Modified α Function for the Peng-Robinson Equation of State To Improve the Vapor Pressure Prediction of Non-hydrocarbon and Hydrocarbon Compounds

On the basis of the available vapor pressures for 59 non-hydrocarbon and hydrocarbon compounds, including heavy alkanes up to n-tritetracontane (n-C43H88), a modified a function for the Peng-Robinson equation of state (PR-EOS) has been developed to more accurately determine the vapor pressure for pure non-hydrocarbon and hydrocarbon compounds, especially heavy components. To balance the characterization of both light and heavy compounds, the Pitzer acentric factor is first redefined in terms of reduced vapor pressure at a reduced temperature of 0.6. In comparison to the evaluated a functions used for the PR-EOS, it is found that the newly developed alpha function with the redefined acentric factor provides a more accurate prediction of vapor pressures with a percentage average absolute deviation of 1.90% and a percentage maximum absolute deviation of 21.22% for the 59 chemical species. In addition, the newly developed alpha function results in the best prediction of the vaporization enthalpy data with an average absolute deviation of 3.92% in comparison to the other existing alpha functions evaluated.

基于59种非烃和烃类化合物（包括直至正四十三烷（n - C43H88）的重烷烃）的现有蒸气压，对彭 - 罗宾逊状态方程（PR - EOS）的a函数进行了修正，以便更准确地确定纯非烃和烃类化合物（尤其是重组分）的蒸气压。为了平衡轻、重化合物的特性，首先根据在对比温度为0.6时的对比蒸气压重新定义了皮策偏心因子。与用于彭 - 罗宾逊状态方程的已评估的a函数相比，发现带有重新定义的偏心因子的新开发的α函数对蒸气压的预测更为准确，对于59种化学物质，其平均绝对偏差百分比为1.90%，最大绝对偏差百分比为21.22%。此外，与所评估的其他现有α函数相比，新开发的α函数对汽化焓数据的预测最佳，平均绝对偏差为3.92%。