Difference and similarity of coke from thermal decomposition or steam reforming of acetic acid

Polymerization/cracking and the reaction of intermediates with steam are the main routes by which the coke of very different properties might formed in steam reforming of acetic acid. This was investigated herein by conducting the steam reforming and decomposition of acetic acid on Ni/SBA-15 at 400, 550 and 700 °C, with particular focus on investigating the nature of resulting coke. Decomposition generated more coke than steam reforming at 400 °C (79.1% versus 24.6%), 550 °C (73.0% versus 45.6%) or 700 °C (39.0% versus 6.8%). More carbonaceous species like *CHx and *CC were the main intermediates, precursors of aromatic coke in decomposition, and their concentration on the catalyst surface let to serious coking at 550 °C, however, in steam reforming, oxygen-containing species like CO or C-O-C where the main intermediates precursors of coke. While larger outer diameter of carbon nanotube was formed in the reaction at 550 °C, smooth surface was formed at 700 °C.