Effects of Axial Ligands on O₂/N₂ Selectivities of Facilitated Oxygen Transport Membranes Using a Cobalt(II) Complex

Abstract

The effects of axial ligands on O₂/N₂ selectivities of oxygen facilitated transport membranes containing a cobalt ( II ) complex, N, N'-bis (3-methoxysalicylidene)-2-methylpropylenediaminato-cobalt ( II )was investigated, using 4-dimethylaminopyridine (4-DMAP), dimethyl sulfoxide (DMSO) and pyrazine as an axial ligand.
The O₂/N₂ selectiv ities of the membrane with 4-DMAP, DMSO and pyrazine were 160, 3 and 2.2, respectively. The oxygenation rate in the DMSO system and the deoxygenation rate in the pyrazine system were remarkably smaller than those of the other systems.
Low O₂/N₂ selectivity in the DMSO system is due to the slow oxygenation of the complex and that in the pyrazine system is attributable to the low deoxygenation rate.
Slow oxygenation in the DMSO system may be due to the s mall overlap of dz² orbital having an unpaired electron with the antibonding orbital of oxygen.