Paper PS+AS-MoM5
Surface-driven CH4 generation from CO2 in Low-pressure Non-thermal Plasma
Monday, October 30, 2017, 9:40 am, Room 23
| Session: |
Plasma Processing of Challenging Materials |
| Presenter: |
Kazunori Koga, Kyushu University, Japan |
| Authors: |
K. Koga, Kyushu University, Japan
S. Toko, Kyushu University, Japan
S. Tanida, Kyushu University, Japan
M. Shiratani, Kyushu University, Japan
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| Correspondent: |
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The methanation of CO2 attracts attention as the way to produce rocket propellant fuels at Mars because CO2 comprises 95% of the atmosphere of Mars and water exists on Mars [1]. This reaction is called the Sabatier process and has been studied using catalysts under high pressure over 1 atm and high temperature above 200 oC to realize a high conversion efficiency. However, the pressure on Mars is 135 times smaller than that of the Earth, and the average temperature is extremely low of -63 oC [2]. A method using low-pressure non-thermal plasma allows methanation under low pressure and low temperature conditions [3]. Therefore, the plasma process is suitable for methanation at Mars. Here, we converted CO2 to CH4 using a capacitively coupled plasma (CCP) together with Cu catalyst. Experiments were carried out using a CCP reactor, excited at a frequency of 60 MHz. The electrode diameter was 50 mm and the distance between the electrodes was 6.1 mm. The electrode material was Cu. CO2 gas flow rate was 1.0 sccm and that of H2 was 6.0 sccm . The pressure was 750 Pa and the temperature was room temperature. The discharge power was set in a range of 10 to 100 W. Gas composition in the discharge plasmas was measured with a quadrupole mass spectrometer. CH4 yield depends on surface condition of Cu electrodes, indicating that surface reactions on Cu electrodes dominate the CH4 generation. Moreover, CH4 generation has a long time constant more than 500 s, whereas CO2 conversion has a short time constant of 80 s. These results indicate that CO2 conversion takes place in gas phase by electron impact dissociation, while CH4 generation involves several reaction steps. I will discuss the detail mechanisms at the conference.Work supported partly by JAXA and JST.
[1] G. Etiope et al., Icarus 224, 276 (2013).
[2] M. Kano, G. Satoh, and S. Iizuka, Plasma Chem. Plasma Process 32, 177 (2012).
[3] S. Toko, et al., Sci. Adv. Mater. In press.