Partial oxidation of methane into C1-oxygenates:: role of homogeneous reactions and catalyst surface area

The influence of the NO concentration (0-1.0vol.%) in the partial oxidation of methane into C-1-oxygenates (HCHO and CH3OH) and C2+ hydrocarbons was examined. Activity measurements conducted with reactors of different diameter, empty and loaded with high specific area V/SiO2 and/or Ba/SiO2 catalysts revealed clearly that CH4 is activated by O-2 only at moderate temperatures (ca. 823 K) if small amounts of NO are present in the feed stream. The role of NO added is to increase the radicals population in the gas phase and to shift selectivity to oxygen-containing molecules. It was observed that CH3OH is easily oxidised in the presence of a high specific area V/SiO2 redox catalyst. This was not in the case of the non-redox Ba/SiO2 catalyst, for which HCHO and CH3OH yields remain at a level only slightly lower than for the homogeneous reaction. On the contrary, higher yields to HCHO (1.7%) and CH3OH (1.6%) can be achieved at 923 K over a low specific area catalyst. (C) 2001 Elsevier Science B.V. All rights reserved.