物理化学学报 >> 2009, Vol. 25 >> Issue (09): 1921-1927.doi: 10.3866/PKU.WHXB20090919

研究论文 上一篇    下一篇

MFI/MFI核壳分子筛合成的影响因素及结晶动力学

孔德金, 邹薇, 郑均林, 祁晓岚, 房鼎业   

  1. 华东理工大学化工学院, 上海 200237|中国石油化工股份有限公司上海石油化工研究院, 上海 201208
  • 收稿日期:2009-03-24 修回日期:2009-06-19 发布日期:2009-09-03
  • 通讯作者: 孔德金 E-mail:djkong@sript.com.cn

Crystallization Kinetics and Influencing Factors in the Syntheses of MFI/MFI Core-Shell Zeolites

KONG De-Jin, ZOU Wei, ZHENG Jun-Lin, QI Xiao-Lan, FANG Ding-Ye   

  1. College of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, P. R. China|Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208, P. R. China
  • Received:2009-03-24 Revised:2009-06-19 Published:2009-09-03
  • Contact: KONG De-Jin E-mail:djkong@sript.com.cn

摘要:

以低硅铝比ZSM-5 为核, 采用二次生长法水热合成了MFI/MFI核壳分子筛. 发现对核相分子筛进行预处理是合成的关键步骤. 通过控制壳相合成过程(如合成温度、合成时间和核相分子筛加入量)可有效控制核壳分子筛的壳层生长. 以异丙苯(IPB)及1,3,5-三异丙苯(1,3,5-TIPB)裂解为探针反应, 发现与核相分子筛相比, 核壳分子筛的IPB裂解反应活性相当. 而1,3,5-TIPB裂解活性下降68%, 与外表面Al含量下降程度相近, 表明MFI/MFI核壳分子筛较好地保留了分子筛的核相反应活性. 结晶动力学计算结果表明, MFI/MFI核壳分子筛的成核活化能为51.5 kJ·mol-1, 生长活化能为26.5 kJ·mol-1.

关键词: 结晶动力学, ZSM-5, MFI/MFI, 核壳分子筛, 成核活化能, 生长活化能

Abstract:

MFI/MFI core-shell zeolites with a low silica to alumina ratio core and a continuous shell of high silica to alumina ratio were successfully synthesized by a novel two-step procedure. This was done by a secondary growth of the ZSM-5 shell onto the modified ZSM-5 crystals and the pre-treatment step played an important role during the synthesis. Critical factors for the growth of the ZSM-5 shell including synthesis temperatures, periods, and core dosages were summarized. Results from cumene and 1,3,5-triisopropylbenzene (1,3,5-TIPB) cracking reactions showed that the core-shell zeolite and the core crystal had comparable activities for the cumene cracking reaction. Compared to the core crystal, the cracking activity of 1,3,5-TIPB of the core-shell zeolite was reduced by 68%, which coincided with the extent of aluminum reduction on the external surface. These results suggested that the acidity of the core crystals was largely preserved in the MFI/MFI core-shell structure. Crystallization kinetics curves were determined at different synthesis temperatures. The apparent energy of crystallization activation was found to be 26.5 kJ·mol-1 and the activation
energy of nucleation was 51.5 kJ·mol-1.

Key words: Crystallization kinetics, ZSM-5, MFI/MFI, Core-shell zeolite, Nucleation activation energy, Crystallization activation energy

MSC2000: 

  • O643