The influence of operating condition on carbon morphology in microwave plasma pyrolysis of methane

Plasma pyrolysis of methane can be used for the production of valuable hydrocarbons, such as acetylene and ethylene, where solid carbon precipitates form as an undesired byproduct. The solid carbon not only reduce the yield of acetylene, but also makes separation difficult. Solid carbon formation can occur in this plasma processes by various mechanisms, which results in different carbon morphologies. We aim to determine the formation and growth mechanism of carbon solids, and in doing so, find optimal operating condition to inhibit the formation of carbon materials during microwave plasma driven pyrolysis of methane. To achieve this, we collected carbon materials from multiple locations in a microwave plasma reactor under different pressure and power, which affects the plasma temperature, chemical kinetics, and reaction time, thus influencing carbon morphology. Using TEM, SEM, Raman, TGA, and GC, we analysed the characteristics of the materials, including microstructure, size, thickness, molecular composition, hydrogen content, and quality. With these results, we aim to validate carbon growth mechanisms in plasma pyrolysis of methane.