High-permeance crosslinked PTMSP thin-film composite membranes as supports for CO2 selective layer formation

In the development of the composite gas separation membranes for post-combustion CO2 capture, little attention is focused on the optimization of the membrane supports, which satisfy the conditions of this technology. The primary requirements to the membrane supports are concerned with their high CO2 permeance. In this work, the membrane supports with desired characteristics were developed as high-permeance gas separation thin film composite (TFC) membranes with the thin defect-free layer from the crosslinked highly permeable polymer, poly[1-(trimethylsilyl)-1-propyne] (PTMSP). This layer is insoluble in chloroform and can be used as a gutter layer for the further deposition of the СО2-selective materials from the organic solvents. Crosslinking of PTMSP was performed using polyethyleneimine (PEI) and poly (ethyleneglycol) diglycidyl ether (PEGDGE) as crosslinking agents. Optimal concentrations of PEI in PTMSP and PEGDGE in methanol were selected in order to diminish the undesirable effect on the final membrane gas transport characteristics. The conditions of the kiss-coating technique for the deposition of the thin defect-free PTMSP-based layer, namely, composition of the casting solution and the speed of movement of the porous commercial microfiltration-grade support, were optimized. The procedure of post-treatment with alcohols and alcohol solutions was shown to be crucial for the improvement of gas permeance of the membranes with the crosslinked PTMSP layer having thickness ranging within 1-2.5 μm. The claimed membranes showed the following characteristics: CO2 permeance is equal to 50-54 m3(STP)/(m2 h bar) (18,500-20,000 GPU), ideal CO2/N2 selectivity is 3.6-3.7, and their selective layers are insoluble in chloroform. Thus, the developed high-permeance TFC membranes are considered as a promising supports for further modification by enhanced CO2 selective layer formation.