Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 1: Dehydration of solvents
Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 1: Dehydration of solvents
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DOI：
10.1016/j.ces.2005.02.059
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发表时间：
2005-08-01
影响因子：
4.7
通讯作者：
Melin, T
中科院分区：
文献类型：
--
作者：
Sommer, S;Melin, T
研究了两种不同的市售管式无机膜的溶剂脱水分离性能。分离层由A型沸石和微孔二氧化硅组成。膜特性被确定为操作条件的函数，例如进料组成、温度以及全蒸发和蒸气渗透中的渗透压力。同批次的不同膜之间，通量和选择性的重现性在10%以内。作为优先渗透组分的水的部分通量随着进料和渗透物之间的水蒸气压差线性增加，并且仅略微依赖于有机组分的性质（粘度影响）。有机（保留）组分的通量较低，可以通过假设与成分无关的物质和膜比渗透率（通量除以分压差）来最好地描述。在进料中水浓度非常低的情况下，人们预计保留组分通过非沸石孔和较大二氧化硅孔的渗透性将大幅增加，正如纯组分测量所预测的那样。然而，在此研究的浓度范围内的混合物中没有观察到这种效应。温度升高以指数方式提高通量率，同时保持高选择性。因此，如果可以选择更高的工作温度，则与聚合物膜相比更高的模块成本可以通过减少膜面积来补偿。随着驱动力的降低，通量和选择性随着渗透压的变化而下降。在无机膜的蒸气渗透中，蒸气进料的过热改善了其性能，而对于聚合物材料，观察到通量急剧下降。从醇中分离水可以获得高通量和选择性。 A型沸石膜的归一化通量值大约为10 kg/m(2) It bar，其中甲醇的混合物选择性为2000，乙醇为4000，正丁醇为8000。无定形二氧化硅膜的平均渗透率高于12 kg/m(2) h bar，其中甲醇的混合物选择性为50，乙醇的混合物选择性为500，正丁醇的混合物选择性为2000。分离机制主要基于在某些情况下通过形状选择性和尺寸排阻增强的吸附和扩散。传输特性可以用基于归一化渗透通量的简单传输模型来描述。关于膜的操作稳定性，在溶剂脱水或从反应混合物中分离水时，没有观察到A型沸石的性能劣化。二氧化硅膜显示出涉及 Si-OH 基团重排的初始调节效果，选择性增加，通量降低约 30%。几个小时后，性能稳定并在进一步操作期间保持恒定。 (c) 2005 Elsevier Ltd. 保留所有权利。
The separation performance of two different commercially available tubular inorganic membranes was studied for solvent dehydration. The separation layers consisted of A-type zeolite and microporous silica. The membrane characteristics were determined as function of operating conditions such as feed composition, temperature, and permeate pressure in pervaporation and vapor permeation. Among different membranes of the same batch, flux and selectivity were reproducible within 10%. The partial flux of water as the preferentially permeating component increases linearly with the water vapor pressure difference between feed and permeate and depends only marginally (viscosity influence) upon the properties of the organic component. The flux of the organic (retained) component is low and can best be described by assuming a substance and membrane specific permeance (flux over partial pressure difference) that is independent of composition. At very low water concentration in the feed one would expect a strong increase in permeability of the retained component through non-zeolite pores and larger silica pores as predicted by pure component measurements. However, this effect was not observed in mixtures within the concentration range studied here. A temperature rise improves flux rates exponentially while selectivity remains high. Thus, higher module cost in comparison to polymeric membranes can be compensated by reduced membrane area if a higher operating temperature can be chosen. Flux and selectivity decline as a function of permeate pressure with decreasing driving force. In vapor permeation with inorganic membranes superheating of the vaporous feed improves their performance while for polymeric materials a steep flux decline is observed. High flux and selectivity are obtained in the separation of water from alcohols. The normalized flux values of the A-type zeolite membrane are roughly 10 kg/m(2) It bar with a mixture selectivity of 2000 for methanol, 4000 for ethanol and 8000 for n-butanol. The average permeance of the amorphous silica membrane lies above 12 kg/m(2) h bar with mixture selectivity of 50 for methanol, 500 for ethanol and 2000 for n-butanol. The separation mechanism is mainly based on adsorption and diffusion enhanced by shape selectivity and size exclusion in some cases. The transport characteristics could be described with a simple transport model based on normalized permeate fluxes. With regard to the operation stability of the membranes, no deterioration of the performance was observed for the A-type zeolite in solvent dehydration or in separation of water from reaction mixtures. The silica membrane showed an initial conditioning effect involving a rearrangement of Si-OH groups with an increase in selectivity and decrease in flux of about 30%. After a few hours the performance stabilized and remained constant during further operation. (c) 2005 Elsevier Ltd. All rights reserved.