Preparation And Properties Of Proton-Electronic Mixed Conductor Hydrogen Permeation Membrane

Compared with other gas separation technologies（such as those based on distillation and absorption processes）,membrane separation technology is a green energy-saving technology for gas separation and purification.Due to their low energy cost,high separation efficiency,small footprint and high reliability,membrane devices can be used for gas separation on a global scale.Doped polybenzimidazole（PBI）membranes have good thermal stability and mechanical properties,and they are a good high-temperature proton conductor,so they have attracted much attention in the field of hydrogen penetration.However,PBI still needs to dope electron conductors and build electron channels to form a hydrogen permeation mechanism based on the mixed conduction mechanism of protons and electrons to obtain hydrogen with high purity.Therefore,this paper mainly uses high-temperature proton conductor PBI as the starting material,uses a bifunctional cross-linking agent for covalent cross-linking to improve the mechanical properties,by doping the proton conductor,forming a mixed channel of electrons and protons,to build a mixed conductor membrane,And used for the purification of hydrogen.Using 3,3′-diaminobenzidine（DABz）and isophthalic acid（IPA）as raw materials,low molecular weight poly[2,2’-（m-phenyl）-5 was prepared by the“melt polymerization method”.5’-bibenzimidazole]（m PBI）;using triglycidyl isocyanurate（TGIC）as cross-linking agent,flake graphite as electronic conductor,impregnated with phosphoric acid to obtain m PBI-TGIC/graphite/H₃PO₄ cross-linked composite membrane.The structural and performance characterization of the cross-linked composite membrane showed that the cross-linked composite membrane has good mechanical strength and oxidation stability.It is used for the separation of H₂/CO₂ mixed gas.At 300°C,the hydrogen selectivity is up to 100%,and the permeation flux is 0.14 m L min^-1 cm^-2.At280°C,it can be operated stably for 160 h,indicating m PBI-TGIC/Graphite/H₃PO₄cross-linked composite membrane has good high temperature resistance.As the temperature increases,the phosphate groups in the membrane gradually decompose,and the proton conductivity of the m PBI-TGIC/graphite/H₃PO₄ cross-linked composite membrane decreases,resulting in a rapid decrease in the hydrogen permeability rate of the m PBI-TGIC/graphite/H₃PO₄ cross-linked composite membrane.In order to solve these problems,doped sulfonated graphene as an electronic conductor cross-links with m PBI,protons are transferred along the cross-linking site between the sulfonic acid group of SG and the imidazole ring of PBI,forming a proton-electron mixed conductor,The m PBI-TGIC/SG cross-linked composite membrane was prepared by casting.Due to the addition of sulfonated graphene（SG）,compared with m PBI-TGIC/graphite/H₃PO₄ cross-linked composite membrane,m PBI-TGIC/SG cross-linked composite membrane has lower swelling rate and better compactness.For the separation of H₂/CO₂ mixed gas,the hydrogen selectivity is still 100%at 300°C,and the permeation flux is as high as 0.22 m L min^-1 cm^-2;at 280°C,it can still operate stably for160 h without attenuation;these It shows that m PBI-TGIC/SG cross-linked composite membrane is expected to be used for high temperature hydrogen separation.