催化学报

催化学报 ›› 2007, Vol. 28 ›› Issue (2): 158-162.

• 研究论文 • 上一篇    下一篇

乙炔在ZSM-5分子筛上的吸附机制及吸附态性质

于青,王新平,陈静,贾翠英   

  1. 大连理工大学化工学院精细化工国家重点实验室, 辽宁大连 116024
  • 收稿日期:2007-02-25 出版日期:2007-02-25 发布日期:2011-01-28

Mechanism of Acetylene Adsorption on ZSM-5 Zeolites and Characteristics of the Surface Species

YU Qing, WANG Xinping*, CHEN Jing, JIA Cuiying   

  1. State Key Laboratory of Fine Chemicals, College of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China
  • Received:2007-02-25 Online:2007-02-25 Published:2011-01-28

PDF

963

被引次数

9

摘要： 在有微量水存在下研究了乙炔在HZSM-5和NaZSM-5上的吸附和脱附. 在80 ℃下, NaZSM-5上乙炔的饱和吸附量约为HZSM-5上的5倍,但在200 ℃以上时吸附的乙炔只有少量可存留于NaZSM-5表面. 这与乙炔在HZSM-5上的较强吸附显著不同. 依据FT-IR对乙炔吸附态的测定,研究了乙炔在ZSM-5分子筛上的吸附机制及吸附态性质. 乙炔与HZSM-5中B酸中心上的水作用形成乙烯醇,后者在升温时变为碳正离子结合在分子筛的 Al-O--Si 上构成强吸附物种. 在NaZSM-5上,乙炔只通过与Na+位上的水作用形成乙烯醇,后者与沸石孔道中的阳离子以静电结合构成弱吸附物种. 与HZSM-5的情况不同, NaZSM-5上的吸附物种在升温过程中被活化前即分解成乙炔脱附.

关键词: 乙炔, ZSM-5分子筛, 吸附, 机理, 吸附态

Abstract: Adsorption and desorption of acetylene on HZSM-5 and NaZSM-5 zeolites were investigated in the presence of trace water. The results showed that saturated adsorption of acetylene on NaZSM-5 was about five times as much as that on HZSM-5 at 80 ℃, but little acetylene could bear the temperature up to 200 ℃, which is in contrast to the strong adsorption of acetylene on HZSM-5. Based on the FT-IR results characterizing the adsorption states of acetylene on the zeolites as well as their evolution with increasing temperature, a mechanism of acetylene adsorption on ZSM-5 zeolites was proposed that acetylene reacts with the water adsorbed on Bronsted acid sites to form vinyl alcohol. The latter is converted to carbonium ions bound to Al[KG-45x]-[KG-20x]O-[KG-45x]-[KG-20x]Si, corresponding to the strongly adsorbed species on HZSM-5. On NaZSM-5, acetylene reacts with the water adsorbed on Na+ sites to form vinyl alcohol bound to the cations in zeolite through static attraction, corresponding to the weakly adsorbed species. Being different from the case of HZSM-5, the species on NaZSM-5 can not be further activated because they are decomposed to acetylene and desorbed with increasing temperature.

Key words: acetylene, ZSM-5 zeolite, adsorption, mechanism, adsorption state