Study on the V-P-O/ SiO2 Catalyst in the Partial Oxidation of Iso-butane

The V2O5/SiO2 and V2O5-P2O5/SiO2 catalysts were prepared by the Sol-gel method. The surface composition，structure，chemisorption and reactivity of the catalysts were systematically studied by using the techniques of XRD，TPR，IR，TPD and icro-reactor. The results showed that the active component was dispersed uniformly on the surface of amorphous SiO2 . There existed Lewis base sites（V=O and V-O-V）and Lewis acid sites （Vn+）on the surface of these catalysts. An addition of PO43- could lower the activity of surface terminal oxygen of Lewis base sites V=O. Iso-butane could chemisorbed on surface terminal oxygen of Lewis base sites V=O by one or two H atoms in -CH3 to form molecular adsorption states. Reaction products of i-C4H10 on the V-P-O/SiO2 catalyst were mainly i-C4H8，MAL，MAA and COx . Conversion of i-C4H10 was 5% and selectivity of partial oxidation products is above 72% at 300℃. The addition of PO43- could improve the selectivity of partial oxidation products on the VSiO catalyst because PO43- could reduce the activity of lattice oxygen in V = O bond，and weaken the adsorption intensity of i-C4H10 .