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

The mechanism of methylal formation by methanol oxidation on unsupported V2O5 catalyst has been investigated in transient isotopic experiments, performing an exchange between CH3 OH and CD3 OD. Adsorbed methoxy groups and hemimehylal (CH3OCH2OH) have been identified as intermediate species, the hemimethylal being formed by reaction between an activated methanol species (. CH2OH) and the surface methoxy groups. The methylal is then obtained by a dehydration reaction between hemimethylal and a methanol molecule or a surface methoxy group. We can also propose that the methyl formate formation (HCOOCH3) could occur by hemimethylal oxidative dehydrogenation, the hemimethylal (CH3OCH2OH) appearing then as the key intermediate in the methanol oxidation to methylal and methyl formate. (C) 2001 Elsevier Science B.V. All rights reserved.