Ternary Liquid – Liquid and Binary Liquid – Liquid, Solid – Liquid, and Vapour – Liquid equilibria of systems containing ε-Caprolactam, Water, n-Hexadecane, and o-Xylene

• Study from the perspective of chemical recycling via pyrolysis of waste plastic • Experimental phase equilibria determination of systems containing Nylon-6 monomer • Results can be used for the design of distillation, extraction, and crystallisation • Thermodynamic modelling with both predictive and correlational models This study reports equilibrium experimental data of binary and ternary systems containing ε-caprolactam. Solid – liquid equilibria (SLE), and isobaric bubble points were measured for the binary system ε-caprolactam + o-xylene. SLE and liquid – liquid equilibria (LLE) were measured for the binary system ε-caprolactam + n-hexadecane. Ternary LLE were measured for the systems ε-caprolactam + water + n-hexadecane or o-xylene at temperatures 298 – 323 K and atmospheric pressure. The isobaric bubble point and the ternary systems’ phase boundaries were predicted prior to the experiments with the universal quasi-chemical functional group activity coefficients – Dortmund modified (UNIFAC–Dortmund) model to ascertain the experimental conditions. Binary interaction parameters for the nonrandom, two-liquid (NRTL) model were regressed based on the measured systems of this work and additional data from the literature sources. Good agreement was found between the experimental data and the NTRL model. The results from this study provide insights into the phase behaviour of mixtures containing ε-caprolactam, facilitating process design in relevant industrial processes.