Derivation of a new cubic equation of state based on partition function for small and large molecules

A three parameter cubic equation of state, EOS, is derived from statistical thermodynamic theoretical stand point using partition function. In this work, generalized Van der Waals theory is used to establish a partition function that considers the effect of density on rotational and vibrational motions. Pure component parameters have been determined for n-alkane series [C1-C8], using vapor pressure data, saturated liquid and saturated vapor volumes and PVT-data. For higher n-alkane, where saturated vapor volume data are not accurate enough or available, determination of the pure component parameters was made by vapor pressure and saturated liquid volume data. The parameters of EOS are correlated with acentric factor. The predicted saturated vapor pressure and saturated liquid density curve near the critical point show that the new equation gives more accurate results than the Sako–Wu – Prausnitz, Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) EOS.

کلیدواژه ها:

Cubic equation of state ، Partition function ، hard sphere ، Hydrocarbons