期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 122, 期 24, 页码 12850-12863出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.8b03186
关键词
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资金
- Bulgarian National Science Fund [DN 19/2]
- Technical Research Council of Turkey (TUBITAK) (BAS) [32-33-41/25.11.2015, 215M170]
- Ministry of Development of Turkey [DPT2006K-120470]
Surface chemistry and the nature of the adsorbed NOx species on a Pt/CeO2- ZrO2/Al2O3 catalyst were investigated by IR spectroscopy, X-ray diffraction, H-2-temperature programmed reduction, and NOx-temperature programmed desorption. Parallel studies were also carried out with benchmark samples such as CeO2/Al2O3, ZrO2/Al2O3, CeO2-ZrO2/Al2O3 and Pt-supported versions of these materials. All samples were studied in their reduced and nonreduced forms. The use of CO as a probe molecule revealed that during the synthesis of the mixed-metal oxide systems, deposited zirconia preferentially interacted with the alumina hydroxyls, while deposited ceria was preferentially located at the Lewis acid sites. Despite the limited extent of Zr4+ ions incorporated into the CeO2 lattice, the reduction of ceria was promoted and occurred at lower temperatures in the presence of zirconia. When deposited on ZrO2/Al2O3, platinum formed relatively big particles and existed in metallic state even in the nonreduced samples. The presence of ceria hindered platinum reduction during calcination and yielded a high platinum dispersion. Subsequent reduction with H-2 led to the production of metallic Pt particles. Consequently, NO adsorption on nonreduced Pt-containing materials was negligible but was enhanced on the reduced samples because of Pt-0-promoted NO disproportionation. The nature of the nitrogen-oxo species produced after NO and O-2 coadsorption on different samples was similar. Despite the high thermal stability of the NOx adsorbed species on the ceria and zirconia adsorption sites, the NO reduction in the presence of H-2 was much more facile over Pt/CeO2 ZrO2/Al2O3. Thus, the main differences in the NO reduction functionalities of the investigated materials could be related to the ability of the catalysts to activate hydrogen at relatively lower temperatures.
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