Liquid chromatography as a novel method for determination of the dispersion of supported Fd particles

Kiraly, Zoltan
Mastalir, Agnes
Csaszar, Agota
Demir, Hilal
Üner, Deniz
Findenegg, Gerhard H.
A solution-based method has been developed for determination of the number of active centers on Pd particles responsible for alkene hydrogenation in the liquid phase. Pd/gamma-Al2O3 was placed in a liquid chromatographic (LC) column, and the CS2 uptake of the catalyst was determined by applying CS2 pulses in methanol solution until surface saturation was attained. The reliability of the LC method was confirmed by quantitative CS2 poisoning of the catalyst in the liquid-phase hydrogenation of styrene to ethylbenzene in methanol solution to give 5.5 +/- 0.3 mol CS2 per 100 mol of total Pd. With the adsorption stoichiometries of Pd/CO = 1 and Pd/H = 1, CO and H-2 adsorption calorimetry furnished DG = 36% for the gas-phase dispersion of the metal. This value is close to the D-TEM = 33% obtained from transmission electron microscopy analysis. With the assumption of Pd/CS2 = 6, gas-phase and liquid-phase dispersion measurements provide mutually consistent results; in this case, the liquid-phase dispersion of the metal is D-L = 33%. However, with the more generally accepted stoichiometry of Pd/CS2 = 2, solution-phase experiments yield D-L = 11%. This result implies that the number of exposed metal atoms determined from chemisorption experiments at the solid-gas interface is not equivalent to the number of catalytically active surface sites at the solid-liquid interface. (c) 2006 Elsevier Inc. All rights reserved.


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Atalik, B.; Üner, Deniz (Elsevier BV, 2006-07-25)
In this study, the effect of particle size on the reaction rate and selectivity of preferential oxidation of CO (PROX) reaction was investigated on 2 wt% Pt/-Al2O3 catalysts prepared by an incipient wetness technique. The particle size of the catalysts was modified by calcination temperature and duration. CO oxidation and preferential CO oxidation reaction were studied on these catalysts at lambda = 2 (P-O2/P-CO) = 1. The CO oxidation reaction activation energy decreased with increasing particle size, consi...
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The interaction of hydrogen on potassium promoted catalysts prepared by both sequential and co-impregnation methods was studied by proton NMR spectroscopy. Potassium addition decreased the amounts of both hydrogen adsorbed on the metal (site blocking) and the support hydroxyl groups. No evidence for a ruthenium-mediated (through-metal) electronic interaction between potassium species and adsorbed hydrogen was found. During catalyst preparation, potassium was incorporated on the support by an exchange with t...
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ARIK, Enis; Altan, Hakan; Esentürk, Okan (American Chemical Society (ACS), 2014-05-01)
Investigation of frequency dependent permittivity of mixture solutions provides information on the role of intermolecular interactions on relaxation processes of solvent and solute molecules. In this study the dielectric properties of ethanol/gasoline mixtures in the terahertz spectral region are investigated. Frequency dependent absorption coefficients, refractive indices, and complex permittivities of pure ethanol and gasoline, and their mixtures at varying ethanol volume percentages (v/v %) are reported....
Self-sustained oscillatory behavior of NO+CH4+O-2 reaction over titania-supported Pd catalysts
OZKAN, UMIT; KUMTHEKAR, MAHESH; Karakaş, Gürkan (Elsevier BV, 1997-10-01)
Self-sustained, regular oscillations were observed in NO + CH4 + O-2 reaction over Pd/TiO2 catalysts at specific temperatures and oxygen concentrations. The oscillatory behavior was investigated combining NO reduction and methane combustion reaction studies with additional catalyst characterization experiments performed under controlled atmospheres. The catalyst was prepared using a wet impregnation technique with Pd-acetate as the precursor for palladium. A fixed-bed, flow reactor system was used to perfor...
Üner, Deniz; KING, TS (Elsevier BV, 1995-09-15)
Metal dispersions of silica-supported ruthenium catalysts determined by the standard volumetric chemisorption technique were found to be inaccurate due to irreversible spillover of hydrogen to the support. Direct evidence was obtained via in situ H-1 NMR for an irreversibly bound component of the hydrogen that migrated from the metal to the support on a time scale of tens of minutes or longer at room temperature. It was also shown in this work that hydrogen saturated the surface of the metal particles on a ...
Citation Formats
Z. Kiraly, A. Mastalir, A. Csaszar, H. Demir, D. Üner, and G. H. Findenegg, “Liquid chromatography as a novel method for determination of the dispersion of supported Fd particles,” JOURNAL OF CATALYSIS, pp. 267–271, 2007, Accessed: 00, 2020. [Online]. Available: