(179b) Application of COSMO-SAC and Molecular Simulation to An Industrially Important Pentenary System

Vrabec, J. - Presenter, University of Paderborn
Hsieh, C. M., University of Paderborn
Merker, T., University of Kaiserslautern
Lin, S. T., National Taiwan University
Hasse, H., University of Kaiserslautern

The oxidation of cyclohexane to cyclohexanol and cyclohexanone is an important industrial reaction and a key step in the nylon production chain. A novel route is to use supercritical carbon dioxide to expand the reactive liquid, which enhances the mobility of both the reactants and the products, to obtain a higher conversion rate and a better yield. However, the available experimental phase equilibrium data base for the design of carbon dioxide expanded oxidation processes is very narrow, especially for high pressure multicomponent systems. In this work, experimental measurements were carried out to broaden this data base, however, the number of independent variables is too large to fully explore the relevant range of states experimentally. Therefore, it is important to study the descriptive and predictive capabilities of thermodynamic models. In this presentation, three theoretical approaches, i.e. molecular simulation, the Peng-Robinson equation of state (PR EOS) and COSMO-SAC, were investigated in a comprehensive study with respect to fluid phase coexistence data of an industrially important pentenary mixture. Overall, the PR EOS provides the poorest performance, while both molecular simulation and COSMO-SAC yield good and similar results. Both molecular simulation and COSMO-SAC are capable to predict multicomponent VLE with an excellent accuracy, if one state-independent binary parameter is introduced. Moreover, it was found that improvements are necessary, especially when no experimental binary data are available. In a strictly predictive mode, deviations of up to 50% in terms of the vapor pressure or the Henry’s law constant were encountered for some systems. The presented data and models can be used for the optimization of the reaction conditions for the oxidation of cyclohexane in carbon dioxide expanded liquids.