Synthesis of Fe-Doped Porous Carbon Catalyst Derived from Coconut Shell Waste using Ferric Nitrate Nonahydrate (Fe(NO3)3.9H2O) as an Iron Precursor

Renewable energy from lignocellulosic biomass is a promising alternative to fossil fuels. Coconut shell (CS) waste is a favorable precursor for porous carbon due to its high carbon content, abundance, and non-food nature. However, conventional biochar often has limited surface area and catalytic active sites, hindering its effectiveness as a catalyst. While Fe-based modifications are promising, the use of ferric nitrate-assisted activation of coconut-shell-derived porous carbon remains underexplored. This research focused on developing an Fe-doped porous carbon catalyst from CS via ultrasound-assisted impregnation, followed by activation in a tube furnace. CS biochar was produced through pyrolysis at 550 °C and subsequently impregnated with ferric nitrate nonahydrate (Fe(NO₃)₃·9H₂O) utilizing ultrasonic mixing. The resulting composite was then activated in a tube furnace to synthesize Fe-doped porous carbon. The catalyst created with 2 wt.% Fe(NO₃)₃·9H₂O showed the highest specific surface area of 262.9 m²/g, representing a 55-fold increase compared to untreated biochar. Structural analysis revealed that Fe activation facilitated pore development via Fe-assisted carbon gasification, while the thermal decomposition of CaCO₃ and K₂CO₃ also contributed to pore formation. These structural enhancements are likely to improve catalytic efficiency by promoting deoxygenation during biomass pyrolysis. The results demonstrate an efficient and cost-effective method for synthesizing iron-doped porous carbon catalysts from CS biomass. This process successfully enhances the material's porosity, making it suitable for catalytic biomass conversion applications. The iron-doped porous carbon produced shows promise as a low-cost catalyst for the catalytic pyrolysis and upgrading of biomass-derived bio-oil.