PdOx/Silicalite-1 Catalyst Prepared by Room Temperature Ozone Treatment: Preparation Chemistry and Catalytic Performance for Methane Combustion

The potential of ozone (O-3) for preparation of supported metal catalyst remained unexplored. In this work, a two-step preparation method comprising ion-exchange and room temperature ozone treatment was developed to prepare a zeolite (silicalite-1) supported palladium catalyst. The fundamental preparation chemistry was examined by diffuse reflectance UV-Vis spectroscopy, IR and Raman spectroscopy, X-ray powder diffraction (XRD), and scanning transmission electron microscopy (STEM). While conventional thermal calcination produced PdOx particles mostly on the external surface of silicalite-1 crystals, ozone treatment produced PdOx clusters mostly within the zeolite crystals. Compared with thermal calcination, room temperature ozone treatment can significantly suppress the migration of palladium species outward to the external surface of the zeolite crystals. PdOx/silicalite-1 catalyst prepared with this method exhibited good catalytic activity and stability for catalytic methane combustion. The methane combustion started at about 250 A degrees C; the T (50) and T (90) (the temperatures at which methane conversion reaches 50 and 90% respectively) were 345 and 403 A degrees C, respectively. The conversion decreased slightly from 100 to 96.1% after 24 h of reaction at 500 A degrees C. Deactivation is due to some growth of PdO crystallite revealed by Raman spectroscopy and still could not be detected by XRD.