Direct Coupling of Methane and Carbon Dioxide on Tantalum Cluster Cations

Abstract

Understanding molecular‐scale reaction mechanisms is crucial for the design of modern catalysts with industrial prospect. Through joint experimental and computational studies, we investigate the direct coupling reaction of CH4 and CO2, two abundant greenhouse gases, mediated by Ta1,4+ ions to form larger oxygenated hydrocarbons. Coherent with proposed elementary steps, we expose products of CH4 dehydrogenation [Ta1,4CH2]+ to CO2 in a ring electrode ion trap. Product analysis and reaction kinetics indicate a predisposition of the tetramers for C−O coupling with a conversion to products of CH2O, whereas atomic cations enable C−C coupling yielding CH2CO. Selected experimental findings are supported by thermodynamic computations, connecting structure, electronic properties, and catalyst function. Moreover, the study of bare Ta1,4+ compounds indicates that methane dehydrogenation is a significant initial step in the direct coupling reaction, enabling new, yet unknown reaction pathways.

Dynamics of carbene formation in the reaction of methane with the tantalum cation in the gas phase

“…18 The reaction of methane with the mono-cations of the 5d series is highly efficient and the thermal rates are close to, or on the order of, the collision rate. 15,21,22,26,27 At low collision energies, the main product channel is a species with the formal composition [M,C,2H] + and molecular hydrogen H 2 . Thermodynamic arguments and recent spectroscopic investigations showed that the carbene M]CH 2 is the favoured isomer compared to the carbyne H-M-CH + .…”