Isobaric vapour-liquid equilibrium of α-terpineol highly diluted in hydroalcoholic mixtures at 101.3 kPa: Experimental measurements and thermodynamic modeling

Abstract : Terpenes are important varietal compounds responsible for the characteristic aromas of alcoholic beverages. Reliable vapor-liquid equilibrium (VLE) data for this class of aroma compounds in hydroalcoholic media is essential to understand their behavior during distillation and thus achieve a desired quality in the distilled products. In this work, experimental measurements for the VLE of α-terpineol highly diluted in ethanol-water mixtures were carried out in a recirculation ebulliometer operating at 101.3 kPa for boiling temperatures from (354.99 to 369.93) K. Equilibrium compositions were determined by gas chromatography for α-terpineol and by density measurements for ethanol. Results show that α-terpineol is expressively more volatile in the dilute region (x Et < 0.01), where it can be up to 30 times more abundant in the vapor phase and twice as volatile as ethanol. Inversely, when x Et > 0.15 α-terpineol can be 10 times richer in the liquid phase. The experimental data were correlated by semi-empirical models NRTL and UNIQUAC and compared with predictions by UNIFAC. The data regressed with the NRTL model showed the best agreement with the experimental data. The binary interaction parameters fitted by the model are suitable to be used in the design and simulation of distillation processes for the production of alcoholic beverages.