Mechanistic aspects of the selective catalytic reduction of NOx by dimethyl ether and methanol over gamma-alumina
Artikel i vetenskaplig tidskrift, 2010

High catalytic activity for selective catalytic reduction of NOx with dimethyl ether and methanol (DME- and methanol-SCR) has been found over a γ-alumina catalyst. The surface species involved in the DME-SCR reaction were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in combination with mass spectrometry and compared to the corresponding species observed during methanol-SCR. Dimethyl ether adsorbs mainly as methoxy groups (OCH3) on the catalyst surface, while methanol adsorbs as methoxy groups and molecularly. With increasing temperature, DME desorbs in two steps, whereas methanol desorbs first as methanol and at higher temperatures as DME. At higher temperatures, the two reducing agents display similar DRIFTS spectra showing first formaldehyde-like species and then formates on the surface. In the presence of NO or NO2, reactions between NO x species and carbon-containing species occur. Formohydroxamic acid (CHON(H)OH) forms isocyanates (NCO), and both are observed at temperatures relevant for DME-SCR. Since these species are likely intermediates for hydrocarbon-SCR over Ag/Al2O3, a partly similar reaction mechanism may be operational for DME-SCR over γ-Al2O 3 despite the fact that Ag/Al2O3 does not catalyze DME-SCR efficiently. The difference is thus due to the reaction steps leading to the formation of formohydroxamic acid that with DME follow a more efficient route over γ-Al2O3 than over Ag/Al 2O3.© 2010 Elsevier Inc. All rights reserved.

Reaction mechanism

Methanol

DME

deNO(x)

SCR

gamma-Al2O3

DRIFT spectroscopy

Författare

Stefanie Tamm

Kompetenscentrum katalys (KCK)

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

Hanna Härelind

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

Kompetenscentrum katalys (KCK)

Magnus Skoglundh

Kompetenscentrum katalys (KCK)

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

Anders Palmqvist

Kompetenscentrum katalys (KCK)

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

Journal of Catalysis

0021-9517 (ISSN) 1090-2694 (eISSN)

Vol. 276 402-411

Drivkrafter

Hållbar utveckling

Styrkeområden

Nanovetenskap och nanoteknik

Transport

Energi

Materialvetenskap

Ämneskategorier

Kemiteknik

Kemi

DOI

10.1016/j.jcat.2010.10.004