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Mechanism of ammonia oxidation over PGM (Pt, Pd, Rh) wires by temporal analysis of products and density functional theory

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Abstract.
The mechanism of ammonia oxidation over Pt, Pd, and Rh wires has been investigated in the Temporal
Analysis of Products (TAP) reactor at relevant temperatures in industrial ammonia burners. The results
of primary (NH3 + O2) and secondary (NH3 + NO) interactions with isotopically labeled ammonia at
1073 K enable to conclude that the overall reaction pathways to NO, N2O, and N2 are equivalent on the
three noble metals. NO is a primary reaction product, while N2 and N2O originate from consecutive NO
transformations. The extent of the secondary reactions determines the net NO selectivity. Rhodium is the
most active catalyst for the unwanted reduction of NO by NH3, while platinum shows the lowest activity.
This explains the superior NO selectivity attained over Pt and, therefore, its industrial application. The
TAP-derived selectivity ranking was substantiated by Density Functional Theory calculations on the (100)
facets of the noble metals. We proved experimentally that NO selectivity approaching 100% at complete
NH3 conversion can be equivalently attained over Pt, Pd, and Rh by increasing the oxygen content in the
feed. For a feed of O2/NH3 = 10, both N2O and N2 production are suppressed due to the impeded NO
dissociation and favored NO desorption at high oxygen coverage.

Keywords:
NH3 oxidation
Mechanism
Platinum
Palladium
Rhodium
Wires
TAP reactor
DFT

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Informasi Detail

Judul Seri

Journal of Catalysis

No. Panggil

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Penerbit

London : Elsevier Inc.., 2009

Deskripsi Fisik

Journal of Catalysis 261 (2009) 217–223

Bahasa

English

ISBN/ISSN

00219517

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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