The nature of carbonaceous species deposited upon MoO3/H-ZSM-5 and Pd/H-ZSM-5 based catalysts during methane activation at 700 degrees C has been studied. TEM evidences the formation of open-ended multi-walled carbon nanotubes on MoO3/H-ZSM-5 based dehydroaromatisation catalysts. Pd/H-ZSM-5 is more active, exclusively towards methane cracking and post-reaction analysis reveals the distribution of different carbonaceous species is more homogeneous which TEM demonstrates to be in the form of closed-end multi-walled carbon nanotubes.