Considerations for Promoting Methane Coupling Reactions

Catalysis Considerations for Promoting Methane Coupling Reactions 

The initial work which promoted interest in conventional heterogeneous catalysis for methane coupling chemistry was first reported in 1982 [56]. In this work, the subject reaction was evaluated using 23 metal oxides supported on a-alumina over the temperature range 500-1000 °C. Methane and oxygen were, however, sequentially introduced into the reaction vessel, suggesting that the overall chemical reaction involved the general Mars-van Krevelen reaction sequence  

CH4 + metal oxide — /2C2H4 + H2O + reduced metal oxide 

Later it was shown that sequential introduction of CH4 and O2 was not necessary to promote methane oxidative dimerization but this could be achieved directly by passing CH4/O2 mixtures over a metal oxide catalyst [57]. Since these early reports, work directed towards investigating the chemical oxidative dimerization of methane has increased with a significant number of papers [58-88] and reviews [89, 90] being published. 

The presence of surface 0 species on catalyst sites has been directly observed using electron paramagnetic resonance (EPR) studies on various metal oxides [108] in heterogeneous reactions using CH4/O2 mixtures, and chemically shown to be active by reaction of methane with metal peroxides [106] which are the dimeric analogs of 0.  

---