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Effect of H2O on catalytic performance of manganese oxides in NO reduction by NH3

Paper ID Volume ID Publish Year Pages File Format Full-Text
40856 45868 2012 10 PDF Available
Title
Effect of H2O on catalytic performance of manganese oxides in NO reduction by NH3
Abstract

The effects of H2O on catalytic performance of hollandite manganese oxide (HMO) and β-MnO2 are comparatively studied in selective catalytic reduction of NO by NH3 (NH3-SCR). The results showed that the HMO possessed higher catalytic activity than β-MnO2 in the presence of H2O, and the NH3-SCR reaction occurring on the HMO predominantly followed an Eley-Rideal mechanism via reacting adsorbed NH4+ with gaseous NO. According to the NH3-TPD analyses, XPS results and the HRTEM observations coupled with the theoretical calculations, the results elucidated that (i) the initial formation of the NH4+(H2O)3OH− double ionic clusters were energetically favorable in the presence of H2O, (ii) the OH− ions from the double ionic clusters reacted with Lewis acid sites of the manganese oxides to transform into Brönsted acid ones, concomitant with release of the NH4+ ions, and (iii) the NH4+ ions both from the double ionic clusters and from reaction of NH3 with Brönsted acid sites can be efficiently adsorbed on the {1 1 0} facets of the HMO to complete the NH3-SCR reaction cycles, whereas the NH4+ ions are not stable on the {1 1 0} facets of β-MnO2. Therefore, the excellent catalytic performance of the HMO predominantly originates from the special structural {1 1 0} facet due to it being suitable for adsorption of NH4+ active species.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (138 K)Download as PowerPoint slideHighlights► The {1 1 0} facets of hollandite manganese oxide (HMO) are catalytically active sites in the NH3-SCR reaction. ► NH4+ ions as active species are more favorably adsorbed on the {1 1 0} facets of HMO than β-MnO2. ► Brönsted acid sites on the {1 1 0} facets of HMO increase in the presence of H2O.

Keywords
Manganese oxides; Selective catalytic reduction; NO; Brönsted acid sites; NH4+
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Effect of H2O on catalytic performance of manganese oxides in NO reduction by NH3
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volumes 437–438, 26 September 2012, Pages 139–148
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
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Full-text PDF Download
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