Reusability of Hydroxyapatite-Ladle Furnace Slag Composite Catalyst in Co-Pyrolysis of Plastic Waste and Oil Palm Fiber

Background and Objective: Ladle Furnace Slag is a major waste in the steel industry. This study aimed to evaluate the reusability of a Ladle Furnace Slag-Hydroxyapatite (HAP) composite catalyst for the co-pyrolysis of biomass waste and plastic to produce bio-oil. Materials and Methods: The HAP-LF catalyst was synthesized and tested for catalytic co-pyrolysis of oil palm fiber and plastic waste using a thermogravimetric analyzer and fixed-bed reactor. The sample was subjected to a temperature ramp from 30-800°C at a rate of 10°C/min, with mass changes monitored to analyze thermal decomposition behavior. To estimate activation energies, the thermograph was divided into three distinct temperature zones: 0-250°C (Zone 1), 250-450°C (Zone 2) and 450-800°C (Zone 3). The study also examined the product yields and composition of organic compounds in the pyrolytic oil across five catalyst reuses. Both TGA and fixed bed experiments were triplicated for reproducibility, with TGA using 0.05 significance in regression and fixed bed reporting average yield and composition. Results: Thermogravimetric analysis revealed that catalytic co-pyrolysis (CCP) with the HAP-LF catalyst achieved a maximum mass loss rate of 11.88%/min, exceeding 9.72%/min from thermal co-pyrolysis. The final residue mass was 15.8% with the catalyst, which was significantly higher than the 4.2% obtained from the thermal processes, indicating a synergistic effect on residue formation. Reusability tests in a fixed-bed reactor at 450°C showed that the catalyst promoted alcohol compound formation, with a maximum yield of 19.35 wt (%) after five consecutive uses compared to 11.07 wt (%) without the catalyst. Conclusion: Remarkably, the HAP-LF catalyst maintained strong performance for at least four cycles without regeneration, highlighting its potential for sustainable industrial applications.