NiMoS/gamma-Al2O3 catalysts: The nature and the aging behavior of active sites in HDN reactions

Karakaş, Gürkan
The work presented in this paper is a continuation of our earlier work aimed at acquiring a fundamental understanding of sulfided Ni-Mo/gamma-Al2O3 catalysts in HDN catalysis, A series of temperature-programmed desorption and reduction experiments were performed over in-situ sulfided bare gamma-alumina support, alumina-supported monometallic Ni, Mo, and bimetallic NiMo catalysts. The TPD and TPR results were linked to the active site assignment of Ni- and Mo-associated centers in HDN reactions. Postreaction XPS and SEM characterizations were performed for catalysts used in HDN for up to 1000 h. One of the major changes during the aging of the Ni-Mo/gamma-Al2O3 catalysts was the loss of some active sites associated with the Ni promoters, The decreased Ni content over the catalyst surface was consistent with the observed decrease in the hydrogenation function of the catalyst. Two possible mechanisms are suggested for the loss of Ni active sites, One is coking that spreads from the alumina support to the nickel sites. Another is segregation of some Ni atoms from the Ni-Mo-S structure due to loss of structural sulfur, (C) 1998 Academic Press.


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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....
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Ab initio potentials are computed for alkali metal cationic partners interacting with He-4 and an overall many-body potential is constructed for each of the ionic dopants in helium clusters. The structures are then obtained via a genetic algorithm approach and results compared with Basin-Hopping Monte Carlo simulations. The classical arrangements are analyzed and quantum effects discussed in comparison with what has been found with Diffusion Monte Carlo calculations. Further corrections to the classical pic...
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The asymmetric synthesis of cis-1,4-amino alcohols with a norbornene backbone was performed starting with (2S,3R)(-)-cis-hemiester 2 (98% ee). Chemoselective amination with NH4OH and HMPTA followed by LAH reduction afforded 5 and 7. respectively. Amido ester 6 was transformed into chiral ligand 9 with Grignard reaction followed by LAH reduction. The chiral ligands 5. 7. and 9 were subjected to asymmetric diethylzinc addition to examine their effectiveness as chiral catalysts. Among these, c chiral ligand 7 ...
Asymmetric synthesis of novel 1,4-aminoalcohol ligands with norbornene and norbornane backbone: use in the asymmetric diethylzinc addition to benzaldehyde
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The asymmetric synthesis of cis-1,4-aminoalcohols with norbornene and norbornane backbone was performed starting with (2S, 3R)-(-)-cis-hemiester 1 (98% ee). Chemoselective amination with HMPTA followed by Grignard reactions and subsequent LAH reductions afforded compounds 5a-d. cis-Hemiester 1 was also transformed into chiral ligands 7a-f and 9a-d with the DCC coupling method followed by LAH reduction using acyclic, heterocyclic amines and various aniline derivatives and p-toluenesulfonamide, respectively. ...
Citation Formats
L. P. ZHANG, G. Karakaş, and U. S. OZKAN, “NiMoS/gamma-Al2O3 catalysts: The nature and the aging behavior of active sites in HDN reactions,” JOURNAL OF CATALYSIS, pp. 457–465, 1998, Accessed: 00, 2020. [Online]. Available: