Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Ethers are known to be suitable octane enhancers for gasoline whose combustion process is optimized in direct-ignition spark-ignition engines, where the fuel is directly injected in the chamber at pressures up to 20 MPa. To know and predict the thermodynamic behavior of the fluid will be very convenient to study these processes. In this work, we report density experimental data for nine linear and branched ethers (butyl methyl, methyl tert-butyl, butyl ethyl, ethyl tert-butyl, dipropyl, diisopropyl, dibutyl, dipentyl, and diisopentyl) in the pressure and temperature range from 0.1 to 65 MPa and from 283.15 to 333.15 K (for methyl tert-butyl ether the temperature range was 283.15e323.15 K). From our measurements, we studied the effect of temperature and pressure on density by calculating isobaric expansibility and isothermal compressibility. Other properties such as internal pressure and solubility parameter, which describe the degree of cohesion of the molecules, were obtained. We compared the experimental and calculated data with the literature and a good agreement is found. Finally, we modeled the phase and volumetric behavior using two Equations of State: PC-SAFT and CPA. The needed parameters were obtained from literature or by fitting of their vapor liquid equilibrium and density data; several linear correlations for these parameters were found. Both EoS provided similar deviations in the density but PC-SAFT predicted better than CPA the phase equilibrium (saturation pressure and density) and the solubility parameter.