(53f) Multi-Property Optimization of Vapor Pressure, Heat of Vaporization, and Liquid and Ideal Gas Heat Capacities

Vapor pressure, heat of vaporization, liquid heat capacity, and ideal gas heat capacity can be measured for pure organic compounds between the triple point and critical point. Additionally, these properties can be connected using temperature derivatives of thermodynamic relationships which provides an avenue to check consistency among data sets. These relationships and experimental data were compared for several compounds to fill gaps in available data and increase consistency amongst these properties. Liquid heat capacity data have been used to improve low temperature vapor pressure [1], but a methodology for assessing the thermodynamic consistency amongst data sets and optimizing the accepted property values has been further developed [2] so that this procedure can be applied to compounds for which there are fewer experimental data available. The process involves critically evaluating available experimental data and critical point predictions, manipulating the correlating vapor pressure equations, and improving low temperature ideal gas heat capacity correlations to improve accuracy of triple point pressure, low temperature vapor pressure, low temperature heat of vaporization, and high temperature liquid heat capacity in particular. The various data are weighted based on their accuracy and on the perceived relative importance of the properties in process design. This process achieves better thermodynamic consistency than fitting experimental data for each property independent of its relationship to the others.

[1] Poling, B.E., J.M. Prausnitz, and J.P. O'Connell, The Properties of Gases and Liquids. 5^thed. 2001: McGraw-Hill.

[2] J.W. Hogge, R. Messerly, N. Giles, T. Knotts, R. Rowley, W.V. Wilding, â??Improving Thermodynamic Consistency among Vapor Pressure, Heat of Vaporization, and Liquid and Ideal Gas Isobaric Heat Capacities Using Multi-Property Optimizationâ? Fluid Phase Equilibria, 2015.