Study On Multicomponent Liquid-Liquid Equilibrium Properties Of Dimethyl Carbonate

Gasoline additives can enhance the octane rating and reduce pollution effects arising outof the combustion process. Particular interest has focused on dimethyl carbonate (DMC) thatare being considered as oxygnated additives. This paper studied multicomponent liquid-liquidequilibrium (LLE) properties of DMC or MTBE, involving three aspects: Measurement ofaccurate LLE data of ternary and quaternary mixtures of DMC or MTBE, pure hydrocarbons,alcohol and water, further discussion on corresponding application of these LLE data to assessthe performance of these fuel additives in clean gasoline and to design separation process ofchemical engineering.Gas chromatograph technique has been applied to determine LLE data for three ternarysystems and four quaternary systems composed of DMC or MTBE, This method is simple, fast,satisfied repetition, and the accuracy of measurements was estimated within±0.001 in molefractiom. The LLE data for the three ternary mixtures of the water+heptane+toluene, water+DMC+n-heptane and the water+DMC+TMP systems, and the four quaternary mixtures ofthe water+ethanol+DMC+TMP, water+ethanol+DMC+n-heptane, water+DMC+n-heptane+toluene and water+MTBE+TMP+toluene systems have been investigated at298.15 K and atmospheric pressure. Analyzing these LLE data, the main conclusions are asfollowing: the addition of DMC alone to a water+hydrocarbon mixtures leads to nomeasurable increase in different types of hydrocarbons solubility in water, such as paraffin andaromatic which are basis of gasoline, furthermore, the addition of DMC with alcohol evenleads to a decrease in these hydrocarbons solubility in water and a visible decrease in theproportion of alcohol in water phase. In other word, DMC won't cause potential waterpollution of clean gasoline, thus the added performances of DMC are better than that of MTBE.DMC could be considered as a suitable alternative gasoline additive to MTBE, it will havegood value in use in the future.The experimental ternary and quaternary LLE data have been satisfactorily correlated byusing a Modified UNIQUAC model with additional ternary and quaternary interactionparameters. Further, the calculated results obtained from the Modified UNIQUAC model arecompacted with those obtained from the Extended UNIQUAC model. The correlated resultsgiven by the Modified UNIQUAC model are in good agreement with the experiment result forall the systems investigated here. This model and these multibody interaction parametersobtained in this work can be applied to predict LLE properties of complicated fluid mixtures inseparation process.