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Mesoporogen‐Free Synthesis of High‐Silica Hierarchically Structured ZSM‐5 Zeolites and their Superior Performance for the Methanol‐to‐Propylene Reaction
Author(s) -
Guo Hangle,
Ge Tongguang,
Lv Jian,
Du Changlin,
Zhou Jian,
Liu Zhicheng,
Hua Zile
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201800926
Subject(s) - microporous material , zsm 5 , mesoporous material , chemistry , catalysis , crystallinity , methanol , chemical engineering , selectivity , space velocity , hydrothermal synthesis , sorption , fourier transform infrared spectroscopy , hydrothermal circulation , crystallization , inorganic chemistry , zeolite , organic chemistry , crystallography , adsorption , engineering
A series of hierarchically structured ZSM‐5 zeolites (ZSM‐5 HSZs) with a Si/Al ratio of about 200 have been successfully synthesized in the absence of additional mesoporous agents. XRD, N 2 sorption isotherms, SEM, TEM and NH 3 ‐TPD results showed that the obtained HSZs materials possess high crystallinity, interconnected micro/mesoporous structures and similar total acid amounts. Meanwhile, in the methanol‐to‐propylene (MTP) reaction, compared to the microporous counterpart, all synthesized ZSM‐5 HSZs demonstrated superior performance benefitting from their hierarchical porous structures. Interestingly, 27 Al MAS NMR and Py‐FTIR results confirmed the inter‐transformation of framework and extra‐framework Al species with the extension of materials crystallization duration and consequently the variation of materials surface acidity. As a result, the optimized catalyst achieved the highest initial propylene selectivity of 54.4 % and the longest catalyst lifetime ( t 90 ) of 175 h under the weight hourly space velocity (WHSV) of 1.0 g g –1 h –1 . Moreover, a new “in situ alkali etching‐hydrothermal restoring“ mechanism has been proposed to elucidate the structural evolution of here reported high‐silica ZSM‐5 HSZs during the synthesis.