Study On Multicomponent Liquid-Liquid Equilibrium Properties Of Ethers As Gasoline Additives

Various ethers have been suggested as gasoline additives that either alone or with other ethers or alcohols can enhance the octane rating and reduce pollution effects arising out of the combustion process. Particular interest has focused on methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), ethyl tert-butyl ether (ETBE), diisopropyl ether (DIPE) and other selected ethers that are used or are being considered as oxygnated additives. This paper studied multicomponent liquid-liquid equilibrium (LLE) properties of DIPE or MTBE, involving three aspects: Measurement of accurate LLE data of ternary and quaternary mixtures of DIPE or MTBE, pure hydrocarbons, alcohols and water, further discussion on corresponding application of these LLE data to assess the performance of these fuel additives in clean gasoline and to design separation process of chemical engineering.Gas chromatograph technique has been applied to determine LLE data for three ternary systems and six quaternary systems composed of MTBE or DIPE, This method is simple, fast, satisfied repetition, and the accuracy of measurements was estimated within ±0.0001 in mole fraction. The LLE data for the three ternary mixtures of the water + methanol + DIPE, water + 2-propanol + MTBE and the water + DIPE + n-heptane systems, and the six quaternary mixtures of the water + methanol + DIPE + toluene, water + ethanol + DIPE + n-heptane, water + 2-propanol + DIPE + toluene, water + 2-propanol + DIPE + n -heptane, water + 2-propanol + MTBE + toluene and water + 2-propanol + MTBE + DIPE systems have been investigated at 298.15 K and atmospheric pressure. Analyzing these LLE data, the main conclusions are as following: DIPE is less solubility in water than that of MTBE, and the addition of DIPE alone to a water + hydrocarbon mixtures leads to no measurable increase in different types of hydrocarbons solubility in water, such as paraffin and aromatic which are basis of gasoline, furthermore, the addition of DIPE with other alcohols even leads to a decrease in these hydrocarbons solubility in water and a visible decrease in the proportion of alcohols in water phase. In other word, DIPE won't cause potential water pollution of clean gasoline, thus the added performances of DIPE are better than that of MTBE. DIPE could be considered as a suitable alternative gasoline additive to MTBE, it will have good value in use in the future.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.