Phase equilibria of glycerol containing systems and their description with the Cubic-Plus-Association (CPA) Equation of State

Abstract Biodiesel is nowadays in Europe the most used biofuel for road transportation. During its production, different separation and purification processes are required for the glycerol rich streams such as the recovery of the unreacted alcohol and the removal of water. The adequate design of the recovery and purification steps requires the knowledge about the vapour–liquid equilibria data for water + glycerol and alcohol + glycerol systems that are surprisingly scarce. To overcome this lack of information, experimental measurements for 5 alcohol + glycerol systems were performed. These data were used to evaluate the capability of the Cubic-Plus-Association Equation of State (CPA EoS) to model systems containing glycerol. To achieve a good description of the experimental data a new association scheme is proposed for the glycerol molecule. It is shown that a very good description of the VLE data with average deviations inferior to 1% for the bubble point temperatures is obtained. Two different cross-associating combining rules were tested with similar results. Furthermore the predictive performance of the model is evaluated for multicomponent systems. Good liquid–liquid equilibria predictions are obtained for the ternary system methanol + glycerol + methyl oleate at four different temperatures.

[1]  Renzo Di Felice,et al.  Component Distribution between Light and Heavy Phases in Biodiesel Processes , 2008 .

[2]  Robert O. Dunn,et al.  Low-temperature properties of alkyl esters of tallow and grease , 1997 .

[3]  M. Michelsen,et al.  Application of the Cubic-Plus-Association (CPA) Equation of State to Cross-Associating Systems , 2005 .

[4]  A. Kleinová,et al.  Cold Flow Properties of Fatty Esters , 2007 .

[5]  E. Weidner,et al.  Biodiesel-Transesterification of Biological Oils with Liquid Catalysts: Thermodynamic Properties of Oil−Methanol−Amine Mixtures , 2005 .

[6]  Stanley H. Huang,et al.  Equation of state for small, large, polydisperse, and associating molecules , 1990 .

[7]  João A. P. Coutinho,et al.  Prediction of Water Solubility in Biodiesel with the CPA Equation of State , 2008 .

[8]  A. McAloon,et al.  A process model to estimate biodiesel production costs. , 2006, Bioresource technology.

[9]  M. Michelsen,et al.  Ten Years with the CPA (Cubic-Plus-Association) Equation of State. Part 1. Pure Compounds and Self-Associating Systems , 2006 .

[10]  I. Marrucho,et al.  Modeling the Liquid−Liquid Equilibria of Water + Fluorocarbons with the Cubic-Plus-Association Equation of State , 2007 .

[11]  E. Beckman,et al.  Prediction of liquid-liquid equilibria in ternary mixtures from binary data , 1994 .

[12]  M. Michelsen,et al.  High-pressure vapor-liquid equilibria of systems containing ethylene glycol, water and methane - Experimental measurements and modeling , 2007 .

[13]  S. Suresh,et al.  Multiphase equilibrium analysis via a generalized equation of state for associating mixtures , 1992 .

[14]  Esteban A. Brignole,et al.  Phase equilibria in ternary mixtures of methyl oleate, glycerol, and methanol , 2008 .

[15]  I. Marrucho,et al.  Surface tension of chain molecules through a combination of the gradient theory with the CPA EoS , 2008 .

[16]  J. Prausnitz,et al.  Phase Equilibria for Systems Containing Hydrocarbons, Water, and Salt: An Extended Peng−Robinson Equation of State , 1998 .

[17]  E. Voutsas,et al.  Prediction of phase equilibria in water/alcohol/alkane systems , 1999 .

[18]  Yujun Wang,et al.  Liquid–Liquid Equilibrium for Systems of (Fatty Acid Ethyl Esters + Ethanol + Soybean Oil and Fatty Acid Ethyl Esters + Ethanol + Glycerol) , 2008 .

[19]  Galen J. Suppes,et al.  Distribution of methanol and catalysts between biodiesel and glycerin phases , 2005 .

[20]  Michael L. Michelsen,et al.  Physical properties from association models , 2001 .

[21]  S. Sandler,et al.  A Simplified SAFT Equation of State for Associating Compounds and Mixtures , 1995 .

[22]  Peter Englezos,et al.  Prediction of Gas Hydrate Formation Conditions in the Presence of Methanol, Glycerol, Ethylene Glycol, and Triethylene Glycol with the Statistical Associating Fluid Theory Equation of State , 2006 .

[23]  João A. P. Coutinho,et al.  Mutual solubilities of hydrocarbons and water with the CPA EoS , 2007 .

[24]  M. Michelsen,et al.  Liquid-liquid equilibria for binary and ternary systems containing glycols, aromatic hydrocarbons, and water : Experimental measurements and modeling with the CPA EoS , 2006 .

[25]  M. Michelsen,et al.  Application of the Cubic-Plus-Association (CPA) Equation of State to Complex Mixtures with Aromatic Hydrocarbons , 2006 .

[26]  E. Voutsas,et al.  Prediction of Phase Equilibria in Binary Aqueous Systems Containing Alkanes, Cycloalkanes, and Alkenes with the Cubic-plus-Association Equation of State , 1998 .

[27]  Günter Wozny,et al.  Liquid−Liquid Phase Equilibrium in Glycerol−Methanol−Methyl Oleate and Glycerol−Monoolein−Methyl Oleate Ternary Systems , 2006 .

[28]  Bin Liang,et al.  Solubility of Multicomponent Systems in the Biodiesel Production by Transesterification of Jatropha curcas L. Oil with Methanol , 2006 .

[29]  M. Michelsen,et al.  Ten Years with the CPA (Cubic-Plus-Association) Equation of State. Part 2. Cross-Associating and Multicomponent Systems , 2006 .

[30]  P. Englezos,et al.  Vapor−Liquid Equilibrium of Systems Containing Alcohols Using the Statistical Associating Fluid Theory Equation of State , 2003 .

[31]  G. Kontogeorgis,et al.  Multicomponent phase equilibrium calculations for water–methanol–alkane mixtures , 1999 .

[32]  E. Voutsas,et al.  Water/Hydrocarbon Phase Equilibria Using the Thermodynamic Perturbation Theory , 2000 .

[33]  M. Michelsen,et al.  Application of the CPA equation of state to glycol/hydrocarbons liquid-liquid equilibria , 2003 .

[34]  M. Michelsen,et al.  Recent applications of the cubic-plus-association (CPA) equation of state to industrially important systems , 2005 .