Permeation mechanism through zeolite NaA and T-type membranes for practical dehydration of organic solvents
Permeation mechanism through zeolite NaA and T-type membranes for practical dehydration of organic solvents
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DOI：
10.1016/j.memsci.2010.05.048
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发表时间：
2010-09-30
影响因子：
9.5
通讯作者：
Kita, Hidetoshi
中科院分区：
文献类型：
--
作者：
Kondo, Masakazu;Kita, Hidetoshi
采用水热法在多孔圆柱莫来石管表面生长沸石NaA和t型膜，对水/有机混合物的渗透汽化（PV）和蒸汽渗透（VP）表现出优异的水透选择性能。两种沸石膜均由管外表面互生的沸石晶体层组成，NaA膜厚度约为10 μ m， t型膜厚度约为20 μ m。它们的沸石晶体层由两层组成，即上表层和下表层中间层。NaA膜的平均开尔文直径为1.4 nm， t型膜的平均开尔文直径为0.8 nm。沸石NaA膜在水/甲醇混合物中也表现出极高的PV和VP性能。除了水/甲醇混合物外，t型膜在水/酒精混合物中也表现出极高的PV和VP性能。从新的理论角度对实验数据进行了讨论。考虑因素包括：一个非常细而窄的非沸石孔隙从沸石晶体层渗透到莫来石载体。顶表面层的大部分沸石孔隙聚集在非沸石孔隙中。进料中的水分子选择性吸附在上表层的沸石孔隙中，再通过沸石孔隙输送到非沸石孔隙中。在非沸石孔隙中较窄的空间发生毛细凝结，然后冷凝物蒸发扩散到渗透侧。(C) 2010 Elsevier B.V.版权所有
Commercially available zeolite NaA and T-type membranes, which were grown on the surface of porous cylindrical mullite tubes by hydrothermal treatment, showed excellent water permselective performance in pervaporation (PV) and vapor permeation (VP) for water/organic mixtures. Both of zeolite membranes were composed of inter-grown zeolite crystal layer on the outer surface of the tube, each of which is ca. 10 mu m for NaA and ca. 20 mu m for T-type membrane in thickness. Their zeolite crystal layer was composed of two layers, namely the top surface layer and the intermediate layer under the top surface. Average Kelvin diameters were 1.4 nm for the NaA membrane and 0.8 nm for the T-type membrane, respectively. Zeolite NaA membranes showed extremely high PV and VP performance even for water/methanol mixture. T-type membranes also showed extremely high PV and VP performance for water/alcohol mixtures except for water/methanol mixture. The experimental data were discussed from the new theoretical consideration. The consideration consists of the following: a very fine and narrow non-zeolitic pore penetrates from the zeolite crystal layer to the mullite support. The majority of zeolitic pores in top surface layer are assembling in the non-zeolitic pore. The water molecules in the feed are selectively adsorbed in zeolitic pores in the top surface layer, and then are transported to the non-zeolitic pore through the zeolitic pores. At narrower space in the non-zeolitic pore, the capillary condensation occurs, and then the condensate evaporates and diffuses into the permeation side. (C) 2010 Elsevier B.V. All rights reserved.