Effect of functional group ratio in PEBAX copolymer on propylene/propane separation for facilitated olefin transport membranes

PEBAX-5513/AgBF(4)/Al(NO(3))(3) membranes were fabricated for mixed olefin/paraffin separation. In order to improve the selectivity of the membranes utilizing PEBAX-1657, PEBAX-5513, which increased the ratio of amide groups from 40% to 60% in the copolymer, was used. The selectivity and permeance of the membranes were 7.7 and 11.1 GPU, respectively. Furthermore, the PEBAX–5513/AgBF(4)/Al(NO(3))(3) membranes had long-term stability because of Al(NO(3)) to have the stabilizing effect on Ag(+) ions acting as an olefin carrier. Unexpectedly, the performance of the membrane selectivity was not improved, and the permeance became rather lower. Generally, when Ag(+) ions was added to the polymer containing amide groups, the selectivity increased with the content of the amide groups. However, Al(NO(3))(3) was added for the stability of Ag(+) ions and there was no increase in selectivity. Since the ratio of amide was high, Ag(+) ions were favorably in coordination with the oxygen of the carbonyl group, but the NO(3)(−) ions in Al(NO(3))(3) had the enhanced interaction with Ag(+) ions as obstacles for olefin complexation. Therefore, the composition ratio of amide/ether in the polymer matrix was negligible for olefin separation.