Effects of oxygen species in perovskite catalysts on the partial oxidation of methane in a low temperature plasma bed

초록

Lanthanum-based perovskites have been employed as catalysts for the partial oxidation of methane in a dielectric barrier discharge plasma bed at ambient temperature. The reaction performance could be improved when a perovskite catalyst and non-thermal plasma were simultaneously used. X-ray photoelectron spectroscopy (XPS) analysis determined that the surface oxygen species of the perovskite catalysts were found to play a crucial role. During the activity tests, methane conversion, H2 selectivity, and CO selectivity of LaAlO3 were 12.3%, 20.9%, and 26.3% higher than those obtained in a test with alpha-Al2O3. To elucidate the effects of the lattice oxygen transfer capability on the performance further, Sr-doped LaAlO3 catalysts were also investigated. Owing to the enhanced O2 transfer capability, the H2 selectivity was significantly improved (increased by 18.3%), and the CO selectivity was slightly higher (increased by 1.9%) than that of the original LaAlO3. Density functional theory calculations were also performed to identify the active intermediate species and elucidate the reaction pathways, including the rate-determining step. LaAlO3 showed smaller activation energy (1.54 eV) than that of alpha-Al2O3 (2.89 eV) at rate-determining step, which demonstrated higher catalytic activity of LaAlO3.

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