Studies of architecture of MoO3–TiO2 catalysts

Abstract

X-Ray diffraction, F.t.i.r., scanning electron microscopy (SEM) and ionscattering spectroscopy (ISS) have been applied to characterize a series of Moo,-TiO, (anatase) samples prepared by the grafting and impregnation methods. The sample prepared with the grafting method exhibits good dispersion of MOO,, whereas the impregnation technique leads to a poorer dispersion of molybdena on the surface of titania. The poorer dispersion of MOO, is due to the clustering of molybdena when the MOO, loading does not exceed the theoretical monolayer coverage (6.3 wt % MOO,). At higher MOO, loading, crystals of MOO, of morphology different from pure MOO, crystals, appear. A possible explanation of this phenomenon is discussed.

Characterization of MoO3/TiO2 (Anatase) Catalysts by ESR, 1H MAS NMR, and Oxygen Chemisorption

“…We have therefore denoted this loading representing the experimentally found monolayer capacity. Several authors reported the structure of monolayer MoO 3 on TiO 2 . − ,− For example, Ng and Gulari 42 reported that as the coverage of TiO 2 by molybdenum approaches one monolayer of tetrahedrally coordinated molybdates, extensive polymerization occurs and octahedrally coordinated polymeric surface species are formed. Bond et al 43 , have reported that the monolayer capacity of MoO 3 supported on TiO 2 (Degussa P-25, SA 52 m 2 g -1 ) was found to be 4.1 wt % MoO 3 .…”

Polarization-Dependent Total-Reflection Fluorescence XAFS Study of Mo Oxides on a Rutile TiO2(110) Single Crystal Surface

“…At first MoO 3 bulk structures with (100), (010), and (001) faces normal to TiO 2 (110) surface were considered, but the calculations based on these structures failed to reproduce the observed data. Preferential growth of MoO 3 layers on TiO 2 has been suggested in the literature . Therefore, next we calculated the layer structures with different orientations.…”

“…Preferential growth of MoO 3 layers on TiO 2 has been suggested in the literature. 22 Therefore, next we calculated the layer structures with different orientations.…”

“…TiO 2 -supported Mo oxide catalysts have drawn much interest in relation to catalytic selective oxidation processes. , Structural characterizations of Mo oxides on TiO 2 have been performed to reveal the plausible structure models by RAMAN and conventional EXAFS. − …”

“…20,21 Structural characterizations of Mo oxides on TiO 2 have been performed to reveal the plausible structure models by RAMAN and conventional EXAFS. [22][23][24][25] In this study, we carried out PTRF-EXAFS analysis to investigate the three-dimensional surface structure of molybdenum oxides supported on a rutile TiO 2 (110) single crystal as a model system for Mo/TiO 2 (powder). Particular interest was paid to the interaction between Mo and TiO 2 surface which may determine the Mo oxide structure.…”