Measurement and modeling of the phase behavior of high-pressure-reaction mixtures and the computation of mixture critical points

We studied the phase equilibria of the reactants and products involved in the allylic epoxidation of trans-2-hexen-1-ol in high pressure carbon dioxide. High pressure experiments were carried out to determine the solubility of each reactant and product in carbon dioxide. The binary phase behavior of each component in carbon dioxide was modeled using the Peng-Robinson equation of state. Multicomponent experiments were performed to determine the solubility of mixtures of products and reactants in carbon dioxide. Modeling was done using only binary interaction coefficients determined in a previous set of experiments. There were differences between the model and actual measurements. To minimize these differences one of the binary interactions coefficients was increased, then better predictions were achieved. Use of pseudocomponent mixtures provided improved predictions of the multicomponent phase behavior. Our implementation for prediction of multicomponent equilibria used a minimal amount of information: the binary interaction coefficients of each reactant and product with carbon dioxide. Exploratory work was done at ultra high pressures to measure and model the volumetric behavior of trans-2-hexen-1-ol.; The last part of our studies dealt with the determination of critical points using interval methods. We were able to determine all the critical points for selected mixtures in reasonable times. No previous implementation provides a mathematical guarantee of finding all the critical points of a mixture. We compared our results to those using other methods and software, and we showed that our implementation arrives to the correct solutions of the cases that were studied. We also present preliminary results of a recent parallel-processing implementation of the critical point program that can solve problems with a larger number of components.