X-ray absorption spectroscopy study of the titania- and alumina-supported tungsten oxide system

EXAFS spectroscopy as a tool to probe metal–support interaction and surface molecular structures in oxide-supported catalysts: application to Al2O3-supported Ni(ii) complexes and ZrO2-supported tungstates

“…While studying WO 3 /TiO 2 catalysts, Hilbrig et al 62 found a similar peak and attributed it to a W-Ti distance resulting from the anchorage of WO x groups on the TiO 2 support. Wong et al 55 explains the fact that the EXAFS signal corresponds to a mixture of bulk WO 3 (peak at ca.…”

Characterization and Hydrodesulfurization Activity of W-Based Catalysts Supported on Al2O3–TiO2Mixed Oxides

“…In spite of these efforts, there is still some controversy on whether the tungsten is in tetra or octahedral coordination on the surface of the alumina (4,12). The reports from the literature indicate that the structure and dispersion of the oxidic tungsten phases present in the alumina supported catalysts, depend on the tungsten load and on the calcination temperature (4,5,12,13,(22)(23)(24)(25)(26)(27). Also, it has been reported that on alumina supported tungsten catalysts the reduction of the W 6+ species takes place in a single step to W 0 (17,28).…”

“…In a work by Hilbrig et al (27), on the characterization of WO 3 /TiO 2 catalysts by EXAFS and XANES, they proposed a structural model in which islands of surface tungstate species are formed by branched chains of WO 5 units with terminal WO 4 units anchored onto the titania surface via W-O-Ti bonds. In this structure, the adsorption of one or two water molecules increases the oxygen coordination to six for all the tungsten surface sites.…”

グリコサーマル合成したTiO₂–SiO₂複合酸化物上に担持したPt–WO₃触媒による<i>n</i>-ヘキサデカンの異性化

“…The shape of the second shell peak of the catalyst was different from that of the WO3 reference and a peak at 2.9 Å was clearly observed for 5 wt% WO3/XG(0.2). As Hilbrig et al reported 16) , this peak seems to correspond to W Ti distance. These results indicates that the double-bond nature of the W O bond in the WOx species in the catalysts with low WO3 loadings is caused by strong interaction of WOx species with the support.…”