NASA has long recognized that travel to Mars, the establishment of permanent bases on the surface of our moon, or any future human exploration of space requiring long duration manned space activities depends on the development and successful implementation of regenerative life support systems (RLSS). It has also been acknowledged that integration of physiochemical and biological technologies into an RLSS is a complex and challenging undertaking. To this end NASA has implemented several ground-based projects aimed at discerning the various issues involved in attainment of the most productive RLSS for future manned space activities.[l] One of the four main ground-based efforts to achieve the above stated objective is underway at NASA/JSC in the Advanced Life Support Systems Group (ALSSG) in the form of a test bed. The RLSS test bed is an atmospherically closed, controlled environment facility for the evaluation of regenerative life support systems using higher plants in conjunction with physiochemical life support systems.[2] This RLSS must ensure removal of all gases which are harmful to the crew and which are generated from all activities in the occupants' environment. Moreover, the RLSS should provide for the most efficient reuse of any waste products, solid or gaseous, so that re supply of the mission does not become a major concern for the personnel involved in the manned space activities. The RLSS should also assure that the higher plants carry out their intended primary purification and addendum food supply source functions for the human inhabitants of the environment. A final objective of the RLSS at NASA/JSC is to ensure that the plants and humans can efficiently use the waste solids and gases generated in a closed-loop, rather than an open-loop system.

In addition to testing and improving the use of plants for the removal of CO2 and generation of O2, the ALSSG at NASA/JSC is currently undertaking human testing of an integrated biological-physiochemical support system as part of the Early Human Testing Initiative (EHTI). The integrated system uses mature, open-loop technology for the physiochemical component of the testing breadboard. The ALSSG is continuously seeking to replace these open-loop technologies with novel technologies which allow for the removal and subsequent on-demand regeneration of CO2 by closed-loop physiochemical technologies, as well as for the conversion of solid wastes from non-edible parts of plants, utensils, and products which arise from human digestion of foods. Realization of a novel physiochemical technology which would achieve both of the aforementioned goals would be a tremendous step forward in the further refinement of the approach being used by the NASA/JSC initiative with regard to generating an RLSS system which has an integrated biological and extremely efficient closed-loop physiochemical component to it.

The research projects currently being conducted by the PI have as their main objective the development of novel technologies for the removal, regeneration, and reutilization of carbon dioxide, carbon monoxide, and nitrogen oxides in a closed-loop fashion which should greatly impact the physiochemical efforts at the NASA/JSC ALSSG. General studies now underway are based on chemical discoveries made in the PI's labs which had previously never been achieved. The general proposed studies are depicted by Scheme 1.

Specific aims
This project deals with the concurrent development of at least three new technologies from novel reagents and reactions, which will allow for the removal, regeneration and reutilization of carbon dioxide, carbon monoxide, and nitrogen oxides. Thus, the PI and the ISSO-sponsored post-doctoral fellow are carrying out research on all three aspects of the project concurrently.

Relevant Preliminary Studies
The PI discovered that the reaction between donor-solvent-free diorganomagnesium compounds and organic amines proceeds readily to afford a new family of reagents which we have named unsolvated diorganomagnesium compounds ([R2N]2Mg).[3] The PI has also been the first to discern the compounds' physical and chemical properties, which are quite different than current theories in organometallic chemistry predict. For example, the majority of the [R2N]2Mg are solids which show excellent thermal and other properties.[3] The PI has also discovered unexpectedly that unsolvated [R2N]2Mg compounds react with carbon dioxide at room temperature and atmospheric pressure, in quantitative or nearly quantitative yield (depending on the structure of the organic groups bonded to nitrogen) to afford yet another previously unknown composition of matter. This composition is the family of reagents which we have named unsolvated bis(N,N'-Diorganocarbamoxy)magnesium compounds. These results are depicted in general below by equations 1 and 2.

(1)

(2)

More recently we have obtained preliminary results which show that the reaction between ([R2NCO2]2Mg) and ethanol allows for the regeneration of carbon dioxide and yields the corresponding unsolvated dialkoxymagnesium compounds.[4] This is depicted by equation 3 below.

(3)

The two biscarbamoxymagnesium compounds which we have been able to convert to the dialkoxymagnesium compounds with regeneration of carbon dioxide, were chosen as models for the cursory research because one is a solid at room temperature (when R is ethyl) and the other is a hydrocarbon soluble reagent. The choice to use ethanol was based primarily on the consideration of using the least toxic commercially available mono-alcohol.

Current Research Focus
Since the results of the cursory research indicate that the regeneration of the carbon dioxide is feasible through this process, we have undertaken a focused study to develop an optimal novel process which is closed-loop and regenerative. One major focus of the present research involves the evaluation of a host of structurally different biscarbamoxymagnesium compounds with various structurally different alcohols. The purpose of this part of the study is to find other candidate alcohols which can be used to bring about the regeneration of carbon dioxide upon reaction with the formed biscarbamoxymagnesium compounds, and which have better physiological properties and better physical properties with respect to manned space activities.

Another part is concentrated on finding the necessary experimental conditions to convert the incipient dialkoxymagnesium compounds formed in the carbon dioxide regeneration step back to the original (R2N)2Mg which can be used again in the fixation of more carbon dioxide. The third part involves the elucidation of a reaction between biscarbamoxymagnesium compounds and other amines. This latter effort attempts to make the fixation and subsequent regeneration of carbon dioxide part of a closed-loop cycle which uses structurally different amines (from the ones that would be generated from the protonation of the biscarbamoxymagnesium compounds) in a reaction with the formed biscarbamoxymagnesium compounds to generate directly a new (R2N)2Mg. This newly formed (R2N)2Mg would then react with additional carbon dioxide to form a new biscarbamoxymagnesium compound, making the whole process totally regenerative. These reactions are depicted in general by equations 4-6 below.

We anticipate that the results which we have obtained in this part of project will be the subject of a manuscript and one invention disclosure. We have also initiated research aimed at evaluating the reaction conditions necessary to effect the fixation of nitrogen dioxide under mild conditions, as well as other effluent gases which would be generated during long duration space activities. We have achieved some quite important cursory results. Since these results hold the potential for use in not only long duration space activities but also for the removal of various pollutants commonly associated with industrial processes, they will be reported to the University of Houston System and NASA.

References
1S. Sun, D. L. Henninger, J. Sager, and T. O. Trio. "NASA's Approach to Integrated System Testing of Regenerative Life Support Systems," Int'l Conf. on Environmental Systems, 1995.
2D. L. Henninger, T. O. Trio, D. J. Bana, and R. S. Stahl. "Johnson Space Center's Regenerative Life Support Systems Test Bed," NASA Report- NASA-TM-107943, l991.
3R. Sanchez, T. Ratham, R. Morrison, and V. J. Mehta. "Ether-Free Organometallic Amide Compositions," U. S. Patent, 4,944,894, 1990.
4R. Sanchez and O. Felan. "Unsolvated Bis(N,N'-Diorganocarbamoxy) Magnesium Compounds: A Novel Family of Reagents For The Storage and Transfer of Carbon Dioxide and the Facile Preparation and Transfer of The N,N'-Substituted Carbamoxy Structural Unit," Main Group Metal Chemistry 18.4, (1995): 225; Invention Disclosure to University of Houston System and commitment of funds for proceeding with patent application, 1995.