Potential for optimisation of fuel yield and hydrocarbon distribution from plastic waste pyrolysis using Nanopyroxene catalysts

Abstract

Plastic waste is a global concern, driven largely by the widespread use of single-use plastics. Despite advances in recycling technologies, scalable, and cost-effective plastic waste management solutions remain limited. Thermal pyrolysis offers a complementary pathway for plastic waste valorisation through energy recovery, but conventional processes are constrained by slow reaction rates, high energy demands, and low fuel yields. This study introduces, for the first time, nanopyroxene as a novel catalytic additive for plastic waste pyrolysis in a locally fabricated batch reactor, aiming to improve fuel yield and hydrocarbon distribution. A mixture of Low-density polyethylene (LDPE), High-density polyethylene (HDPE), and polypropylene (PP) (2:1:2 ratio) was thermally decomposed under catalysed and non-catalysed conditions. The physico-chemical properties of the resulting plastic-derived fuel oils (PDFOs) were benchmarked against commercial diesel. Catalytic pyrolysis significantly increased the fuel oil yield to 77 %, compared to 56 % from non-catalytic pyrolysis (p < 0.05). The catalyst promoted the formation of light hydrocarbons (C1–C9) and reduced intermediate fractions but increased ultraheavy hydrocarbons (C25–C56), which potentially affects combustion efficiency. Physical characterisation revealed no statistically significant differences (p > 0.05) between PDFOs and commercial diesel in key fuel properties, all of which fell within recommended standards. However, PDFOs exhibited higher volatility, density, and flammability, with lower flash and fire points (39 ◦C, 48 ◦C), suggesting suitability for high-energy combustion applications. These findings demonstrate the potential of nanopyroxene to enhance fuel yield and quality from plastic pyrolysis, though further optimisation, detailed catalytic mechanisms, and comprehensive environmental impact assessments are necessary for large-scale adoption.