Preparation Of High-performance CO₂ Separation Membranes By Incorporating Amine-rich Gas Transport Nanochannels

Efficient separation of CO₂ plays an important role in greenhouse gas emissions reduction and energy gases upgradation and purification.Membrane separation technology with broad application prospects has the characteristics of low energy consumption,large operation flexibility and environmental friendliness.However,the commercial CO₂ separation membranes with low CO₂ permselcetivity have limited large-scale application.Therefore,it is important to develop separation membranes with excellent CO₂ perm-selectivity.Facilitated transport membranes with functional groups as carriers can achieve efficient CO₂ separation.Polyvinylamine（PVAm）is a typical kind of material for facilitated transport membranes.However,commercialized PVAm with extremely high hydrolysis degree is accompanied by the strong intermolecular hydrogen bonding force,resulting in the high crystallinity.Such kind of PVAm is difficult to be used to prepare the high-performance CO₂ separation membrane.Therefore,there is a need to improve the production process of PVAm to improve the permselectivity of the membranes made by it.In addition,in order to further improve the separation performance,porous materials are introduced into PVAm to prepare mixed matrix membranes（MMMs）.However,the interface compatibility between most porous materials and PVAm matrix is usually not good enough,and the modified porous materials are difficult to retain its inherent gas transfer channels,thus the increase of membrane separation performance is limited.In this paper,two aspects of work have been carried out to solve the problems mentioned above.Firstly,with HCl served as the hydrolysis catalyst,the synthesis process of PVAm was optimized to adjust the hydrolysis degrees of PVAm by adjusting the HCl concentration,hydrolysis temperature and hydrolysis duration.The regulated PVAm was coated on the modified polysulfone ultrafiltration membrane（m PSf）to prepare PVAm/m PSf composite membranes,which are tested with CO₂/N₂,CO₂/CH₄ and CO₂/H₂ mixed gases respectively.The results show that the PVAm synthesized under HCl concentration at 10 wt%,hydrolysis temperature at 70℃and hydrolysis duration at 4 h has a relatively low crystallinity and a large number of carriers,by which the membranes made possess a high CO₂ separation performance.Secondly,a new kind of porous materials with high amine density—high-valence metal-induced porous polymer（HMMP-1）was synthesized by using a modified polymer-directed chemical synthesis（PDCS）method.Due to the existance of high-value metals Cr³⁺and polyethyleneimine（PEI）,HMMP-1 nanoparticles possess outstanding alkaline stability and polymer interfacial compatibility.Then,HMMP-1nanoparticles are blended with the high-performance PVAm prepared above to prepare the HMMP-1-PVAm/m PSf composite MMMs with facilitated transport characteristics.Due to the excellent interfacial compatibility of HMMP-1 nanoparticles,the membranes retain the appropriately sized amine-rich nanochannels for facilitated transport.The membranes are all tested with the CO₂/N₂,CO₂/CH₄ and CO₂/H₂ mixed gases respectively.The results show that HMMP-1-PVAm/m PSf membranes exhibit extremely high CO₂/N₂,CO₂/CH₄,and CO₂/H₂ mixed gases separation performance when the HMMP-1 loading is at 44.4 wt%.A techno-economic evaluation suggests that this membrane is feasible for carbon capture from post-combustion flue gas.