Comparative evaluation of the Peng-Robinson equation and its variants Mathias-Copeman and Stryjek-Vera, for pure methane in subcritical regime.

Authors

DOI:

https://doi.org/10.21712/lajer.2025.v12.n3.p64-72

Keywords:

Peng-Robinson, Mathias-Copeman, Stryjek-Vera, Methane, Saturation Pressure

Abstract

This study evaluates the Peng-Robinson (PR) equation of state and two variants using the Mathias-Copeman (MC) and Stryjek-Vera (SV) alpha correction functions for pure methane, adopting the Setzmann-Wagner ancillary equations as reference. The formulations were implemented in Python to calculate the saturation pressure , the saturated liquid density , and the saturated vapor density . For , a good visual agreement with the reference is observed, and the mean absolute percentage deviations indicate the best overall performance for MC, followed by SV and then PR, although the differences among the curves are small. For , the models show overestimation at low temperatures, with a progressive reduction of the deviation as temperature increases; PR, MC, and SV exhibit very similar trends, but with large deviations relative to the reference. For , the three models remain close to the reference over most of the interval, with a slight advantage for MC and SV, while PR tends to show somewhat larger deviations, without relevant discrepancies.

Downloads

Download data is not yet available.

Author Biographies

  • Wilson José Feroni, Instituto Federal de Educação do Espírito Santo

    Professor EBTT do Instituto Federal de Educação do Espírito Santo – Ifes, campus Colatina, ES, Brasil  

  • Rita de Cassia Feroni, Federal University of Espírito Santo

    Holds a bachelor’s degree in Mathematics from the Federal University of Espírito Santo, UFES (2007). Also holds a bachelor’s degree in Civil Production Engineering from Faculdade do Centro Leste, UCL (2009), with qualifications as a full Production Engineer and Civil Engineer. Has a master’s degree (2010) and a PhD (2015) in Environmental Engineering from the Federal University of Espírito Santo, UFES. Works in the following interdisciplinary areas, Production Engineering, specifically in Operations and Production Process Engineering, and Sustainability Engineering

  • Oldrich Joel Romero, Federal University of Espírito Santo

    Graduated in Mechanical Engineering from the National University of Engineering, UNI, Lima, Peru (1994). Holds a master’s degree (1999) and a PhD (2003) in Mechanical Engineering from the Pontifical Catholic University of Rio de Janeiro, PUC-Rio. He is a Full Professor at the Federal University of Espírito Santo, Ufes, São Mateus campus, ES. He has been part of the Graduate Program in Energy since 2011 and the Undergraduate Program in Petroleum Engineering since 2008. His main areas of expertise include flow in porous media, enhanced oil recovery, oil lifting, hydrogen transport in pipelines, non-Newtonian fluids, flows with free surfaces and interfaces at the microscale, numerical methods and substrate coating processes. He is the leader of the GPetro research group at CNPq. Faculty sponsor of the SPE-Ufes student chapter. Coordinator of Petroufes. Editor of the Latin American Journal of Energy Research, Lajer. Coordinator of PRH 53/Ufes.

References

CoolProp (2026) ‘Methane fluid properties, CoolProp, fluid properties database’. https://coolprop.org/fluid_properties/fluids/Methane.html (accessed 14 January 2026).

Coquelet, C, Chapoy, A, Richon, D (2004) ‘Development of a new alpha function for the Peng–Robinson equation of state: Comparative study of alpha function models for pure gases (natural gas components) and water–gas systems’, International Journal of Thermophysics. https://doi.org/10.1023/B:IJOT.0000022331.46865.2f

Echeverry, JSL, Acherman, SR, Lopez, EA (2017) ‘Peng-Robinson equation of state: 40 years through cubics’, Fluid Phase Equilibria. http://dx.doi.org/10.1016/j.fluid.2017.05.007

Mathias, PM, Copeman, TW (1983) ‘Extension of the Peng–Robinson equation of state to complex mixtures: Evaluation of the various forms of the local composition concept’, Fluid Phase Equilibria. https://doi. org /10.1016/0378-3812(83)80084-3

NIST (2025) ‘NIST Chemistry WebBook’, U.S. Department of Commerce, National Institute of Standards and Technology. https://doi.org/10.18434/T4D303

Peng, DY, Robinson, DB (1976) ‘A new two-constant equation of state’, Industrial & Engineering Chemistry Fundamentals. https://doi.org/10.1021/i160057a011.

Sharifzadegan, A, Behnamnia, M, Monfared, AD (2023) Artificial intelligence-based framework for precise prediction of asphaltene particle aggregation kinetics in petroleum recovery. Scientific Reports. https://doi.org/10.1038/s41598-023-45685-0

Soave, G (1972) ‘Equilibrium constants from a modified Redlich–Kwong equation of state’, Chemical Engineering Science. https://doi.org/10.1016/0009-2509(72)80096-4

Stryjek, R, Vera, JH (1986a) ‘An improved cubic equation of state’, American Chemical Society. https://doi.org/10.1021/bk-1986-0300.ch027

Stryjek, R, Vera, J H (1986b) ‘PRSV: An improved Peng–Robinson equation of state for pure compounds and mixtures’, The Canadian Journal of Chemical Engineering. https://doi.org/10.1002/cjce.5450640224.

Stryjek, R, Vera, JH (1986c) ‘PRSV2: a cubic equation of state for accurate vapor—liquid equilibria calculations’, The Canadian Journal of Chemical Engineering. https://doi.org/10.1002/cjce.5450640516

Setzmann, U, Wagner, W (1991) ‘A new equation of state and tables of thermodynamic properties for methane covering the range from the melting line to 625 K at pressures up to 1000 Mpa’, Journal of Physical and Chemical Reference Data. https://doi.org/10.1063/1.555898

Turnaoglu, T, Shiflett, MB (2019) ‘110th Anniversary: The first thermodynamic and kinetic analysis of ammonia in imidazolium-based ionic liquids using a gravimetric microbalance’, Industrial & Engineering Chemistry Research. https://doi.org/10.1021/acs.iecr.9b00274

Downloads

Published

11/29/2025

Issue

Vol. 12 No. 3 (2025)

Section

Petróleo e Gás Natural

License

Copyright (c) 2025 Latin American Journal of Energy Research

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

O autor, no ato da submissão do artigo, transfere o direito autoral ao periódico.

How to Cite

Feroni, W.J., Feroni, R. de C. and Romero, O.J. (2025) “Comparative evaluation of the Peng-Robinson equation and its variants Mathias-Copeman and Stryjek-Vera, for pure methane in subcritical regime”., Latin American Journal of Energy Research, 12(3), pp. 64–72. doi:10.21712/lajer.2025.v12.n3.p64-72.