ChemInform Abstract: An EXAFS Study of the Spreading of MoO3 on the Surface of γ‐ Al2O3.

Abstract

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Structure of Isolated Molybdenum(VI) Oxide Species on γ-Alumina: A Periodic Density Functional Theory Study

“…The bond lengths predicted for the molybdenyl ModO double bonds on the (110) face are well consistent with the reported value of 1.70 Å, determined by EXAFS. 49 The obtained values are also close to DFT calculated ModO distances for isolated molybdenum oxide entities supported on titania. 50 The most stable surface molybdenum oxide structure under dehydrated conditions, predicted in that work, 50 is a distorted tetrahedral monooxo species, i.e., similar to the 100_5, 110_4 and 110_5 models from this present study.…”

“…These values are longer by 0.01−0.02 Å than the MoO length calculated for tetrahedral MoO 2 Cl 2 (Table ). Experimental MoO distances of 1.70 or 1.74 Å, determined by EXAFS, were reported for calcinated molybdena-alumina systems. In the latter case, four equivalent MoO bonds were predicted for the surface species and a tetrahedral species, interacting by two oxygens with only one surface aluminum atom was proposed .…”

Spreading and Wetting

“…The intensity ratios extrapolated to zero fluence are characteristic of the virgin surface being unaffected by sputtering processes. These conclusions were supported by XAFS [96] for the MoO 3 − Al 2 O 3 mixture and by the pre-edge and X-ray absorption nearedge (XANES) structure for the MoO 3 − TiO 2 system [97]. Because of the surface sensitivity of the LEIS technique, the Mo/Ti intensity ratio, when extrapolated to zero fluence, is expected to approach infinity if a monolayer of molybdenum oxide is formed on the TiO 2 surface.…”

“…As an example, Fig. Therefore, laser Raman spectroscopy (LRS) [9,76,86,[93][94][95] and X-ray absorption spectroscopy (XRAS) [96,97] have been applied to elucidate the structural characteristics of the two-dimensional oxide films. Profile (a) characterizes the physical mixture prior to thermal treatment; the second profile (b) was obtained after thermal treatment of the same mixture at 720 K for 5 h in a flow of oxygen saturated with 32 × 10 2 Pa (1 mbar = 10 2 Pa) H 2 O vapor.…”

One-Pot Transformation of Levulinic Acid to 2-Methyltetrahydrofuran Catalyzed by Pt–Mo/H-β in Water

“…These results revealed that both Pt 0 nanoparticles and Mo 6+ oxide clusters were highly dispersed on the surface of the H-β zeolite. 26,27 Initially, various solid-acid-supported Pt−Mo catalysts were examined in the reaction of LA using water as a solvent at 403 K and under H 2 at 5 MPa for 24 h (Table 1). Among the solid supports scrutinized, zeolites were found to be effective for the production of MTHF.…”