Diffuse Reflection Infrared Spectroscopy (Drifts): Application to the in Situ Analysis of Catalysts

Abstract

Résumé -Spectroscopie infrarouge en réflexion diffuse (DRIFTS) : application à l'analyse in situ de catalyseurs -La technique infrarouge de spectroscopie de réflexion diffuse (DRIFTS), moins pratiquée que la transmission en raison de ses limitations, est extrêmement utile, en effet indispensable, pour les matériaux non transparents et/ou pour des mesures in situ à la température élevée. Les auteurs décrivent les principes de cette technique et ses avantages par rapport à la spectroscopie infrarouge en transmission. L'application de DRIFTS à la caractérisation des catalyseurs est illustrée par deux études : sur l'interaction du molybdène avec le précurseur de catalyseurs de désulfuration de carburant, et sur les modifications in situ sous gaz réactifs des catalyseurs de réduction des composés azotés dans les gaz d'échappement. Abstract -Diffuse Reflection Infrared Spectroscopy (DRIFTS): Application to the in situ Analysis of Catalysts -The diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) technique, less practiced than the transmission mode because of its limitations, is extremely useful, indeed indispensable, for non-transparent materials and/or for in situ measurements at elevated temperature. The authors describe the principles of this technique and its advantages over transmission infrared spectroscopy. The application of DRIFTS to the characterization of catalysts is illustrated by two studies conducted on the interaction of molybdenum with the precursor of fuel desulphurization catalysts, and on the in situ modifications under reactive gases of catalysts for reducing nitrogen compounds in exhaust gases.

In situ DRIFTS study of hygroscopic behavior of mineral aerosol

“…The absorption fraction is easily known from the LambertBeer law. The reflection fraction in the case of infinite thickness (2-3 mm) could be a similar expression to the absorption expression after applying the Kubelka-Munk function (Armaroli et al, 2004). Therefore, the KubelkaMunk conversion leads to a linear relationship between concentration and reflected radiation intensity for DRIFTS spectra.…”

“…(Armaroli et al, 2004). In addition, (1.7, 4.8, 7.4, 15.9, 23.9, 31.6, 39.3, 48.0, 56.9, 67.0, 72.0, 74.2, 76.1, 78.1, 82.4, 87.2, 94.6) (a).…”

“…Gaining quantitative information from the spectra is non-trivial because the Beer-Lambert law used in transmittance is not applicable in this case. However, Kubelka-Munk theory can be applied to improve the linearity of the dependence of signal intensity upon concentration (Armaroli et al, 2004). The DRIFTS spectrum contains both reflection and absorption signals of incident flux on a particle.…”

“…Because it is ease for sample preparation, and it is able to analyze nontransparent materials as well as to make in situ measurement at elevated temperature, in situ diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) has been demonstrated as a useful technology for surface science and heterogeneous reactions analysis (Fuller and Griffiths, 1978;Armaroli et al, 2004;He et al, 2005). However, the utilization of in situ DRIFTS for the hygroscopic behavior of mineral dusts was little reported.…”

Silica deposition as an approach for improving the hydrothermal stability of an alumina support during glycerol aqueous phase reforming

“…The peaks at 3765, 3725 and 3672 cm −1 were assigned to terminal, doubly-bridged and triply-bridged OH groups, respectively. The broad peak at 3590 cm −1 has been attributed to hydrogen-bonded OH groups [47,48]. Upon modication with TEOS, a sharp peak centered at 3742 cm −1 appeared, attributed to isolated silanols, considered to be Brønsted acid sites [44,49].…”