Partial oxidation of methane to hydrogen and carbon monoxide (POM) over a Ni/TiO2 catalyst has been investigated using a fixed-bed reactor. Ni/TiO2 catalyst has high initial activity but undergoes deactivation during POM. Activation of methane on NiTiO2 was studied by employing a pulse reaction technique in the absence of gas phase oxygen. Methane pulse reactions demonstrate that the methane oxidation mechanism changes as the nickel oxidation state changes over NiTiO2. CH4 is efficiently oxidized into CO and H-2 via a direct oxidation mechanism when NiTiO2 is reduced; while CH4 may be converted by a non-selective oxidation process over oxidized Ni/TiO2. (C) 2004 Elsevier B.V. All rights reserved.