Catalytic Transformation of Ethanol over Microporous Vanadium Silicate Molecular Sieves with MEL Structure (VS-2)

Ethylene and Acetaldehyde Production by Selective Oxidation of Ethanol Using Mesoporous V−MCM-41 Catalysts

“…33 High ethylene selectivity of the V-MCM-41 catalyst synthesized in this work is expected to be strongly related to the coordination of the V, Si, and O atoms in the catalyst structure. As it was also reported by Kannan et al, 23 diethyl ether and ethylene production was probably due to the simultaneous involvement of vanadyl (VdO) and V-O-Si groups in the lattice structure of the catalyst, while VdO was responsible for the formation of acetaldehyde. Critical functionality of the V-O-Si bridging bonds in the selective oxidation reactions and oxygen liberation of the surface redox sites of mixed metal oxide catalysts were also demonstrated by Wachs and coworkers, 38,39 in methanol oxidation reaction.…”

“…It is generally believed that redox sites produce acetaldehyde in the presence of oxygen. Involvement of the surface vanadyl (VdO) species of the vanadium silicate molecular sieves in the formation of acetaldehyde during the selective oxidation of ethanol was also demonstrated in the work of Kannan et al 23 Elimination of an hydrogen atom from the adsorbed ethoxy species (hydrogen atom connected to the carbon atom of the ethoxy species which was bonded to the catalyst site) by a lattice oxygen of the catalyst may be responsible for the formation of acetaldehyde on the catalyst surface. A similar mechanism, involving the removal of the R-hydrogen from the adsorbed ethoxy species in the formation of acetaldehyde was also reported by Tesser et al 16 The reduction of the catalytic activity and the corresponding decrease in the acetaldehyde yield in the absence of gas-phase oxygen, indicated the consumption of the surface lattice oxygen of the catalyst.…”

“…[16][17][18][19][20][21][22] However, in some of these studies formation of small amounts of ethylene was also indicated. Kannan et al 23 also indicated the formation of ethylene, together with acet-aldehyde and diethyl ether, by selective oxidation of ethanol over microporous vanadium silicate molecular sieves.…”

A hierarchically ordered porous novel vanado-silicate catalyst for highly efficient oxidation of bulky organic molecules

“…The Turn Over Number (TON) calculated based on the moles of cyclooctene converted (38.5%) per mole of vanadyl species present (1.16 Â 10 À6 moles in 0.1 g catalyst) in the calcined MH0.01 was 3019. The TON value for the present system is exceptionally high compared to the TON value reported 7,20 for vanadyl species in MEL and MFI zeolite systems for oxidation of toluene. A poor conversion (o0.1%) of cyclooctene was observed when V-impregnated HOPS was used for similar reaction.…”

Vanadium-modified molecular sieves: preparation, characterization and catalysis

“…In the transformation of ethanol, for instance, Kannan et al 56 claim that only V=O species are selective for acetaldehyde while both V=O and V-O-Si species are selective for diethyl ether. This reaction is important for the production of value-added chemicals from bio-based ethanol.…”