Temporal Analysis of Products (TAP) Reactor Study of the Dynamics of CO2 Interaction with a Ru/g-Al2O3 Supported Catalyst II: Interaction Strength, Formation of Intermediates and Oxygen Exchange

Continuing a comprehensive study of the reduction of COx over supported Ru catalysts, we explored the interaction of CO2 with Ru/g-Al2O3 by TAP reactor measurements, focusing on dynamic aspects in adsorption/desorption, reaction and oxygen exchange processes. Pulse shape analysis in H2/CO2 multipulse sequences provides information on the interaction of reactant/product species with the catalyst. The measurements provide information on the dynamic build-up of reaction intermediates and more stable adspecies during pulsing, and its relation to CH4 formation. Facile oxygen exchange between CO2 and catalyst, followed by isotope labelling experiments, is quantitatively reconciled in a simple model, relating the ratio between different CO2 isotopologues to the 18O : 16O ratio in the total exchangeable oxygen on the surface and in the CO2 pulse. The results provide detailed insight into various aspects of the interaction between CO2 and Ru/Al2O3 catalysts important for a mechanistic understanding of various catalytic reactions involving CO2.