Catalytic activity and structure of molybdenum trioxide highly dispersed on silica

Abstract

The structure of Mo-Si oxides has been investigated by XRD, FT-IR, laser Raman, and photoluminescence techniques. At low Mo content, an X-ray amorphous phase is formed, which is characterized by surface molybdates dispersed on SiOz. The surface concentration of amorphous Moo3 as well as the rate of oxidative dehydrogenation of CzH50H shows a maximum at about 1 atom % Mo. The change in the rate runs parallel with the change in the concentration of amorphous MOO,, i.e. surface polymolybdate. The concentration of tetrahedrally coordinated Mo ions in Mo-Si oxides determined by the photoluminescence technique shows a maximum again at about 1 atom % Mo content, becoming zero in the range above 3 atom % Mo content. A good parallelism between the concentration of tetrahedrally coordinated Mo ions and the rate of the metathesis reaction of propene is observed. ( 6 ) Cheng, C. P.; Schrader, G. L. J. Coral. 1979, 60, 276. ( 7 ) Jeziorowskii, H.; Knozinger, H.; Grange, P.; Gajardo, P.

Potential of UV–Raman Spectroscopy for Characterization of Sub-monolayer MoOxModel Catalysts at Ambient Pressure

“…For MoO x (6)/SiO 2 /Si the maximum of the broad band shifted to higher wavenumbers (~956) compared to MoO x (6)/Al 2 O 3 /Si. This can be attributed to Mo@O stretching vibrations from to surface polymolybdate species on SiO 2 as reported in literature [4,15]. The relatively sharp peak at 880 cm )1 present at high molybdenum oxide loading can be assigned to hydrated polymolybdate species [16].…”

The modification of MoO3 nanoparticles supported on mesoporous SBA-15: characterization using X-ray scattering, N2 physisorption, transmission electron microscopy, high-angle annular darkfield technique, Raman and XAFS spectroscopy

“…Molybdenum-based catalysts have been investigated intensively [19][20][21][22][23][24] because of their importance in the technical processes, such as propene metathesis [25,26], propene oxidation [27,28], methanol oxidation [29], ethanol oxidative photochemical reaction, and most importantly in hydrodesulfurization (HDS) processes, which represent one of the largest groups of catalytic steps in petroleum and petrochemical reactions. Recently, SBA-15-supported MoO 3 materials were used as an intermediate for the preparation of MoS 2 catalysts.…”

Spectroscopic Studies on ZrO2Modified with MoO3and Activity for Acid Catalysis

“…These systems are active for various reactions, such as partial oxidation of hydrocarbons and alcohols, [1][2][3][4][5] hydrogenolysis and hydrodesulfurization of crude oil, 6,7 metathesis of alkenes, 8 hydrogenation of benzene, 9 and cracking of hydrocarbons. 10 The conventional way to prepare the catalysts is to impregnate the high surface area support oxide with an aqueous solution of ammonium heptamolybdate followed by calcining the solid in air.…”