In this work, we use gPROMS (PSE, London, UK) to characterize a large number of Arrhenius constants using many sets of liquid-vapor, semi-batch reaction data. The components and phase equilibrium were previously characterized using the electrolyte non-random, two-liquid property method in Aspen Plus (Aspen Technology, Cambridge, MA, USA). Our goal was to determine the reaction constants in a manner consistent with the predefined physical properties and vapor-liquid equilibrium. We encountered several difficulties when developing a gPROMS model that made calls to Aspen properties through the CAPE-OPEN interface. The principal difficulty was that simulating one reaction experiment took 11 minutes of CPU time. For us, this meant that a single parameter estimation run took about nine days. We found that more than 98% of the CPU time was taken up by the liquid-phase property calculations through the CAPE-OPEN interface, such as those for the density and the fugacity coefficient. To work around this problem, we developed empirical expressions fitted to data generated by the property method itself. We implemented these expressions directly in the model code, freeing it from having to make calls to Aspen Properties via the CAPE-OPEN interface. By doing so, we were able to reduce the model run time by more than a factor of 50.

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