TITLE:
Direct Preparation of Hydrogen and Carbon Nanotubes by Microwave Plasma Decomposition of Methane over Fe/Si Activated by Biased Hydrogen Plasma
AUTHORS:
Katsuya Konno, Kaoru Onoe, Yasuyuki Takiguchi, Tatsuaki Yamaguchi
KEYWORDS:
Hydrogen; Methane Decomposition; Carbon Nanotubes; Microwave Plasma; Methane; H2 Plasma Treatment
JOURNAL NAME:
Green and Sustainable Chemistry,
Vol.3 No.1,
February
26,
2013
ABSTRACT: Methane was decomposed to hydrogen and carbon nanotubes (CNTs)
by microwave plasma, using Fe/Si catalyst activated by biased (—150
V) hydrogen plasma for various treatment times. Upon exposure to biased
hydrogen plasma, the catalyst surface becomes lumpy within 1 min, coheres
between 5 and 10 min and forms particles after 20 min. The methane conversion
increased up to 93% over the treatment time of 5 min. The hydrogen yield showed
as similar tendency as the methane conversion and kept 83% at treatment time of 5
min. The treatment time up to 1 min increased the amount of deposited carbon,
and after treatment time of 5 min it dropped; then again after treatment time
of 20 min, it increased to reach a maximum value of 22 gc/gcat.
Deposited carbon was found to be consisted of carbon nanotubes. It grew
vertically on the catalyst surface and reached a maximum length of 30.7 nm
after treatment time of 10 min. Multiple types of CNTs were present, and the CNT
diameters decreased with increasing plasma treatment time.