Phase equilibria and volumetric properties in binary mixtures containing branched chain ethers (methyl 1,1-dimethylethyl ether or ethyl 1,1-dimethylethyl ether or methyl 1,1-dimethylpropyl ether or ethyl 1,1-dimethylpropyl ether)

The solid-liquid equilibrium (SLE) has been measured above 280 K for eight mixtures of n-alkanes (octadecane, eicosane, docosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane) with methyl 1,1-dimethylethyl ether (MTBE). Experimental results of solubility are compared with values calculated by means of the Wilson, UNIQUAC, and NRTL equations utilizing parameters taken from the SLE. The existence of a solid-solid first-order phase transition in hydrocarbons has been taken into consideration in the solubility calculations. The solubility of hydrocarbons in branched chain ethers is lower than that in n-alkanes but higher than that in cycloalkanes, branched alkanes, 1-alcohols, and tert-alcohols. The best correlation of the solubility data has been obtained by the NRTL equation, where the average root-mean-square deviation of the solubility temperatures is 0.46 K. The liquid-liquid equilibrium (LLE) has been measured between 300 and 360 K for binary mixtures of water with ethyl 1,1-dimethylethyl ether, methyl 1,1-dimethylpropyl ether, and ethyl 1,1-dimethylpropyl ether. The solubility of water in branched chain ether increases with increasing temperature, whereas the solubility of ether in water is decreasing up to 330 K and at the higher temperatures is slightly increasing. The excess molar volumes V-m(E) have been measured at the temperatures 298.15 K and 308.15 K for binary mixtures of hexane, octane, decane, dodecane, tetradecane, hexadecane, cyclohexane, and 1-heptyne with ethyl 1,1-dimethylpropyl ether. The excess molar volumes of all mixtures except for 1-heptyne are positive over the whole composition range. The experimental results have been correlated with the Redlich-Kister polynomial and compared with the results predicted from Prigogine-Flory-Patterson theory. The interchange parameter X-12, which minimized V-m(E) experimental data, was adjusted and then used to predict the heat of mixing.