Evaluation of Optimal Methods for Critical Properties and Acentric Factor of Biodiesel Compounds with Their Application on Soave–Redlich–Kwong and Peng–Robinson Equations of State

In
this work, different methods capable of estimating some properties
of fatty acid methyl esters (FAMES) and fatty acid ethyl esters (FAEES)
have been evaluated. The results for Tb indicated that the methods of Constantinou and Gani and Marrero
and Gani should be applied for FAMES and FAEES, respectively. The
evaluation of the methods for critical properties and acentric factor
was performed by comparisons between the experimental values and output
values by the Racket–Soave equation. The results indicated
that different packages should be applied for FAMES, FAEES, and hydroxy-esters.
For critical volume estimations, the method of Marrero and Pardillo
should be used for any alkyl ester present in biodiesel. Three versions
of the group contribution (GCVOL) method as well as the Rackett–Soave
equation were employed to estimate pure alkyl esters and biodiesel
density. All these methods showed good results in moderate temperatures,
but only Rackett–Soave is indicated for high temperatures.
A final validation of the chosen packages for critical properties
and acentric factor was performed by applying the estimated values
of these properties on Peng–Robinson and Soave–Redlich–Kwong
equations of state. Additionally, a fully predictive translated volume
methodology has been proposed and presented good accuracy.