skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Characteristics of Desulfation Behavior for Pre-Sulfated Pt-BaO/CeO2 Lean NOx Trap Catalysts: The Role of the CeO2 Support

Abstract

The desulfation of pre-sulfated Pt-BaO/CeO2 lean NOx trap catalysts was investigated by H2 TPRX (temperature programmed reaction), in-situ TR-XRD (time-resolved X-ray diffraction) and in-situ S K-edge XANES (X-ray absorption near edge spectroscopy) techniques. Compared with Pt-BaO/Al2O3 materials, the reductive treatment in H2 for a CeO2 supported sample up to 1073 K hardly removes any sulfur species. However, the results of in-situ TR-XRD measurements demonstrate that the quantity of a BaS phase formed on Pt-BaO/CeO2 is much smaller than that on Pt-BaO/Al2O3, implying that the formation of BaS crystallites, which occurs during the reduction from sulfate (SO42-) to sulfide (S2-), is significantly suppressed in the CeO2-supported catalyst. As the desulfation temperature increases under reducing conditions (in H2), the in-situ S XANES spectra show that, compared with alumina-supported samples, the reduction temperature for sulfates (S6+) decreases by about 150 K. Concomitantly, the formation of sulfur species with lower oxidation states (S2- - S4+) is enhanced. The step jump of S XANES spectra before and after desulfation are very similar, implying that the amount of sulfur-containing species removed during the reductive treatment is negligible, in agreement with the results of H2 TPRX. These results suggest that H2S produced by the reduction of BaSO4more » is readily re-adsorbed on the ceria support to form ceria-sulfur complexes (e.g. CeS2). The high affinity of ceria for H2S, combined with the ease of reducibility of the ceria support gives rise to various oxidation states of sulfur after high temperature H2 treatments. Thus, the results of this study clearly show that the ceria support strongly affects the overall desulfation mechanism. The intrinsic role of the ceria support during desulfation, and its effect on the overall NOx storage processes are discussed on the basis of the characterization results obtained here.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
972334
Report Number(s):
PNNL-SA-67217
Journal ID: ISSN 1932-7447; 35404; 19800; 17507; VT0401000; TRN: US201006%%920
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry C, 113(50):21123-21129
Additional Journal Information:
Journal Volume: 113; Journal Issue: 50; Journal ID: ISSN 1932-7447
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; AFFINITY; CATALYSTS; SPECTRA; SPECTROSCOPY; STORAGE; SULFATES; SULFIDES; SULFUR; VALENCE; X-RAY DIFFRACTION; Environmental Molecular Sciences Laboratory

Citation Formats

Kim, Do Heui, Kwak, Ja Hun, Szanyi, Janos, Wang, Xianqin, Li, Guosheng, Hanson, Jonathan C, and Peden, Charles HF. Characteristics of Desulfation Behavior for Pre-Sulfated Pt-BaO/CeO2 Lean NOx Trap Catalysts: The Role of the CeO2 Support. United States: N. p., 2009. Web. doi:10.1021/jp9062548.
Kim, Do Heui, Kwak, Ja Hun, Szanyi, Janos, Wang, Xianqin, Li, Guosheng, Hanson, Jonathan C, & Peden, Charles HF. Characteristics of Desulfation Behavior for Pre-Sulfated Pt-BaO/CeO2 Lean NOx Trap Catalysts: The Role of the CeO2 Support. United States. doi:10.1021/jp9062548.
Kim, Do Heui, Kwak, Ja Hun, Szanyi, Janos, Wang, Xianqin, Li, Guosheng, Hanson, Jonathan C, and Peden, Charles HF. Thu . "Characteristics of Desulfation Behavior for Pre-Sulfated Pt-BaO/CeO2 Lean NOx Trap Catalysts: The Role of the CeO2 Support". United States. doi:10.1021/jp9062548.
@article{osti_972334,
title = {Characteristics of Desulfation Behavior for Pre-Sulfated Pt-BaO/CeO2 Lean NOx Trap Catalysts: The Role of the CeO2 Support},
author = {Kim, Do Heui and Kwak, Ja Hun and Szanyi, Janos and Wang, Xianqin and Li, Guosheng and Hanson, Jonathan C and Peden, Charles HF},
abstractNote = {The desulfation of pre-sulfated Pt-BaO/CeO2 lean NOx trap catalysts was investigated by H2 TPRX (temperature programmed reaction), in-situ TR-XRD (time-resolved X-ray diffraction) and in-situ S K-edge XANES (X-ray absorption near edge spectroscopy) techniques. Compared with Pt-BaO/Al2O3 materials, the reductive treatment in H2 for a CeO2 supported sample up to 1073 K hardly removes any sulfur species. However, the results of in-situ TR-XRD measurements demonstrate that the quantity of a BaS phase formed on Pt-BaO/CeO2 is much smaller than that on Pt-BaO/Al2O3, implying that the formation of BaS crystallites, which occurs during the reduction from sulfate (SO42-) to sulfide (S2-), is significantly suppressed in the CeO2-supported catalyst. As the desulfation temperature increases under reducing conditions (in H2), the in-situ S XANES spectra show that, compared with alumina-supported samples, the reduction temperature for sulfates (S6+) decreases by about 150 K. Concomitantly, the formation of sulfur species with lower oxidation states (S2- - S4+) is enhanced. The step jump of S XANES spectra before and after desulfation are very similar, implying that the amount of sulfur-containing species removed during the reductive treatment is negligible, in agreement with the results of H2 TPRX. These results suggest that H2S produced by the reduction of BaSO4 is readily re-adsorbed on the ceria support to form ceria-sulfur complexes (e.g. CeS2). The high affinity of ceria for H2S, combined with the ease of reducibility of the ceria support gives rise to various oxidation states of sulfur after high temperature H2 treatments. Thus, the results of this study clearly show that the ceria support strongly affects the overall desulfation mechanism. The intrinsic role of the ceria support during desulfation, and its effect on the overall NOx storage processes are discussed on the basis of the characterization results obtained here.},
doi = {10.1021/jp9062548},
journal = {Journal of Physical Chemistry C, 113(50):21123-21129},
issn = {1932-7447},
number = 50,
volume = 113,
place = {United States},
year = {2009},
month = {12}
}