Setup for periodic-transient catalytic experiments

• Subject Area: Process Engineering, Technical Chemistry
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568916751

Transient catalytic experiments allow the elucidation of reaction mechanisms and provide the data basis for the parameterization of microkinetic models. The experimental challenges lie in the precise quantification of balanceable state variables under realistic reaction conditions, i.e. at higher temperatures and pressures. To overcome these challenges, the instrument allows periodic step experiments to be carried out for heterogeneously catalyzed gas phase reactions, in which the composition of the gas phase and the surface adsorbates can be statistically verified and quantified based on the amount of substance with high temporal resolution. Accordingly, the transient experimental unit (main unit) allows the dosing of flexible gas mixtures in two separate gas lines, which are passed alternately through the reactor in a stepwise manner. Two reactor types are envisaged: A tubular reactor enables spatially resolved sampling from the gas phase along the flow direction and an in situ DRIFTS (diffuse reflectance infrared fourier transform spectroscopy) cell enables the quantification of adsorbed species on the solid catalyst surface. A mass spectrometer (MS) allows the composition of the gas phase to be measured with high temporal resolution, while a Fourier transform infrared spectrometer (FTIR) in combination with the DRIFTS cell monitors the formation dynamics of the surface species. The instrument will primarily be used to further develop the 'Periodic Transient Kinetics' method, which was developed in the applicant's working group. The focus is on the transient quantification of the surface species and the balancing relationship with measurement results of the composition of the gas phase. By combining the profile reactor with the DRIFTS cell, the dynamic behavior along the reaction progress in the profile reactor can also be investigated. The hydrogenation of CO/CO2 to hydrocarbons is chosen as an example reaction. By varying the operating conditions, the chain growth can be adjusted almost continuously, so that the methodology can also be transferred to cases with an additional liquid phase in the future. In addition to the method development focus, the discrimination and parameterization of microkinetic models will also be carried out, which will allow deeper insights into the reaction mechanism. The role of the carrier material and the transport of reactive species via the hetero-contact between the active and carrier material will be the focus of the investigations. Ultimately, the device will also be used to determine the kinetics and capacity of the adsorption of gas species on solid surfaces.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Versuchsanlage für periodisch-transiente katalytische Experimente
• Instrumentation Group: 1120 Spezielle Reaktionsapparaturen (Blitzlicht-, Laser-, Photolyse, Stopped Flow)
• Applicant Institution: Universität Ulm
• Leader: Professor Dr.-Ing. Robert Güttel