Integrating microwave pyrolysis and hydrotreating for converting low-density polyethylene into jet fuel

With the increasing plastic waste and its environmental impact, finding effective recycling solutions is essential. Cracking plastic waste followed by hydrogenation could be a promising method for producing jet fuels. In the present work, microwave-assisted pyrolysis (MAP) with MgO combined with hydrotreating with a Ni/Biochar catalyst was firstly proposed to convert low-density polyethylene (LDPE) into jet fuel. The pyrolysis process yielded 48.5 wt% of liquid product, with C5−C15 hydrocarbons and olefins accounting for 87.6% and 65.5%, respectively. During the hydrotreating process with 10% Ni/Biochar at 300°C of temperature and 2 MPa of initial H2 pressure, the pyrolysis oil was successfully hydrotreated, resulting in 98.4% paraffins and 1.6% aromatics with liquid yield of 80.6 wt%. Among them, C5−C15 hydrocarbons created 96.1%. The kinetic analysis indicated an activation energy of 89.9 kJ/mol for hydrogenated LDPE pyrolysis oil (HPPO). Characterization of the Ni/Biochar catalyst after reaction showed a BET surface area of 438 m2/g, similar to that of the fresh catalyst, with minimal coke formation noted via XRD, TEM, and TG analyses. XPS and FTIR indicated negligible oxidation of Ni0 during hydroprocessing. After 6 cycles, the catalyst remained high abundance for paraffins and C5−C15 hydrocarbons, namely, 98.4% and 94.0%, respectively, demonstrating its stability.