Abstract
The characterization of Pt/SiO2, Pt/CoOx/SiO2, Pt/MnOx/SiO2, CoOx/SiO2, and MnOx/SiO2catalysts with 5 wt% Pt, 25 wt% MnO2, 50 wt% Co3O4, and 3 wt% Co3O4is described. The Pt/CoOx/SiO2catalyst is particularly active in low-temperature CO oxidation, while the Pt/MnOx/SiO2catalyst is more active in NO reduction by CO than the unpromoted Pt catalyst. The characterization techniques used are (1) X-ray diffraction, to determine the average particle size and possible alloy formation; (2) CO chemisorption, to determine the specific Pt surface area; and (3) Fourier transform infrared spectroscopy, to study the adsorption of CO and NO and the interaction between CO and NO. The influence of a reductive or oxidative pretreatment is also examined. After a reductive pretreatment the high-loaded Pt/50CoOx/SiO2catalyst shows the formation of a PtCo alloy and Co0metal. No alloy formation was detected for the Pt/3CoOx/SiO2catalyst. Fourier transform infrared measurements show the characteristic bands of linearly adsorbed CO on Pt at 2070 cm−1, and linear and bent NO on cobalt oxide at 1870 and 1790 cm−1, respectively. For the high-loaded Pt/50CoOx/SiO2a shoulder at 2023 cm−1is observed and ascribed to CO linearly bound to cobalt metal. An isocyanate band at 2200 cm−1is found for the Pt/3CoOx/SiO2, Pt/50CoOx/SiO2, Pt/MnOx/SiO2, and MnOx/SiO2catalysts on coadsorption of CO and NO.
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