Seed-assisted, OSDA-free synthesis of MTW-type zeolite and "Green MTW" from sodium aluminosilicate gel systems
Seed-assisted, OSDA-free synthesis of MTW-type zeolite and "Green MTW" from sodium aluminosilicate gel systems
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DOI：
10.1016/j.micromeso.2011.05.038
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发表时间：
2012-01-01
影响因子：
5.2
通讯作者：
Okubo, Tatsuya
中科院分区：
文献类型：
--
作者：
Kamimura, Yoshihiro;Itabashi, Keiji;Okubo, Tatsuya
近年来，晶种辅助法为在环境友好条件下无有机结构导向剂（OSDA）合成工业上有用的沸石提供了一条新的途径。本文研究了以四乙基氢氧化铵（TEAOH）为催化剂，煅烧ZSM-12晶种，水热处理铝硅酸钠凝胶合成MTW型分子筛过程中的各种参数。更重要的是，首次实现了以不含有机硅的合成产物为晶种生产绿色MTW型沸石，简称“绿色MTW”。X射线衍射（XRD）、场发射扫描电子显微镜（FE-SEM）和固体Al-27 MAS NMR结果表明，MTW型沸石和绿色MTW的结晶度优于焙烧ZSM-12晶种。当初始反应物凝胶中不存在晶种而形成ZSM-5（MFI型沸石）和/或丝光沸石（MOR型沸石）时，不能获得MTW型沸石。水化样品的热重（TG）分析结果证实了MTW型分子筛具有足够的水化体积，而MTW型分子筛和绿色MTW的氮吸附-脱附测试结果表明，MTW型分子筛的氮吸附容量低于种子的氮吸附容量，这可能是由于MTW骨架的一维孔道系统中存在部分孔道堵塞。(C)2011 Elsevier Inc. All rights reserved.
Recently, the seed-assisted methods have provided a new route for the organic structure-directing agent (OSDA)-free synthesis of industrially useful zeolites under environmentally-friendly conditions. In this paper, the various parameters are investigated in the OSDA-free synthesis of MTW-type zeolite by the hydrothermal treatment of sodium aluminosilicate gel with the aid of calcined ZSM-12 seed crystals prepared using tetraethylammonium hydroxide (TEAOH). More importantly, the green production of MTW-type zeolite referred as "Green MTW" is achieved for the first time, by using the product of OSDA-free synthesis as seeds. The X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and solid-state Al-27 MAS NMR results exhibit better crystallinity of MTW-type zeolite and Green MTW than those of calcined ZSM-12 seeds. MTW-type zeolite is not obtained when seeds are absent in the initial reactant gel while ZSM-5 (MFI-type zeolite) and/or mordenite (MOR-type zeolite) are formed. The results of thermogravimetric (TG) analysis of hydrated samples confirm the enough micropore volume in MTW-type zeolite whereas nitrogen adsorption-desorption measurements of MTW-type zeolite and Green MTW show nitrogen adsorption capacity lower than that of the seeds, which might be attributed to the partial pore blocking in the one-dimensional channel systems of the MTW framework. (C) 2011 Elsevier Inc. All rights reserved.