Üner, Deniz
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 shorter time scale, on the order of minutes. Based on H-1 NMR, optimum conditions for the volumetric chemisorption method were determined in order to alleviate the interference of spillover with measurements of hydrogen uptake on the metal. Ruthenium dispersions obtained from the optimized volumetric chemisorption technique were more accurate and agreed well with the results of the H-1 NMR method. (C) 1995 Academic Press, Inc.


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...
A new and efficient chemoenzymatic route to both enantiomers of alpha '-acetoxy-alpha-methyl and gamma-hydroxy-alpha-methyl cyclic enones
Demir, Ayhan Sıtkı; Findik, H; Kose, E (Elsevier BV, 2004-03-08)
A chemoenzymatic synthesis of both enantiomers of the pharmacologically interesting alpha'-acetoxy-alpha-methyl and gamma-hydroxy-alpha-methyl cyclic enones starting from alpha-methyl-beta-methoxy cyclic enones is reported. Manganese(Ill) acetate-mediated acetoxylation followed by the enzyme-mediated hydrolysis of alpha'-acetoxy enone provides acetoxy enones 1a and 2a and hydroxy enones 1b and 2b with high enantiomeric excesses in good yields. The reduction of the acetoxy and hydroxy enones furnished both e...
Inverse relation between the catalytic activity and catalyst concentration for the ruthenium(0) nanoparticles supported on xonotlite nanowire in hydrogen generation from the hydrolysis of sodium borohydride
Akbayrak, Serdar; Özkar, Saim (Elsevier BV, 2016-12-01)
Ruthenium(0) nanoparticles supported on xonotlite nanowire (Ru(0)/X-NW) were prepared by the ion exchange of Rua* ions with Ca2+ ions in the lattice of xonotlite nanowire followed by their reduction with sodium borohydride in aqueous solution at room temperature. Ru(0)/X-NW show high catalytic activity and long life time in hydrogen generation from the hydrolysis of sodium borohydride with a turnover frequency value up to 305 min(-1) and a total turnover number of 63,100 mol H-2/mol Ru in hydrogen generatio...
Structure sensitivity of selective CO oxidation over Pt/gamma-Al2O3
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...
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. (Elsevier BV, 2007-01-25)
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 ethy...
Citation Formats
D. Üner and T. KING, “OPTIMIZATION OF THE VOLUMETRIC HYDROGEN CHEMISORPTION TECHNIQUE FOR DISPERSIONS OF RU/SIO2 CATALYSTS,” JOURNAL OF CATALYSIS, pp. 60–64, 1995, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/34576.