Abstract
Palladium precursors and solvents were studied for their effects on the activities of alumina-based palladium catalysts in methane combustion and the resistance of the catalysts to thermal aging. The properties of the catalysts were compared with those of a commercial reference. The palladium precursors were Pd(propionate) 2, Pd(acetate) 2 and Pd(acetyl acetonate) 2 and the solvents were acetone, acetic acid, propionic acid and toluene. Catalysts were prepared by the wet impregnation method. Catalysts were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). The surface areas were measured by Brunauer–Emmett–Teller method (BET). Acidity of the alumina support was measured by NH 3 desorption. Activities of the catalysts in methane oxidation were screened under lean burn conditions. In methane oxidation with fresh catalyst, the best performance was obtained with a combination of Pd(acetate) 2 and acetic or propionic acid. The light-off temperatures of the fresh catalysts (562 K and 557 K, respectively) were slightly lower than the light-off temperature (567 K) of the commercial reference. Differences between the light-off temperatures of the aged and fresh catalysts were least when the catalysts were prepared with Pd(acetyl acetonate) 2 as Pd precursor and in acetic or propionic acid as solvent: +12 K and +18 K, respectively. The corresponding value for the reference was +64 K. For several of the fresh catalysts, conversion in methane oxidation at 623 K was over 90%. A comparison of methane combustion and NH 3 desorption results indicated that acidity of the support material affects catalysts activity.
Published Version
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