Chemical Engineering & Technology, Vol.25, No.7, 729-733, 2002
Vapor-liquid equilibrium of MTBE-methanol, MTBE-methanol-calcium chloride and MTBE-methanol-lithium chloride mixtures
Isobaric vapor-liquid equilibria of methyl tert-butyl ether (MTBE)-methanol, MTBE-methanol-calcium chloride, and MTBE-methanol-lithium chloride mixtures were measured at 93.57 kPa using a Malanowski equilibrium still which circulates both the vapor and liquid phases. The experimental results of the salt-free system showed that MTBE-methanol forms a minimum boiling azeotrope of 69.80 mol.-% MTBE at 93.57 kPa and 322.67 K. The experimental results of the salt-free system were predicted using the original UNIFAC and the UNIFAC-Dortmund methods, where the vapor-phase compositions were predicted with root-mean-square deviations (RMSD) of 0.0046 and 0.0091, respectively, and the bubble point temperatures were predicted with RMSD of 0.36 and 0.71 K, respectively. The Wilson and the nonrandom two-liquid (NRTL) models could satisfactorily correlate the experimental data of the salt-free mixtures with RMSD in the vapor-phase compositions calculation of 0.0047 and 0.0059, respectively and in bubble-point temperatures calculation of 0.20 and 0.40 K, respectively. Addition of either calcium chloride or lithium chloride to the MTBE-methanol mixtures resulted in salting-out the MTBE and shifting the azeotropic point to a vapor composition of 76.5 mol.-% and 93.0 mol.-% MTBE, respectively. Both the Tan-Wilson and Tan-NRTL models could satisfactorily predict the bubble-point temperatures of the MTBE-methanol-calcium chloride mixtures with RMSD of 0.143 and 0.130 K, respectively, and the vapor phase compositions with RMSD of 0.0055 and 0.0041, respectively.