Study On Liquid-Liquid Equilibrium Of Oil-water System By Using Solution Thermodynamic Models

Di-isopropyl ether (DIPE), dimethyl carbonate (DMC) have been suggested as gasoline oxygenate, which are usually used as oxygenated gasoline additives to blend with gasoline fuel to improve combustion and reduce particulate emissions and to control the contaminations of condition. This paper studied multicomponent liquid-liquid equilibrium (LLE) properties of DIPE or DMC, pure hydrocarbons, alcohols and water. And give further discussion on phase separation behavior of these fuel additives in oil-water system.Gas chromatograph technique has been applied to determine LLE data for three ternary systems and two quaternary systems at 298.15 K and atmospheric pressure. The ternary systems respectively are below:water+n-propanol+DIPE, water+n-propanol+TMP and water+ n-propanol+DMC; the quaternary systems respectively are below:water+n-propanol+DIPE+ TMP, water+n-propanol+DMC+TMP. Analyzing these LLE data with the distribution coefficient, the main conclusions are as following:The distribution coefficient of DIPE and DMC is small, the solubility in the aqueous phase is also small.The addition of them into gasoline can't lead to water pollution. And the added performances are very good. The addition of the mixture of DIPE, DMC and 1-propanol into gasoline leads to no measurable increase hydrocarbons solubility in water, therefore, it won't cause the potential pollution.The experimental ternary and quaternary LLE data have been satisfactorily precited and correlated by using Modified UNIQUAC and Extended UNIQUAC model, and get the best value interaction parameters. For all the ternary and quaternary systems, the average root-mean-square deviations of correlation obtained by the Modified UNIQUAC model is 0.74% and 0.99%, respectively; the average root-mean-square deviations of correlation obtained by the Extended UNIQUAC model is 1.55% and 1.21%, respectively. The correlated results are in good agreement with the experiment result for all the systems investigated here. These multibody interaction parameters of Modified UNIQUAC model obtained in this work can be applied to predict LLE multicomponent systems.