Fluid Phase Equilibria 200 (2002) 41–51 Vapor–liquid equilibria and excess properties of octane + 1,1-dimethylpropyl methyl ether (TAME) mixtures Armando del R´ ıo a , Baudilio Coto b , Concepción Pando a , Juan A.R. Renuncio a,∗ a Departamento de Qu´ ımica F´ ısica I, Universidad Complutense, E-28040 Madrid, Spain b ESCET, Universidad Rey Juan Carlos, E-28933 Móstoles, Madrid, Spain Received 24 September 2001; accepted 18 December 2001 Abstract Vapor–liquid equilibrium (VLE) data are reported for the binary mixtures formed by octane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs–van Ness type apparatus was used to obtain total vapor pressure measurements as a function of composition at 298.15, 308.15, 318.15 and 328.15 K. The system shows positive deviations from Raoult’s law. These VLE data are analyzed together with data previously reported for octane + TAME mixtures: VLE data at 323.15 and 423.15 K, excess enthalpy (H E m ) data at 298.15 and 313.15 K and excess volume (V E m ) data at 298.15K. The UNIQUAC model, the lattice–fluid (LF) model, and the Flory theory are used to simultaneously correlate VLE and H E m data. The two latter models are then used to predict V E m data. The original UNIFAC group contribution model and the modified UNIFAC (Dortmund model) are used to predict VLE data. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Binary liquid mixtures; Vapor pressure; Vapor–liquid equilibria; Branched ether 1. Introduction In recent years, the interest in oxygenated gasoline has resulted in a large number of studies on the thermophysical properties of branched ethers and their binary and ternary mixtures. These ethers are synthesized by the reaction between an isoolefin and an alcohol in excess. The ether purification and the gasoline blending operation require an accurate knowledge of the phase equilibrium and excess properties for the involved mixtures. Both the 1,1-dimethylethyl methyl ether (tert-butyl methyl ether or MTBE) and the 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME) are being widely used as gasoline blending agents and a program is underway at our laboratory to measure the vapor–liquid equilibrium (VLE) data of mixtures formed by MTBE or TAME and a hydrocarbon or an alcohol. VLE data (and Abbreviations: LF, lattice–fluid; MTBE, 1,1-dimethylethyl methyl ether (tert-butyl methyl ether); TAME, 1,1-dimethyl-propyl methyl ether (tert-amyl methyl ether); VLE, vapor–liquid equilibrium ∗ Corresponding author. Fax: +34-91-3944-135. E-mail address: renuncio@quim.ucm.es (J.A.R. Renuncio). 0378-3812/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0378-3812(02)00011-0