Study On Multicomponent Liquid-Liquid Equilibrium Properties Of Carbonate Esters As Gasoline Additives

Diethyl carbonate(DEC) is one of the important environmentally benign chemicals.In recently,it was founded that DEC could be used as gasoline additive to replace the traditional gasoline additive methyl tert-butyl ether(MTBE) because of its good anti-knocking property.In this paper,multicomponent liquid-liquid equilibria(LLE) properties of DEC were studied,and the LLE data of ternary and quatemary mixtures which containing DEC with dimethyl carbonate (DMC) or MTBE or heptane or alcohol and water was accurately measured,and the corresponding application of the LLE data to assess the performance of DEC in clean gasoline was discussed.Gas chromatograph technique has been applied to determine LLE data for six ternary systems and five quaternary systems composed of DEC or MTBE.The LLE data for the six ternary mixtures of the water + methanol + DEC,water + ethanol + DEC,water + DEC + heptane,water + MTBE + DEC,water + DMC + DEC and the water +MTBE +heptane systems, and the five quaternary mixtures of the water + ethanol + DEC + heptane,water + ethanol + MTBE + DEC,water + MTBE + DEC + heptane,water + ethanol + DMC + DEC and the water + DMC + DEC + heptane systems have been investigated at 298.15 K and atmospheric pressure. Calculating the distribution coefficients for each component based on the LLE data,and analyzing the effect of DEC on water and gasoline compared with the formers studies,the main conclusions are as following: the addition of DEC alone to a water + heptane mixtures leads to no measurable increase in heptane solubility in water;the addition of DEC with ethanol to a water + heptane mixtures leads to an evident decrease in the intersolubility of water and ethanol,and no measurable increase in heptane solubility in water,it can aviod the phenomenon of phase separation;the addition of DEC with DMC to a water + heptane mixtures leads to a decrease in DMC solubility in water and a decrease in water solubility in oil and no measurable increase in heptane solubility in water; but the addition of DEC with MTBE to a water + heptane mixtures leads to a little increase in MTBE solubility in water;DEC could be considered as a suitable alternative gasoline additive to MTBE in the view of the intersolubility of water and gasoline.The experimental ternary and quaternary LLE data have been satisfactorily correlated by using a Modified UNIQUAC model with additional ternary and quaternary interaction parameters.Further,the calculated results obtained from the Modified UNIQUAC model are compared with those obtained from the Extended UNIQUAC model.The correlated results given by the Modified UNIQUAC model are in good agreement with the experiment result for all the systems investigated here.This model and these multibody interaction parameters obtained in this work can be applied to predict LLE properties of complicated fluid mixtures in separation process.