Adsorption of Normal Paraffins from Binary Liquid Solutions by 5A Molecular Sieve Adsorbent
Adsorption of Normal Paraffins from Binary Liquid Solutions by 5A Molecular Sieve Adsorbent
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DOI：
10.1021/i260024a020
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发表时间：
1967-10
期刊：
影响因子：
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通讯作者：
P. Roberts;R. York
中科院分区：
文献类型：
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作者：
P. Roberts;R. York
在差动再循环装置中，测定由可吸附正链烷烃和不可吸附溶剂组成的二元液体溶液中的正链烷烃的分子筛吸附速度。在研究的温度和浓度范围内，平衡是不可逆的。开发了一种用于预测浓度阶跃变化后的吸附速率的理论。该速率取决于沸石扩散速率常数 kz、有效大孔扩散率 Dei、颗粒尺寸 a、流体相浓度 C 和外部传质系数 kc。对于 25 G 的正己烷，kz 为 1.94 X 1 0-4 sec.-1，比十二烷高 30%，比十六烷高 100 倍。己烷的 kz 活化能为 7.5 kcal。每克摩尔。分子筛颗粒的弯曲系数为2.30±3%。开发了一种预测固定床吸附突破曲线的方法，并将其应用于先前公布的从苯中分离己烷以及从空气中分离水的数据。沸石具有根据大小和形状定量选择性吸附分子的独特性质。合成沸石由林德公司生产，商品名为分子筛。特别令人感兴趣的是林德 5A 型分子筛，它能够吸附正链烷烃和烯烃，尽管分子筛吸附是一种从混合物中去除直链烃的技术，但本研究的目的是研究分子筛吸附中的传质机制。
In a differential recycle apparatus, the rate of adsorption bymolecular sieves was measured for normal paraffins from binary liquid solutions consisting of an adsorbable normal paraffin and nonadsorbable solvent. The equilibrium was irreversible over the range of temperatures and concentrations studied. A theory was developed for predicting the rate of adsorption following a step change in concentration. This rate depends upon the zeolite diffusion rate constant, kz, the effective macropore diffusivity, Dei the pellet size, a, the fluid phase concentration, C, and the external mass transfer coefficient, kc. For n-hexane at 25 G, kz is 1.94 X 1 0-4 sec.-1, 30% higher than for dodecane and 100 times higher than for hexadecane. The activation energy for kz for hexane is 7.5 kcal. per gram mole. The tortuosity factor for molecular sieve pellets is 2.30±3%. A method was developed for predicting breakthrough curves for fixed bed adsorption and applied to previously published data on the separation of hexane from benzene and of water from air.Zeolites have the unique property of selectively adsorbing" molecules quantitatively on the basis of size and shape. Synthetic zeolites are produced by the Linde Co. under the trade name Molecular Sieves. Of particular interest are Linde Type 5A molecular sieves, which have the ability to adsorb normal paraffins and olefins, but to exclude branched-chain, cyclic, and aromatic hydrocarbons. Although molecular sieve adsorption is a technique by which several commercial processes remove straight-chain hydrocarbons from mixtures, relatively little has been reported about the fundamental mass transfer involved. The purpose of this research was to study the mechanism of mass transfer in adsorp-tion by molecular sieves.