Improved esmaeilzadeh-roshanfekr equation of state for ionic liquids

Document Type

Journal Article

Publication Title





Centre for Sustainable Energy and Resources




Shiraz University


Heidari, S., Esmaeilzadeh, F., & You, Z. (2024). Improved esmaeilzadeh-roshanfekr equation of state for ionic liquids. Ionics, 30(5), 2851-2868.


In this study, the densities of 27 pure components of ionic liquids (ILs) are analyzed using the Esmaeilzadeh-Roshanfekr (ER) equation of state and its modified version (mER EoS). The critical properties necessary for EoS calculations, including Tc, Pc, νc, and , are determined through the fragment contribution-corresponding states (FC-CS) method based on a dataset comprising 3272 experimental data points originating from 128 diverse ILs. The dataset comprises 1222 measurements within the temperature range of 273.15 to 473.15 K at ambient pressure, with 1682 data points collected at ambient temperature and pressures up to 200 MPa. The modified alpha function parameters (m1, m2) and critical compressibility factor ( c) in the mER EoS lead to improved density predictions, reflected in a reduced average absolute deviation. Specifically, the mER EoS achieves an average absolute deviation of 4.62 and 5.99%, showcasing its superior precision over the original ER EoS, which exhibits a deviation of 14.66 and 16.75% at atmospheric and high pressures, respectively. To emphasize the exceptional efficacy of the mER model formulated in this investigation, group increments for 294 varied ILs underwent systematic fitting using the Patel–Teja (GC-PT), Peng-Robinson (GC-PR), and van der Waals (GC-VW) EoS. Through this comparative examination, valuable insights into the outstanding performance of the proposed model were revealed, as evidenced by its notably low AARD of 10.07. Additionally, the mER EoS is tailored for predicting IL densities, introducing global parameters (m1, m2, and c) crucial for accurately capturing the complex thermodynamic behaviors of ILs. To apply the mER EoS effectively, users must obtain the critical temperature (Tc), critical pressure (Pc), and the acentric factor ( ) for a specific IL. Methodologies incorporating group contribution and molecular structure considerations have been devised to estimate these critical parameters, enhancing the practicality and usability of the mER EoS across a wide range of ILs.



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