The　partial　oxidation　of　methane　to　dimethyl　ether　(DME)　was　studied　on　palladium　supported　on　SiO2,　SiO2-ZrO2,　and　ZrO2　at　225-375　&　DEG;C　and　0.1　MPa　using　either　O2　or　a　mixture　of　NO　and　O2　as　the　oxidants.　The　NO　+　O2　mixture　was　more　reactive　than　the　O2　toward　methane,　probably　due　to　the　formation　of　active　surface　nitrate　species.　The　formation　of　DME　on　the　catalysts　was　influenced　by　the　support,　with　the　Pd/ZrO2　catalyst　producing　DME　and　the　Pd/　SiO2　catalyst　producing　only　CO2,　irrespective　of　the　oxidant　used.　The　Pd/SiZrO2　catalyst　formed　DME　only　when　O2　alone　was　used　as　the　oxidant.　For　the　reaction　with　NO　+　O2,　in　situ　Fourier　transform　infrared　(FTIR)　measurements　showed　that　the　partial　oxidation　activity　on　Pd/ZrO2　was　related　to　its　ability　to　form　surface-bridged　nitrate　species,　likely　due　to　the　presence　of　basic　sites.　However,　an　inhibitory　effect　of　basicity　on　CH4　turnover　frequency　(TOF)　was　attributed　to　surface　nitrate-induced　structural　modification　deduced　from　X-ray　absorption　fine　structure　spectroscopy　measurements.　For　the　reaction　with　only　O-2,　the　formation　of　DME　over　Pd/ZrO2　and　Pd/SiZrO(2)was　attributed　to　the　reported　ability　of　ZrO2　to　retain　methoxy　intermediates.　Furthermore,　a　weak　structural　effect　on　the　TOF　observed　with　O2　was　attributed　to　competing　effects　of　decreasing　activity　for　C-H　activation　and　increasing　resistance　to　Pd　oxidation　with　increasing　particle　size.