Low-Pressure Vapor–Liquid Equilibrium Measurements and Thermodynamic Modelling of Binary Systems Containing p -Cymene and Alcohols

This study investigated terpene (p-cymene) solvent as the potential replacement for traditional petrochemical solvents such as n-hexane that have been used for decades in chemical industries. The traditional solvents cause harm in human being and environment. The selected terpene solvent has been identified as potential natural green solvent due to that they are environmental benign, non-toxic, biodegradable, sustainable and produce minimum vapours. New isobaric vapour-liquid equilibrium (VLE) data were measured at 50 kPa for binary systems containing the p-cymene with selected six alcohols. The investigated binary systems comprised p-cymene + {ethanol or 1-propanol or 2-propanol or 1-butanol or 1-pentanol or 1-hexanol}. The experimental measurements were conducted using low pressure recirculation dynamic equilibrium still. All systems exhibited positive deviations from Raoult’s law, attributed to weak interactions between the non-polar terpene molecules and strongly hydrogen-bonding alcohols. The degree of non-ideality decreased with increasing alcohol chain length owing to improved dispersion interactions between the terpene and alcohol molecules. Most p-cymene systems did not exhibit azeotropic behaviour; however, a minimum-boiling azeotrope was observed for the p-cymene + 1-hexanol system. The experimental data were successfully correlated using the NRTL and Wilson activity coefficient models, both of which provided excellent agreement with the measured equilibrium data. The generated VLE data contribute to the optimisation of separation processes using p-cymene as green solvents. The terpene solvent shows the good separation, which it can be used as alternative solvent over tradition solvent n-hexane.