-540.