Nickel-Catalyzed Pyrolysis of Low-Density Polyethylene: Pyrolysis Pathways, Product Distribution, and Kinetic Analysis

Waste plastic recycling continues to be a significant challenge for sustainable material management. In this study, we present a single-stage pyrolysis method using nickel nitrate as a catalyst precursor to facilitate the controlled catalytic pyrolysis of low-density polyethylene (LDPE). A comparison between pyrolysis and Ni-catalyzed pyrolysis indicates distinct reaction pathways and product distributions. Systematic evaluation of the effects of temperature, heating rate, and nickel loading shows that Ni catalysis selectively promotes the cracking of LDPE-derived tar and wax fractions, forming hydrogen-rich gas and minor Ni-doped carbon nanotubes. Kinetic analysis via Miura and Flynn–Wall–Ozawa methods confirms that Ni catalysis decreases the activation energy barrier for LDPE pyrolysis compared to pyrolysis alone.