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

Shosuke YAMANOUCHI*, Kazuhiro OKABE, Masaru SHIOTANI† and Hiroshi SAKURAI†

Osaka R/D Laboratories, Sumitomo Electric Industries, Ltd.; 1-1-3Shimaya, Konohana-ku,
Osaka-shi 554-0024 Japan
† Department of Applied Physics and Chemistry, Faculty of Engineering, Hiroshima University;
Higashi-Hiroshima-shi 739-8527 Japan

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 selectivities 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 small overlap of dz2 orbital having an unpaired electron with the antibonding orbital of oxygen.


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