Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (09): 2209-2216.doi: 10.3866/PKU.WHXB20110806

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Influences of V2O5 Loadings on V2O5/Al2O3 Oxidative Activation Performances for n-Heptane Catalytic Cracking

HU Xiao-Yan, LI Chun-Yi, YANG Chao-He   

  1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266555, Shandong Province, P. R. China
  • Received:2011-03-14 Revised:2011-05-30 Published:2011-08-26
  • Contact: LI Chun-Yi
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2006CB202505).

Abstract: X-ray diffraction (XRD), nitrogen adsorption-desorption, ammonia-temperature programmed desorption (NH3-TPD), and pyridine-Fourier transform infrared (pyridine-FT-IR) spectroscopy analyses were performed to characterize V2O5/Al2Ox with different V2O5 loadings. We conclude that a 20%-25% (w) V2O5 loading corresponds to the monolayer coverage of VOx units over the surface of V2O5/Al2O3 according to the VOx unit surface density values. The impregnation of V2O5 led to a decrease in the Lewis acidity of the alumina and the formation of Brønsted acid sites, which resulted from the V―OH groups of the oxidized VOx units. With an increase in V2O5 loading the amount of Brønsted acid sites increased and reached a maximum at a V2O5 loading of about 20%. The influence of V2O5 loading in V2O5/Al2O3 on the oxidative activation performance during n-heptane catalytic cracking was studied. The results show that the highest promotion was obtained upon introducing V2O5/Al2O3 with a 20%-25% V2O5 loading into the HZSM-5 equilibrium catalyst. V2O5/Al2O3 (20%-25% V2O5) had a monolayer coverage of VOx units over its surface and it provided the largest amount of surface lattice oxygen and thus the strongest oxidative activation toward n-heptane was achieved. The performance decreased when the V2O5 loading increased further because of the inhibited participation of surface lattice oxygen in the reaction, which was caused by the formation of bulk V2O5 and AlVO4.

Key words: V2O5/Al2O3, Vanadia loading, VOx configuration, Lattice oxygen, Oxidative activation


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