IR of adsorbed

Studies using IR of adsorbed pyridine are numerous and, like most other zeolite studies, have concentrated on H-ZSM-5 and zeolites. The majority of... 

T emperature-programmed desorption (TPD) of ammonia and infrared spectroscopy (IR) of adsorbed pyridine are probably the most extensively used methods for characterising acidity (number, strength and nature of acid sites) in zeolites [17,18]. Fig. 1 shows the diffuse-reflectance infrared spectra of pyridine adsorbed on H-Y, H-Y(d5o%) and H-Y(d64%) samples at... 

In most studies, ratios between B and L sites as obtained by XPS were compared with those measured by IR of adsorbed pyridine. While good agreement... 

Fig. 12a, b. Evaluation of basicity by XPS and IR of adsorbed pyrrole correlation between the partial charge on N as derived from the Sanderson electronegativity equalization principle and the (a) N Is BE and (b) wavenumber of the NH vibration. Taken from HuzmgM.Adnot A, Kaliaguine S (1992) J Am Chem Soc 114 10005, with kind permission from the American Chemical Society... 

The influence of the zeolite environment on the XPS BE of dispersed ions (vide supra) means that reference compoimds for this type of investigation are not easily available. This is not so much a problem for the starting material for which the highest oxidation state of the element is often plausible, but the identification of intermediate states, and sometimes of the final state of reduction, is not straightforward. As a first approximation, BE shifts known from bulk components (e.g., coordination compounds) are often used in the analysis of zeolite systems. Combination with bulk techniques sensitive to electronic structure can provide additional information notwithstanding possible differences between the conditions in the bulk crystallite and the surface layer. Thus, IR of adsorbed CO has been used to differentiate between Pt andPt(O) atoms in H-ZSM-5 [131], EXAFS was able to detect very small intra-zeolite Cu(0) clusters formed from Cu+ with almost identical XPS/XAES signature [108], Mossbauer spectroscopy suggested the presence of Fe in zeolites with doubtftil Fe 2p satellites [116], and ESR was employed to support the occurrence of Pd+ in the reduction of intra-zeolite Pd(II) [126,127]. 

Bronsted as well as Lewis acidity were reported for WO3 — Si02, Ti02, AI2O3 by IR of adsorbed pyridine.Structure of WO3—AI2O3 have been studied by ISS. ... 

First approach to directional catalyst synthesis is based on chemical interaction of Pd with support. In a series of Pd supported on oxides catalysts on modified zirconia with second oxide content of 1 and 5% were the most active. Complete trichlorobenzene dechlorination in hquid phase was achieved within 20 min. Moreover, catalysts on modified zirconia were more stable than catalysts on individual oxides. Total converted amount of trichlorobenzene was 500 mol per 1 mol of Pd. According to TPR and IR of adsorbed CO data both Pd° and Pd are presented on the catalysts surface. Pd most likely to be a part of compounds like Pd-Zr-0. 

The data may then be expressed in conventional ir-versus-tr or ira-versus-ir plots, as shown in Fig. Ill-17. The behavior of adsorbed pentane films was that of a nonideal two-dimensional gas, as can be seen from the figure. 

The external reflection of infrared radiation can be used to characterize the thickness and orientation of adsorbates on metal surfaces. Buontempo and Rice [153-155] have recently extended this technique to molecules at dielectric surfaces, including Langmuir monolayers at the air-water interface. Analysis of the dichroic ratio, the ratio of reflectivity parallel to the plane of incidence (p-polarization) to that perpendicular to it (.r-polarization) allows evaluation of the molecular orientation in terms of a tilt angle and rotation around the backbone [153]. An example of the p-polarized reflection spectrum for stearyl alcohol is shown in Fig. IV-13. Unfortunately, quantitative analysis of the experimental measurements of the antisymmetric CH2 stretch for heneicosanol [153,155] stearly alcohol [154] and tetracosanoic [156] monolayers is made difflcult by the scatter in the IR peak heights. 

IR, FTIR Infrared absorption Transmission absorption Analysis state of adsorbed... 

Fig. XVI-4. (a) RAIRS for propene on Pt(III) at 340 K. (b) Transmission IR of propane on Pt/Si02 at -300 K (c) same as (b) but with propene adsorbed. II denotes pro-pylidyne assignments. (From Ref. 73.) (Reproduced by permission of Royal Society of Chemistry.)...

In 1960, Harrick demonstrated that, for transparent substrates, absorption spectra of adsorbed layers could be obtained using internal reflection [42]. By cutting the sample in a specific trapezoidal shape, the IR beam can be made to enter tlirough one end, bounce internally a number of times from the flat parallel edges, and exit the other end without any losses, leading to high adsorption coeflScients for the species adsorbed on the external surfaces of the plate (Irigher than in the case of external reflection) [24]. This is the basis for the ATR teclmique. 

It has been recrystd from H2O (fine needles) and is freely soluble in boiling H2O. Crysts also from H2O by addition of acetone. Purified by chromatography on Dowex 1 (in formate form), eluting with 0.25M formic acid. It was then adsorbed onto charcoal (which had been boiled for 15min with M HCI, washed free of chloride and dried at 100°), and recovered by stirring three times with isoamyl alcohol/H20 (1 9 v/v). The aqueous layer from the combined extracts was evaporated to dryness under reduced pressure, and the product was crystallised twice from hot H2O. [Morrison and Doherty Biochem J19 433 7967]. It has A-max 259nm (e 15,400) in H2O at pH 7.0. [Alberty et al. J Biol Chem 193 425 7957 Martell and Schwarzenbach Heh Chim Acta 39 653 7956]. The acridinium salt has m 208° [Baddiley and Todd J Chem Soc 648 1947 Pettit Synthetic Nucleotides, van Nostrand-Reinhold, NY, Vol 1 252 1972 NMR Sarma et al. J Am Chem Soc 96 7337 1974 Norton et al. J Am Chem Soc 98 1007 1976 IR of diNa salt Miles Biochem Biophys Acta 27 324 1958],... 

As revealed by IR-spectroscopy, the attachment of the polymer proceeds via acylation of aminopropyls absorbances of both amides (1650 cm-1) and esters (1740 cm-1) contribute to the spectrum of polyacrylate-coated aminopropyl-Aerosil (specific surface area 175 m2/g) [55], During the reaction, the accumulation of p-nitrophenyl ester groups in the support is accompanied by the liberation of p-nitrophenol into the contacting solution. Thus, the evaluation of the conformational state of adsorbing macromolecules can be performed by the simultaneous study of both processes by UV-spectroscopy as shown in Fig. 7. Apparently, at... 

Knowledge of the stracture and bonding of molecnles to snrfaces has been obtained from such techniques as LEED, electron energy-loss spectroscopy (EELS), secondaiy-ion mass spectrometry (SIMS), infrared spectroscopy (IRS), Raman spectroscopy, and NMR spectrometiy. The scope of snch studies needs to be greatly expanded to include the effects of coadsorbates, promoters, and poisons. Greater emphasis should be given to developing new photon spectroscopies that would permit observation of adsorbed species in the presence of a gas... 

The vibrations of molecular bonds provide insight into bonding and stmcture. This information can be obtained by infrared spectroscopy (IRS), laser Raman spectroscopy, or electron energy loss spectroscopy (EELS). IRS and EELS have provided a wealth of data about the stmcture of catalysts and the bonding of adsorbates. IRS has also been used under reaction conditions to follow the dynamics of adsorbed reactants, intermediates, and products. Raman spectroscopy has provided exciting information about the precursors involved in the synthesis of catalysts and the stmcture of adsorbates present on catalyst and electrode surfaces. 

IR spectra of adsorbed precursors on alumina were recorded before and after solvent removal with a Bruker lFS-66v spectrometer with a resolution of 4 cm. ... 

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