Abstract Nowadays, membrane processes are together with cryogeny, absorption and adsorption considered to be a key technology for gas separation applications. Process selectivity is of primary importance in order to respect the specifications but can in some cases be limited due to a too low membrane selectivity. Parallel to improvements in the membrane selectivity of certain materials, unsteady membrane operations can also be attempted in order to achieve a higher separation selectivity, but this strategy remains largely unexplored. A novel, simple, unsteady-state process, complementary to the strategies already proposed by the previous authors, is reported in this study. A systematic comparison of steady state, short-class (i.e. with time lag) and long-class (i.e. pseudo steady-state) processes is described for O2/N2 (PPO membrane), He/Kr (PEMA membrane) and H2/CO2 (polyimide and a reverse selective PEBAX membrane) separations. Based on a selectivity composition path chart, the maximal purity or process selectivity achievable by steady and unsteady processes was compared. The new long-class process was shown to offer similar or increased selectivity compared to steady-state operation, at the expense of a lower productivity. Finally, the applicability to industrial separations and the remaining challenges are also discussed.

中文翻译：

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稳态与非稳态膜气体分离过程

摘要 目前，膜工艺与低温、吸收和吸附一起被认为是气体分离应用的关键技术。为了遵守规格，工艺选择性是最重要的，但在某些情况下，由于膜选择性太低，可能会受到限制。在提高某些材料的膜选择性的同时，也可以尝试非稳态膜操作以实现更高的分离选择性，但这种策略在很大程度上仍未得到探索。本研究报告了一种新颖、简单、不稳定的过程，对先前作者已经提出的策略进行了补充。描述了 O2/N2（PPO 膜）的稳态、短期（即具有时间滞后）和长期（即伪稳态）过程的系统比较，He/Kr（PEMA 膜）和 H2/CO2（聚酰亚胺和反向选择性 PEBAX 膜）分离。基于选择性组成路径图，比较了稳定和不稳定过程可达到的最大纯度或过程选择性。与稳态操作相比，新的长级工艺显示出相似或更高的选择性，但以较低的生产率为代价。最后，还讨论了工业分离的适用性和剩余的挑战。以降低生产力为代价。最后，还讨论了工业分离的适用性和剩余的挑战。以降低生产力为代价。最后，还讨论了工业分离的适用性和剩余的挑战。