Crystallite-pore network model of transport and reaction of multicomponent gas mixtures in polycrystalline microporous media
Crystallite-pore network model of transport and reaction of multicomponent gas mixtures in polycrystalline microporous media
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DOI：
10.1016/j.cej.2014.05.081
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发表时间：
2014-10-15
影响因子：
15.1
通讯作者：
Dittmeyer, Roland
中科院分区：
文献类型：
--
作者：
Ding, Wenjin;Li, Hui;Dittmeyer, Roland
已经开发了三维孔网络模型来模拟具有共存的晶内微孔和晶间介孔（即，缺陷）。这些孔隙中的输运分别用Krishna [11]提出的广义Maxwell-Stefan表面扩散模型和Knudsen扩散模型建模。该模型的一个新的特点亮点是多晶介质的微晶孔隙网络模型的代表。与以前的孔隙网络模型相比，微晶孔隙网络模型具有通过分配给每个微晶两个参数来描述其取向来对形成多晶层的微晶内部的各向异性输运进行建模的新颖方面。该模型用于模拟多晶ZSM-5沸石膜中的二甲苯异构化，Haag等人已在Wicke-Kallenbach电池中对其进行了实验研究[13]。首先，他们的实验数据被用来估计吸附和扩散参数的二甲苯异构体在ZSM-5膜通过拟合单气体渗透数据的二甲苯异构体。其次，采用这些参数，二甲苯异构化的实验数据被用来确定二甲苯异构化在ZSM-5膜的动力学参数。最后，选定的结构参数的影响-缺陷的浓度，缺陷的连接性，微晶取向，和微晶尺寸-进行了研究，使用所获得的吸附，扩散和反应参数。模拟结果表明，对二甲苯的高选择性需要在多晶层中的缺陷浓度低，二甲苯异构体在膜中的负载低。该模型也适用于许多其它反应体系。(C)2014爱思唯尔有限公司版权所有。
A three-dimensional pore network model has been developed to simulate anisotropic multicomponent diffusion and reaction in polycrystalline microporous media with coexisting intracrystalline micropores and intercrystalline mesopores (i.e., defects). Transport in these pores is modeled with the generalized Maxwell-Stefan surface diffusion model proposed by Krishna [11] and the Knudsen diffusion model, respectively. A new feature highlight of this model is the representation of polycrystalline media with a crystallite-pore network model. In contrast to previous pore network models, the crystallite-pore network model has the novel aspect of modeling the anisotropic transport inside the crystallites forming a polycrystalline layer by assigning to every crystallite two parameters to describe its orientation. The model was applied to simulate xylene isomerization in a polycrystalline ZSM-5 zeolite membrane, which had been experimentally investigated in a Wicke-Kallenbach cell by Haag et al. [13]. First, their experimental data were used to estimate adsorption and diffusion parameters of the xylene isomers in the ZSM-5 membrane via fitting single-gas permeance data of the xylene isomers. Second, adopting these parameters, the experimental data for xylene isomerization were used to determine kinetic parameters for xylene isomerization in the ZSM-5 membrane. Finally, effects of selected structural parameters - concentration of defects, connectivity of defects, crystallite orientation, and crystallite size - were investigated using the obtained adsorption, diffusion, and reaction parameters. The simulation results show that high selectivity towards p-xylene requires a low concentration of defects in the polycrystalline layer and a low loading of xylene isomers in the membrane. The novel crystallite-pore network model is also applicable to many other reaction systems. (C) 2014 Elsevier B.V. All rights reserved.