Hydrogasification of Carbon in an Atmospheric Pressure Microwave Plasma

Hydrogasification of carbon (C + 2H
₂
rarr CH
₄
) was studied using a microwave plasma in atmospheric pressure Ar/H
₂
mixtures. When the activated Ar/H
₂
gas stream interacted with cold carbon particles downstream of the microwave cavity, CH
₄
(methane) was the only stable gasification product, as measured by gas chromatography. However, when carbon particles were injected into the plasma within the microwave cavity, both C
₂
H
₂
(acetylene) and C
₂
H
₄
(ethylene) were measured in addition to CH
₄
. To identify a gasification mechanism by the microwave plasma, UV emission and minimum operational power required to maintain plasma were measured. From the experimental results, the initial reaction step leading to CH
₄
is thought to be a chemisorption-desorption reaction of hydrogen radical onto a carbon particle. For the C
₂
H
₂
and C
₂
H
₄
generation, hydrogen ion reaction with a carbon particle is suggested.