Vapour phase oxidation of 4-methylanisole to anisaldehyde over V2O5 /MgO-Al2O3 catalysts

The vapour phase selective oxidation of 4-methylanisole to anisaldehyde was investigated over different V2O5 /MgO-Al2O3 catalysts at 673 K and normal atmospheric pressure. Among various catalysts investigated the 16 wt% V2O5 /MgO-Al2O3 catalyst provided good conversion and product selectivity. The MgO-Al2O3 mixed oxide was obtained by a co-precipitation method and V2O5 was impregnated from ammonium metavanadate. The MgO-Al2O3 support and various V2O5 /MgO-Al2O3 catalysts were characterized by means of X-ray diffraction, FT-infrared, electron spin resonance, scanning electron microscopy, ammonia and carbon dioxide chemisorption methods. The characterization results suggest that vanadia does not form layer structures on the support surface, instead interacts very strongly with the support, in particular with MgO, and forms amorphous compounds. The NH3 and CO2 uptake results provide an interesting information on the acid-base characteristics of these catalysts and correlate with their catalytic properties.