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Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects

Paper ID Volume ID Publish Year Pages File Format Full-Text
54232 47001 2015 9 PDF Available
Title
Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects
Abstract

•The SCR activity of mechanochemically prepared Ag catalysts has been compared to that of a conventionally prepared Ag catalyst.•Higher activity was observed for all the ball milled catalysts even when the choice of reductant was varied.•High speed ball milling reduced the activity due to a phase change in the alumina support.•Transient DRIFTS analysis provided insight into different mechanistic features.•Isocyanates are formed at significantly higher surface concentration in the case of the ball milled catalyst.

Mechanochemical preparation of Ag/Al2O3 catalysts used for the selective catalytic reduction of NOx using hydrocarbons has been shown to substantially increase the activity of the catalyst in comparison with Ag/Al2O3 prepared by wet impregnation. The effect of using different ball-milling experimental parameters on both the structure of the material as well as the catalyst activity has been investigated and the optimum conditions established. A phase transition from γ- to α-alumina was observed milling at high speeds which was found to result in lower catalyst activities. At lower milling speeds both fracturing and agglomeration of the alumina support can be observed depending on the grinding time. However, due to ball-milling, a general enhancement in the NOx reduction activity was observed for all catalysts compared with the conventionally prepared catalysts irrespective of the reductant used. Transient DRIFTS-MS experiments were performed to investigate the effect of H2 in the absence and presence of water on the SCR reaction over catalysts prepared by both ball milling and wet impregnation. In-situ DRIFTS-MS analysis revealed significant differences in both gas phase and surface species. Most notably, isocyanate species were formed significantly more quickly and at higher surface concentration in the case of the mechanochemically prepared catalyst.

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Keywords
Ball-milling; Ag/Al2O3; NOx reduction; HC-SCR; n-octane; Transient kinetics; H2 effect; DRIFTS-MS; isocyanates
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Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 246, 15 May 2015, Pages 198–206
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