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RESEARCH PRODUCT

Phase equilibria and multiple azeotropy in the associating system methanol + diethylamine

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description

Vapor−liquid equilibrium has been measured for the binary system of methanol (1) + diethylamine (2) at 101.3 and 300 kPa. Both equilibrium isobars show strong deviations from ideal behavior and a single maximum boiling point azeotrope of practically constant composition x1 ≈ 0.76, corresponding to a temperature of 339.8 K at 101.3 kPa and 370.0 K at 300 kPa. The trend of the high-pressure isobar data is consistent with the formation of a second minimum boiling azeotrope, confirming the multiple azeotropic behavior found by others at a higher temperature (398.58 K). Furthermore, the excess Gibbs energy is negative and inflects markedly with composition with increased pressure. The equilibrium behavior and polyazeotropy are discussed in terms of self-association and cross-association of hydroxyl and amino groups. The data were satisfactorily correlated using the Margules equation, the UNIQUAC model modified for association, and the Wisniak−Tamir equation.