Valorization of Plastic Waste into Hydrogen: Ni–Co/Al ₂ O ₃ –ZrO ₂ Nanocatalyst for Efficient Steam Reforming of Low‐Density Polyethylene (LDPE)

Plastic waste, particularly low-density polyethylene (LDPE), poses severe environmental challenges due to its low bio-degradability and limited recycling potential. In this study, a solvent-assisted catalytic steam reforming approach is investigated, in which LDPE is finely dispersed in ethylene glycol (EG) to enable homogeneous feed delivery for hydrogen production. Steam reforming experiments were conducted over 20 wt% Ni-Co/Al₂O₃-ZrO₂ catalyst synthesized via sol-gel and wet impregnation methods. The bimetallic catalyst exhibited high surface area (136 m² g^- ¹), strong metal-support interaction (SMI), and improved thermal stability confirmed through characterization techniques including XRD, BET, FESEM, FTIR, and TGA-DSC analyses. Systematic optimization of operating parameters such as metal loading, steam-to-carbon ratio (S/C), gas hourly space velocity (GHSV), and temperature revealed optimal conditions at S/C = 9, GHSV = 810 h^- ¹, and 500°C. Under these conditions, it achieved 95% feed conversion, 92.72% hydrogen yield, and 97.6% selectivity. The synergistic interaction between Ni and Co enhanced reforming kinetics and suppressed coke formation, enabling stable operation. Compared to previous reports on ethylene glycol or PET reforming, the current work improved hydrogen yield by 5-10%, validating its potential for direct plastic-to-hydrogen conversion. Overall, the results demonstrate the potential of solvent-assisted reforming as a controlled platform for hydrogen generation from waste polymer-derived carbon.