Modifications of vanadium phosphorus oxides by aluminium phosphate for n-butane oxidation to maleic anhydride

Aluminium phosphate associated with vanadium phosphorus oxide is demonstrated in improving both the catalytic performance for the production of maleic anhydride from n-butane and the time of activation of the catalyst as compared to conventional vanadium phosphorus oxide catalysts. Aluminium phosphate is prepared at a fixed pH and then added during the preparation of the VOHPO 4 , 0.5 H 2 O precursor. The morphology of the VPO precursor is influenced by the nature of the A1PO material. The VPO-A1PO catalyst is then activated in situ under an-butane/air atmosphere. During the activation, (VO) 2 P 2 O 7 is formed and the original amorphous A1PO material crystallizes. No new ternary VA1PO phase is observed. The improvement in the catalytic properties of the mixed VPO-A1PO oxide system cannot solely be explained in terms of a doped V(Al)P0 catalyst (Al/V= 1%) prepared independently, for which the catalytic performances are lower.