Catalytic methane oxidation over Pd supported on nanocrystalline and polycrystalline TiO2, Mn3O4, CeO2 and ZrO2

The catalytic oxidation of methane has been examined over Pd supported on nanocrystalline (n-) and polycrystalline (p-) TiO2, Mn3O4, CeO2 and ZrO2. In all cases the Pd supported on the nanocrystalline oxides performs better on a mass basis than Pd supported on the polycrystalline oxides. Conversion vs temperature curves indicate that n-ZrO2 is more active than p-ZrO2 and that calcining both nZrO(2) and p-ZrO2 at 500 degrees C produces better catalysts than calcining at 280 degrees C. n-CeO2 is a very good catalyst for methane oxidation, while p-CeO2 is not, and Pd supported on n-CeO2 performs much better than bare n-CeO2 and somewhat better than Pd supported on p-CeO2; Pd supported on n-Mn3O4 or p-Mn3O4 does not perform as well as CeO2-supported Pd catalysts. The 5 wt.% Pd/n-ZrO2 catalyst calcined at 500 degrees C performs very well, achieving 100% conversion at 320 degrees C for the reactor conditions used, while 5 wt.% Pd/n-CeO2 exhibits initial activity at the lowest temperature of about 100 degrees C. The best catalyst tested in this study is 30 wt.% Pd/n-TiO2, which achieves 100% conversion at 300 degrees C.