کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
62674 47650 2009 6 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Understanding the nature of surface nitrates in BaO/γ-Al2O3 NOx storage materials: A combined experimental and theoretical study
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Understanding the nature of surface nitrates in BaO/γ-Al2O3 NOx storage materials: A combined experimental and theoretical study
چکیده انگلیسی

A combined experimental-theory approach was applied to unambiguously determine the nature of “surface nitrates” in BaO/γ-Al2O3 NOx storage materials. High resolution scanning transmission electron microscopy images reveal that at a low BaO coverage of 2 wt% on γ-Al2O3 monomeric BaO units are present almost exclusively. These molecularly dispersed BaO units are concentrated on the (100) facets of the alumina crystallites, while other facets remain practically BaO-free The results of the density functional theory calculations predicted adsorption geometries for the (BaO)x (x=1x=1 and 2) units. The energetically most favorable BaO monomer and dimer units anchor to pentacoordinate Al3+ sites on the (100) facets of γ-Al2O3 in such geometries that maximize their interactions with the support surface. The calculated vibrational frequencies of the energetically most favorable nitrate species formed upon the interaction of NO2 with the monomeric and dimeric BaO units agree remarkably well with those observed experimentally by infrared spectroscopy and identified as “surface nitrates.”

A combined experimental–theory investigation showed that isolated (BaO)x (x=1x=1 or 2) species interact strongly with Al3+penta on γ-Al2O3(100) surfaces and react with NO2 to form surface nitrates with characteristic vibrational spectra.Figure optionsDownload high-quality image (73 K)Download as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 261, Issue 1, 1 January 2009, Pages 17–22
نویسندگان
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