Synthesis of Hybrid Fuel via Thermocatalytic Co-Pyrolysis of Mixed Plastics Waste and Biomass over Zeolite 3A

Abstract

Amid fossil fuel depletion and rising greenhouse emissions, converting waste into economic hybrid fuels is crucial for the global energy transition. This study evaluates process parameters on liquid product characteristics from the co-pyrolysis of mixed plastic waste (PP/HDPE/LDPE/PS) and biomass over a Zeolite Molecular Sieve 3A catalyst (5 wt%). Biomass addition reduces oil yield to 15.14% at a 1:1 ratio due to secondary lignocellulosic polymerization. Zeolite 3A’s size-exclusion effect (~3 Å) restricts branched alkanes, directing selectivity toward straight-chain hydrocarbons. At 450°C and a 1:0.25 ratio, the catalyst optimizes aromatic fraction formation (48.12%) via external acid sites, producing a hybrid fuel rich in monocyclic aromatics (C₆–C₈) and methyl esters (32.28%). The product exhibits a safe pH (5.4–6.8) and high calorific value (42867–43653 J/g). The non-catalytic 1:0.25 formulation yields an excellent cetane number of 64.5 and a RON of 87.1. Although catalytic treatment improves viscosity (1.35 mm²/s) and meets Heavy Fuel Oil (MFO) density standards, oxygenated compound microemulsions hindered octane test readings for catalytic samples. This liquid product shows great potential as a hybrid fuel, stationary diesel blending agent, or industrial MFO, requiring further upgrading before transport engine application.