Operando monitoring of Supported Ionic Liquid Phase (SILP) catalysts by microwave-based methods exemplarily investigated for the water gas shift reaction

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Immobilized ionic liquids (ILs) are attractive materials for catalysis, e.g., for the Supported Ionic Liquid Phase (SILP) concept, where the IL that contains a homogeneous catalyst is immobilized on a solid support. The application focuses on the water gas shift (WGS) reaction. For WGS with a Ru-SILP catalyst, the influence of the pore filling degree of the support and the catalyst concentration in the IL on the effective activity has been demonstrated, but is only incompletely understood. Often, the stability of the homogeneous catalyst depends on the feed gas. Thus, Ru nanoparticle formation was observed by the reduction of the metal complex with H2. In technical processes, catalyst deactivation is often observed only by measuring the decrease in activity. Only subsequent investigations of the catalyst (surface, composition, etc.) allow to deduce possible reasons for this. In the envisaged project, the contactless radio frequency (RF)-based operando state monitoring of SILP catalysts for the WGS reaction will be investigated for the first time under process conditions. The WGS reaction was selected, because of its significance (e.g. NH3 synthesis) and because we have already gained good experience with SILP systems. Preliminary studies show that the RF method can be used to diagnose the state of the SILP catalyst. The overall objective is therefore to determine whether and to what extent the non-contact RF method is suitable for continuous process monitoring. The planned investigations base on three pillars: 1) on the preliminary work of the Jess group on the WGS reaction with SILP, 2) on the experience of the Moos group on RF-based state monitoring of exhaust gas catalysts, and 3) on joint work on RF-based water loading detection of SILP gas drying systems. In the project, the dielectric material properties of the support that contains the IL and the catalyst are to be systematically investigated as a function of the pore filling degree and the catalyst loading of the IL. The influence of temperature is also to be taken into account. It should also be clarified how much the dielectric properties of the pure IL differ from those of the SILP and how much the catalytic material influences the dielectric material properties. Accompanying kinetic studies of the WGS reaction are essential. The RF method will eventually be used to establish a relationship between the decrease in catalytic "performance" and changes in RF resonance parameters. This will be used to monitor the SILP catalyst operando. Modeling of the chemical reaction processes and their interactions on the dielectric material parameters is also envisioned. This linkage would allow the processes in the reaction chamber to be understood and quantitatively described with spatial and temporal resolution from the measured RF data.