A unique solid amine sorbent useful for capturing low concentrations of carbon dioxide

A novel CO2 sorbent has been developed that has proven useful in removing carbon dioxide at very low CO2 partial pressures (1-5 mm Hg). This sorbent combines the high surface area of a polymeric adsorbent support with the proven CO2 removal efficacy of a liquid amine, We have demonstrated its ability to reduce CO2 partial pressures from 1-5 mm Hg in ambient pressure gas streams down to less than 0.5 mm Hg, when operated in a pressure swing adsorption (PSA) mode. This sorbent relies on the affinity of an amine coating to a polar support, to provide a solid amine sorbent. Polyethyleneimine (PEI) and diethanolamine (DEA) represent two amines that have been applied to support surfaces. Both of these amines combine the low vapor pressure and secondary amine functionality preferred for the CO2 removal application. These solid amine sorbent formulations have proven to be especially useful at providing CO2 removal from enclosed habitats, NASA presently uses a PEI coated formulation on long duration missions to regenerably remove CO2 from the space shuttle orbiter crew cabin. NASA is also investigating the use of variations of this solid amine sorbent for regenerable CO2 removal from space suits, spacecraft and planet based habitats. In order to investigate amine-support interactions, surface morphologies, and the affinity of CO2 with the sorbent, studies were performed using TGA (Thermal Gravimetric Analysis), SEM (Scanning Electron Microscopy) and AFM? (Atomic Force Microscopy). Experiments were also conducted to determine pressure swing adsorption/desorption CO2 capacities, as a function of temperature, CO2 and H2O partial pressures. The thickness of the amine coating and the optimum temperatures for desorbing CO2, water, and amine have been determined.