Partial oxidation of CH4 using molecular oxygen has been carried out over various commercial silicas and alumina doped silica catalysts using a flow reactor system. Partial oxidation products such as C2H6, C2H4, HCHO, CH3OH, and CO were formed over these catalysts as well as over a quartz reactor only. The presence of Al ions in silica remarkably enhanced the formation Of C2H6, H-2, HCHO, and CO even at low O-2 concentrations. States of Al ions in silica were studied using MAS NMR of Al-27. The results indicated that tetrahedrally coordinated Al(4) ions seem to be present and be isolated in silica. The mechanism of CH4 oxidation is proposed under the heterogeneous participation of O-2 activated on such sites. (c) 2008 Elsevier B.V. All rights reserved.