Transport properties of alumina-supported MFI membranes made by secondary (seeded) growth
Transport properties of alumina-supported MFI membranes made by secondary (seeded) growth
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DOI：
10.1016/s1387-1811(99)00300-5
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发表时间：
2000-07
影响因子：
5.2
通讯作者：
George K. Xomeritakis;S. Nair;M. Tsapatsis
中科院分区：
文献类型：
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作者：
George K. Xomeritakis;S. Nair;M. Tsapatsis
采用水热法将粒径小于100 nm的Silicalite-1胶体晶种沉积在α-Al_2O_3多孔载体表面，制备了厚度为1-40 μm的MFI型沸石膜。这些膜表现出有吸引力的分离特性，判断与丁烷和二甲苯异构体的渗透测量。在22°C下，正丁烷的渗透通量和50 kPa/50 kPa二元混合物的正丁烷/异丁烷比分别在1.0-4.0 mmol m−2s− 1和30-70的范围内变化。正丁烷通量表现出对温度和进料分压的依赖性，与吸附相的活化扩散符合Langmuir等温线，但对膜厚度不敏感。对于最好的膜，在100°C下的单组分对二甲苯通量和对二甲苯/邻二甲苯通量比分别在10-30 μmolm−2s− 1和30-130的范围内。邻二甲苯的渗透通量在对二甲苯的存在下显著增加，导致帕拉/邻位选择性的显著损失（最大值为0.05），这种效应可能归因于MFI骨架在与其骨架紧密配合的分子存在下的柔性。在100°C下，当对二甲苯进料分压低于0.05kPa时，观察到帕拉/邻位选择性（> 20）。
Zeolite MFI membranes with thicknesses in the range of 1–40 μm have been prepared by hydrothermal growth of colloidal silicalite-1 seed crystals of particle sizes ∼100 nm deposited on the surface of α-Al2O3porous support disks. These membranes exhibit attractive separation characteristics as judged by permeation measurements with butane and xylene isomers. At 22°C, the permeation flux of n-butane and the n-butane/isobutane ratio from 50 kPa/50 kPa binary mixtures vary in the range of 1.0–4.0 mmol m−2s−1and 30–70, respectively. The n-butane flux exhibited a dependence on temperature and feed partial pressure consistent with activated diffusion of an adsorbed phase obeying Langmuir isotherm but was rather insensitive to the membrane thickness. For the best membranes, the single-component p-xylene flux and the p-xylene/o-xylene flux ratio at 100°C was in the range of 10–30 μmolm−2s−1and 30–130, respectively. The permeation flux of o-xylene increases dramatically in the presence of p-xylene resulting in a substantial loss in para/ortho selectivity (maximum of ∼5), an effect that may be attributed to the flexibility of the MFI framework in the presence of molecules with a close fit to its framework. At 100°C para/ortho selectivities (> 20) are observed when the p-xylene feed partial pressure is below 0.05 kPa.