Production of hydrogen and nanocarbon via catalytic pyrolysis of waste polyolefin over nickel-impregnated coal flyash catalyst

Abstract

The conversion of waste polyolefins into valuable products like hydrogen and nanocarbon offers a promising pathway for waste management and resource recovery. This study investigates the catalytic pyrolysis using coal flyash (FA) and nickel-impregnated flyash (Ni-FA) as catalysts. Coal flyash, rich in Al₂O₃ and SiO₂, serves as a sustainable and low-cost support for Ni impregnation, enhancing catalytic efficiency. Characterization using TPR, XRD, and FESEM confirmed effective dispersion of Ni on the surface of flyash. The catalysts were then used during pyrolysis of LDPE, HDPE, and PP in a fixed-bed reactor. Ni-FA catalyst yielded 60–75 vol% H₂ as compared to 25–60 vol% obtained using FA alone. The nanocarbon structures formed on the Ni-FA catalysts were predominantly multi-walled carbon nanotubes with diameters ranging from 10 to 60 nm, as confirmed by Raman spectroscopy, FESEM, and HRTEM. The findings indicate that Ni-FA is a cost-effective and sustainable catalyst, leveraging industrial waste material to address both plastic pollution and the growing demand for H₂ and nanocarbon. This study highlights the dual benefit of waste valorization and energy recovery, offering a scalable and environmentally friendly approach for a circular economy. Future research will delve into enhancing the ability of the catalyst by recovering the nanocarbon and regenerating the catalyst for further cycles.