Pt nanoparticles inside the mesopores of TiO2–MCM-48: synthesis, characterization and catalytic activity for CO oxidation
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TiO2 and Pt nanoparticles were deposited in the channels of siliceous MCM-48 via a sequential incipient wetness-impregnation method employing (NH4)2PtCl4 as platinum source. The resulting composite Pt/TiO2–MCM-48 (1 wt% Pt, ca. 3 wt% Ti) was characterized using XRD, TEM, nitrogen physisorption, hydrogen chemisorption, UV–vis spectroscopy, and XPS; its catalytic activity for CO oxidation was also explored. These data were compared with those of Pt/MCM-48 prepared via an analogous route. The results reveal that the platinum was deposited inside the intact pore system in both cases. It remains inside upon mild reduction but tends to segregate out of the pore system at higher reduction temperatures or during CO oxidation. Both composites were found to be highly active in CO oxidation, with 50% conversion at 460–475 K after activation of the unreduced catalysts in the (net oxidizing) feed. Striking differences in this activation process between Pt/MCM-48 and Pt/TiO2–MCM-48 suggest that the precursor reduction is influenced by an interaction with the TiO2 component in the latter.
KeywordsTiO2 Pore System Conversion Curve Precursor Decomposition Chemisorption Capacity
We acknowledge financial support provided by the Deutsche Forschungsgemeinschaft in the frame of the Sonderforschungsbereich ‘‘Metal-substrate interactions in heterogeneous catalysis’’, SFB 558 (Projects B3 and A3). The authors are grateful to Ms. S. Buse for her help during chemisorption measurements.
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