Res. Chem. Intermed., Vol. 27, No. 3, pp. 225–236 (2001) Ó VSP 2001. Vapour phase oxidation of 4-methylanisole to anisaldehyde over V 2 O 5 /MgO-Al 2 O 3 catalysts BENJARAM M. REDDY ¤ , D. GIRIDHAR and M. VIJAYA KUMAR Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad, 500 007, India Received 5 June 2000; accepted 1 August 2000 Abstract—The vapour phase selective oxidation of 4-methylanisole to anisaldehyde was investigated over different V 2 O 5 /MgO-Al 2 O 3 catalysts at 673 K and normal atmospheric pressure. Among various catalysts investigated the 16 wt% V 2 O 5 / MgO-Al 2 O 3 catalyst provided good conversion and product selectivity. The MgO-Al 2 O 3 mixed oxide was obtained by a co-precipitation method and V 2 O 5 was impregnated from ammonium metavanadate. The MgO-Al 2 O 3 support and various V 2 O 5 /MgO-Al 2 O 3 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 NH 3 and CO 2 uptake results provide an interesting information on the acid-base characteristics of these catalysts and correlate with their catalytic properties. INTRODUCTION Supported vanadium oxide catalysts have received a great deal of attention recently because of their commercial applications in several industrial heterogeneous cat- alytic processes, such as partial oxidation of alkanes, ammoxidation of aromatic compounds, selective catalytic reduction of nitrogen oxides, and oxidative dehy- drogenation of alkanes [1– 5]. Activity and selectivity of these catalysts is known depend on the nature of support material, amount of active component deposited, and the method of preparation. As per the literature reports, the selective oxida- tions greatly depend on both surface acid-base characteristics and redox proper- ties of the catalysts [6]. Vanadium oxide, when supported on basic oxides such as MgO (V-Mg-O) shows better performance than on the acid supports like alu- mina, titania, and silica-alumina for selective oxidation reactions [7, 8]. It has been reported recently that the V-Mg-O catalysts exhibit good activity and selec-