Preparation And Properties Of Inorganic Nanosheets-based Composite Membrane For CO₂ Separation

A large amount of CO₂ is emitted to atmosphere. This may lead to green house effect, sea level rise and abnormal climate, so the research of CO₂ and other acidic gases capture has become one of the important subjects on energy and environment. Membrane technology has the advantages of good economical efficiency, simple operation process and efficient separation. It’s been widely used in the research of CO₂ separation. Ether groups have a strong affinity with CO₂ and they can increase CO₂ solubility in the membrane. However, the application of polymeric membranes in gas separation shows intrinsic trade-off between permeability and selectivity. Incorporating inorganic materials into polymer to fabricate mixed matrix membrane can increase permeability and selectivity at the same time. It’s promising to transcend the Robeson upper bound curve. In this paper, a series of inorganic nanosheets-based composite membranes for CO₂ separation were prepared by means of interfacial polymerization, expecting the membranes could achieve a higher permselectivity for CO₂. The main contents are as follows:（1） Preparation of poly（PEA-TMC）/PS composite membranes and poly（PEGda-PEA-TMC）/PS composite membranesPoly（ PEA-TMC） /PS composite membranes were prepared by interfacial polymerization from aqueous phase to organic phase on polysulfone（PS）support membrane, with polyetheramine（PEA）containing ether groups as monomer of aqueous phase and trimesoyl chloride（TMC）as monomer of organic phase. Poly（ PEGda-PEA-TMC） /PS composite membranes were prepared with another monomer diaminopolyethylene glycol（PEGda）containing ether groups mixed with PEA as aqueous monomer. The results showed that a polyamide separation layer containing ether groups formed on PS membrane. Poly（PEA-TMC）/PS composite membrane displayed CO₂ permeance of 55 GPU and CO₂/N2 selectivity of 103 at 1wt% PEA concentration and 1 bar of feed gas pressure. With the incorporation of PEGda, CO₂ permeance and CO₂/N2 selectivity were increased obviously. Poly（PEGda-PEA-TMC）/PS composite membrane represented CO₂ permeance of 93 GPU and CO₂/N2 selectivity of 266 at PEGda/PEA concentration ratio of 0.2 and 1 bar of feed gas pressure.（2） Preparation of poly（PEA-MMT-TMC）/PS composite membranes and poly（PEA-HT-TMC）/PS composite membranesMontmorillonite（MMT）was exfoliated to nanosheets by vigorous agitation. Poly（ PEA-MMT-TMC） /PS composite membranes were prepared by interfacial polymerization with the resulting colloidal solution added into PEA aqueous monomer. The prepared Mg-Al hydrotalcite（HT）was exfoliated to nanosheets by ultrasonic. Poly（ PEA-HT-TMC） /PS composite membranes were prepared by interfacial polymerization with HT colloidal solution added into PEA aqueous monomer. The results showed that with the incorporation of MMT and HT nanosheets, CO₂ permeance was increased but CO₂/N2 selectivity was decreased. Poly（PEA-MMT-TMC）/PS composite membrane exhibited CO₂ permeance of 95 GPU and CO₂/N2 selectivity of 37 at MMT concentration of 0.068wt% and 1 bar of feed gas pressure. Besides, poly（PEA-HT-TMC）/PS composite membrane exhibited CO₂ permeance of 90 GPU and CO₂/N2 selectivity of 45 at HT concentration of 0.25wt% and 1 bar of feed gas pressure.（3） Preparation of poly（PEA-PRG-TMC）/PS composite membranesPorous reduced graphene oxide（PRG）was prepared by chemical treatment of graphene oxide（GO）. Poly（PEA-PRG-TMC）/PS composite membranes were prepared by interfacial polymerization with PRG added into PEA aqueous monomer. The results showed that PRG could shorten the transport path and provide fast transport channels for CO₂ separation. With the incorporation of PRG, CO₂ permeance and CO₂/N2 selectivity were both increased. Poly（PEA-PRG-TMC）/PS composite membrane represented CO₂ permeance of 70 GPU and CO₂/N2 selectivity of 130 at PRG concentration of 0.05wt% and 1 bar of feed gas pressure.Inorganic nanosheets-based composite membrane showed higher CO₂ permeance and laid foundation for the realization of industrialization.