Process for reversibly binding oxygen
Reference Number: N 04-08
Inventors: Ramprasad, Dorai; Meier, Ingrid K.; Pearlstein, Ronald M.; Pez, Guido P.
Owner: NISTAC
USPTO Link:5294418
Invention Summary
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.