Hydrogasification of Carbon in an Atmospheric Pressure Microwave Plasma

Hydrogasification of carbon (C + 2H₂ rarr CH₄) was studied using a microwave plasma in atmospheric pressure Ar/H₂ mixtures. When the activated Ar/H₂ gas stream interacted with cold carbon particles downstream of the microwave cavity, CH₄ (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 C₂H₂ (acetylene) and C₂H₄ (ethylene) were measured in addition to CH₄. 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 CH₄ is thought to be a chemisorption-desorption reaction of hydrogen radical onto a carbon particle. For the C₂H₂ and C₂H₄ generation, hydrogen ion reaction with a carbon particle is suggested.