A new ceramic supported zeolite-polyphosphazene membrane will be developed for air revitalization in life support systems. A 20% potassium exchanged zeolite A with a pore diameter around 3.3 A has proven to be suitable for separation of H2 (2.89 A) and C02 (3.3 A) from N2 (3.64 A), O2 (3.46 A) and CH4 (3.8 A). However, selective adsorption on granular zeolites is a non-continuous process. In addition, potassium zeolite A has special affinity to H20. Therefore, a desiccant bed is needed before a C02 absorbent bed in the current separation process. The proposed composite membranes have a thin film of hydrophobic polyphosphazene coated on zeolite particles to prevent them from coming in contact with H20. Therefore, this new membrane separation system can effectively separate C02 from cabin air or separate unreacted H2 and C02 from Bosch reactor exhaust gas mixtures in the life support systems of space stations. This continuous separation process has several advantages over alternative processes, including ease of operation, low maintenance, cost, volume, weight and energy consumption. Phase I work will consist of various experiments to demonstrate the technical and economic feasibility of the proposed technology. The deposition process as well as the selectivity in desired gas mixture separations of new ceramic supported zeolite- polyphosphazene membranes will be investigated in detail. The technology developed in Phase I will provide a technical foundation for the Phase II scale-up process. Pilot tests in Phase II will be designed to allow for the future commercial production and application.Separation properties of the proposed zeolite-polyphosphazene membranes can be tailored easily to specific applications. Therefore, the potential of these composite membranes in commercial gas and liquid separations are enormous. In addition to the air revitalization of closed environmental systems such as submarines and spacecraft, this separation system can be applied to hydrogen recovery from petroleum refining, removal of carbon dioxide from natural gas, olefin and paraffin separations, etc. All these applications are of strong commercial and petrochemical interest. The many economic advantages of the proposed technology will allow them to penetrate the market segments discussed above at an accelerated pace.
Keywords: Phase_I, NASA, Abstract, FY94
