A comprehensive study of catalytic pyrolysis of antibiotic fermentation residue over red mud-Ca(OH)₂ composites

This study focuses on the in-situ catalytic pyrolysis of the Penicillin fermentation residue (PFR), a typical antibiotic fermentation residues (AFR), using a red mud-Ca(OH)₂ composite (RM-xCa) to enhance syngas production, tar conversion, and desulfurization. The invesitigation explored the effects of different preparation methods, amount of CaO addition, and final pyrolysis temperature on the performance of RM-xCa composites. The RM-xCa composite prepared by the hydrothermal method with pressure exhibited higher catalytic activity due to the formation of soluble Na through cation exchange. The amount of CaO added determined the sulfur adsorption capacity of RM-xCa, as well as the amount of H₂O and CO₂ involved in tar reforming and char gasification reactions. Final pyrolysis temperature significantly influenced the reduction state of Fe₂O₃ and decomposition of Ca(OH)₂, affecting the catalytic activity and sulfur adsorption behavior of RM-xCa composites. The optimized RM-xCa composite, RM-4Ca-HT, decreased tar and H₂S formationby 34 % and 38 %, respectively, at 700 °C. Additionally, RM-xCa composites can lower the oxygen and sulfur content of tar. Solid residues from PFR catalytic pyrolysis were found suitable for reused as catalysts in further tar removal process.