Adsorption/desorption studies of NOx on well-mixed oxides derived from Co-Mg/Al hydrotalcite-like compounds

Yu, Jun Jie, Jiang, Zheng, Zhu, Ling, Hao, Zheng Ping and Xu, Zhi Ping (2006) Adsorption/desorption studies of NOx on well-mixed oxides derived from Co-Mg/Al hydrotalcite-like compounds. The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical, B110 9: 4291-4300. doi:10.1021/jp056473f


Author Yu, Jun Jie
Jiang, Zheng
Zhu, Ling
Hao, Zheng Ping
Xu, Zhi Ping
Title Adsorption/desorption studies of NOx on well-mixed oxides derived from Co-Mg/Al hydrotalcite-like compounds
Formatted title  Adsorption/desorption studies of NOx on well-mixed oxides derived from Co-Mg/Al hydrotalcite-like compounds
Journal name The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical   Check publisher's open access policy
ISSN 1520-6106
Publication date 2006
Year available 2006
Sub-type Article (original research)
DOI 10.1021/jp056473f
Volume B110
Issue 9
Start page 4291
End page 4300
Total pages 10
Editor George C. Schatz
Place of publication Washington, D. C., U. S. A.
Publisher American Chemical Society
Collection year 2006
Language eng
Subject C1
291804 Nanotechnology
670799 Other
Formatted abstract

CoxMg3-x/Al hydrotalcite-like compounds (where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) were synthesized by the coprecipitation method and characterized by the XRD and TGA techniques. Incorporation of Co for x = 0.0−3.0 gradually decreased the transformation temperature of the hydrotalcites to the corresponding oxides from 444 to 246 °C and also decreased the surface area from 162.7 to 21.6 m2/g upon calcination at 800 °C for 4 h in air. The resultant oxide was generally composed of a poor MgO phase and a spinel phase, with more spinel phase at higher Co incorporation. The derived oxides were tested as the storage/reduction catalysts for NOx adsorption/desorption. The storage capacity for NOx was highly dependent on the catalyst composition and storage temperature. In general, more NOxwas stored at lower temperature (100 °C) than that at higher temperature (300 °C), and tertiary catalysts (x = 0.5−2.5) stored more NOx than binary catalyst (x = 0.0 or 3.0). The catalytic conversion of NO to NO2 and the catalytic decomposition of NOx were observed on the tertiary catalysts during NOx adsorption at 300 °C, which was highly related to the loading of cobalt. The reducibility of catalysts was determined by TPR experiments, and the reduction of cobalt cations started at 150−200 °C in H2. In situ IR spectra of catalysts adsorbing NOx revealed that the major NOx species formed on the catalysts were various kinds of nitrites and nitrates, together with some forms of dimers, such as N2O22- and N2O4(or NO+NO3-). The storage/reduction mechanism and the function of Co in the mixed oxides are proposed and discussed on the basis of these observations.

Keyword Chemistry, Physical
Selective Catalytic-reduction
Lean-burn Engine
Na-y Zeolite
In-situ Ftir
Storage-reduction
Nitric-oxide
Exhaust-gas
Adsorption
Cu
Decomposition
Q-Index Code C1
Additional Notes Publication Date (Web): February 3, 2006

 
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Created: Wed, 15 Aug 2007, 10:30:28 EST