Application of microfabricated reactors for operando Raman studies of catalytic oxidation of methanol to formaldehyde on silver
Operando Raman-GC studies of the catalytic oxidation of methanol to formaldehyde on silver using a microfabricated reactor as a reactor cell are presented. The microreactor is made of silicon and glass with a wide reaction channel of 8 mm and a channel depth of 120 μm. The silver catalyst is incorpo...
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Published in | Catalysis today Vol. 126; no. 1; pp. 119 - 126 |
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Main Authors | , , , |
Format | Journal Article Conference Proceeding |
Language | English |
Published |
Amsterdam
Elsevier B.V
15.08.2007
Elsevier Science |
Subjects | |
Online Access | Get full text |
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Summary: | Operando Raman-GC studies of the catalytic oxidation of methanol to formaldehyde on silver using a microfabricated reactor as a reactor cell are presented. The microreactor is made of silicon and glass with a wide reaction channel of 8
mm and a channel depth of 120
μm. The silver catalyst is incorporated into the microchannel by sputter coating. The reaction is performed at atmospheric pressure, temperature between 723 and 813
K with a feed containing 8.75% CH
3OH, 3.5% O
2 and 6.63% H
2O (He as balance) at residence time of 6–7
ms at reaction temperature. Raman spectra of the silver catalyst after exposure to 4.1% O
2 (He as balance) at 773
K show the presence of subsurface (at 640
cm
−1) and surface (at 810
cm
−1) atomic oxygen species. During an activation procedure consisting of repeated oxidation/reaction cycles at 773
K, the 810
cm
−1 band disappears immediately after introducing a CH
3OH/O
2/H
2O/He mixture, indicating that this surface atomic oxygen species participates in the reaction. The 810
cm
−1 band is not observed in the subsequent oxidation/reaction cycles; instead a broad feature between 400 and 800
cm
−1 appears which may be associated with a severe restructuring of the catalyst by methanol oxidation. The catalyst stabilizes after three oxidation/reaction cycles as shown by improved and approximately constant CH
2O selectivities. This is accompanied by Raman spectra with sharp definition of the 400–800
cm
−1 band, indicating the importance of stabilization of subsurface oxygen species in obtaining high CH
2O selectivity. Deactivation of the catalyst due to carbon deposition is observed when a feed without H
2O is introduced into the reactor, as demonstrated by bands at 1350 and 1585
cm
−1 in the Raman spectra and by decreased conversion of CH
3OH with reaction time. The work presented demonstrates that microfabricated reactors can be easily integrated with Raman spectroscopy and GC for
operando studies. |
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ISSN: | 0920-5861 1873-4308 |
DOI: | 10.1016/j.cattod.2006.11.002 |