BROWSE

Related Researcher

Author's Photo

Kwak, Ja Hun
Molecular Catalysis lab
Research Interests
  • Heterogeneous catalysis, molecular catalysis, ASlumima, zeolites

ITEM VIEW & DOWNLOAD

Roles of Pt and BaO in the sulfation of Pt/BaO/Al2O3 lean NOx trap materials: Sulfur K-edge XANES and Pt L-III XAFS studies

Cited 16 times inthomson ciCited 16 times inthomson ci
Title
Roles of Pt and BaO in the sulfation of Pt/BaO/Al2O3 lean NOx trap materials: Sulfur K-edge XANES and Pt L-III XAFS studies
Other Titles
Roles of Pt and BaO in the sulfation of Pt/BaO/Al2O3 lean NOx trap materials: Sulfur K-edge XANES and Pt L-III XAFS studies
Author
Kim, Do HeuiKwak, JahunSzanyi, JanosCho, Sung JunePeden, Charles H. F.
Keywords
RAY-ABSORPTION SPECTRA; STORAGE CATALYSTS; EXPOSURE CONDITIONS; REDUCTION CATALYST; GAMMA-ALUMINA; DEACTIVATION; SO2; SPECTROSCOPY; TOLERANCE; OXIDATION
Issue Date
2008-02
Publisher
AMER CHEMICAL SOC
Citation
JOURNAL OF PHYSICAL CHEMISTRY C, v.112, no.8, pp.2981 - 2987
Abstract
The roles of barium oxide and platinum during the sulfation of Pt-BaO/Al2O3 lean NOx trap catalysts were investigated by S K edge XANES (X-ray absorption near-edge spectroscopy) and Pt L-III XAFS (X-ray absorption fine structure). All of the samples studied [Al2O3, BaO(x; x = 8 or 20 wt %)/Al2O3, Pt(2.5 wt %)/Al2O3, and Pt(2 wt %)-BaO(x; x = 8 or 20 wt %)/Al2O3] were pre-sulfated prior to the X-ray absorption measurements. It was found that barium oxide itself has the ability to directly form barium sulfate even in the absence of Pt and gas-phase oxygen. In the platinum-containing samples, the presence of Pt-O species plays an important role in the formation of sulfate species. For the case of the BaO(8)/Al2O3 sample, where the barium coverage is about 0.26 ML, both baria and alumina phases are available for sulfation. S XANES results show that barium sulfates are formed preferentially over aluminum sulfates. When oxygen is absent from the gas phase, the sulfation route that involves Pt-O is eliminated after the initially present Pt-O species are completely consumed. In this case, formation of sulfates is suppressed unless barium oxide is also present. Pt L-III XAFS results show that the first coordination sphere around the Pt atoms in the Pt particles is dependent upon the gas mixture used during the sulfation process. Sulfation under reducing environments (e.g., SO2/H-2) leads to formation of Pt-S bonds, while oxidizing conditions (e.g., SO2/O-2) continue to show the presence of Pt-O bonds. In addition, a reducing environment was found to cause Pt sintering in greater extent than an oxidizing one. This result explains why samples sulfated under reducing conditions had lower NOx uptakes than those sulfated under oxidizing conditions. Therefore, our results provide needed information for the development of optimum practical operation conditions (e.g., sulfation or desulfation) for lean NOx trap catalysts that minimize deactivation by sulfur
URI
Go to Link
DOI
10.1021/jp077563i
ISSN
1932-7447
Appears in Collections:
ECHE_Journal Papers
Files in This Item:
jp077563i.pdf Download

find_unist can give you direct access to the published full text of this article. (UNISTARs only)

Show full item record

qrcode

  • mendeley

    citeulike

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

MENU