Abstract CO2 and CH4 mixed-gas solubility was measured in 3,3′-dihydroxy-4,4′-diamino-biphenyl (HAB) 2,2′-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) polyimide and in its thermally rearranged (TR) derivative, TR450. Due to competitive sorption effects, the solubility of both species in mixed-gas conditions is lower than the corresponding pure-gas solubility at the same fugacity. CH4 sorption is significantly affected by the presence of the second gas, while CO2 behavior is hardly altered. Therefore, the multicomponent solubility-selectivity is higher than the ideal value calculated from pure-gas sorption data, and this has a positive impact on CO2/CH4 separation properties. The multicomponent solubility data were modelled with the Non-Equilibrium Lattice Fluid (NELF) model, using only pure component parameters and binary interaction parameters obtained from pure-gas sorption data available in the literature, with no parameters determined from the mixed-gas sorption data. Although it is easier to use, the multicomponent Dual Mode Sorption (DMS) model yielded less accurate predictions of mixed-gas sorption. Mixed-gas sorption experiments and modelling, coupled with mixed-gas permeation data, enabled a better fundamental understanding of the separation properties of these materials. Unlike the case of pure-gas experiments, where diffusivity contributes more to the overall ideal selectivity, competitive sorption is the main effect governing the permselectivity of these membrane materials at multicomponent conditions. A systematic comparison with literature data on mixed-gas CO2/CH4 sorption and permeability revealed these to be generalized trends, obeyed by materials of very different chemical constitution. This finding can inform on the criteria that make polymers performing better in multicomponent scenarios, with potential impact on the design and synthesis strategies of new materials.

中文翻译：

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CO2/CH4 分离中的竞争吸附：HAB-6FDA 聚酰亚胺及其 TR 衍生物的案例及其对多组分条件下玻璃态聚合物选择性影响的一般分析

摘要 CO2 和 CH4 混合气体溶解度在 3,3'-二羟基-4,4'-二氨基-联苯 (HAB) 2,2'-双-(3,4-二羧基苯基) 六氟丙烷二酐 (6FDA) 聚酰亚胺和在其热重排 (TR) 衍生物 TR450 中。由于竞争吸附效应，两种物质在混合气体条件下的溶解度低于相同逸度下相应的纯气体溶解度。CH4 吸附受第二种气体存在的显着影响，而 CO2 行为几乎没有改变。因此，多组分溶解选择性高于根据纯气体吸附数据计算的理想值，这对 CO2/CH4 分离性能有积极影响。多组分溶解度数据用非平衡晶格流体 (NELF) 模型建模，仅使用从文献中可用的纯气体吸附数据中获得的纯组分参数和二元相互作用参数，而没有从混合气体吸附数据中确定的参数。虽然它更容易使用，但多组分双模式吸附 (DMS) 模型对混合气体吸附的预测不太准确。混合气体吸附实验和建模，再加上混合气体渗透数据，可以更好地了解这些材料的分离特性。与纯气体实验的情况不同，扩散率对整体理想选择性的贡献更大，竞争吸附是控制这些膜材料在多组分条件下的渗透选择性的主要影响。与有关混合气体 CO2/CH4 吸附和渗透性的文献数据的系统比较表明，这些是普遍趋势，由化学成分非常不同的材料所遵循。这一发现可以告知使聚合物在多组分场景中表现更好的标准，并对新材料的设计和合成策略产生潜在影响。