Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution method

خانه / مقاله / Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution method

Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution method

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Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution methodReviewed by رضا فرضی on Apr 29Rating: 5.0Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution methodPrediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution method
Prediction of densities of pure ionic liquids using Esmaeilzadeh-Roshanfekr equation of state and critical properties from group contribution method
Reza Farzi, Feridun Esmaeilzadeh*

Chemical and Petrochemical Engineering Department, Shiraz University, Shiraz, Iran

Journal of Fluid Phase Equilibria, vol. 423, pp.101-108, 2016.
Abstract

In this paper, the group contribution Esmaeilzadeh-Roshanfekr (GC-ER) was used to obtain the group increments for normal boiling point, critical temperature, and critical pressure on the basis of 1775 experimental density data for 294 pure ionic liquids forming 35 groups (28 non-ring groups and 7 group rings) at temperature in the range of 273.15 K to 473.15 K and ambient pressure. The average absolute relative deviation (AARD) of the proposed model is 11.49%. For validating the model, density of 53 ionic liquids were predicted and compared with 520 experimental literature density data at different temperatures and ambient pressure that average absolute relative deviation is 9.33%. Also the accuracy of model was compared with the group contribution-Patel Tejja (GC-PT), group contribution-Peng Robbinson (GC-PR), and the group contribution-Van der Waals (GC-VW) model. The results showd that the error of the model is lower than that of the other equations that assess in this work.

 

Keywords: Ionic Liquids, Density, Critical Properties, Group Contribution Method, Esmaeilzadeh-Roshanfekr Equation of State

 

* Corresponding author at: Department of Chemical and Petrochemical Engineering, Faculty of Engineering, Namazi Square, Shiraz, Iran

E-mail addresses: re.farzi.chem.eng@gmail.com (R.Farzi),

Esmaeil@shirazu.ac.ir (F. Esmaeilzadeh).

  1. Introduction

In recent years, because of unique properties of ionic liquids (ILs) and their useful general and industrial applications, many researchers have been attracting to these new liquids. Actually, ILs are salts with low melting point [1] such that they exist in liquid phase at low. Among interesting properties of these liquids, we can noted high thermal and chemical stability, wide temperature operation range, low vapor pressure, high solubility and thermal conductivity [2]. These liquids are known as new generation of solvents [3] and green solvent [4] that have shown promising results in material synthesis and catalytic processes [3].

ILs have cations and anions in their structure that are next to each other [5]. The properties of an IL are function of the cation and the anion type that exist in its structure and the structure of an IL has direct effect on its physical properties [6]. Correct understanding the physical and chemical properties of ionic liquids is essential in order to use of them in the industrial processes. Among the various physical and chemical properties of ILs, the density is most important property. We will need density directly due to calculation of phase equilibria, heat capacity, viscosity, amount of heat transfer, and phase change of them [7]. The value of density of various ILs reported in a range of 0.5 g cm-3 to 1.65 g cm-3 at temperature of 298 K [8-21]. Number of carbons in structure of ionic liquids affect on their density so that density decreases with increasing molecular weight [22, 23].

With development of knowledge, number of ionic liquids has reached up to 1500 but it is possible to synthesis millions of them due to possibility of combining various cations (with different alkyl branch) with various anions (usually inorganic compound and sometimes organic compound with different alkyl branches) [24]. Therefore, because of the large number of liquids, we need methods to predict properties in different conditions in order to save time and facilitate selection of them in the industrial processes.

At the moment, there is no particular method for predict ionic liquids’ properties and works in this regard are based on the molecular thermodynamic modification and correction in order to achieve equations for ionic liquids [25]. Recently, predictive methods based on quantum chemistry have emerged [26, 27] that using of them is difficult.

Group contribution method is a method for calculating the properties of various materials as pure or in mixture which predicts the properties of given material by using group or atomic increments of groups or atoms that appear in structure of materials. This method is very useful for unknown compounds because we can easily determine their properties only by understanding the structure of them.

One application of this method is calculation of ionic liquids properties. Valderrama et.al, by using group contribution method, calculated the critical properties, normal boiling temperature and acentric factor of 50 ionic liquids [28]. Due to inaccessibility of accurate values of this properties, the accuracy of method was evaluated by density calculation and compared with experimental data gathered from different papers. Results indicate efficiency of the method in order to use it in engineering calculations and equations of state. In another study, Valderrama et.al, by using similar process, calculated critical properties, normal boiling temperature and acentric factor of 200 ionic liquids and their results showed high accuracy [29]. Gardas et.al calculated density of 5 imidazolium-based ionic liquids by using group contribution method and they reported high accuracy based on the experimental density reported by other researcher’s work [30].

The Esmaeilzadeh-Roshanfekr equation of state obtained based on the Patel-Teja equation of state and Peng-Robbinson equation of state that reform these equations especially near the critical areas and offers the better results than these two equations. In this work, the group contribution-Esmaeilzadeh Roshanfekr (GC-ER) was used to obtain the group increments for normal boiling point, critical temperature, and critical pressure on the basis of 1775 experimental density data for 294 pure ionic liquids forming 35 groups (28 non-ring groups and 7 ring groups) at temperature in the range of 273.15 K to 473.15 K and ambient pressure. We shall validate the accuracy of the proposed model. For this reason, density of 53 ionic liquids were calculated by the proposed model in different temperatures and compared with 520 experimental literature data. Also the accuracy of model was compared with the group contribution-Patel Tejja (GC-PT), group contribution-Peng Robbinson (GC-PR), and the group contribution-Van der Waals (GC-VW) model. the results showd that the error of the proposed model is close to the error of the GC-PT and lower than the error of  GC-PR and the GC-VW model.

 

 

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