Methane Activation and Catalytic Ethylene Formation on Free Au_2~+

摘要

Practical interest in the catalytic activation and conversion of methane into valuable products, such as methanol, formaldehyde, or light olefins, and in particular ethylene, is driven by industrial and economical considerations, and has motivated extensive research aimed at the identification and development of heterogeneous catalyst materials for these processes. However, the required high reaction temperatures and/ or the use of highly active reactants to activate the stable O-H bond of methane (bond dissociation energy 440 kJ mol~(-1)) renders a selective synthesis of the desired products difficult. As pointed out in a recent Review, the selective catalytic functionalization of C(sp~3)-H bonds in general poses a longstanding central problem in organometallic chemistry which is still unsolved. The complexity of these processes suggests that molecular-level insights into the methane-activation mechanism would be necessary for a successful formulation and implementation of versatile and selective catalytic reaction routes. Toward this goal we have embarked on a joint experimental and theoretical investigation of free metal clusters as catalytic model systems, with the expectation that these judiciously selected systems will allow us to gain fundamental understanding of the pertinent catalytic processes, while alleviating some of the complications that accompany other model systems, particularly supported catalysts.