Modeling gas permeability and diffusivity in HAB-6FDA polyimide and its thermally rearranged analogs
Modeling gas permeability and diffusivity in HAB-6FDA polyimide and its thermally rearranged analogs
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DOI：
10.1016/j.memsci.2017.05.015
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发表时间：
2017-09-01
影响因子：
9.5
通讯作者：
Freeman, Benny D.
中科院分区：
文献类型：
--
作者：
Galizia, Michele;Stevens, Kevin A.;Freeman, Benny D.
采用基于非平衡晶格流体（NELF）理论的热力学模型描述了HAB-6 FDA聚酰亚胺及其热重排类似物的气体渗透性。这项研究是一个正在进行的努力，从理论上描述TR聚合物的气体吸附和传输行为的一部分。氢、氮和甲烷在宽范围的压力（高达32个大气压）和温度（-10至50摄氏度）下的渗透率用每个温度下的一个可调参数计算，即，无限稀释迁移率系数。对于高度可溶的，膨胀气体，如CO2，基质塑化占第二个可调参数，塑化因子，它描述了渗透剂的流动性对浓度的依赖。模型参数与膜结构和气体性质相关。在固定温度下，无限稀释流度与渗透剂临界体积和聚合物自由体积分数有关。对于每一种渗透剂，无限稀释迁移率的温度依赖性由阿克里乌斯定律描述。基于模拟结果，TR聚合物独特的分离性能是其强尺寸筛分能力的表现。最后，扩散系数和理想的选择性预测没有可调的参数。
Gas permeability in HAB-6FDA polyimide and its thermally rearranged analogs was described using a thermodynamic model based on the non-equilibrium lattice fluid (NELF) theory. This study is part of an ongoing effort to describe gas sorption and transport behavior of TR polymers theoretically. Hydrogen, nitrogen and methane permeability over a broad range of pressures (up to 32 atm) and temperatures (-10 to 50 degrees C) was calculated with one adjustable parameter at each temperature, i.e., the infinite dilution mobility coefficient. For highly soluble, swelling gases, such as CO2, matrix plasticization was accounted for by a second adjustable parameter, the plasticization factor, which describes the dependence of penetrant mobility on concentration. Model parameters correlate with membrane structure and gas properties. At fixed temperature, the infinite dilution mobility correlates with penetrant critical volume and polymer fractional free volume. For each penetrant, the temperature dependence of infinite dilution mobility is described by the Arrhenius law. Based on the modeling results, unique separation performance of TR polymers is a manifestation of their strong size-sieving ability. Finally, diffusion coefficients and ideal selectivities were predicted with no adjustable parameters.