[P-PS14] 宇宙における物質の形成と進化

[PPS14-06] 鉄基板上でのFT型触媒反応実験における反応効率の温度依存性

*木村 勇気¹、佐藤 理佳子¹、土山 明²、永原 裕子³、羽馬 哲也¹、日高 宏¹、渡部 直樹¹、香内 晃¹ (1.北海道大学低温科学研究所、2.京都大学、3.東京大学)

キーワード：触媒反応、有機分子、実験

Fischer-Tropsch type catalytic reaction has been believed to be one of simplest and most fundamental formation processes of organic molecules, which dominantly occurred on the surface of cosmic dust particles, such as iron, magnetite, amorphous iron silicate and graphite, in the period from the late stage of molecular cloud to the solar nebula. Experimental approaches to find the environment, where catalytic reaction was progressed efficiently, have been attempted in laboratories [1-5]. In the experimental studies, organic molecules ranging from methane (CH₄), ethane (C₂H₆), benzene (C₆H₆) and toluene (C₇H₈), to more complex species such as acetone (C₃H₆O), methyl amine (CH₃NH₂), acetonitrile (CH₃CN) and N-methyl methylene imine (H₃CNCH₂) have been produced at temperature above 573 K and relatively high pressure (10⁵ Pa). In case of actual environment in the early nebula environment, the temperature and pressure should be below 500 K and under 10² Pa, respectively. It is not obvious that the results of the reaction experiments are able to extrapolate to the actual early nebula environment. Therefore, we newly developed an experimental system to test the catalytic chemical reactions in the lower temperature (100-800 K) and pressure (10^-3-10⁰ Pa) using an iron substrate. Our experimental system has a temperature-controlled substrate, a Fourier transform infrared spectrometer (FT-IR), and two quadrupole mass spectrometers (Q-MSs). Although FT-IR is able to measure the vibration modes of adsorbed and produced molecules on the surface, we have not been used it during the first experiment at higher temperature. We found a strong signal of mass 20 in the Q-MSs spectra in a continuous gas flow of a mixture gas of D₂ and CO. The intensity of the signal decreases as temperature decrease from 800 to 400 K and becomes weaker than the detection limit below 300 K. The mass 20 corresponds to D₂O and CD₄, which are first products in the Fischer-Tropsch type reaction. In our presentation, the detail results using iron substrate will be presented as a function of temperature.

References
[1] H. G. M. Hill, J. A. Nuth, Astrobiology, 3 (2003) 291.
[2] J. A. Nuth, N. M. Johnson, S. Manning, The Astrophysical Journal, 673 (2008) L225.
[3] N. M. Johnson, M. McCarthy, J. A. Nuth III, 45^th Lunar and Planetary Science Conference, (2014) 2702.
[4] J. A. Nuth, Y. Kimura, C. Lucas, F. Ferguson, N. M. Johnson, The Astrophysical Journal Letters, 710 (2010) 98.
[5] Y. Kimura, J. A. Nuth, N. M. Johnson, K. D. Farmer, K. P. Roberts, S. R. Hussaini, Nanoscience and Nanotechnology Letters, 3 (2011) 4.