Determination of Intermediates and Mechanism for Soot Combustion with NO^sub x^/O^sub 2^ on Potassium-Supported Mg-Al Hydrotalcite Mixed Oxides by In Situ FTIR

The soot combustion with NO... and/or O... on potassium-supported Mg-Al hydrotalcite mixed oxides under tight contact condition was studied using temperature-programmed oxidation (TPO), isothermal reaction and in situ FTIR techniques. The presence of NO... in O... favors the soot combustion at lower...

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Bibliographic Details
Published in:Environmental science & technology 2010-11, Vol.44 (21), p.8254
Main Authors: Zhang, Zhaoliang, Zhang, Yexin, Su, Qingyun, Wang, Zhongpeng, Li, Qian, Gao, Xiyan
Format: Article
Language:English
Subjects:
Environmental science
Fourier transforms
Nitrates
Nitrogen dioxide
Oxidation
Potassium
Spectrum analysis
Studies
Temperature effects
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Summary:The soot combustion with NO... and/or O... on potassium-supported Mg-Al hydrotalcite mixed oxides under tight contact condition was studied using temperature-programmed oxidation (TPO), isothermal reaction and in situ FTIR techniques. The presence of NO... in O... favors the soot combustion at lower temperatures (300 ...C), which was accompanied by a substantial NO... reduction. The ketene (C=C=O) and isocyanate (NCO...) species were determined as the reaction intermediates. In NO... + O..., NO... directly interacts with the free carbon sites (C=C*) through two parallel reactions: (1) NO... + C=C* ... C=C=O + NO; (2) NO... + C=C* ... NCO... + CO... The two reactions can proceed easily, which accounts for the promotion effect of NO... on soot combustion at lower temperatures. The further oxidation of NCO... by NO... or O... is responsible for the simultaneous reduction of NO... However, the reactions between NO... and C=C* are limited by the amount of free carbon sites, which can be provided by the oxidation of soot by O... at higher temperatures. The interaction of NO... and catalyst results in the formation of nitrates and nitrites, which poisoned the active K sites. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0013-936X