Vapor pressures and latent heats of vaporization of Poly(oxymethylene) Dimethyl Ethers (OME_3 and OME_4) up to the vicinity of the critical temperature

摘要

The here investigated Poly(oxymethylene) Dimethyl Ethers (OME3 and OME4) are pressurized and passed into a fused silica microcapillary, located in a heating block. By increasing the system pressure at constant temperature, the saturated vapor pressure is determined optically by detecting bubble or film formation, which indicates the transition from vapor to liquid phase. The therefrom obtained vapor pressure data are not yet available in the archival literature and are thus only compared to extrapolated and simulated data, both based on the same and only available low temperature data set of Richard H. Boyd. The experimental method was validated by measuring the vapor pressure curves up to the critical points of ethanol and 1-octanol. The obtained experimental results are in good agreement with literature data, showing low average absolute deviations of 2.1% (ethanol) and 4.1% (1-octanol). The heats of vaporization of the Poly(oxymethylene) Dimethyl Ethers are derived by the Clapeyron equation. Therein the saturated molar volumes were obtained by the Peng Robinson EOS (for the vapor phase) and the correlation of Rackett, Spencer and Danner (for the liquid phase).