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Synthesis of Organics Using Metal-Silicate Smokes

Synthesis of Organics Using Metal-Silicate Smokes. presented by Natasha Johnson 1,2. in collaboration with Joe Nuth 1 , Jason Dworkin 1 , Millie Martin 3 , Anita Ganesan 4. 1 Astrochemistry Lab, NASA-GSFC, 2 USRA Research Scientist, 3 Catholic University, 4 JHU-APL. Introduction.

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Synthesis of Organics Using Metal-Silicate Smokes

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  1. Synthesis of Organics Using Metal-Silicate Smokes presented by Natasha Johnson1,2 in collaboration with Joe Nuth1, Jason Dworkin1, Millie Martin3, Anita Ganesan4 1Astrochemistry Lab, NASA-GSFC, 2USRA Research Scientist, 3Catholic University, 4JHU-APL

  2. Introduction • Organics identified in meteorites and comets • What is the origin of the organics? • Interstellar dust most likely played a role in forming organics • Laboratory-synthesized dust analogs created to simulate Fisher-Tropsch Type (FTT) reactions in the solar nebula

  3. Method in a Nutshell • Generate amorphous Fe or Mg silicate grains • Deposit organics on grains via Fischer-Tropsch type reactions • Measure change in reaction rate • Analyze generated organics: solid and gas (e.g. transmission FTIR,UV-Vis,GCMS) • Ultimately, compare with observed organics (such as those identified in meteorites and comets)

  4. Fischer-Tropsch Type (FTT) Reactions CO + H2=> CxHy + water catalyst • Reaction monitored by analyzing gases using FTIR (e.g. decrease in CO) • As reaction progresses, catalyst is poisoned • Hydrocarbons are generated and organics are deposited on grains

  5. Amorphous Grain Generator

  6. FTT Reaction System Hill and Nuth, Astrobiology 2003

  7. Analytical Methods • Gases * FTIR * Gas Chromatograph • Solids * Gas Chromatograph Mass Spectrometer (GCMS) e.g., Pyrolysis GCMS (rapid heating) * Extractions and derivatizations * Demineralization (concentrates organics)

  8. Fourier Transform Infrared Spectroscopy CO2 CO2 CH4 H2O CO

  9. Many natural surfaces promote the disproportionation of CO Bronzite SiOx Iron silicate Mg-SiOx SiO2 CH4 production at 400°C using different catalysts Plot of CO decay as a function of time for different catalysts at 400ºC SiOx SiO2 Iron silicate promotes methane production, but so do many other silicates. Iron silicate Bronzite Mg-SiOx

  10. Predicted products Major: CO2, H2O, CH4 Minor (concentrated) aliphatics aromatics oxygenated organics -actetone & benzoic acid complex organics H3C-N=CH2 Reaction Progress

  11. 2145 cm-1 4.7 μm 2285 cm-1 4.4 μm 3017 cm-1 3.3 μm Decrease in Catalytic Efficiency

  12. Organic Chloroform (CHCl3) Acetonitrile (CH3CN) Methanol (CH3OH) Formic Acid (HCOOH) Sodium Hydroxide (NaOH) Magnesium Chloride (MgCl2) Acid Base Salt Analysis of Organic Deposition Extraction of organics in various solvents …and derivatizations

  13. Demineralized reacted grains Analyzed by pyrolysis-GCMS Analysis of Organic Deposition

  14. Pyrolysis-GCMS Results • Demineralized samples are rich in a variety of organic compounds. • Identified the following classes of material: saturated and unsaturated hydrocarbons alkyl-benzenes phenols styrenes traces of polycyclic aromatics

  15. Cold Trap Analysis • Cold trap the volatile organics and analyze by GCMS. • Benefit: greater sensitivity. • Identified the following: benzenes, substituted benzenes toluene napthalene (Mg-silicate only) • Need to adjust procedure…

  16. …and more tests… • TEM images showed that carbon was deposited on the grains • Hydrated coated grains at various temperatures and times displayed different morphologies as well as a shift in organic residue.

  17. Hydrated Post-catalyzed Grains saturated hydrocarbons only 90 °C 65 °C 23 °C

  18. Summary(1 of 2) • No definitive signature for meteoritic organics, need to compare classes and ranges. • We synthesized macromolecular organic phases • Comparable to insoluble organic fractions of Murchison • Ideally, would like to compare with many other carbonaceous meteorites.

  19. Summary(2 of 2) • Surface-mediated reactions could have produced organics observed in cometary comae and meteorites • While not conclusive evidence for origin of meteoritic organics – supports FTT as a viable hypothesis

  20. Future • Proven method to produce raw ‘organic’ starting material for additional experiments • Secondary processing of reacted dust • (i.e hydration, annealing) • Temperatures, starting materials • Kinetic analysis • Identify trends in organic deposition

  21. References HILL, H.G.M. and NUTH, J.A (2003) The Catalytic Potential of Cosmic Dust: Implications for Prebiotic Chemistry in the Solar Nebula and Other Protoplanetary Systems. Astrobiology 3, 291-304. KRESS, M.E and TIELENS, A. G. (2001) The Role of Fisher-Tropsch Catalysis in Solar Nebula Chemistry. Meteorites & Planetary Science 36, 75-91.

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