Manipulation Of Hierarchical Structure And Intensification Of Gas Transport Mechanisms Of PEO-based Carbon Capture Membranes

Highly efficient CO₂ capture technology is the key to both greenhouse gas control and energy gas purification.Membrane technology has evolved as one of the most promising CO₂ capture technology for its low cost and high operation elasticity.Therefore,CO₂ separation membrane materials with high permeability,high selectivity and high stability are the key for successful application of CO₂ separation membranes.Consequently,it is necessary to reveal the in-depth gas transport mechanism within membrane and design highly specific and efficient membrane structures for gas transport.This study aimed at synergistically intensifying solution and diffusion mechanisms of CO₂ separation membranes.With PEO-based polymer as the multifunctional modifier,a series of novel CO₂ separation membranes with appropriate CO₂ affinity and free volume properties were designed and fabricated by facile and versatile methods.The solution and diffusion mechanisms were synergistically intensified by individually manipulating the matrix,interface,surface and channel structure of the membranes.Therefore,high CO₂/N₂ and CO₂/CH₄ separation performance were achieved.This study is expected to offer theoretical and technological guidance and support to large-scale fabrication of high-performance CO₂ separation membranes.The details were summarized as follows:Membrane matrix manipulation and transport mechanism intensification: Polymer-inorganic hybrid membranes were prepared by introducing PEG polymer or silane gel networks into rubbery polymer-Pebax.CO₂ solubility in hybrid membrane was enhanced by introducing CO₂-philic PEG.Meanwhile,CO₂ diffusivity in hybrid membranes was enhanced because of the decreased crystallinity of Pebax.Hybird membrane containing both PEGDMA and CNT showed high CO₂ permeability of 743 Barrer and CO₂/N₂ selectivity of 108,surpassing the 2008 Robeson upper bound.Moreover,the introduction of silane gel network dramatically enhanced the membrane mechanical stability.Membrane interface manipulation and transport mechanism intensification: A novel method was proposed by introducing organic PEG microsphere into glassy polyimide membrane to improve the polymer-filler interface morphology and enhance the interface transport property.The ideal polymer-filler interface morphology and CO₂-philic properties of the interface synergistically enhanced solution and diffusion mechanism of the membranes.Compared with pristine PI membrane,PI-PEGSS?20?with 20 wt% PEGSS loading showed an increase of 35% in CO₂ permeability and an increase of 104% in CO₂/N₂ selectivity.Membrane interface manipulation and transport mechanism intensification: A novel method was proposed by using surface segregation method to construct CO₂-philic surface of asymmetric membranes.In this study,glassy polymer PES was utilized as the membrane matrix and PEO-containing block copolymer F68 was utilized as modifier.The surface segregation and enrichment of PEO enhanced CO₂ solubility on the membrane surface.Meanwhile,the free volume property was enhanced by the anchor block PPO.Consequently,the solution and diffusion mechanisms were synergistically enhanced.Asymmetric membrane with 20 wt% F68 showed an increase of 210% in CO₂ permeance and an increase of 105% in CO₂/N₂ selectivity.Membrane channel manipulation and transport mechanism intensification: By utilizing inorganic GO as the matrix,CO₂-philic PEGDA as the cross-linker,GO-based composite membranes were fabricated.By synergistic manipulation of the CO₂-philic property and size of the channel,solution and diffusion mechanisms were enhanced synergistically.GO-PEGDA500 membrane,by using PEGDA500 as the cross-linker,showed an increase of 284% in CO₂ permeance and an increase of 294% in CO₂/CH₄ selectivity.