焙烧对HZSM—5分子筛酸性的影响

THE INFLUENCE OF CALCINATION ON THE ACIDITY OF HZSM-5 ZEOLITE

本文运用FTIR及TPD等手段，以氢和吡啶作探针，研究了焙烧温度和升温速率对分子筛结构和酸性的影响。研究表明，随着焙烧温度的升高，HZSM—5分子筛骨架上的铝不断地从骨加上脱除下来进入分子筛孔道而形成骨架外铝，与此同时，分子筛的酸性受到影响。较低温度（＜650℃）时，耐酸性的影响不大；高温（＞650℃）焙烧则使得HZSM—5分子筛的B酸位大幅减少，L酸位有所增加。升温速率对HZSM－5分子筛的酸性基本无影响。

The influence of calcination (temperature and heating rate)on the acidity of HZSM-5 zeolite has been studied by means of FTIR and TPD using NH, and pyridine as probes. It has been found that the framework aIuminum escapes from HZSM-5 structure and forms extraframework Al species during caIcination.With increasing calcination temperature, Bronsted sites decrease severely (>650 ℃)and Lewis sites increase. It has also been indicated that the heating rate of calcina-tion has basically no effect on the acidity of HZSM-5 zeolite.