Towards automated characterisation of liquid–liquid equilibria

A highly automated 2-step method for measuring and correlating liquid–liquid equilibria (LLEs) is presented: In step 1, samples are prepared and measurements are performed; step 2 covers data extraction and correlation with thermodynamic models. The procedure has been optimised such that a sample volume of 1 mL per LLE is sufficient for reliable measurements. The experimental setup consists of commercially available modules assembled such that the setup automatically prepares the sample mixtures, waits for equilibrium, takes samples, and analyses them. Gas chromatography (GC) is employed to maximise flexibility with respect to the mixtures that can be studied. For GC analysis, neither further dilution nor addition of an external standard is needed. In step 2, the gathered data are converted into concentration data and the gE-models UNIQUAC and NRTL are adjusted to the data. The automated 2-step method is validated for the ternary systems cyclohexane–toluene–methanol, isooctane–o-xylene–methanol, and 1-octanol–ethanol–water. Good agreement with literature data is achieved while experimental effort is reduced significantly.