This study of methane pyrolysis was designed to look at carbon deposition on the internal reactor and wafer surface during CH4 pyrolysis. The rate of carbon deposition on the internal reactor surfaces could be reduced with: lower methane/oxygen ratios, shorter residence times, and lower temperatures. The type of carbon formed appeared to have a significant effect on the pyrolysis process. Pyrolytic carbon with a lower order structure produces a higher selectivity for carbon formation compared to carbon with a higher order structure. Form a process perspective, there are two obvious means of addressing this: deposited carbon could be regularly removed; and/or pyrolysis conditions are selected that produce carbon with a higher order structure. From the results, it is very clear that any development of a commercial process for natural gas pyrolysis in ceramic reactor systems would have to carefully address the selection of reactor material. (c) 2018 American Institute of Chemical Engineers