Abrasion-assisted methane pyrolysis in a bubbling fluidized bed using low-surface-area carbon-sphere–supported Fe/Co/Ni catalysts that shed pyrolytic carbon

• Abrasion-assisted bubbling FBR sheds pyrolytic carbon from carrier spheres. • Low-area carbon spheres support 5 wt% Fe, Co and Ni catalysts. • Wet-impregnated catalysts sustain high CH 4 conversion for 72 h at 800 °C. • Second-run tests show partial activity retention after simple sieving reload. • Separated carbon fines are metal-free and include MWCNTs and Co-derived nanocoils.