Strong chemical interaction between PdO and SnO 2 and the influence on catalytic combustion of methane

Abstract

Several palladium-tin oxide (PdO-SnO 2) catalysts were prepared by the impregnation (PdO/SnO 2) and co-precipitation (PdO-SnO 2) methods. Among the catalysts tested, the SnO 2-supported 11 wt.% PdO catalyst prepared by the impregnation method showed the highest conversion at low temperatures. The reduction and adsorption properties of PdO/SnO 2 were quite different from those of PdO/Al 2O 3 and PdO/ZrO 2. X-ray diffraction (XRD) of these catalysts revealed that 10 nm PdO particles were supported on SnO 2 for the impregnated catalysts, while the co-precipitated catalysts were composed of uniform PdO-SnO 2 mixed oxide particles. Even at room temperature, the PdO particles in PdO/SnO 2 were easily reduced to metallic Pd and absorbed H 2 with the H 2/Pd weight ratio of 0.3%. In both PdO/SnO 2 and PdO-SnO 2 samples, adsorption of CO was significantly suppressed because of the interaction between Pd and SnO 2; the metal surface area was difficult to estimate by the CO pulse technique.