Adsorption of dimethyl ether (DME) on zeolite molecular sieves
Adsorption of dimethyl ether (DME) on zeolite molecular sieves
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DOI：
10.1016/j.cej.2014.07.001
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发表时间：
2014-11
影响因子：
15.1
通讯作者：
Jai Lad;Yassir T. Makkawi
中科院分区：
文献类型：
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作者：
Jai Lad;Yassir T. Makkawi
近年来，人们对使用二甲醚（DME）作为替代燃料越来越感兴趣。在本研究中，采用体积吸附法对 DME 在 4 Å (Mol4A) 和 5 Å (Mol5A) 分子筛上的吸附进行了实验研究。获得了吸附等温线、吸附热和吸附动力学数据，并用于得出结论并比较两种吸附剂的性能。在考虑的条件下，发现 Mol5A 的吸附容量比 Mol4A 的吸附容量高约八倍。据观察，吸附剂在真空中的低温吸附和热预处理有利于提高吸附容量。两种吸附剂的吸附等温线均符合 Freundlich 模型，并提出了相应的模型参数。吸附动力学分析表明，Mol5A 上的 DME 吸附受晶内扩散阻力控制，而 Mol4A 上的 DME 吸附主要受表面分层阻力控制，扩散仅发生在吸附开始时且持续时间非常有限。吸附热是通过基于吸附池内直接温度测量的量热法计算的。通过热力学方法（克拉修斯-克拉佩龙方程）计算的等量热始终显示较低的值。 Mol4A 和 Mol5A 的最大吸附热分别为 25.9 kJ mol−1 和 20.1 kJ mol−1；从而表明相互作用是物理吸附类型。
In recent years there has been growing interest in the use of dimethyl ether (DME) as an alternative fuel. In this study, the adsorption of DME on molecular sieves 4 Å (Mol4A) and 5 Å (Mol5A) has been experimentally investigated using the volumetric adsorption method. Data on the adsorption isotherms, heats of adsorption, and adsorption kinetic have been obtained and used to draw conclusions and compare the performance of the two adsorbents. Within the conditions considered, the adsorption capacity of Mol5A was found to be around eight times higher than the capacity of Mol4A. Low temperature adsorption and thermal pre-treatment of the adsorbents in vacuum were observed to be favourable for increased adsorption capacity. The adsorption isotherms for both adsorbents were fitted to the Freundlich model and the corresponding model parameters are proposed. The adsorption kinetic analysis suggest that the DME adsorption on Mol5A is controlled by intracrystalline diffusion resistance, while on Mol4A it is mainly controlled by surface layering resistance with the diffusion only taking place at the start of adsorption and for a very limited short time. The heats of adsorption were calculated by a calorimetric method based on direct temperature measurements inside the adsorption cell. Isosteric heats, calculated by the thermodynamic approach (Clasius–Clapeyron equation), have consistently shown lower values. The maximum heat of adsorption was found to be 25.9 kJ mol−1and 20.1 kJ mol−1on Mol4A and Mol5A, respectively; thus indicating a physisorption type of interactions.