Carbon Dioxide Management in Spacecraft Atmospheres.

O NE OF THE methods currently being investigated for the regenerable removal of carbon dioxide from space vehicle atmospheres involves its adsorption on synthetic zeolites. These materials, known commercially as "molecular sieves" (Linde Company) or "microtraps" (Davison Chemical Company) are crystalline alumino silicates of alkali and alkaline earth metals. Synthetic zeolites being crystalline are characterized by a large number of channels of regular diameter in the crystal lattice. The diameter of these channels can be varied by changing the nature of the alkali ion associated with the alumino-silicate groupings. In this manner, synthetic zeolites can be prepared to adsorb molecules of specific size, although it must be remembered that molecular forces, in addition to molecular size, influence adsorption. Thus, synthetic zeolites can be prepared which show an appreciable adsorption capacity for carbon dioxide. Synthetic zeolites are classified according to structure type and pore diameter. Materials which have been found to have good adsorption capacity for carbon dioxide are listed in Table I.