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Catalytic performances of ceria and ceria-zirconia materials for the combustion of diesel soot under NOx/O2 and O2. Importance of the cerium precursor salt

Paper ID Volume ID Publish Year Pages File Format Full-Text
40859 45868 2012 7 PDF Available
Title
Catalytic performances of ceria and ceria-zirconia materials for the combustion of diesel soot under NOx/O2 and O2. Importance of the cerium precursor salt
Abstract

Two different cerium precursors (Ce(NO3)3·6H2O or (NH4)2Ce(NO3)6) and two different calcination temperatures (500 °C or 1000 °C) were used in the synthesis by coprecipitation method of CexZr1−xO2 mixed oxides with three different Ce/Zr ratios (Ce0.8Zr0.2O2, Ce0.5Zr0.5O2 and Ce0.2Zr0.8O2) along with pure cerium and zirconium oxides, obtaining a wide range of oxides with very different textural and structural features. These catalysts were tested for soot combustion in loose-contact mode both under NOx/O2 and O2 atmosphere, pointing out that the choice of the (NH4)2Ce(NO3)6 precursor leads to mixed oxides with better catalytic activity in the two atmospheres proved with regard to the Ce(NO3)3·6H2O precursor. Catalysts with ceria-rich compositions showed better catalytic behaviour than the corresponding zirconia-rich compositions, demonstrating that BET surface area is not the only parameter to be considered for this application, since the catalytic activity of the prepared samples is not proportional to surface area of the solids. Important contribution of the NO2-assisted mechanism exists both to initiate and continue soot combustion under loose-contact mode in NOx/O2, when the ceria-based material produces NO2 at low temperatures (425–450 °C), being the capability of the catalyst to produce NO2 the most important feature to explain the soot combustion. However, this role becomes minor when the ceria-based material produces NO2 at higher temperatures. Under O2, in a loose-contact situation, a good Zr-insertion into the lattice affects positively to the soot combustion activity.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (195 K)Download as PowerPoint slideHighlights► We report new insights into the role of NO2 and active oxygen in the soot combustion. ► It is possible active-oxygen transfer from a catalyst (submitted to a high temperature calcination) to the soot. ► The degree of contact among soot and catalyst and the presence of NOx are crucial to explain the order of activity.

Keywords
Catalyst; Ceria-zirconia mixed oxide; Soot combustion; NO2; Active oxygen
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Catalytic performances of ceria and ceria-zirconia materials for the combustion of diesel soot under NOx/O2 and O2. Importance of the cerium precursor salt
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 437–438, 26 September 2012, Pages 166–172
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us