Effect of coagulation bath on selective separation of PEI-PEG1000 methane dehydration membrane

In order to prepare high-performance natural gas dehydration membranes, effects of coagulation bath were studied during a non-solvent-induced phase separation (NIPS) process. Specifically, concentrations of N-methyl-2-pyrrolidone (NMP) and polyethylene glycol 1000 (PEG 1000) were investigated respectively on the structure and properties of polyetherimide (PEI)-PEG1000 blend membranes. Studies have shown that both coagulation baths, namely, NMP and PEG1000, can affect membrane structures and improve the overall separation performance of the blend membranes. The presence of NMP in the coagulation bath formed a dissolution equilibrium with the membrane to modify the membrane structure and slow down the rate of phase separation, and the separation coefficient was 151.8 with 8% NMP. With the increase of PEG1000 concentration in the coagulation bath, the hydrophilicity of the membrane enhanced, and a separation coefficient of 585.7 was reached at 10% PEG1000.