Ammoxidation of 2-methylpyrazine. Characterisation of catalyst
The effect of changing the relative ratios of the active components in Sb–V–Mn mixed oxides, their concentration on the support and the nature of the latter has been analysed by employing several techniques, such as X-ray diffraction, scanning electron microscopy, electron probe microanalysis and electron spin resonance spectroscopy, together with chemical analysis, a titration of the surface acidity, and determinations of both the B.E.T. surface area and the porosity. A close dependence of activity and selectivity on the nature of the support was observed, connected with the ability of the latter to suppress the formation of microporosity. The catalytic activity is due to Sb4+ species. V and Mn both act as a structural promoter, conferring electrical conductivity on the solid and so improving the rapid electron transfer from the bulk to the surface, and vice versa.