DRIFTS spectroscopy

DRIFT spectroscopy was used to determine Av0h shifts, induced by adsorption of N2 and hexane for zeolite H-ZSM-5 (ZSM-a and ZSM-b, Si/Al=15.5 and 26), H-mordenite (Mor-a and Mor-b, Si/AI— 6.8 and 10) and H-Y (Y-a and Y-b, Si/Al=2.5 and 10.4) samples. Catalysts were activated in 02 flow at 773 K in situ in the DRIFTS cell and contacted than with N2 at pressures up to 9 bar at 298 K or with 6.1% hexane/He mixture at 553 K, i.e., under reaction conditions. Catalytic activities of the solids were measured in a flow-through microreactor and kapp was obtained as slope of -ln(l-X0) vs. W/F plots. The concentration of Bronsted acid sites was determined by measuring the NH4+ ion-exchange capacity of the zeolite. The site specific apparent rate constant, TOFBapp, was obtained as the ratio of kapp and the concentration of Bronsted acid sites. 

Liu, Ruettinger, Farrauto, and coworkers—loss of catalytic activity during shutdown/restart cycles linked to formation of carbonates. Liu and coworkers435 at Engelhard reported on the loss of catalytic activity when Pt/ceria catalysts were exposed to shutdown/restart cycles. Utilizing DRIFTS spectroscopy, the authors... 

Weiland, J.J. and Guyonnet, R. (2003). Study of chemical modifications and fungi degradation of thermally modified wood using DRIFT spectroscopy. Holz als Roh- and Werkstoff, 61(3), 216-220. 

Persson et al. (1991) used diffuse reflection infrared Fourier transform (DRIFT) spectroscopy to study the interactions between galena, pyrite sphalerite and ethyl xanthate. They provided the evidence that the DRIFT spectrum of oxidized galena treated with an aqueous solution of potassium ethyl xanthate is practically identical with that of solid lead (II) ethyl xanthate, which can be formed as the only detectable siuface species on oxidized galena. Dialkyl dixanthogen is formed as the only siuface species in the reaction between oxidized pyrite and aqueous solution of potassium alkyl xanthate. 

Kaiser, K. Guggenberger, G. Haumaier, L. Zech,W. (1997) Dissolved organic matter sorption on subsoils and minerals studies by 13C-NMR and DRIFT spectroscopy. Fur. J. Soil Sci. 48 301-310... 

The commercial Pd/Al203 catalyst used in this pilot scale study was characterized via DRIFT spectroscopy. In situ DRIFT spectra of carbon monoxide, MIBK, acetone... 

Agatonovic-Kustrin, S. Tucker, I.G. 8t Schmierer, D., Solid state assay of ranitidine HC1 as a bulk drug and as active ingredient in tablets using DRIFT spectroscopy with artificial neural networks Pharm. Res. 1999, 16, 1477-1482. 

Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopy... 

Diffuse reflectance IR spectroscopy has become an attractive alternative to mulls with the introduction of DRIFT cell by Griffiths,29 later modified by Yang.30 Since materials are dispersed in a nonabsorbing medium and not subjected to thermal or mechanical energy during sample preparation, DRIFT spectroscopy is especially suitable for the qualitative/quantitative analysis for polymorphs, which are prone to solid-state transformations. The Kubelka-Munk (K-M) equation,31 which is analogous to Beer s law for transmission measurements, is used to quantitatively describe diffusely-reflected radiation ... 

Infrared microscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and photoacoustic spectroscopy (PAS) techniques may be suitable for some types of sample but the use of... 

DRIFT spectroscopy is of special interest in studying wood surface phenomena, for example, the effects of oxidation, photooxidation, and weathering. Moreover, it is advantageous for the analysis of highly absorbing materials... 

Faix O, Nemeth K (1988) Monitoring of wood photodegradation by DRIFT-spectroscopy Holz Roh- Werkst 46 112... 

Kohler and Kirkland noted that for chromatographic column packings analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and chromatographic behavior, silica appears to possess associated and isolated surface silanol groups [ I9. The associated silanol (possessing weak-acid characteristics) is identified with a silanol hydrogen-bonded to its nearest neigh-... 

Summary Silylester fimctionalized copolymers have been synthesized by free radical polymerization of alkenyl ethoxysilanes and vinyl acetate. The alkenyl ethoxysilane monomers and the preformed polymers have been applied to silica surfaces with hydroxy flmctions. Both treatments led to covalently modified samples of different properties as shown by DRIFT spectroscopy. 

Interaction with the support was enhanced after catalytic reaction, as indicated by the detection of new strong Lewis acid sites by DRIFT spectroscopy measure-... 

In order to evaluate whether or not the epoxy group is preserved during anchoring of the silane molecule, a systematic study of silylated silica and alumina substrates was performed. In a first series, the reactions were carried out at elevated temperatures using different procedures Pure silane without solvent (50°C), silylation in water at pH 3-4 and 75°C [5], and silylation in toluene under reflux [5,6], (further experimental details in [7]). DRIFT spectroscopy was applied to follow the reaction sequence. 

Molecular and structural characteristics of methoxysilane SA-layers deposited on inorganic subtrates can be obtained using DRIFT spectroscopy in combination with TOF-SIMS. The hydrolysis rates are strongly influenced by the acid/base properties of the oxide surface. In accord to this, the contribution of residual Si-OCHs units is much lower for SA-layers on the basic alumina. The outmost layers of the polysiloxanes consist of completely hydrolyzed species. In case of methylsilanes, the SIMS spectra indicate the presence of T and T OH silsesquioxanes whereas for higher alkylsilanes the formation of T OH isomers is likely. This hypothesis has to be addressed in future studies with particular focus on structural aspects. 

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