(207b) Vapor-Liquid Equilibrium of a Ternary System Containing Dimethyl Ether (Dme) and Light Hydrocarbons

Recently, dimethyl ether (DME) can be produced directly from water gas, carbon monoxide and hydrogen, by use of a new type catalyst dispersed in some fluids. Considering the molecular structure, the physical properties of DME are similar to those of propane or butane. Then a large amount of DME will be supplied as an alterative fuel for liquefied petroleum gas (LPG) in Japan. However, there are few vapor-liquid equilibrium (VLE) data, especially for the multi-component system containing DME. In this study, a recirculate type apparatus was designed to measure VLE for the ternary system, propane + DME + butane, at 313.15 K. The cell, with the inner volume about 200 cm3, was made of stainless steal. Two windows and an automatic back-pressure regulator were also equipped with the cell. Using the back-pressure regulator, the mixture, of the different composition, can be successively loaded without changing temperature and pressure. The resolutions of the temperature and pressure measurements were 0.01 K and 0.0001 MPa, respectively. The precision of the composition analysis was estimated within 0.001 mole fraction by use of a gas chromatograph equipped with a capillary column. In the measurement, VLE was measure for propane + DME + butane at 313.15 K and 0.8830 MPa. Vapor-liquid-liquid equilibrium (VLLE) was not observed, and VLE was maintained at given temperature and pressure. The VLE was also estimated by using Benedict-Webb-Rubin equation of state with optimized binary parameters. Since the calculation showed a good reproducibility, the VLE, of this ternary system at 313.15 K, were predicted in the whole range of pressure.