Abstract:

Three kinds of defect micropore models, i.e., random defect, averaged defect and partial defect models, were established based on the defect-free zigzag pore model in carbon membrane. Adsorption and diffusion behaviors of equimolar CO₂/CH₄ gas mixture within pores of carbon membrane were investigated in an effort to discuss the influences of pore defect in carbon membranes on gas separation. Results showed that under the operating temperatures ranging from 273 to 348 K, both equilibrium adsorption capacities and diffusion coefficients of CO₂ and CH₄ in the defect pore models were smaller than those of the defect-free pore model. Total CO₂/CH₄ separation coefficient of the partial defect pore model was relatively low compared with the defect-free pore model and the other two defect pore models. When the temperature was less than 298 K, total separation coefficients of the random defect and averaged defect pore models were greater than the defect-free pore model, and the total separation coefficients of random defect pore model are beneficial to the averaged defect pore model. Random carbon atom deletion approach is more reasonable than average deletion and partial deletion. The results could provide a basis for the further study of gas permeation mechanism in carbon membranes.

Key words: molecular simulation, carbon dioxide, methane, carbon membranes, defect pore model

摘要：

基于炭膜无缺陷Z字形孔模型研究结果，建立随机缺陷、均匀缺陷与局部缺陷3种不同缺陷方式的炭膜微孔模型，研究等摩尔CO₂/CH₄混合气在缺陷膜孔中的吸附和扩散过程，探讨缺陷对炭膜气体分离的影响。结果表明，在273~348 K的温度范围内，CO₂与CH₄在缺陷炭膜孔模型内的平衡吸附量与扩散系数均低于无缺陷炭膜孔模型；与无缺陷、均匀缺陷和随机缺陷孔模型相比，局部缺陷孔模型的CO₂/CH₄总分离系数最低；温度低于298 K时，随机缺陷和均匀缺陷孔模型的总分离系数均大于无缺陷孔模型；随机缺陷孔模型的总分离系数大于均匀缺陷孔模型，说明随机删除碳原子的方式比均匀删除和局部删除更加合理。研究结果可为炭膜气体渗透机理的深入研究提供依据。

关键词: 分子模拟, 二氧化碳, 甲烷, 炭膜, 缺陷孔模型