Effect of Vanadium Oxides Composition Loaded on γAl₂O₃ Catalyst for Oxidative Dehydrogenation of Propane to Propylene

Abstract

The catalysts were prepared by impregnation method, and the mass fraction of vanadium on γAl 2 O 3 was 3%, 6%, 9%, 12%, 15%, respectivley (denoted as 3 V-γAl 2 O 3 , 6 V-γAl 2 O 3 , 9 V-γAl 2 O 3 , 12 V-γAl 2 O 3 and 15 V-γAl 2 O 3 ). X-ray diffraction(XRD), Raman spectroscopy(Raman), cyclic voltammetry(CV) and in-situ infrared spectroscopy (FT-IR) were used to study the properties of series of vanadium oxides composition loaded on γAl 2 O 3 catalyst for oxidative dehydrogenation of propane to propylene. The results show that the VÀ O-Al bond and the V=O bond are formed at the 3 V-γAl 2 O 3 and 6 V-γAl 2 O 3 catalysts, and the vanadium oxides are uniformly dispersed on γAl 2 O 3 . With the increasing of vanadium loading, for 9 V-γAl 2 O 3 , 12 V-γAl 2 O 3 and 15 V-γAl 2 O 3 catalysts, except VÀ O-Al and V=O bond, there was appeared VÀ O-V bond, indicating the formation of V 2 O 5 crystal supported on γAl 2 O 3 obviously. The uniform dispersion for low vanadium loading on γAl 2 O 3 , is favorable for the selectivity of propylene, and for high vanadium loading catalysts, the V 2 O 5 crystal will accelerate the deep oxidation of propane. At 500°C, the propylene selectivity of the 3 V-γAl 2 O 3 catalyst was 75.9%, and the propane conversion was 12.5%. Whereas the propylene selectivity of the 15 V-γAl 2 O 3 catalyst was 67.3%, and the propane conversion was 10.7%.[a] J.