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Crystallization Mechanism and Performance in Methanol to Olefins Reaction of SAPO-18 Molecular Sieve
Author NameAffiliationE-mail
GUO Yun-Ya Institute of Fine Chemical Engineering, Chemical Engineering Institute, Taiyuan University of Technology, Taiyuan 030024, China  
LIANG Guang-Hua Taiyuan Dacheng Huaneng Chemical Co. Ltd., Taiyuan 030024, China  
ZHANG Yan-Ting Taiyuan Dacheng Huaneng Chemical Co. Ltd., Taiyuan 030024, China  
HE Zu-Guang Institute of Fine Chemical Engineering, Chemical Engineering Institute, Taiyuan University of Technology, Taiyuan 030024, China  
LIANG Ya-Ning Taiyuan Dacheng Huaneng Chemical Co. Ltd., Taiyuan 030024, China  
LI Ning Taiyuan Dacheng Huaneng Chemical Co. Ltd., Taiyuan 030024, China  
LI Xiao-Feng Institute of Fine Chemical Engineering, Chemical Engineering Institute, Taiyuan University of Technology, Taiyuan 030024, China lixiaofeng6008@163.com 
DOU Tao Institute of Fine Chemical Engineering, Chemical Engineering Institute, Taiyuan University of Technology, Taiyuan 030024, China
Taiyuan Dacheng Huaneng Chemical Co. Ltd., Taiyuan 030024, China 
dtaol@163.com 
Abstract: SAPO-18 molecular sieves with the different crystallization times were prepared by hydrothermal method, which respectively taking the pseudo-boehmite, silica sol and phosphoric acid as the aluminum source, silicon source, phosphorus source, and N,N-diisopropylethylamine as the template. The samples at different crystallization times and its MTO (methanol to olefins) catalytic performance were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), NH3-TPD, 29Si MAS NMR,27Al MAS NMR, FT-IR and other methods. The characterization results combined with the catalytic performance of MTO indicated that the growth process of SAPO-18 molecular sieve in the hydrothermal system could be divided into three stages:initial crystallization (≤ 2 h), rapid growth (6~12 h) and stable growth (1~3 d). In the early stage of crystallization, only a small amount of silicon enter the Al(PO)4 intermediates. The silicon atoms then enter the Al(PO)4 intermediates and SAPO-18 crystal, and replace phosphorus and aluminum atoms. SMⅡ mechanism is as the priority and SMⅢ mechanism is as the auxiliary pole in the fast growing period. The two substitution mechanisms of growth stabilization are in the opposite order.
Keywords: SAPO-18  crystallization mechanism  hydrothermal synthesis  methanol-to-olefins
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GUO Yun-Ya,LIANG Guang-Hua,ZHANG Yan-Ting,HE Zu-Guang,LIANG Ya-Ning,LI Ning,LI Xiao-Feng,DOU Tao.Crystallization Mechanism and Performance in Methanol to Olefins Reaction of SAPO-18 Molecular Sieve[J].Chinese Journal of Inorganic Chemistry,2019,35(2):185-193.
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Chinese Journal of Inorganic Chemistry