Diffuse reflectance FTIR

Fig. 2. Diffuse reflectance FTIR spectra showing evidence of Pb-O-Si bonding at a silane/lead oxide interface (from Ref. [30]).

Characterization. In-situ diffuse reflectance FTIR (DRIFT) experiments were carried out with undiluted samples of the zeolites in a Spectratech DRIFT cell and a Nicolet Magna 550 spectrometer. Most experiments were carried out in a flow mode, passing 0.84 ml/s of a gas mixture containing inert (He, Ar or N2) and N2O, NO, CO or mixtures of these gases continuously through the cell at atmospheric pressure. Each spectrum was recorded by addition of 256 scans and a resolution of 8 cm. ... 

Characterization of the Cu-ZSM-5 catalyst by in-situ diffuse reflectance FTIR spectroscopy after treatments in CO, air and NjO is presented in figure 10, the CO adsorption in figure 11. 

Diffuse reflectance FTIR (DRIFT) spectra were recorded on a Bio-Rad FTIR spectrometer (EXCALIBUR FTS3000). A high-temperature cell was attached to a flow system that allows in-situ sample treatment, adsorption and desorption of probe molecules at different temperatures. 

Ming, J., Koizumi, N., Ozaki, T., and Yamada, M. 2001. Adsorption properties of cobalt and cobalt-manganese catalysts studied by in-situ diffuse reflectance FTIR using CO and CO+H2 as probes. Appl. Catal. A Gen. 209 59-70. 

It has been called to our attention by a referee that Young and Chang(11) have recently observed the endo-exo thermal isomerization in addition polymer prepregs of LARC-160 by diffuse reflectance FTIR. This technique may prove useful in the present work as well. 

Persson, I., Persson, P., Valli, M., Fozo, S., Malmensten, B., 1991. Reaction on sulphide mineral surfaces in connection with xanthate flotation studied by diffuse reflectance FTIR spectroscopy, atomic absorption spectrophotometry and calorimetry. In K. S. E. Forssberg (ed.). Flotation of Sulphide Mineral. Inter. J. Miner. Process, 33 67 - 81 Peters, E., 1977. The electrochemistry of sulphide minerals. In J. O M. Bockris, D. A. J. Rand, B. J. Weich (eds.). Trends in Electrochemistry. New York Plenum Press, 267 - 290 Peters, E., 1986. Leaching of sulphides. In P. Sortunasundaran (ed.). Advances in Mineral Processing. Proc. Sym. Honoring N. Arbiter on His 75th Birthday, SME, Inc. Colorado, 445-462... 

In this context, diffuse reflectance FTIR spectroscopy has been applied to analyze the influence of mixing variables (i.e. treatment concentration, time and temperature of mixing) on both the ultimate flller coating level and possible reaction between the treatment and flller surface [127]. 

A differential flow microreactor was used for the preparation of the nitrided catalyst and the TPD, TPR, and NH3-TPD measurements. Nitriding of the molybdena-alumina and alumina was carried out by temperature-programed reaction with NH3 (NH3-TPR).1719 The MoCV A1203 precursor was oxidized at 723 K for 24 h, cooled to 573 K, reacted with NH3 at 49.6 (xmols-1 from 573 to 773, 973 or 1173 K at a rate of 0.0167 Ks-1, held at the nitriding temperature for 3 h, and then cooled to room temperature (RT) in flowing NH3. The catalysts were characterized by TPD, TPR, and NH3-TPD under in situ conditions, while BET and diffuse reflectance FTIR measurements were carried out after passivation. For the diffuse reflectance FTIR study, the catalysts after NH3 treatment... 

Figure 17.11 Diffuse reflectance FTIR spectra of NH3 adsorption of 12.5% Mo03/AI203 at...

Diffuse reflectance FTIR spectra of the ground Mo03/Al203 catalysts were recorded on an FTIR instrument (Nicolet, Model 740, MCT detector). The microreactor in the flow system was replaced by an FTIR cell. The cell used a Harrick diffuse reflectance accessory (DRA-2CO) fitted with a controlled environmental chamber (HVC-DRP). Spectra (500 scans, 4 cm 1 resolution) were presented in Kubelka-Munk units and recorded at RT. 

Figure 9 In situ diffuse reflectance FTIR spectra of A07 on Ti02 surface (0.10 mmoles of A07/g of Ti02) during steady-state photolysis. The spectra were recorded at time intervals of (a) 0, (b) 60 min, and (c) 24 h of irradiation with visible light. (From Ref. 258.)...

Stafford, U. Gray, K. A. Kamat, P. V. Varma, A. An in situ diffuse reflectance FTIR investigation of photocatalytic degradation of 4-chlorophenol on a Ti02 powder surface, Chem. Phys. Lett. 1993, 205, 55. 

The total acidity deterioration and the acidity strength distribution of a catalyst prepared from a H-ZSM-5 zeolite has been studied in the MTG process carried out in catalytic chamber and in an isothermal fixed bed integral reactor. The acidity deterioration has been related to coke deposition. The evolution of the acidic structure and of coke deposition has been analysed in situ, by diffuse reflectance FTIR in a catalytic chamber. The effect of operating conditions (time on stream and temperature) on acidity deterioration, coke deposition and coke nature has been studied from experiments in a fixed integral reactor. The technique for studying acidity yields a reproducible measurement of total acidity and acidity strength distribution of the catalyst deactivated by coke. The NH3 adsorption-desorption is measured by combination of scanning differential calorimetry and the FTIR analysis of the products desorbed. 

Figure 12 The Spectra-Tech Collector diffuse reflectance accessory. A typical accessory for the study of particles and powders by diffuse reflectance FTIR. 

The in situ diffuse reflectance FTIR studies were carried out on a Perkin Elmer (model 2000) instrument, including a diffuse reflection unit and a reaction chamber. The gas flow of 30 ml min"1 was passed through the reaction chamber, containing the catalyst on an alumina sample holder. The spectra were measured in the reflection mode, with 25 scans and 8 cm 1. 

With the aid of thermal analysis, X-ray diffraction and diffuse reflectance FTIR, it was possible to deduce that the removal of the zeolitic water brought about a partial structural transformation of the VPI-5 to AlP04-8. Schmidt etal. (1992) have studied this phase transition in some detail and have shown that it can be avoided if the sample is heated slowly under reduced pressure (10-5 hPa). In this manner, VPI-5 can be heated to 450-500°C without any detectable change of structure. 

Recently, Schneider et al. [96] characterized the active surface species of vanadia on titania by means of diffuse reflectance FTIR. Their results supported the mechanism proposed by Janssen et al. [86]. From the signal intensities at 1435 and 1660 cm it was concluded that ammonia adsorbs on Bronsted sites [96]. The 1435 cm band was assigned to the n4(F) bending mode of ammonia adsorbed on Bronsted sites. The corresponding n2(E) feature was observed as a shoulder at 1660 cm . ... 

Surface species formed on the sample during the CO hydrogenation was observed by the diffuse reflectance FTIR (DRIFT) spectroscopy with a high-pressure chamber equipped with ZnSe window (Spectra-Tech Inc.) (18-23). After the sulfidation of Ae precursor in the same manner as described above, the... 

Novel chitosan based catalytic systems for hydrogenation of unsaturated compounds in the liquid phase were prepared. The catalytic performance of the obtained systems depended significantly on the chitosan forms (as the micro beads or chitosan deposited on the mineral supports), their preparation method and chemical modification of chitosan as well. The obtained chitosan based carriers and catalysts were examined by transmission and diffuse-reflectance FTIR spectroscopy. 

The obtained chitosan carriers and catalytic systems on their base were studied by transmission and diffuse-reflectance FTIR spectroscopy. IR-spectra were obtained in Nicolet Impact 410 equipment. To record the diffuse-reflectance spectra the samples were evacuated at 100°C for 2 h. The quantitatively spectrum analyses were performed using Kubelka-Munk equation according to the program OMNIC [5]. 

Schraml-Marth et al. [89] studied the two types of chromia by means of diffuse reflectance FTIR and Raman spectroscopy. Amorphous chromia has a higher density of labile oxygen sites than that of crystalline chromia in the temperature range 423-473 K and is accordingly more active. 

The adsorption of NO on in-situ synthesized CuZSM-5/cordierite monolithic catalysts of different Si/Al ratios was studied by diffuse reflectance FTIR spectroscopy at different NO partial pressures from 500 ppm to 2000 ppm and temperatures from 298 K to 773 K. At room temperature, Cu mostly exists in oxidized Cu form. A lot of N2O species were observed on the surface even at room temperature. A band at 2133 cm is attributed to NO -Oiattice and only related to the number of lattice A1 in the zeolite. There may exist a copper-zeolite-substrate interaction on such as synthesized monolithic catalysts. 

The acid sites of iron-exchanged Y zeolite were studied using NH3-TPD and diffuse reflectance FTIR spectroscopy. The Bronsted acids of three iron-exchanged Y zeolites were correlated with the activity for dibenzothiophene HDS at 240 and 280°C and 10.1 MPa. The FTIR data on NH3 and NO adsorption showed that Fe ions on the zeolites was correlated with their activities during dibenzothiophene HDS. 

Diffuse reflectance FTIR in combination with a multivariate calibration chemometric approach to data analysis could be used to effect the rapid quantification of a pharmaceutical product (ampicillin) in a (variable) biological background E. coli cells), a situation representative of metabolite over-production in a screening or titre improvement programme... 

---