高等学校化学学报 ›› 1991, Vol. 12 ›› Issue (4): 436.

• 论文 • 上一篇    下一篇

FTIR研究不同硅铝比HZSM-5沸石的酸性质

吴恩源, 李全芝   

  1. 复旦大学化学系, 200433
  • 收稿日期:1989-09-08 出版日期:1991-04-24 发布日期:1991-04-24
  • 通讯作者: 李全芝
  • 基金资助:

    国家自然科学基金;中国石化总公司资助课题

A FTIR Spectroscopy Study on Acidic Properties of HZSM-5 Zeolites with Different SiO2/Al2O3Ratios

Wu En-yuan, Li Quan-zhi   

  1. Department of Chemistry, Fudan University, Shanghai, 200433
  • Received:1989-09-08 Online:1991-04-24 Published:1991-04-24

摘要: 用IR和NH3-TPD测定了硅铝比为31.4~137.1的HZSM-5沸石样品的酸中心数;由Lang-muir吸附模型推导出B、L酸的吸附热公式,并由此计算了B酸的吸附热。发现在Al/u.c.为3.64附近,酸中心数与Al/u.c的关系发生了转折,并发现B酸吸附符合Langmuir模型,L酸强度不均匀而不符合该模型,测定了HZSM-5分子筛的B、L酸消光系数8B=7.52×105cm·mol-1、8L=1.09×106cm·mol-1

关键词: 吸附热, FTIR, HZSM-5沸石, 硅铝比, 酸性质

Abstract: Numbers of acid sites of a series of HZSM-5 zeolites with SiO2/Al2O3from 31. 4 to 137. 1 were determined using IR and NH3-TPD spectra. To calculate respectively the adsorption heats of Bronsted and Lewis acid sites, an equation, ln0/[(1 - 0)P]=Q/RT+C, was established with the help of Langmuir model, and the adsorption heats of Bronsted acid sites were calculated with this equation. It was found that there is a transition of the relationship between Al/u. c. and acidic concentration at Al/u. c.=3. 64. The calculated results show that the adsorption on Bronsted acid sites accords with Langmuir model and the adsorption heats of samples with different SiO2/Al2O3are almost the same, but the strength of Lewis acid sites is heterogeneous and adsorption on Lewis acid sites does not accord with Langmuir model. The extinction coefficients of Bronsted and Lewis sites of HZSM-5 zeolites were also determined, εB=7. 52×10 cm·mol-1and εL=1. 09×10 cm·mol-1.

Key words: Adsorption heat, FTlR, HZSM-5 zeolite, SiO2/Al2O3ratios, Acidic properties

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