Transient isotopic study of methanol oxidation on unsupported V2O5 - Mechanism of methylal formation

The mechanism of methylal formation by methanol oxidation on unsupported V2 O5 catalyst has been investigated in transient isotopic experiments, perfor ming an exchange between CH3 OH and CD3 OD. Adsorbed methoxy groups and hem imehylal (CH3OCH2OH) have been identified as intermediate species, the hemi methylal being formed by reaction between an activated methanol species (. CH2OH) and the surface methoxy groups. The methylal is then obtained by a d ehydration reaction between hemimethylal and a methanol molecule or a surfa ce methoxy group. We can also propose that the methyl formate formation (HC OOCH3) could occur by hemimethylal oxidative dehydrogenation, the hemimethy lal (CH3OCH2OH) appearing then as the key intermediate in the methanol oxid ation to methylal and methyl formate. (C) 2001 Elsevier Science B.V. All ri ghts reserved.