Phase composition, surface characterization and catalytic performance of VPO and thulium doped VPO catalysts were investigated by means of NH3-TPD, XPS,XRD and IR. Experimental results showed that when Tm/V (atomic ratio) ＜0.10, both Bronsted and Lewis acidities on the surface of VPO catalysts with the addition of thulium were stronger than those of VPO catalyst, the doped catalyst accelerated the dehydrogena tion step of the oxidation reaction of n-butane. Conversion of n-butane and selectivity to maleic anhydride were enhanced. While Tm/V■0.10, the surface acidity of the catalysts was decreased and the activity of catalysts was dropped.
