Supported Ionic Liquid Phase (SILP) catalyst systems have been successfully applied in continuous gas phase reactions using homogenous catalysts in fixed bed reactors. The homogenously dissolved transition metal complex is immobilized in the thin film of an ionic liquid (IL) dispersed on the high area surface of an inorganic support, thus bridging the gap between homogenous and heterogeneous catalysis.
A technical important reaction is the water gas shift reaction (WGS), what is a key reaction in hydrogen production. Commonly used heterogeneous catalysts only work at high temperatures. However, due to the exothermic reaction, mild conditions are thermodynamically favorable and thus yield higher equilibrium conversions of hydrogen. Werner et al. show the great potential of homogenous catalysis using SILP catalysts for the WGS reaction.
In this work we present a rigorous thermodynamic reaction modeling for this particular reaction. The conversion can only be measured in the bulk gas phase. In order to account for the actual conditions in the reactive IL phase, the phase equilibria of all components are used. The kinetics of the reaction is described by a power law expression, but in comparison to the commonly used concentrations, activities are used for the modeling. Therefore, a consequent thermodynamic description of the kinetics can be achieved. Further, it is possible to predict the equilibrium conversion and use it in the modeling process.
For the validation of the model, we used experimental data sets of two SILP-catalysts systems, [BMMIM][OTf] and [Bu4P][MePO3] with the homogenous catalyst RuCl3 in the temperature range of 370K – 420K. The CO/H2O ratio is varied to obtain the partial orders of the reactants. With the derived model, the WGS reaction can be described properly in both IL.
 Werner, S.,Szesni, N., Bittermann, A., Schneider, M.J., Haerter, P., Haumann, M., Wassescheid, P.; Appl. Catal. A; 277, 70-75, 2010