M. Baltes et al., The adsorption of VO(acac)(2) on a mesoporous silica support by liquid phase and gas phase modification to prepare supported vanadium oxide catalysts, J POROUS MA, 5(3-4), 1998, pp. 317-324
Supported vanadium oxide catalysts are prepared by adsorption and subsequen
t calcination of the vanadyl acetylacetonate complex on silica by liquid ph
ase and gas phase modification. The influence of the pretreatment temperatu
re and the effect of the solvent in the liquid phase are discussed. Two typ
es of gas phase deposition processes are used: flow-type reactions and vacu
um deposition. The bonding mechanism, the influence of pretreatment tempera
ture of the support and the influence of the reaction temperature are inves
tigated by FTIR, XRD, TGA and chemical analysis. After calcination the obta
ined vanadium oxide layer is characterized by XRD and UV-Vis diffuse reflec
tance spectroscopy. The gas phase modification enables the creation of well
dispersed supported VOx catalysts. Loadings up to 1.4 mmol g(-1) (7 wt% V)
without the formation of a crystalline fraction can be achieved. The selec
tive oxidation of methanol to formaldehyde is used as a probe reaction to a
ssess the catalytic activity and selectivity of the catalysts. It is shown
that not the concentration of vanadium species, but their surface configura
tion is the determining factor in catalytic reactions.