(279c) BWR Equation of State for 1-Pentyne and VLE Calculation Concerning Dimethyl Ether

Recently, dimethyl ether (DME) has been paid much attention as a clean fuel. DME has many advantages as a substitute for liquefied petroleum gas (LPG). Sulfur oxides (SOx), and particulate matters (PM) are not produced at the combustion. Infrastructures and equipments for LPG can be used with slight improvements, because physical properties of DME are similar to those of LPG. Generally, tert-Butyl mercaptan (TBM) has been added in LPG as an odorant, for the safty at gas leakage. However, sulfur compounds were not preferable for DME. Then, some alkines have a strong stink similar to that of TBM, and they are expected to be a new odorant for DME. So, the saturated vapor pressure was measured for 1-pentyne by use of a static type apparatus in the temperature range from 233.30 to 463.04 K. Using the same apparatus, P-V-T relationship was measured at 485.00 K. For the practical usage, bubble point pressure was also measured for DME + 1-pentyne at 303.15 K.

In this study, the eight constants in Benedict-Webb-Rubin (BWR) equation of state were optimized for 1-pentyne. Though BWR eq. has been widely used for the prediction of phase equilibrium concerning light hydrocarbon mixtures, the constants have not been available for 1-pentyne. Since the critical temperature and pressure have not yet reported for 1-pentyne, at first, the experimental data of the vapor pressure were correlated with Antoine eq. Then, we can assume that the critical temperature and pressure should be located at the extrapolation of the saturated vapor pressure curve. Using the assumed critical point, the acentric factor was evaluated by its definition. If the critical temperature, the pressure, and the acentric factor were available, the eight constants can be evaluated by applying Joffe's corresponding theory, and Lee-Kesler eq. After P-V-T relationship was calculated, the calculation results were compared with the experimental data. Abovementioned procedures were repeated, until the deviation from the experimental data was minimized.

The calculation results using the optimized constants showed a good reproducibility not only for vapor pressure and P-V-T relationship but for vapor-liquid equilibrium.