Spectroscopy adsorption

The pros and cons of oxidative dehydrogenation for alkene synthesis using doped cerianites as solid oxygen carriers are studied. The hydrogen oxidation properties of a set of ten doped cerianite catalysts (Ce0.9X0.1Oy, where X = Bi, In, La, Mo, Pb, Sn, V, W, Y, and Zr) are examined under cyclic redox conditions. X-ray diffraction, X-ray photoelectron spectroscopy, adsorption measurements, and temperature programmed reduction are used to try and clarify structure-activity relationships and the different dopant effects. 

Keywords Fullerene Arc discharge Chromatography, Mass spectroscopy Adsorption properties... 

An extensive list of TVj for quartz, silica gel, rutile, anatase, Sn02, CeOa, a and X AI2O3, boehmite, hematite, amorphous Fe(OH)3, o-FeOOH, MgO and ZnO determined by means of isotope exchange, IR spectroscopy, adsorption-desorption of water, acid-base titration (in this case the number of acidic and basic sites can substantially differ) and chemical reactions of surface OH groups with different species after removal of physisorbed water has been collected by James and Parks [9]. 

Heterogeneous isotopic exchange using deuterated (D2, D2O, CH3OD, CF3COOD, and so forth) and tritiated (HTO) substances, combined with mass spectrometry, IR spectroscopy and NMR spectroscopy Adsorption and wetting ... 

Baillie CA, Watts JF, Castle JE, Determination of the acidity of carbon fiber surfaces by means of X-ray photoelectron spectroscopy adsorption isotherms, J Mater Chem, 2(9), 939-944, 1992. 

Yehia, A. Atia, A.A., and Ateya. B.G.. The adsorption of sulphonate on fluorite single crystals as examined by in-situ FT-IR internal reflectance spectroscopy. Adsorpt Sci. Technol.. 15(9). 685-694 (1997). 

Keywords Fourier-Transform Infrared Spectroscopy Adsorption of surfactants Trisiloxane surfactants AMTIR Teflon AF... 

HREELS High-Resolution Electron Energy Loss Spectroscopy adsorption species... 

Montagne, X., Lynch, J., Freund, E., et al. (1987). A study of the adsorption sites on thoria by STEM and FTIR spectroscopy. Adsorption and desorption of water and methanol. J. Chem. Soc. Faraday Trans. /, 83, pp. 1417-1425. 

H. Ibach and S. Lehwald, Analysis of adsorption processes and surface reactions by vibrational spectroscopy Adsorption of NO on Pt(lll), Surface Sci. 76 1 (1978). 

Madey and co-workers followed the reduction of titanium with XPS during the deposition of metal overlayers on TiOi [87]. This shows the reduction of surface TiOj molecules on adsorption of reactive metals. Film growth is readily monitored by the disappearance of the XPS signal from the underlying surface [88, 89]. This approach can be applied to polymer surfaces [90] and to determine the thickness of polymer layers on metals [91]. Because it is often used for chemical analysis, the method is sometimes referred to as electron spectroscopy for chemical analysis (ESCA). Since x-rays are very penetrating, a grazing incidence angle is often used to emphasize the contribution from the surface atoms. 

XANES X-ray adsorption nearedge spectroscopy [178a] Same as NEXAFS Same as NEXAFS... 

Electron Spin Resonance Spectroscopy. Several ESR studies have been reported for adsorption systems [85-90]. ESR signals are strong enough to allow the detection of quite small amounts of unpaired electrons, and the shape of the signal can, in the case of adsorbed transition metal ions, give an indication of the geometry of the adsorption site. Ref. 91 provides a contemporary example of the use of ESR and of electron spin echo modulation (ESEM) to locate the environment of Cu(II) relative to in a microporous aluminophosphate molecular sieve. 

The following several sections deal with various theories or models for adsorption. It turns out that not only is the adsorption isotherm the most convenient form in which to obtain and plot experimental data, but it is also the form in which theoretical treatments are most easily developed. One of the first demands of a theory for adsorption then, is that it give an experimentally correct adsorption isotherm. Later, it is shown that this test is insufficient and that a more sensitive test of the various models requires a consideration of how the energy and entropy of adsorption vary with the amount adsorbed. Nowadays, a further expectation is that the model not violate the molecular picture revealed by surface diffraction, microscopy, and spectroscopy data, see Chapter VIII and Section XVIII-2 Steele [8] discusses this picture with particular reference to physical adsorption. 

Infrared Spectroscopy. The infrared spectroscopy of adsorbates has been studied for many years, especially for chemisorbed species (see Section XVIII-2C). In the case of physisorption, where the molecule remains intact, one is interested in how the molecular symmetry is altered on adsorption. Perhaps the conceptually simplest case is that of H2 on NaCl(lOO). Being homo-polar, Ha by itself has no allowed vibrational absorption (except for some weak collision-induced transitions) but when adsorbed, the reduced symmetry allows a vibrational spectrum to be observed. Fig. XVII-16 shows the infrared spectrum at 30 K for various degrees of monolayer coverage [96] (the adsorption is Langmuirian with half-coverage at about 10 atm). The bands labeled sf are for transitions of H2 on a smooth face and are from the 7 = 0 and J = 1 rotational states Q /fR) is assigned as a combination band. The bands labeled... 

Still another type of adsorption system is that in which either a proton transfer occurs between the adsorbent site and the adsorbate or a Lewis acid-base type of reaction occurs. An important group of solids having acid sites is that of the various silica-aluminas, widely used as cracking catalysts. The sites center on surface aluminum ions but could be either proton donor (Brpnsted acid) or Lewis acid in type. The type of site can be distinguished by infrared spectroscopy, since an adsorbed base, such as ammonia or pyridine, should be either in the ammonium or pyridinium ion form or in coordinated form. The type of data obtainable is illustrated in Fig. XVIII-20, which shows a portion of the infrared spectrum of pyridine adsorbed on a Mo(IV)-Al203 catalyst. In the presence of some surface water both Lewis and Brpnsted types of adsorbed pyridine are seen, as marked in the figure. Thus the features at 1450 and 1620 cm are attributed to pyridine bound to Lewis acid sites, while those at 1540... 

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