Oxidation of Methane to Methanol with Hydrogen Peroxide Using Supported Gold-Palladium Alloy Nanoparticles

摘要

The direct conversion of methane to methanol remains a key challenge. The current commercial production of methanol from methane has been fine-tuned over many decades of operation and gives a high selectivity for the formation of methanol, but involves a high energy input two-stage process. Direct conversion of methane to methanol in a single step would clearly provide many advantages. Catalysts identified that operate at high temperature can give a high methanol selectivity at low conversion. Using milder reaction conditions catalysts do not give closed catalytic cycles. Recently we have shown that CuFe-ZSM-5 is an effective catalyst for the conversion of methane to methanol with a closed catalytic cycle when H2O2 was used as an oxidant. This has prompted us to investigate the use of other catalysts with this oxidant. We have previously shown that supported Au-Pd nanoparticles are highly effective catalysts for the direct synthesis of H2O2, the oxidation of alcohols, and the oxidation of primary C—H bonds in toluene. We consider that all these reactions are linked by the formation of a hydroperoxy intermediate from dioxygen. We considered that a hydroperoxy species may be effective for the oxidation, since it is known that H2O2 or tert-butyl hydroperoxide (TBHP) have been used to oxidize methane. In view of this we have used hydrogen peroxide as oxidant and here we show that Au-Pd supported nanoparticles are active for the oxidation of methane, giving a high selectivity for the formation of methanol, especially when the reaction is carried out in the presence of hydrogen peroxide generated in situ from hydrogen and oxygen.