The role of alkali-metal promotion on CO oxidation over PdO/SnO2 catalysts

Karakaş, Gürkan
Sol-gel prepared PdO/SnO2 and Na-PdO/SnO2 catalysts were investigated by X-ray photoelectron spectroscopy (XPS), diffuse reflectance IR (DRIFTS), temperature-programmed reaction spectroscopy (TPRS) and impulse techniques. Alkali-metal promotion was observed to enhance CO oxidation rate and decreases light-off temperatures of PdO/SnO, XPS analysis revealed that alkali-metal promotion resulted in the segregation of Pd atoms and promoted the oxygen storage capacity of the catalysts. The presence of super-oxide species was also observed over Na-PdO/SnO2 catalyst and the formation of a relatively stable ternary oxide of sodium and palladium (NaxPd3O4) was postulated. Surface titration experiments utilizing pulse technique showed that alkali-metal-promoted sample was able to preserve part of its CO oxidation activity even after reduction pretreatment and that oxygen diffusion from bulk of the catalyst effectively promoted the activity of Na-PdO/SnO2 sample at 150 degrees C.


Effect of hydrogen ion-exchange capacity on activity of resin catalysts in tert-amyl-ethyl-ether synthesis
Boz, N; Doğu, Timur; Murtezaoglu, K; Dogu, G (Elsevier BV, 2004-08-10)
Activities of ion-exchange resin catalysts, having different hydrogen exchange capacities ranging between 5.1 and 1.3 meq H+/g, on the etherification reactions of 2M1B (2-methyl-1-butene) and 2M2B (2-methyl-2-butene) with ethanol were experimentally tested in a fixed bed reactor. These catalysts were prepared by the heat treatment of Amberlyst-15 catalysts at 220 degreesC at different durations of time and also by the synthesis of sulfonated styrene divinyl benzene cross-linked resins. Activity of these cat...
In situ DRIFTS characterization of wet-impregnated and sol-gel Pd/TiO 2 for NO reduction with CH4
Karakaş, Gürkan; Ozkan, Umit S. (Elsevier BV, 2002-05-01)
The adsorption/desorption behavior of 2%Pd/TiO2 catalysts synthesized by wet-impregnation and modified sol–gel techniques were examined in NO–CH4–O2 reaction using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The catalyst prepared by the modified sol–gel method showed significantly higher resistance toward oxygen while maintaining a 100% NO conversion. Under NO+CH4+O2 flow, the main adsorbed NO species was identified as the linearly adsorbed NO on metallic palladium (Pd0–NO)...
Determination of the dispersion of supported Pt particles by gas-phase and liquid-phase measurements
Kivrak, Hilal; Mastalir, Agnes; Kiraly, Zoltan; Üner, Deniz (Elsevier BV, 2009-02-15)
The dispersion of a Pt/gamma-Al2O3 catalyst was investigated by various experimental techniques. The values obtained by gas-phase hydrogen and carbon monoxide adsorption and transmission electron microscopy (TEM) were consistent for the metal:adsorbate stoichiometry of 1:1. However, these methods overestimated the number of active sites available for a liquid-phase reaction. For the hydrogenation of styrene in the presence Of CS2 as a catalyst poison, only the defect sites were found to be active in the cat...
NO oxidation and NOx storage over Ce-Zr mixed oxide supported catalysts
Caglar, B.; Üner, Deniz (Elsevier BV, 2011-02-10)
NO oxidation and NO storage behavior of 1% Pt/10% BaO/CexZr1-xO2 (x=0, 0.25, 0.5, 0.75, 1) catalysts prepared by the Pechini method were investigated via Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) spectroscopy. DRIFTS study revealed that in the presence of Pt/BaO/Ce0.5Zr0.5O2, NO is oxidized to NO2 in the absence of gas phase O-2 at room temperature due to high oxygen mobility in the support material.
Mechanisms of CO oxidation reaction and effect of chlorine ions on the CO oxidation reaction over Pt/CeO2 and Pt/CeO2/gamma-Al2O3 catalysts
Oran, U; Üner, Deniz (Elsevier BV, 2004-12-20)
The reaction orders and activation energies of CO oxidation reaction over Pt/gamma-Al2O3, Pt/CeO2 and Pt/CeO2/Y-Al2O3 were investigated for stoichiometric gas mixtures. The effect of residual chlorine originating from catalyst precursors on the CO oxidation activity of Pt/gamma-Al2O3, Pt/CeO2 and Pt/CeO2/gamma-Al2O3 was also studied. Indirect evidence was collected indicating that platinum was selectively deposited on alumina surface when Pt/CeO2/gamma-Al2O3 catalyst was prepared from the physical mixture o...
Citation Formats
B. MİRKELAMOĞLU and G. Karakaş, “The role of alkali-metal promotion on CO oxidation over PdO/SnO2 catalysts,” APPLIED CATALYSIS A-GENERAL, pp. 84–94, 2006, Accessed: 00, 2020. [Online]. Available: