文献类型：期刊文献

英文题名：Unraveling the non-classic crystallization of SAPO-34 in a dry gel system towards controlling meso-structure with the assistance of growth inhibitor: Growth mechanism, hierarchical structure control and catalytic properties

作者：Zheng, Jingwei[1];Zhang, Weiping[2];Liu, Zhiting[1];Huo, Qisheng[3];Zhu, Kake[1];Zhou, Xinggui[1];Yuan, Weikang[1]

机构：[1]E China Univ Sci & Technol, State Key Lab Chem Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China;[2]Dalian Univ Technol, State Key Lab Fine Chem, 2 Lingjing Rd, Dalian 116024, Peoples R China;[3]Jilin Univ, State Key Lab Inorgan Synth & Preparat Chem, Coll Chem, 2699 Qianjindajie, Changchun 130012, Peoples R China

年份：2016

卷号：225

起止页码：74

外文期刊名：MICROPOROUS AND MESOPOROUS MATERIALS

收录：;EI(收录号：20155301739132);WOS:【SCI-EXPANDED(收录号:WOS:000373421700007)】；

基金：XZ is sponsored by the National Natural Science Foundation of China (U1162112). WP is sponsored by Natural Science Foundation of China (21373035). KZ is grateful for the financial support from National Natural Science Foundation of China (21576082), Fundamental Research Funds for the Central Universities (WB 1213004-1).

语种：英文

外文关键词：SAPO-34; Orientated attachment crystallization; Hierarchical structure; Chloromethane conversion; Light olefins

摘要：Understanding silicoaluminophosphate formation mechanism lays the foundation for their structure manipulation via crystallization process control. Crystallization of SAPO-34 from a dry gel using tetraethyl ammonium hydroxide as structure-directing agent was monitored to unravel the formation mechanism. The initial gel was found to form a lamellar precursor first, which subsequently underwent phase transformation to discrete SAPO-34 nanocrystallites. The nanocrystallites thereafter mutually aligned with neighboring ones via a non-classic oriented attachment growth mechanism, affording large crystals as a result of grain boundary elimination. A new protocol to prepare hierarchical SAPO-34 was designed by hindering the aggregation of primary nanocrystallites with a growth inhibitor 1,2,3-hexanetriol. The structure of hierarchical SAPO-34 was characterized by XRD, N-2 physisorption, mercury intrusion, SEM, TEM, as well as Al-27, Si-29, P-31 MAS NMR spectra and compared with a conventional SAPO-34. More Si islands were formed via combined SM3 (Al+P pairs substitution by 2Si) and SM2 (P substitution by Si) mechanism for hierarchical SAPO-34 as Si was not fully incorporated into the precursor lamellar phase. NH3-TPD showed that hierarchical SAPO-34 has comparable acidic strength to conventional SAPO-34. The obtained hierarchical SAPO-34 is comprised of <100 nm crystallites and possesses well-connected mesopores, both factors are crucial to mass transfer in zeotype materials. Hierarchical SAPO-34 exhibited a 1.5 times lifetime increase in catalytic chloromethane to olefin conversion with respect to a conventional counterpart. (C) 2015 Elsevier Inc. All rights reserved.