1,721,104 research outputs found
Reaction between soot and stored NOX over K-based LNT catalysts investigated by temperature programmed methods and labeling isotopic experiments
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Soot combustion: reactivity of alkaline and earth-alkaline metal oxides in full contact with soot
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Intrinsic reactivity of alkaline and alkaline-earth metal oxide catalysts for oxidation of soot
No full textThe reactivity of selected alkaline (Na, K, Cs) and alkaline-earth (Ca, Ba, Mg) oxide catalysts in the
oxidation of a model soot sample (Printex U) is investigated in this study. With the aim of obtaining
information about the intrinsic reactivity of these elements, samples have been prepared in which the
active elements have been directly deposited on the soot (‘‘full contact’’ conditions). In this way the
reactivity of the catalytic elements is not controlled by the type of contact with the soot. It is found that
the combustion of soot is greatly enhanced by the presence of either alkaline or alkaline-earth oxides,
with Cs and Mg exhibiting the highest and the lowest activity, respectively. Notably, the reactivity in the
soot combustion is found to nicely correlate with the electropositivity of the investigated metal ions, in
line with literature indications pointing out the relevance of the electron-donor characteristics of the
active elements. The correlation between electropositivity and activity in the soot combustion is not
apparent in the absence of a close contact, i.e. under loose contact conditions. Under these conditions it is
suggested that the catalytic activity is governed by the mobility of the surface species, which favors the
soot–catalyst contact. Accordingly the poor performances observed in the case of the alkaline-earth
metal oxides suggest for these elements a poor mobility of the active surface species, as opposite to
alkaline oxide based catalysts showing a high reactivity even under loose contact conditions
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