High-Purity Nitrogen By Pressure-Swing Adsorption Using Supported Cyanocobaltate Adsorbents
Publication Date: 2003-Sep-12
The IP.com Prior Art Database
A family of cyanocobaltate complexes which demonstrate reversible pressure-swing oxygen sorption capacity have been developed. These materials possess a unique set of properties which make them attractive adsorbents for the production of nitrogen from air by Pressure Swing Adsorption (PSA), including (1) reasonably high equilibrium oxygen capacity, (2) high working capacity for oxygen over a standard PSA pressure envelope, (3) a Type I isotherm without hysteresis, (4) comparatively rapid adsorption and desorption kinetics, (5) infinite selectivity to oxygen, and (6) excellent chemical stability over a large number of adsorption/desorption cycles. While pellets of the neat complexes do show high equilibrium PSA capacity, their relatively slow sorption/desorption kinetics makes it advantageous to support these complexes on an inert support for use in a PSA system. A number of such supported materials have been prepared, using the complex Li3Co(CN)5 1.42DMF 0.48DMAc, 1, where DMF is N,N-Dimethylformamide and DMAc is N,N-Dimethylacetamide. Characterization of the resulting materials has shown that the support affects both the oxygen uptake kinetics and oxygen capacity. Three materials were evaluated: neat 1 extrudate, 1 supported on diatomaceous earth (Celite-631, average pore diameter of 6 microns), and 1 supported on silica (Philadelphia Quartz, average pore diameter of 300Å). These were first characterized by measuring their equilibrium oxygen uptakes and by fitting the transient uptake data to a distributed-resistance mass transfer model (DRM). The DRM assumes that the particles of 1 are present as small spheres and that both reaction on the surface of the sphere and oxygen diffusion through the bulk of the sphere contribute to the mass transfer resistance.