Studies on The Phase Equilibrium Of Fatty Acids

Abstract

In any of the process separation is the most important step. To separate any substance from mixture, phase equilibrium study is a must. The phase equilibrium study of fatty acids is useful for biodiesel production. For phase equilibrium study through equation of state, proper values of critical properties are required. Moreover for accurate prediction of VLE one also needs to have suitable cohesion factor (alpha function). In the project ten methods for predicting critical temperature and critical pressure and nine methods for predicting acentric factor were used. From these methods best methods were selected by comparing it with reference data available in the literature and they were used to predict vapor pressure data through equation of state. Prediction of vapor pressure using equations of state for Fatty acids and their esters were found to be better compared to other methods such as Ambrose and Reidel methods. Various alpha functions available in the literature were collected and compared based on accurate prediction of vapor pressure. It was found that the component specific alpha function works better compared to generalized alpha function. However, for obtaining compound specific constant one must have vapor pressure data. In present work based on the experimental data a new generalized expression for alpha was developed based on compound specific constant. This expression was found to provide better results compared to available generalized expressions. Oil contains mixture of fatty acids in different composition and biodiesel made from this oil contains esters. The boiling point of oil is an essential property. So, the boiling point of oil was predicted using Equation of state. However, in the absence of the experimental data it was not possible to authenticate the results generated. After predicting vapor pressure data vapor-liquid equilibrium data have been generated for binary system of fatty acids or fatty acid methyl esters with CO2 or methanol. The data of vapor – liquid equilibrium has been also compare with experimental data. It was found the prediction was not as accurate as it should be. Binary interaction parameter for all the system was not considered in the study and that may be the reason for the loss in accuracy. Keywords: Fatty Acid, Fatty acid Methyl Ester (FAME), Critical temperature, Critical pressure, Acentric factor, vapor pressure, VLE, boiling point.