物理化学学报 >> 2002, Vol. 18 >> Issue (09): 786-790.doi: 10.3866/PKU.WHXB20020904

研究论文 上一篇    下一篇

HZSM-5分子筛焙烧脱铝的27Al MQMAS NMR研究

陈雷;邓风;叶朝辉   

  1. 中国科学院武汉物理与数学研究所,波谱与原子分子国家重点实验室,武汉 430071
  • 收稿日期:2002-01-02 修回日期:2002-03-25 发布日期:2002-09-15
  • 通讯作者: 邓风 E-mail:dengf@wipm.ac.cn

Dealumination of HZSM-5 Zeolite by Calcination:27Al Multiple Quantum MAS NMR Study

Chen Lei;Deng Feng;Ye Chao-Hui   

  1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071
  • Received:2002-01-02 Revised:2002-03-25 Published:2002-09-15
  • Contact: Deng Feng E-mail:dengf@wipm.ac.cn

摘要: 用29Si、27Al魔角旋转固体核磁共振(MAS NMR)结合二维多量子魔角旋转(2D MQMAS)技术对焙烧脱铝的HZSM-5分子筛中铝的配位状态进行了研究.结果表明,HZSM-5分子筛经焙烧后,在化学位移(δ)45处出现一宽峰信号,其主要来自扭曲四配位铝.通过二维三量子铝谱计算出扭曲四配位铝的四极作用常数约为5.2 MHz.对700和750 ℃焙烧样品的铝谱进行分峰拟合,发现在δ 30处又出现一个小峰,归属为非骨架五配位铝.同时,在750 ℃焙烧样品的二维多量子铝谱中直接观察到非骨架五配位铝的信号.焙烧温度低于700 ℃,脱铝不明显;高于700 ℃,引起分子筛骨架的显著脱铝.焙烧还造成部分骨架铝的信号变得“不可观测”.

关键词: HZSM-5, NMR, MQMAS, 脱铝, 焙烧

Abstract: The coordination states of aluminum species in calcined HZSM-5 zeolites have been investigated using 29Si, 27Al MAS and 2D MQMAS NMR methods. A broad peak at δ 45 in presents in the 27Al MAS NMR spectra of calcined HZSM-5 zeolites. From the 27Al 3QMAS NMR spectrum, it is evident that the peak at δ 45 comes mainly from the distorted tetrahedral Al with a quadrupolar-coupling constant of 5.2 MHz. Simulation of the 27Al 1D MAS NMR spectra of samples calcined at 700 and 750 ℃ shows that a small peak at about δ 30 emerges, which is probably due to 5- coordinated non-framework Al. The existence of this Al species is also confirmed by 27Al 3QMAS NMR.HZSM-5 zeolite calcined at temperature higher than 700 ℃ suffers severe dealumination. Calcination causes part of the Al species “NMR invisible” in the corresponding 27Al MAS spectra.

Key words: HZSM-5, NMR, MQMAS, Dealumination, Calcination