Scaling up of defect-free flat membrane with ultra-high gas permeance used for intermediate layer of multi-layer composite membrane and oxygen enrichment

Multi-layer composite membrane has attracted more and more attention in the field of gas separation, especially for CO2 separation, and the intermediate layer (or gutter layer) has a significant influence on the performance of the multi-layer composite membrane. However, due to low gas permeance, current commercial gas separation membranes cannot be used as the intermediate layers with which to fabricate multi-layer composite membranes with high gas permselectivity. Aiming at oxygen enrichment application and developing proper large-area intermediate layer for multi-layer composite membrane, the scaling-up process of the flat membrane with ultra-high permeance was investigated in detail by using the most common material for intermediate layer and a substrate with extremely high gas permeance. In the lab-scale, through simply adjusting the relative humidity and prepolymer concentration, the coating solution with an appropriate cross-linking degree could be successfully prepared in 10 min. In view of the low viscosity of the coating solution, a consecutive membrane fabrication machine with the dip-blade coating unit was specifically designed to scale up the membrane. Using a firstly proposed wet-dry combined coating method, the defect-free flat membrane with a width of 1 m was successfully prepared, which had uniform performance in both the transverse and longitudinal directions. The O-2 and CO2 permeance of the prepared large-area membrane could reach 2000 and 10,000 GPU respectively, which was the highest among the reported membranes prepared with similar materials.