物理化学学报 >> 2011, Vol. 27 >> Issue (09): 2209-2216.doi: 10.3866/PKU.WHXB20110806

催化和表面科学 上一篇    下一篇

V2O5负载量对V2O5/Al2O3氧化活化正庚烷催化裂解反应的影响

胡晓燕, 李春义, 杨朝合   

  1. 中国石油大学(华东), 重质油国家重点实验室, 山东青岛 266555
  • 收稿日期:2011-03-14 修回日期:2011-05-30 发布日期:2011-08-26
  • 通讯作者: 李春义 E-mail:chyli@upc.edu.cn
  • 基金资助:

    国家重点基础研究发展规划项目(973) (2006CB202505)资助

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 E-mail:chyli@upc.edu.cn
  • Supported by:

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

摘要: 采用X射线衍射, 低温氮气吸脱附, 氨气程序升温脱附和吡啶吸附红外光谱分析方法对不同活性组分负载量V2O5/Al2O3的性质进行了表征. 根据表面VOx单元密度, 推测V2O5负载量为20%-25% (w)对应着V2O5/Al2O3表面达单层覆盖状态; V2O5的负载使Al2O3表面Lewis 酸量减少, 并出现Brønsted 酸, 对应着氧化态VOx单元中的V―OH; 随着负载量的增加, Brønsted 酸量增加至负载量为20%时达到最大值. 对V2O5/Al2O3中活性组分负载量对其氧化活化正庚烷催化裂解反应的影响进行了考察. 结果表明, 在V2O5负载量为20%-25%时,V2O5/Al2O3的引入对正庚烷在HZSM-5 平衡剂上催化裂解反应的促进作用最明显, 此时VOx单元在V2O5/Al2O3表面形成单层覆盖状态, 可提供最大量的表面晶格氧, 因而对正庚烷具有最强的氧化活化作用; V2O5负载量继续增加形成体相的V2O5和AlVO4, 不利于晶格氧参与正庚烷的转化, 因而反应性能有所下降.

关键词: V2O5/Al2O3, V2O5负载量, VOx结构形态, 晶格氧, 氧化活化

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

MSC2000: 

  • O643