Abstract
A radical route from methane to methanol
The conversion of methane into chemicals usually proceeds through high-temperature routes that first form more reactive carbon monoxide and hydrogen. Agarwal
et al.
report a low-temperature (50°C) route in aqueous hydrogen peroxide (H
2
O
2
) for oxidizing methane to methanol in high yield (92%). They used colloidal gold-palladium nanoparticles as a catalyst. The primary oxidant was O
2
; isotopic labeling showed that H
2
O
2
activated methane to methyl radicals, which subsequently incorporated O
2
.
Science
, this issue p.
223
Methyl radicals generated catalytically from methane with aqueous hydrogen peroxide are converted to methanol with oxygen.
The selective oxidation of methane, the primary component of natural gas, remains an important challenge in catalysis. We used colloidal gold-palladium nanoparticles, rather than the same nanoparticles supported on titanium oxide, to oxidize methane to methanol with high selectivity (92%) in aqueous solution at mild temperatures. Then, using isotopically labeled oxygen (O
2
) as an oxidant in the presence of hydrogen peroxide (H
2
O
2
)
,
we demonstrated that the resulting methanol incorporated a substantial fraction (70%) of gas-phase O
2
. More oxygenated products were formed than the amount of H
2
O
2
consumed, suggesting that the controlled breakdown of H
2
O
2
activates methane, which subsequently incorporates molecular oxygen through a radical process. If a source of methyl radicals can be established, then the selective oxidation of methane to methanol using molecular oxygen is possible.