Experimental investigation and thermodynamic modeling of wax disappearance temperature for n-undecane + n-hexadecane + n-octadecane and n-tetradecane + n-hexadecane + n-octadecane ternary systems

• WDTs for n-C11 + n-C16 + n-C18 and n-C14 + n-C16 + n-C18 systems are measured at atmospheric pressure.
• Measured WDTs are predicted thermodynamically using thirteen different models.
• Combination of p-Wilson model and regular solution theory leads to the most accurate results for both studied systems.

In this investigation, the wax disappearance temperatures (WDT) of two ternary n-alkane systems including n-undecane + n-hexadecane + n-octadecane and n-tetradecane + n-hexadecane + n-octadecane are measured using a homemade visual-based apparatus working under atmospheric pressure (0.9 bar). The two aforementioned ternary systems are modeled thermodynamically without using any adjustable parameter to predict the wax disappearance temperature. Two methods are used for modeling. In one method, perturbed-chain statistical associating fluid theory (PC-SAFT) is used to describe the liquid phase while the solid phase is described by a solid solution model. In the other method, the nonidealities of the liquid and solid phases are both captured using activity coefficient models. Ideal solution, regular solution theory and predictive Wilson are used separately for description of the liquid phase while ideal solution, regular solution theory, predictive Wilson, predictive UNIQUAC and UNIFAC activity coefficient models are used to describe the nonideality of the solid phase. The obtained results show that the use of regular solution theory for the liquid phase and predictive Wilson for the solid phase leads to closer results to the experimental data compared with other combinations of models for both examined systems.