A catalytic reactor suitable for in situ and operando high energy X-ray scattering studies

The study of heterogeneous catalytic reactions under industrially relevant conditions is crucial for understanding catalyst stability and deactivation mechanisms, and it requires insight into the catalyst structure under operating conditions. However, real-time structural investigations remain challenging due to the demanding reaction environments, often at high temperature and pressure, and in the presence of liquids and high-density gases. In this study, we present the design of a reactor optimized for studies in liquid and gaseous media under commercially relevant conditions, engineered to enable in situ and operando X-ray diffraction measurements at synchrotron facilities. This reactor design integrates key features to facilitate synchrotron studies, such as a packed bed of commercial catalyst that can be combined with a model catalyst, allowing for in situ X-ray analysis while maintaining realistic chemical environments, even in case of using model catalysts. The reactor is optimized to minimize X-ray background while allowing real-time monitoring of catalyst structural evolution alongside simultaneous measurement of reaction parameters and catalytic activity. It enables to study the influence of various operational factors, including temperature, pressure, catalyst position within the bed, and catalyst treatments. Proof-of-concept experiments performed at the ID31 beamline of the European Synchrotron Radiation Facility demonstrate the reactor’s capabilities and the high sensitivity of the in situ measurements for the case of a model Pt/ Al 2 O 3 catalyst during dehydrogenation of a liquid organic hydrogen carrier. Grazing incidence wide-angle and small-angle X-ray scattering, measured quasi-simultaneously, show that the catalyst is structurally stable and suggest adsorbate accumulation. • Reactor design enabling operando XRD at industrial conditions. • Design optimizing reaction environment and X-ray measurement for real-time monitoring. • Grazing incidence X-ray confirm confirms structural stability. • Data suggest LOHC reaction product accumulation on catalyst surface.