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.
Highlights
Hydrogen production from methane is conventionally preformed with following reactions by steam reforming or partial oxidation. (1) (2) the reactions produce CO, it is usually removed by the oxidation to CO2 for the purpose of hydrogen production
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
We investigated that the effect of catalyst treatment time of biased hydrogen plasma on microwave
Summary
The reactions produce CO, it is usually removed by the oxidation to CO2 for the purpose of hydrogen production. This is an inconvenient fact to emit large quantities of CO2, greenhouse effect gas. Shah et al obtained the hydrogen yield of 80 90 vol%, decomposing methane at 700 ̊C - 800 ̊C under Fe-M (M = Pd, Mo and Ni) catalyst supported on alumina [10]. In these studies, the hydrogen concentration is high (80% - 90%), the methane conversion is not so high. Onoe et al reported that the high selectivities of acetylene and hydrogen are performed with a high CH4 conversion by the microwave plasma technique with following reaction [11]
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