Study of the Metal Phosphate Gatalysts for Selective Oxidation of Lower Alkanes

2. (VO)_2P_2O_7 is a unique catalyst possessing a surprisingly high selectivity for the oxidation of n-butane to maleic anhydride. We reports that (VO)_2P_2O_7 mixed with a divalent metal orthophosphate can be used to synthesize maleic anhydride from n-butane oxidation with high selectivity and activity. The catalyst of (VO)_2P_2O_7 mixed with M^<2+>_3 (PO_4)_2 (M^<2+>=Fe, Ni, Co, Zn) has extremly high activity for n-butane oxidation to maleic anhydride. The M^<2+>_3 (PO_4) _2 grains are easly covered by the (VO)_2P_2O_7. The (100) plane of (VO)_2P_2O_7 in mixed catalysts has a more regular configuration compared to the simple (VO)_2P_2O_7. This regularity of the (100) plane causes the high activity and selectivity for n-butane oxidation. The promotion effect of the metal phosphate for (VO)_2P_2O_7 is in the order of M^<2+>_3 (PO_4)_2 > M^<2+>_2P_2O_7 > M^<3+>PO_4. The different promotion effects come from the degree of surface regularity by intercaleted metal phosphates with different structure.