Measurements Of Multicomponent Liquid-Liquid Equilibrium For Fuel Additives

Branched ethers such as methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE) have been the subject of numerous investigations in the recent years because of their anti-knock properties and relatively low cost that make them good candidates to be used as additives in lead free gasoline. These fuel additives can reduce air pollution HC from petrol-engine as well as being substitution of the lead and some aromatics hydrocarbon. As the used mostly ether of fuel additives in present, MTBE has the drawbacks of easily dissolving in water and of difficult removal from water. These facts have promoted research on the possible use of ethers higher molecular weights, harmless for the environment. DIPE as another branched ether is excellent than ethyl tert-methyl butyl ether (ETBE) or TAME, for it is effective in reducing automotive CO emissions and has been considered a good alternative to MTBE as an oxygenated additive. And the resources of DIPE are easier obtained than MTBE. There is a considerable current interest to study the liquid-liquid equilibrium (LLE) and vapor-liquid equilibrium (VLE) of DIPE.To assess the effect of the additives in gasoline reformulation, we need a fundamental knowledge about multi-component phase equilibrium of the mixtures containing these ether compounds. Although many liquid-liquid equilibrium (LLE) investigations of ternary mixtures formed by MTBE or TAME have been made, only a few LLE data of ternary or quaternary mixtures with DIPE were reported. In this work we measured some ternary and quaternary mixtures of DIPE with water, alcohol, hydrocarbon, toluene, MTBE, et al. These systems include three ternary mixtures and four quaternary mixtures. The one ternary mixture formed by DEPE-water-toluene and the four quaternary mixtures formed by water-ethanol-DIPE-toluene, water-methanol-MTBE-DIPE, water-ethanol-MTBE-DIPE and water-toluene-MTBE-DIPE were measured at the temperature 298.15 K and ambient pressure. The other two ternary systems for DIPE-water-iso-octane and DIPE-water-MTBE were measured at different temperature and ambient pressure.We present accurate description of the experimental LLE data of the ternary and quaternary systems by using a modified form of the UNIQUAC model bought forward by Chen Yao et al in 2000 which include additional ternary and quaternary parameters coming from three-body and four-body interactions and a extended UNIQUAC model obtained by Nagata in 1982. The calculated results from modified UNIQUAC model are compared with those obtained from the extended UNIQUAC model. The results indicate the ternary and quaternary LLE data correlated by the modified UNIQUAC model give slightly better agreement with the experimental results than those predicted by the extended UNIQUAC model.