Methane　oxidation　using　O-2　over　transition　metal　oxides　often　requires　severe　conditions　(＞500　degrees　C)　to　achieve　detectable　conversion.　In　this　study,　NO　was　used　to　transfer　oxygen　atoms　from　O-2,　through　the　facile　gas-phase　formation　of　NO2　at　moderate　conditions　(0.1　MPa　and　300-400　degrees　C),　to　oxidize　methane　over　silica-supported　transition　metal　oxides　(VOx,　CrOx,　MnOx,　NbOx,　MoOx,　and　WOx).　In　situ　infrared　spectroscopy　measurements　indicated　that　the　reaction　likely　proceeded　by　the　formation　of　surface　monodentate　nitrate　intermediates.　These　nitrate　species　were　formed　by　the　interaction　between　adsorbed　NO2　and　the　supported　metal　oxides.　During　the　reaction,　the　oxides　of　vanadium,　molybdenum,　and　tungsten　formed　formaldehyde　and　CO2,　whereas　the　oxides　of　chromium,　manganese,　and　niobium　produced　only　CO2.　These　results　are　consistent　with　the　known　hydrocarbon　oxidation　chemistry　of　the　metal　oxides.　Contact　time　measurements　on　VOx/SiO2　indicated　that　formaldehyde　was　a　primary　product　and　CO2　was　the　final　product;　conversely,　analogous　measurements　on　MnOx/SiO2　showed　that　CO2　was　the　sole　product.　The　formaldehyde　production　rate　on　VOx/SiO2,　MoOx/SiO2,　and　WOx/SiO2,　based　on　surface　sites　measured　by　high　temperature　oxygen　chemisorption,　compared　favorably　to　oxygenate　production　rates　for　stronger　oxidants　(N2O　and　H2O2)　reported　in　the　literature.　(c)　2021　Elsevier　Inc.　All　rights　reserved.