Comparative study on methane oxidation over CeO₂, ZrO ₂ and CeO₂-ZrO₂ mixed oxides

Methane oxidation was carried out over CeO₂, ZrO₂ and CeO₂-ZrO₂ solid solution and it has been found that almost total oxidation is favorable over the CeO₂ catalyst but partial oxidation is possible over both ZrO₂ and CeO ₂-ZrO₂ catalysts with a CH₄/O₂ ratio of 2. The CeO₂-ZrO₂ catalyst performed partial oxidation of methane with good activity in the initial stage of the reaction, but it deactivated with time on stream. It is speculated that oxygen vacancies in reduced CeO₂-ZrO₂ solid solution activate CH₄ molecules to produce synthesis gas and O₂ molecules supplied from the reactant will change the oxidation state of Ce from 3+ to 4+ resulting in the catalyst deactivation.