Tailoring silica-alumina-supported Pt-Pd as poison-tolerant catalyst for aromatics hydrogenation

The tailoring of the physicochemical and catalytic properties of mono- and bimetallic Pt-Pd catalysts supported on amorphous silica alumina was studied. Electron-energy-loss spectroscopy and extended X-ray absorption fine structure analyses indicated that bimetallic Pt-Pd and relatively large monometallic Pd particles were formed, whereas the X-ray absorption near edge structure provided direct evidence for the electronic deficiency of the Pt atoms. The heterogeneous distribution of metal particles was also shown by high-resolution transmission electron microscopy. The average structure of the bimetallic particles (Pt-rich core and Pd-rich shell) and the presence of Pd particles led to surface Pd enrichment, which was independently shown by IR spectra of adsorbed CO. The specific metal distribution, average size, and surface composition of the Pt Pd particles depend to a large extent on the metal precursors. In the presence of NH3 ligands, Pt Pd particles with a fairly homogeneous bulk and surface metal distribution were formed. Also, high Lewis acid site concentration of the carrier leads to more homogeneous bimetallic particles. All catalysts were active for the hydrogenation of tetralin in the absence and presence of quinoline and dibenzothiophene (DBT). Monometallic Pt catalysts had the highest hydrogenation activity in poison-free and quinoline-containing feed. When DBT was present, bimetallic Pt Pd catalysts with the most homogenous metal distribution showed the highest activity. The higher resistance of bimetallic catalysts toward sulfur poisoning compared to their monometallic Pt counterparts results from the weakened metal sulfur bond on the electron-deficient Pt atoms. Thus, increasing the fraction of electron-deficient Pt on the surface of the bimetallic clusters increases the efficiency of the catalyst in the presence of sulfur-containing compounds. (C) 2013 Elsevier Inc. All rights reserved.     «

The tailoring of the physicochemical and catalytic properties of mono- and bimetallic Pt-Pd catalysts supported on amorphous silica alumina was studied. Electron-energy-loss spectroscopy and extended X-ray absorption fine structure analyses indicated that bimetallic Pt-Pd and relatively large monometallic Pd particles were formed, whereas the X-ray absorption near edge structure provided direct evidence for the electronic deficiency of the Pt atoms. The heterogeneous distribution of metal partic...     »

ISI Document Delivery No.: 174JX Times Cited: 1 Cited Reference Count: 66 Yu, Yanzhe Gutierrez, Oliver Y. Haller, Gary L. Colby, Robert Kabius, Bernd van Veen, J. A. Rob Jentys, Andreas Lercher, Johannes A. Jentys, Andreas/D-4622-2009 Jentys, Andreas/0000-0001-5877-5042 Department of Energy's Office of Biological and Environmental Research; EMSL Parts of this research were carried out at the light source facility DORIS III at DESY, a member of the Helmholtz Association (HGF). The authors are grateful to the HASYLAB staff for their kind assistance during the experiments at the beamline X1. A portion of this research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research, and with the support of the EMSL William R. Wiley postdoctoral fellowship. 1 Academic press inc elsevier science San diego     «

ISI Document Delivery No.: 174JX Times Cited: 1 Cited Reference Count: 66 Yu, Yanzhe Gutierrez, Oliver Y. Haller, Gary L. Colby, Robert Kabius, Bernd van Veen, J. A. Rob Jentys, Andreas Lercher, Johannes A. Jentys, Andreas/D-4622-2009 Jentys, Andreas/0000-0001-5877-5042 Department of Energy's Office of Biological and Environmental Research; EMSL Parts of this research were carried out at the light source facility DORIS III at DESY, a member of the Helmholtz Association (HGF). The authors are gr...     »