Infrared adsorption

Upon exposure of our samples at room temperature to a CO2 pressure of 50 Torr, no adsorption was observed on sample B on sample A0 some reaction took place, but the resulting infrared adsorption bands were too weak to permit proper identification. Distinct absorption spectra were obtained on the other samples these are shown in Fig. 9. 

Cutlip and Kenney (44) have observed isothermal limit cycles in the oxidation of CO over 0.5% Pt/Al203 in a gradientless reactor only in the presence of added 1-butene. Without butene there were no oscillations although regions of multiple steady states exist. Dwyer (22) has followed the surface CO infrared adsorption band and found that it was in phase with the gas-phase concentration. Kurtanjek et al. (45) have studied hydrogen oxidation over Ni and have also taken the logical step of following the surface concentration. Contact potential difference was used to follow the oxidation state of the nickel surface. Under some conditions, oscillations were observed on the surface when none were detected in the gas phase. Recently, Sheintuch (46) has made additional studies of CO oxidation over Pt foil. 

Misawa,T. Suetaka.W. Shimodaira, S. (1969) Infrared adsorption spectra and oxidation of iron(II) hydroxide and green rust. Bull. 

For comparison of these results with results of other authors, one may assume that the NO-Mo and NO-Co or NO-Ni infrared adsorption coefficients are the same. With this assumption, one can transform Topspe s data into a form resembling those of Burch and Collins. Figure 20 shows such... 

The variations of acidic properties in the surface layers and in the bulk solid catalysts after calcination, reduction, or coking were examined by pyridine Nls XPS [4,7] and by the pyridine infrared adsorption techniques, respectively. This provides a means to compare the changes in the characteristic BrBnsted and Lewis acidity functions after those treatment conditions. First of all, TPD of ammonia revealed that both coked and regenerated samples exhibited much decreased acidity as compared with either calcined or reduced samples before the reaction of n-heptane conversion in either N2 or H2 stream [7]. The adsorption of pyridine may cause further perturbation to the Pt4+ or Pt 2+ species in the zeolite as indicated by the increase in binding energies of Pt3d5/2 electrons, as shown in Table 3 and Figure 4,... 

One should be able to observe shifts in the infrared adsorption bands of various adsorbents as a function 0 in first-layer physical adsorption if Model 3 is a correct one. Furthermore, if Model 2 applies, the infrared technique of Wadsworth et al. (14), Mapes and Eischens (16), and others should be capable of demonstrating the predicted polarization effects by using the KI or KBr window and double-beam technique. So far as the author is aware, studies of this sort have not yet been attempted. 

A prerequisite for the development indicated above to occur, is a parallel development in instrumentation to facilitate both physical and chemical characterization. TEM and SPM based methods will continue to play a central role in this development, since they possess the required nanometer (and subnanometer) spatial resolution. Optical spectroscopy using reflection adsorption infrared spectroscopy (RAIRS), polarization modulation infrared adsorption reflection spectroscopy (PM-IRRAS), second harmonic generation (SFIG), sum frequency generation (SFG), various in situ X-ray absorption (XAFS) and X-ray diffraction spectroscopies (XRD), and maybe also surface enhanced Raman scattering (SERS), etc., will play an important role when characterizing adsorbates on catalyst surfaces under reaction conditions. Few other methods fulfill the requirements of being able to operate over a wide pressure gap (to several atmospheres) and to be nondestructive. 

N. Le Calve, B. Pasquier Z. Ouafik (1997). Chem. Phys., 222, 299-313. Vibrational study by inelastic neutron scattering, infrared adsorption and Raman scattering of potassium, rubidium and cesium dihydrogen arsenate crystals . Comparison with thallium dihydrogen arsenate. 

Figure 2. Plots of atomic O/C ratio and the infrared adsorption peak characteristic of carboxyl and carbonyl groups in Type III kerogen (circles) and coals (squares) as a function of vitrinite reflectance. (Reproduced with permission from Ref. 22. Copyright 1980 Editions Technip).

Table 2.3 Infrared Adsorption Bands on Carbon Surfaces and Their Corresponding Assignments to Oxygenated Functionalities...

Infrared adsorption bands on carbon surfaces and their corresponding assignments to oxygenated functionalities [235]. Reprinted with permission from P.E. Fanning and M.A. Vaimice, Carbon, 31 (1991) 721... 

Infrared adsorption frequencies and line broadening (X5,1 6) have been interpreted to show that water is bound 0 downwards to the HO M. The lifetime, and population, of aggregates and hydration sheaths is strongly affected by the rotational freedom of the water molecules. In bulk water this is restricted by hydrogen bond breaking. In adsorbed layers the interaction with the adsorbate dominates reorientation for all molecules within six to ten molecular dieurneters. 

An example of the mid-infrared adsorption spectra of the silane deposited from 0.2 and 2.5 wt.% solutions of MS compared to the spectrum of the undiluted monomeric silane is shown in Fig. 1. The greatest differences between the spectra are in the ranges of -OCH3 (2840 cm" ), Si-O-Si... 

Chen et al. [95], very recently, prepared Au thin-film electrodes made by electroless deposition for in situ electrochemical attenuated total-reflection surface-enhanced infrared adsorption spectroscopy (ATR-SEIRAS) which consisted of 46 nm Au nanoparticles deposited on a Si infrared window. Very interestingly, they observed that a square-wave treatment of the Au film led to a much enhanced ORR activity (02-saturated 0.1 M HCIO4) as a consequence of the surface reconstruction of the nanoparticle film. Thus, whereas the ORR activity of the initial Au... 

Infrared Adsorption Peaks and Signals for Different Surface Groups on Carbons... 

Infrared adsorption spectroscopy has greatly aided the study of heterogeneous catalysis and is in principle applicable to electrode adsorption studies. The major problems involved are, (a) To obtain an adequate spectrogram several monolayers of adsorbate must be... 

Table 10. Detection of Adsorbed Oxygen Species by Infrared Adsorption...

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