IR characterization

There have been a few other experimental set-ups developed for the IR characterization of surfaces. Photoacoustic (PAS), or, more generally, photothemial IR spectroscopy relies on temperature fluctuations caused by irradiating the sample with a modulated monocliromatic beam the acoustic pressure wave created in the gas layer adjacent to the solid by the adsorption of light is measured as a fiinction of photon wavelength... 

The effect of oxidizing atmospheres on the reduction of NO over rhodium surfaces has been investigated by kinetic and IR characterization studies with NO + CO + 02 mixtures on Rh(lll) [63], Similar kinetics was observed in the absence of oxygen in the gas phase, and the same adsorbed species were detected on the surface as well. This result contrasts with that from the molecular beam work [44], where 02 inhibits the reaction, perhaps because of the different relative adsorption probabilities of the three gas-phase species in the two types of experiments. On the other hand, it was also determined that the consumption of 02 is rate limited by the NO + CO adsorption-desorption... 

Di or trivalent cations are able to induce the dissociation of coordinated water molecules to produce acidic species such as MOH+ (or MOH2+ for trivalent metal cations) and H+. Several infrared studies concerning rare-earth or alkali-earth metal cation exchanged Y zeolites have demonstrated the existence of such species (MOH+ or MOH2+) [3, 4, 5, 6]. However, the literature is relatively poor concerning the IR characterization of these acidic sites for LTA zeolites. The aim of the present work is to characterize 5A zeolite acidity by different techniques and adsorption tests carried on 5A zeolite samples with different ion exchange. 

Lamotte, Lavalley, and coworkers—IR characterization of Type II bridging OH groups and formate species. In the 1980s, Lamotte et al.503 506 also concluded that primarily formate species formed upon CO adsorption to H2-treated thoria. Comparison of the spectra of ceria with the previous studies on thoria gave them a... 

IR = Characterization by infrared spectroscopy. ED = Characterization by electron diffraction. 

Rhodium-siloxy complexes have been of great interest since 1980 as models of metal complexes supported on silica surfaces. The groups of Basset and Ugo [16] proposed a formulation of the oxidized species with Rh(CO)2 moieties bonded to the support by SiO bonds (e.g.. Figure 7.2), which was confirmed by the IR characterization of [ Rh( i-OSiMe3)(CO)2 2] [17]. 

Extensive 11 [-. 13C-NMR, and IR characterization data supplied by author of the current invention. 

Figure 4. IR characterization of graftings on polyoctenamer (film thickness = 100 p.m) (reproduced with permission from reference 10)...

Experimental Technique. The IR spectra of dehydrated samples were recorded by UR 10 spectrometer (VEB Carl Zeiss Jena). To obtain spectra for dehydrated zeolites, samples were activated for 10 hours in air at 570°C, cooled to room temperature in the presence of P4O10, and ground with Nujol. The accuracy of the band maximum determination of the D6-ring band was 1.5 cm-1. IR characterization of the zeolites after CO adsorption was done in a cell with NaCl windows as described by Dunken and coworkers (9). The samples were heated at 550° C for 3 hours under vacuum. After cooling under vacuum to room temperature, CO was adsorbed (pco = 450 torr), and the spectra were recorded. 

Y. Kojima, Y. Kawai, IR characterization of lithium imide and amide , J. Alloys Compd. 395... 

The comparison of the results of MEK and water adsorption with those of IR characterization (Fig. 3) and of the effect of higher temperature treatment with 02 and N2 (Fig, 1) suggests that initially (clean surface) the supported catalysts are very active, but probably the MEK formed is rapidly consecutively converted to acetate species which remain on the surface together with the MEK formed. The progressive formation of a water layer on the surface as well as the effect of the catalytic reaction itself leads to an in-situ change in the surface reactivity with a decrease in the rate of 1-butene conversion, but an... 

Table 7 shows the IR characterization of RuNaY, using parent complexes of different chemical nature. Several conclusions can be drawn from these data ... 

It is appropriate to end with the caveat that it is a weakness shared by many of these studies of high-temperature salt molecules that the IR characterization of the species does not extend to motions of the cation. Hence the location of the cation, or cations, has to be inferred circumstantially from the perturbation experienced by the anion. The basis of the argument does make the results vulnerable to misinterpretation, and there is no doubt that the surest results relate to molecules whose identities can be vouched for independently, for example by gas electron diffraction studies. 

---