Impact of the outermost layer of various solid metal vanadate catalysts on ammoxidation of 2-methyl pyrazine to 2-cyanopyrazine

• XPS and LEIS allow detecting variation of the composition normal to the surface.
• Only V-enriched outermost surface layers lead to selective catalysts.
• The stability of these layers under feed is crucial for the catalytic performance.

Metal vanadates are promising catalysts for the ammoxidation of 2-methylpyrazine to 2-cyanopyrazine, an important intermediate in the production of pyrazinamide as an effective anti-tubercular drug. Low-Energy Ion Scattering (LEIS) investigations supplementing X-ray Photoelectron Spectroscopy (XPS) measurements showed the variation of the composition in the near-surface region. Only with this experimental approach it was possible to elucidate, how important are stable vanadium-enriched or pure vanadia outermost surface layers for a selective catalyst. In contrast, mixed oxide outermost layers are detrimental for the catalytic performance.

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