State-of-the-Art in Process Enthalpy and Free Energy Calculations

Enthalpy, entropy, and heat capacity calculations are critical to the chemical industry, particularly for process design, safety, chemical reactions, and catalysis. In this presentation, we describe the state-of-the-art methodologies to calculate these quantities for use in process simulations. Typical methods in industrial practice for estimation of ideal gas properties based on atomic and group contribution theories will be discussed, with a focus on the workhorse Benson method. The uncertainties, successes, and failures associated with these empirical approaches will then be compared with predictions using modern computational chemistry methods in the context of industrially relevant examples. An important conclusion of our industrial practice is that regardless of the chosen estimation method, quantities should be calculated using a consistent set of assumptions to take advantage of any available error cancellation or to avoid unneeded propagation of errors.