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Modeling vapor pressure of fatty acid and fatty acid methyl esters using cubic equations of state
Author(s) -
Joshipura M. H.,
Patel R. J.
Publication year - 2014
Publication title -
asia‐pacific journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.348
H-Index - 35
eISSN - 1932-2143
pISSN - 1932-2135
DOI - 10.1002/apj.1859
Subject(s) - vapor pressure , cohesion (chemistry) , boiling point , chemistry , thermodynamics , cubic function , biodiesel , vapor phase , equation of state , vapor–liquid equilibrium , boiling , fatty acid methyl ester , high pressure , fatty acid , organic chemistry , chromatography , mathematics , physics , mathematical analysis , catalysis
Abstract Biodiesel is one of the most promising alternates to fossil fuels. Production process of biodiesel requires separation of fatty acids (FAs) and their esters from the other products and reactants. This requires the phase equilibrium studies of the FA and their esters. For phase equilibrium study through equation of state (EOS), accurate prediction of vapor pressure is necessary. It was shown that most of the predictive methods fail to estimate acceptable values of vapor pressure. Peng–Robinson EOS was used in the present study to predict the vapor pressure. Proper values of critical properties are required for accurate prediction of vapor pressure through cubic EOS. Obtaining experimental critical properties of FAs and their ester are difficult. Ten methods for the prediction of critical properties were compared, and suitable methods for FA, FAME, and their mixtures were proposed. For accurate prediction of vapor pressure using cubic EOS, one requires suitable cohesion factor model. Predictive cohesion factor models did not perform well; hence, four compound‐specific cohesion factor models were compared. Constants for all the four models for the compound considered were presented, and the models were compared for the accurate prediction of vapor pressure. It was observed that modified Trebble–Bishnoi type of cohesion factor model outperformed other models. Boiling points for pure FA and FAME were obtained with these four models. Prediction of boiling points for real‐world biodiesel was also carried out. Modified Trebble–Bishnoi type model was found to be suitable for predictions of boiling points as well. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.