Process for reversibly binding oxygen
Reference Number: N 04-08
Inventors: Ramprasad, Dorai; Meier, Ingrid K.; Pearlstein, Ronald M.; Pez, Guido P.
The present invention is a class of solid state compositions comprising one or more cyanocobaltate complexes comprising a cobalt (II)-containing anion having from three and five cyanide ligands and having at least one cyanide stretching mode, as measured by infrared spectroscopy, in the range of 2074 cm.sup.-1 .ltoreq..nu..sub.CN .ltoreq.2140 cm.sup.31 1. Additionally, the complex contains a charge-balancing cation having a molecular volume in excess of 40.ANG..sup.3. The cation may be comprised of a solvated ion or may be a cationic complex, cluster or polymer. These solid state compositions are capable of selectively binding (i.e., sorbing) oxygen thereby making them useful for removing oxygen from oxygen-containing fluid streams. These complexes operate by chemically reacting with oxygen to form oxygenated stable complexes which are the corresponding oxygen adducts of the above cyanocobaltate complexes.
The above described process for selectively binding or sorbing oxygen can be reversed to cause the release of the bound oxygen to regenerate the complex and recover the oxygen. This can be achieved by heating the adduct or by any means which reduces the partial pressure of O.sub.2 above the adduct, such as evacuating or passing a sweep gas over the adduct.
The above cyanocobaltate complexes are advantageous over prior art oxygen sorption materials in that the present solid state materials rapidly sorb oxygen, and even at equilibrum have a high capacity and selectivity for oxygen over nitrogen and other gases. This is due in part to the fact that these cyanocobaltate complexes have a reversible chemical affinity for oxygen, rather than relying primarily on their physical characteristics for adsorbing oxygen as is the case with zeolites and carbon molecular sieves. This chemical binding reduces or eliminates problems encountered in prior processes relating to kinetically dependent adsorption and poor adsorption at or near equilibrium conditions. An additional advantage in using the present complexes is that they can be used in a non-aluminosilicate environment (i.e., they do not have to be encapsulated in the cage of a zeolite) to reversibly bind oxygen.