Vapor–Liquid Equilibrium Data for Methyl tert-Butyl Ether–Ethanol Mixtures at 90.0 and 101.3 kPa

Abstract

Isobaric vapor–liquid equilibrium (VLE) has been measured using the modified Othmer circulation still for the 2-methoxy-2-methylpropane (MTBE)–ethanol mixtures at 90.0 and 101.3 kPa. Such oxygenate mixtures are being considered for use as octane enhancers in gasoline. The experimental data showed that at 101.3 kPa, this system has an azeotropic point at 95.02 mol% MTBE and 328.06 K. Reducing the pressure to 90.0 kPa did not result in a significant alteration of the VLE of this system. The experimental data were compared with those predicted by the ASOG, the original UNIFAC and the UNIFAC–Dortmund methods of prediction which predicted the bubble point temperature with a root-mean-square deviation (RMSD) at 90.0 kPa of: 1.66, 0.36, and 0.71 K, respectively, and with an RMSD at 101.3 kPa of: 1.97, 0.90, and 1.00 K, respectively. RMSD values of the vapor phase composition given by these models at 90.0 kPa were: 0.0201, 0.0046, and 0.0102, respectively, and at 101.3 kPa the RMSD values of the vapor phase composition were: 0.0222, 0.0107, and 0.0117, respectively. Moreover, the experimental data were correlated to the Wilson and the NRTL models. The parameters obtained for these models were used to calculate the bubble point temperature and the vapor phase composition. The calculated data were in a good agreement with the experimental results.