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T. C. Smith (NASA/University of Maryland), R. F. Ferrante (U S Naval Academy), M. H. Moore (NASA/Goddard Space Flight Center), S. L. Hallenbeck (NRC-NASA/Goddard Space Flight Center)
We have begun a set of laboratory measurements to study the possible conversion of CO into CH4 and other alkanes via Fischer-Tropsch catalysis in the presence of interstellar dust analogs containing iron. The dust analogs are sub-micron size iron silicate smokes made in a grain condensation chamber by reacting SiH4 with O2 in the presence of Fe (CO)5 . The smokes are amorphous in phase and composition; based on our gas adsorption measurements they have a surface area of near 125 m2g-1. In the catalytic experiment, a mixture of H2 + CO (2 : 1) is continuously circulated in a closed system through ~ 0.1 g of iron silicate smoke. The smoke is heated to near 300 C while the gas reacts for a 3 hour period. The reacted gas is condensed onto a 10 K mirror attached to the tail of a cryostat. The infrared spectrum of the condensed gas is used to identify new species formed by catalysis. There is evidence for the conversion of CO into CH4, C2H6 and C2H4. Similarly obtained background spectra not containing the catalyst do not show the same spectral signatures. Further experiments will quantitatively determine the efficiency of this conversion to determine if grain-catalyzed reactions such as these could play an important role in the chemistry of the solar nebula.NASA/Goddard