Cross-Linked PEG Membranes of Interpenetrating Networks with Ionic Liquids as Additives for Enhanced CO₂ Separation
2019
Deng, Jing | Yu, Junbo | Dai, Zhongde | Deng, Liyuan
Polyethylene glycol (PEG)-based membranes have recently been reported with excellent CO₂ separation performances. However, the commonly exhibited high crystallinity may deteriorate the gas permeation properties in this type of membrane. In this work, a two-stage cross-linking method was employed to fabricate PEG membranes with interpenetrating networks to reduce the crystallinity. Ionic liquids (ILs) were incorporated into the resultant membranes to further increase CO₂ diffusivity and the CO₂ affinity of the membranes. By increasing the length of the PEG-based acrylate monomers and optimizing the ratio of the amine-functionalized cross-linker to the acrylate monomers, we significantly enhanced the CO₂ permeability of the resultant membranes (from 0.6 to 85.0 Barrer) with slightly increased CO₂/N₂ selectivity. Four conventional ILs (i.e., [Bmim][BF₄], [Bmim][PF₆], [Bmim][NTf₂] and [Bmim][TCM]) with different anions were added into the optimized cross-linked PEG membranes. The addition of ILs endows superior gas transport properties at high loadings, and the [Bmim][TCM] gives the best CO₂ separation performance of the membranes; CO₂ permeability of up to 134.2 Barrer with the CO₂/N₂ selectivity of 49.5 was documented. The anions in ILs were found contributing the most in promoting the CO₂ permeation, and the higher CO₂ affinity endows the better CO₂ separation performance in the resultant membranes.
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