The performance of different Ce-modified PdO/ZrO2 catalysts for methane oxidation in lean mixtures
(5000 ppm of CH4) in presence of external water has been studied in this work. Deactivation experiments
carried out in presence of 20,000 ppm of external water showed that water reversibly inhibits the reaction.
However, it was observed that these catalysts can increase their activity in presence of water at low
temperature (350 C).
In order to explain this behaviour, different samples of this catalyst were treated with wet air
(20,000 ppm of H2O for 30 h). After this pre-treatment, their activity and stability for methane combustion
were studied by recording light-off curves for the fresh catalysts and the catalyst after 50 h on stream
for the oxidation of methane at 500 C. As general trend, the hydro-ageing at the lowest temperature
(300 C) leaded to a very active catalyst (similar activity than the parent one), but it was more markedly
deactivated. Hydro-ageing of the catalyst at higher temperatures enhanced its thermal stability.