Effect of support structure on methane combustion over PdO/ZrO2

Abstract

Publisher Summary This chapter investigates Pd supported on zirconia support with different crystal structure for low temperature combustion of methane emphasizing the relationship between active phase and support structure. X-ray diffraction (XRD) patterns show that the thermodynamically metastable t-ZrO 2 remains about 30 at.% when the final catalysts are acquired. On both monoclinic and monoclinic-tetragonal mixed supports, PdO presents no characteristic reflection even when the Pd loading attains 3 wt.%. This implies that PdO fails to aggregate into large crystallite on zirconia support. Further investigation by CO pulse reveals that the dispersion of Pd component on these two zirconia supports is quite different. The monoclinic zirconia evidently promotes the dispersion of palladium component thereon. This is more pronounced on the lower Pd-loading samples. In the case of 0.5wt.% Pd supported on monoclinic zirconia, the dispersion is 23.8%, nearly quadruple the value for the sample supported on t+m type zirconia, of which the specific surface area is even three fold larger than that for the m-type support. The high dispersion of palladium on the less available surface implies a favorable interaction between PdO and m-ZrO 2 .