An investigation of the relationship between microstructure and permeation properties of ZSM-5 membranes
An investigation of the relationship between microstructure and permeation properties of ZSM-5 membranes
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DOI：
10.1016/s0376-7388(01)00489-6
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发表时间：
2001-11
影响因子：
9.5
通讯作者：
L. Au;K. Yeung
中科院分区：
文献类型：
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作者：
L. Au;K. Yeung
研究了ZSM-5分子筛膜的微观结构对分子筛膜传质性能的影响。在氧化铝载体上逐层生长了（101）和（002）晶向的两种沸石膜。膜形态保持恒定，以及构成多晶沸石膜层的单个晶粒的形状保持恒定。采用膜厚度（τ）、晶粒尺寸（d）、晶粒形态（M）、沸石数量（N）、晶体共生（Ic）和膜取向6个微观结构参数对膜微观结构进行表征和量化。以He、H_2、N_2、Ar、CH_4、n-C_4 H_（10）、i-C_4 H_（10）和SF_6等8种不同气体为探针，研究了不同膜厚下膜的输运过程。通过保持相当的非沸石流动，证明了（101）-和（002）-取向的ZSM-5膜具有相当的传输阻力。此外，使用不同尺寸的分子探针的多厚度比较的结果表明，通过这两种膜的运输机制和扩散途径具有很强的相似性。实验表明，晶界是膜中非沸石分子筛的主要扩散通道，通过晶粒生长消除晶界可以改善膜的性能。
The influence of membrane microstructure on the transport properties of ZSM-5 membranes was investigated. Two zeolite membranes with (101)- and (002)-orientations were grown layer-by-layer onto seeded alumina support. The membrane morphology was kept constant as well as the shape of the individual crystal grains that made up the polycrystalline zeolite membrane layer. The membrane microstructure were characterized and quantified using six microstructural parameters that include membrane thickness (τ), grain size (d), grain morphology (M), zeolite population (N), crystal intergrowth (Ic) and film orientation. Eight different gases including He, H2, N2, Ar, CH4, n-C4H10, i-C4H10and SF6were used as molecular probes to investigate the transport processes through the membrane of different thicknesses. By maintaining a comparable non-zeolite flow, it was demonstrated that the (101)- and (002)-oriented ZSM-5 membranes have comparable transport resistance. Also, the results of the multi-thickness comparison using the different sized molecular probes indicate a strong similarity in the transport mechanism and diffusion pathway through these two membranes. The experiment suggests that the grain boundary is the main non-zeolite diffusion pathway in the membrane and their elimination through grain growth can result in better membrane performance.