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.本研究对可估算脂肪酸甲酯（fatty acid methyl esters, FAMES）与脂肪酸乙酯（fatty acid ethyl esters, FAEES）部分性质的多种方法开展了系统评估。针对正常沸点（Tb）的评估结果显示，应分别采用康斯坦蒂努与加尼（Constantinou and Gani）法、马雷罗与加尼（Marrero and Gani）法来计算脂肪酸甲酯与脂肪酸乙酯的相关性质。本研究通过对比实验测量值与拉克特-索夫（Racket–Soave）方程的计算输出值，完成了临界性质及偏心因子估算方法的评价。结果表明，针对脂肪酸甲酯、脂肪酸乙酯与羟基酯，需采用不同的计算程序包。在临界体积估算场景下，针对生物柴油中存在的各类烷基酯，应选用马雷罗与帕尔迪略（Marrero and Pardillo）法。本研究采用三种版本的基团贡献体积（group contribution volume, GCVOL）法以及拉克特-索夫方程，对纯烷基酯与生物柴油的密度进行估算。所有方法在中等温度条件下均表现出良好的计算精度，但仅拉克特-索夫方程适用于高温工况。本研究通过将临界性质与偏心因子的估算值代入彭-罗宾逊（Peng–Robinson）与索夫-里德里希-匡（Soave–Redlich–Kwong）状态方程，完成了所选计算程序包的最终验证。此外，本研究提出了一种完全预测型平移体积法，该方法展现出了优异的计算准确性。