Influence of doped ZrO2 on the selective oxidation of methanol to methylformate on vanadium oxide catalysts

It is well known that methanol can be oxidized to formaldehyde in the presence of air and Ag or V2O5-based catalysts. Next to the formaldehyde production, a small amount of methylformate is produced. The activity increases with increasing V2O5 content on doped as well as on undoped supports, which detrimental to selectivity to methylformate. Doping with lanthanum decreases the activity and selectivity dramatically. The more lanthanum is present the less active the catalyst is. Possibly Lanthanum forms an inactive compound with V2O5. ESCA measurements indicate mixed oxide formation between this dope and vanadium. Yttrium has a beneficial effect on the selectivity to methylformate, it can give higher conversion and at the same time higher selectivities than vanadium on zirconia, although this can also be because of the higher surface area of these catalysts. However, in both cases (doped and undoped zirconias), a low coverage by V2O5 seem to be beneficial for the metylformate formation. Possibly, the uncovered support plays an important role in the methylformate formation, possibly by increasing the formation of the necessary methoxy groups.