Production of hydrogen and carbon nanotubes from methane using a multi-pass floating catalyst chemical vapour deposition reactor with process gas recycling

Converting natural gas into hydrogen and solid carbon materials using methane pyrolysis presents a promising opportunity to produce sustainable fuels and materials. Hydrogen and bulk carbon nanotube (CNT) production via methane pyrolysis have been demonstrated independently, but con- current production from the same reactor remained elusive. Here, we present a multi-pass floating catalyst chemical vapour deposition (FCCVD) reactor that converts methane into hydrogen and CNT aerogel. Whereas prior FCCVD CNT production consumed hydrogen, the multi-pass reactor recycles the carrier gas to eliminate any hydrogen input. This results in a net output of 85 vol% hydrogen alongside CNT aerogel, and a 440-fold increase in molar process efficiency. Further, the demon- strated use of biogas to produce CNT aerogel enables potential net sequestration of CO2 from the atmosphere. The results of this study are extrapolated to a pilot-scale reactor, using data gathered at a commercial facility, to consider challenges and opportunities associated with scale-up.