α Function for a Series of Hydrocarbons to Peng−Robinson and van der Waals Equations of State

Abstract

This paper reports estimated coefficients for the α function based on vapor pressure data to a series of 438 components, mainly hydrocarbons, for both van der Waals and Peng−Robinson equations of state (EoS). The α function utilized for the attractive term is the one proposed by Mathias and Copeman in 1983, and it improves the cubic EoS calculations. Accurate vapor-pressure correlations and critical data required for the estimation of the constants were retrieved from two databases, i.e., AIChE DIPPR and the Reid et al. (The Properties of Gases and Liquids; McGraw-Hill: New York, 1987) reference book. The method of calculation is described, and the constants are tested with respect of their representation of thermodynamic properties, mainly in terms of the vapor-pressure deviations. The behavior of density and enthalpy EoS predictions is also evaluated. The estimated coefficients for the α function are reported in the Supporting Information and may be applied as a data bank in a simulator, providing more accurate thermodynamic property calculations in the recommended temperature range, as demonstrated.

Representation of phase equilibria and densities for complex systems using a van der Waals volume translated equation of state with a UNIFAC mixing rule

“…This suitable representation of the vdW EoS has also been observed for 438 components (Chiavone-Filho et al, 2001). …”

Comparative Study between Cubic and non-Cubic Equations of State Using Carnahan-Starling Repulsive Term: Application of Temperature-Dependent Alpha and Beta Functions

“…In these works, the AAD in terms of vapor pressure for various pure compounds are showed and compared to the deviations obtained by Soave [2] and Peng and Robinson Taking to consideration the deviations values obtained using the Eqs. (2), (7) and (8), it is possible to observe a sensible improvement in the results when compared with deviations presented in [2][3], [5], [14], and [24]. This improvement can be attributed to the substitution of original repulsive term in equation (1) by Carnahan-Starling repulsion term, whose theoretical importance and correct representation of intermolecular repulsions behavior in real fluids is confirmed in several works in the literature [6], [13], and [15][16][17][18].…”

“…In the reference [5], as well as in works of Coquelet et al [14] and Chiavone-Filho et al [24], EOS and/or generalized alpha functions are proposed. In these works, the AAD in terms of vapor pressure for various pure compounds are showed and compared to the deviations obtained by Soave [2] and Peng and Robinson Taking to consideration the deviations values obtained using the Eqs.…”

Comparative Study between Cubic and non-Cubic Equations of State Using Carnahan-Starling Repulsive Term: Application of Temperature-Dependent Alpha and Beta Functions

“…In the reference [5], as well as in works of Coquelet et al [14] and Chiavone-Filho et al [24], EOS and/or generalized alpha functions are proposed. In these works, the AAD in terms of vapor pressure for various pure compounds are showed and compared to the deviations obtained by Soave [2] and Peng and Robinson [3] EOSs.…”

“…In these works, the AAD in terms of vapor pressure for various pure compounds are showed and compared to the deviations obtained by Soave [2] and Peng and Robinson [3] EOSs. (To illustrate, methane is accounted as an example and percentage deviations values are showed in [2][3], respectively: in the Nasrifar and Moshfeghian [5], 1.71 % and 2.08 %; in Coquelet et al [14], 1.54 % and 0.70 %; in Chiavone-Filho et al [24] only for Peng and Robinson [3] -2.32 %. )…”