Hope College Department of Physics and Engineering Research Experiences for Undergraduates Summer 2005 Project Summary

The Antoine equation is attractive to chemical engineers because it is simple and gives good approximations for vapor pressure. However, it requires substance-specific constants which are accurate over a limited temperature range, usually at or below the normal boiling point. More complicated equations of state like Soave-Redlich-Kwong (SRK) may be used to predict vapor pressure over a wide temperature range. Estimates for the Antoine constants as expressions of acentric factor were used to calculate vapor pressures. These were compared to exact SRK vapor pressures for several subranges of reduced temperatures between 0.65 and 1.00. The observed error was less than 0.1 percent, and it varied with temperature and with acentric factor. Analysis of the average value and slope of each error curve led to the derivation of a correction method to further reduce the error. After correction, the method was shown to be accurate to reduced temperatures as low as 0.6, subranges were allowed to become wider, while error decreased below 0.1 percent.

Publications and Presentations:
DeDoes, A.J., Goetz, M.D., and Misovich, M.J., "A Simple Approach to Generalized Vapor Pressure Prediction", Chem Eng. Progr., 103(1), 39-44 (2007).

Misovich, M.J., K.F. Blohm, A.J. DeDoes, M.D. Goetz, E.J. Walsh, and K. Wadelton. "Explicit Phase Equilibrium Calculations from Cubis Equations of State", AIChE Annual Meeting CD-ROM Proc. New York, NY: AIChE. 2005. Results from this work have been presented at the AIChE Annual Meeting for 2005.