Liquid–Liquid Equilibrium for Cottonseed Biodiesel + Water + Alcohol (Methanol/Ethanol) Systems at (293.15 and 313.15) K: Experimental Data and Thermodynamic Modeling

Abstract

During the biodiesel production process, generally, two purification steps are performed. The first is a settling process in order to remove the main byproduct (glycerol). Nevertheless, this simple stage is insufficient to achieve purity levels required for commercial specifications. Second, a water washing is used to remove an excess of alcohol and other contaminants. Given the importance of equilibrium data for operation and optimization for liquid−liquid extraction unit operation, the study of liquid−liquid equilibrium (LLE) for methylic cottonseed biodiesel + methanol + water and ethylic cottonseed biodiesel + ethanol + water systems are studied at (293.15 and 313.15) K at atmospheric pressure. LLE data have been quantified by intermediate of two different techniques (titration and densimetric). From these experimental data, distribution coefficients and selectivity have been calculated. As expected, a good extraction capacity of water to remove alcohol has been observed. The reliability of the experimental data has been verified by the correlation proposed by Othmer−Tobias. In order to describe the LLE for the experimental systems studied, three predictive thermodynamic models were used, as follows: UNIFAC, UNIFAC-LLE, and UNIFAC-Dortmund. A root-mean-square deviation (RMSD) has been used as the statistical parameter, and it shows the follow deviations: 3.27 %, 3.62 %, and 4.00 % for the models UNIFAC, UNIFAC-Dortmund, and UNIFAC-LLE, respectively. Therefore, best representation of the LLE systems followed the order: UNIFAC > UNIFAC-Dortmund > UNIFAC-LLE.

Liquid–liquid equilibria for ternary mixtures of water + 2-propanol + 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids at 298.15 K

“…2 Many papers about the LLE containing alcohols and water have been reported recent years [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Some researchers among these papers present the influences of traditional organic solvent on the LLE of alcohols and water [3][4][5][6][7]14].…”

Liquid–Liquid Equilibrium for Ternary Systems of Water + 2,2,3,3-Tetrafluoro-1-propanol + Anisole/1-Octanol at 298.2, 308.2, and 318.2 K

“…The different methods of measurement and procedure or accuracy limitation and the precision of the measurement could result the deviations. 27 The capacity of anisole/1-octanol to extract TFP from aqueous solution is assessed by distribution coefficients (D) 28 and separation factors (S): 29 temperature has an insignificant effect on this system. In addition, the increasing TFP concentration in the aqueous phase led to the increase of the distribution coefficients of which indicates a good consistency of the experimental data in this work.…”

“…The capacity of anisole/1-octanol to extract TFP from aqueous solution is assessed by distribution coefficients ( D ) and separation factors ( S ): where superscripts I and II stand for organic phase and aqueous phase, respectively; w 2 and w 1 denote the mass fractions of TFP and water, respectively. Table and Figures and summarize the corresponding distribution coefficients and separation factors for the studied systems.…”

Ternary Liquid–Liquid Equilibrium of Azeotropes (Water +2-Propanol) with Ionic Liquids ([Dmim][NTf2]) at Different Temperatures

“…Many scholars have studied systems including alcohols and ILs, − and many of them researched the effect of temperature on the extraction power. Some researchers studied systems of alcohols and esters with ILs .…”