Study of new catalysts based on vanadium oxide supported on mesoporous silica for the partial oxidation of methane to formaldehyde: Catalytic properties and reaction mechanism

Determining the Structure of Silica-Supported Monomeric Vanadium Oxide Catalysts Based on Synthesis Method and Spectral Data from Theoretical Calculations

“…The co-condensation of monomeric vanadium VO 2 (OH) 2 -and Si(OC 2 H 5 ) 4 at a pH inbetween 5 and 6 in a solution containing template was described by Nguyen et al 36 With this technique, the support is generated at the same time as the VO 2 (OH) 2 -is deposited. This increases the chance that multiple bonds to the silica precursor are formed from the VO 4 species.…”

“…This increases the chance that multiple bonds to the silica precursor are formed from the VO 4 species. Nguyen et al report in their paper 36 that they suspect that two species are present on the surface: the pyramid model ( Figure 1A) and the two-legged variant with one OH group on top ( Figure 1B). In their Raman spectrum, 36 an intense band is found at 1037 cm -1 , which is the VdO stretch vibration.…”

“…On the basis of experimental and theoretical IR and Raman spectra, it can be concluded that for the incipient wetness impregnation techniques 35 the umbrella model ( Figure 1C) poses as a good candidate for the VO 4 species on the surface. The co-condensation technique introduced by Nguyen et al 36 leads to two structures. Model B (Figure 1B) will always be present; next to this structure the umbrella model ( Figure 1C) is present.…”

“…35 Another interesting method recently described is the cocondensation of monomeric vanadium VO 2 (OH) 2 -and Si-(OC 2 H 5 ) 4 species in a solution, as described by Nguyen 36 and used before by other groups in a slightly different manner [37][38][39] Apart from these wet techniques, there is a nonchemical preparation of the supported VO x species that is used by Freund Figure 1. The molecular structure of the six cluster models studied in this paper: (a) the pyramid model consisting of a VdO unit bonded to the support with three Si-Os-V bonds; (b) a species with two SiOs-V support bonds, a VdO, and a V-OH group; (c) the umbrella model with only one support Si-Os-V bond, a VdO group, and a perturbed oxygen molecule bound to the V-atom; and (d) the hydrogenated version of the umbrella model in which the oxygen molecule is replaced by two OH groups.…”

MCF Material as an Attractive Support for Vanadium Oxide Applied as a Catalyst for Propene Epoxidation with N2O

“…Additionally, Raman spectra recorded for all the studied samples revealed a broad band at about 920-930 cm −1 and a weak band at 1070 cm −1 . These bands, according to Nguyen et al [27], Magg et al [28], and also to Keller et al [24] should be attributed to V-O-Si out-of-phase vibrations and they confirm a high distribution of vanadium species.…”