The critical role of steam during activation process on the catalytic performance of VPO for n-butane selective oxidation to maleic anhydride

Abstract

Vanadium phosphorus oxide (VPO) catalyst activation method is essential for the catalytic oxidation form n-butane to maleic anhydride. Here, we evaluate the effect of steam content on VPO catalyst during the activation process and validate the adjustment of the steam content could modulate the VPO activity. The DRIFTS results reveal that the steam content governs the formation of P-OH and V-OH species on the surface of VPO catalyst, whereas these sites would not enhance the catalytic activity directly. In contrast, the L acid site V5+-O-PO, forming a mutual transformation relationship with the P-OH species under steam/O2 conditions, is the main active site that dominates the conversion of n-butane, and a moderate amount of steam plays a role in stabilizing the V5+-O-PO site.