S K-edge

Oxidation of these model sulfur compounds was studied without solvent to investigate the chemical structure of the products using S K-edge XANES. A solvent free tri-phase (organic/ H202aq./catalyst) was used under the described conditions. Figure 1 shows the XANES spectra from the organic and aqueous phases as well as reference materials. The thiophene oxidized to thiophene-sesquioxide [3a,4,7,7a-tetrahydro-4,7-epithiobenzo[b]-thiophene 1,1.8-trioxide ] first.. The sesquioxide solid precipitated from the solvent free reaction mixture and was identified by NMR, IR and C,H,S elemental analytical. The sesquioxide oxidized to sulfate. 2-MT and 2,5 DMT also oxidized to... 

Boye K, Almkvist G, Nilsson SI, Eriksen J, Persson I. Quantification of chemical sulphur species in bulk soil and organic sulphur fractions by S K-edge XANES spectroscopy. Eur. J. Soil Sci. 2011 62 874-881. 

These correspond to the S Is — M d7t(e) and Sis > M d<7(t2) transitions split in energy by 10Dq (in the d6 final state). The resolved intensities provide the n and cr covalencies (i.e., thiolate S character) in the d-orbitals of this site. In a comparison of the S K-edge data for the iron-sulfur model complexes of Holm and collaborators58 to the proteins with structurally congruent sites, the intensity is generally decreased... 

The spectra of the tribofilms generated from mixtures of ZDDP/MoDTC have also been recorded at the (S) K-edge using the surface TEY technique in the energy range 2460 to 2490 eV (Kasrai et al., 1998). The main peaks of the starting materials, ZDDP/MoDTC, lie between first peak MoS2 (-2741 eV) and second peak ZnS (-2473 eV), see Table 5.12. 

Table 5.12. The tribofilms generated from mixture of ZDDP/MoDTC and recorded at the sulfur (S) K-edge using XANES surface TEY technique...

The (S) L-edge XANES bulk (FY mode) spectra recorded were very weak, indicating that the film is thin (<10 nm), (Kasrai et al., 1998). The (S) K-edge XANES spectra of tribofilms along with neat MoDTC, MoS2 and Na2S04, recorded in the TEY (surface ) mode, are shown in Fig. 5.6. 

The unused bed is quite homogenous, as seen in Fig. 4 for test I. As the test proceeds, two main trends in the compositional distributions are apparent. The distribution spreads out towards the Al+Si/ Na+P+S+K-edge on one hand, and to the Mg+Ca+Ti+Fe-comer on the other. The first trend is cormected to the formation of sodium-rich adhesive material in small agglomerates fomied around quartz impurities... 

Indeed, test 11 where the bed contained no quartz irr urities did not indicate a tendency towards agglomeration, and consequently no shift of the compositional distribution towards the Al+Si/Na+P+S+K edge was detected. 

In this manuscript, the third factor was studied by sulfur K-edge X-ray absorption near-edge structure (XANES). Infrared absorption spectroscopy is often used to monitor the adsorbed/intermediate species on the surface. However, by infrared absorption, the atoms dissociated from reactant molecules that are buried into the catalysts are often inaccessible, e.g. sulfur atom of SO dissociated and reacted to form the RuS phase. The major objective of this paper is to monitor both adsorbed and buried sulfur atoms by S K-edge XANES in the preparation process of supported ruthenium catalysts. 

The database to identify and evaluate the adsorbed, intermediate, and incorporated sulfur species was listed in Table 1 to investigate the SO reduction and possibly also the desulfurization reaction. Further discussion of reaction mechanism of catalysis will need the combination of S K-edge XANES and pulse reaction measurements at beamline. 

EXAFS data of either element s K-edge. The cobalt atoms are considered to be located on the periphery of these M0S2 particles. Analysis of the cobalt edge has indicated an environment of 5 or 6 sulphur atoms with a bond length of 2.33 or 2.238. There has also been a suggestion of a proportion of oxygen neighbours at 2.038. In this system only a small proportion ( - 10%) of the cobalt atoms are considered to be adsorption sites (as probed by NO), so it has been difficult to obtain definitive information about these centres.. 

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