Catalytic activity of flame-synthesized Pd/TiO2 for the methane oxidation following hydrogen pretreatments
Nafeng Wanga, Fang Niub, Shuhao Wanga, Yun Huanga,*
A nanocatalyst composed of 10 wt% Pd supported on TiO2 was synthesized using one-step flame spray pyrolysis with a highly-quenched premixed stagnation flame. The as-prepared nanoparticles, having a mean diameter of approximately 10 nm, were then subjected to isothermal oxidation and reduction in a fixed bed reactor. The potential roles of Pd and PdO as well as possible synergistic effects between these two active species were explored during methane conversion. The lowest light-off temperature T20 was obtained at a Pd ratio of 53% and this result can be reasonably explained based on a surface Pd–PdO site pair mechanism. Additionally, differences in the hysteresis behavior during methane oxidation were noted throughout a heating–cooling cycle over the temperature range of 200–600 °C, such that the degree of hysteresis was strongly correlated with the Pd ratio.
Catalytic oxidation; Palladium-based catalysts; Flame-assisted spray pyrolysis; Nanoparticles