Elsevier

Journal of Catalysis

Volume 182, Issue 1, 15 February 1999, Pages 48-55
Journal of Catalysis

Regular Article
Platinum-Oxide Species Formed on Progressive Oxidation of Platinum Crystallites Supported on Silica and Silica–Alumina

https://doi.org/10.1006/jcat.1998.2304Get rights and content

Abstract

Samples of platinum crystallites finely dispersed on silica and silica–alumina were prepared by impregnating a series of SiO2–Al2O3supports with aqueous PtCl4solutions. Reduced platinum samples were oxidized by dioxygen to examine variations of platinum-oxides (Pt-Ox) species formed with the oxidation temperature (TO). Both PtO and PtO2species were verified to coexist on oxidized Pt/SiO2samples according to characterizations by techniques of X-ray photoelectron spectroscopy and temperature-programmed reduction (TPR). TPR spectra of oxidized platinum species dispersed on SiO2–Al2O3supports exhibited six peaks of different reduction temperatures (Tr). These peaks were assigned to PtO and PtO2species dispersed in silica-rich grains (Tr=−40 and 20°C, respectively), in alumina-rich grains (Tr=50 and 90°C), and in pores of the grain boundary (Tr=110 and 130°C), respectively. The contribution of these six species varied with both the temperature of oxidation treatments and the Al2O3/SiO2ratio of sample supports.

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