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SO2-induced stability of Ag-alumina catalysts in the SCR of NO with methane

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Abstract.
We report on a stabilization effect on the structure and activity of Ag/Al2O3 for the selective catalytic
reduction (SCR) of NOx with CH4 imparted by the presence of SO2 in the exhaust gasmixture. The reaction
is carried out at temperature above 600 oC to keep the surface partially free of sulfates. In SO2-free gases,
catalyst deactivation is fast and measurable at these temperatures. Time-resolved TEM analyses of used
samples have determined that deactivation is due to sintering of silver from well-dispersed clusters to
nanoparticles to micrometer-size particles with time-on-stream at 625 oC. However, sintering of silver
was dramatically suppressed by the presence of SO2 in the reaction gas mixture. The structural
stabilization by SO2 was accompanied by stable catalyst activity for the NO reduction to N2. The direct
oxidation of methane was suppressed, thus the methane selectivity was improved in SO2-laden gas
mixtures. In tests with high-content silver alumina with some of the silver present in metallic form, an
increase in the SCR activity was found in SO2-containing gas mixtures. This is attributed to redispersion of
the silver particles by SO2, an unexpected finding. The catalyst performance was reversible over many
cycles of operation at 625 oC with the SO2 switched on and off in the gas mixture.

Keywords: Silver catalyst, Alumina, Sintering, Dispersion, SO2, SCR of NO, CH4, NOx reduction

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Informasi Detail

Judul Seri

Applied Catalysis B: Environmental

No. Panggil

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Penerbit

London : Elsevier B.V.., 2009

Deskripsi Fisik

Applied Catalysis B: Environmental 88 (2009) 98–105

Bahasa

English

ISBN/ISSN

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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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