Analysis and prediction of the alpha-function parameters used in cubic equations of state. (14th April 2015)

• Record Type: Journal Article
• Authors: Privat, Romain; Visconte, Maxime; Zazoua-Khames, Anis; Jaubert, Jean-Noël; Gani, Rafiqul
• Is Part Of: Chemical engineering science. Volume 126(2015)
• Page Start: 584
• Page End: 603
• Publication Date: 2015-04-14
• Subjects: Alpha function -- Cubic equation of state -- Twu -- Mathias–Copeman -- Group contribution -- Pitfalls; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2014.12.040
• Languages: English
• ISSNs: 0009-2509

Abstract

Abstract: The performance of two generalized alpha functions (Soave and generalized Twu functions requiring the acentric factor as input parameter) and two parameterizable alpha functions (Mathias–Copeman and Twu) incorporated in cubic equations of state (Redlich–Kwong and Peng–Robinson) is evaluated and compared regarding their ability to reproduce vapor pressure, heat of vaporization, liquid heat capacity, liquid density and second virial coefficient data. To reach this objective, extensive databanks of alpha function parameters were created. In particular, pitfalls of Twu-type alpha functions were evidenced and fixed. A new class of purely predictive alpha functions was derived by applying group-contribution (GC) methods to the prediction of alpha function parameters. The interest of such an approach is discussed and compared to another predictive approach (use of generalized alpha functions coupled with GC methods to predict the acentric factor). Abstract : Graphical abstract: Abstract : Highlights: Various strategies to evaluate α functions (cubic equations of state) are compared. Caloric and vapor–liquid equilibrium data were considered. New group-contribution methods are proposed to predict α -function parameters.