From e-waste to aromatic fuel oil: catalytic microwave pyrolysis of brominated ABS via an optimized Fe/SiC process

Abstract

Microwave-assisted catalytic pyrolysis (MAP) of brominated acrylonitrile–butadiene–styrene (Br-ABS) e-waste plastic was investigated using silicon carbide (SiC) and iron-impregnated SiC (Fe/SiC) as microwave susceptor and catalytic susceptor, respectively. Response surface methodology coupled with Box-Behnken design (RSM-BBD) optimized four process variables using SiC: microwave power, argon carrier gas flow rate, susceptor-to-plastic weight ratio, and final temperature, for maximum pyrolytic oil recovery. A reduced quadratic model accurately described the experimental response. Optimal conditions were 471 °C, a microwave power of approximately 490 W, 215 mL/min argon, and a susceptor/plastic ratio of 0.05 (w/w), yielding 56.97 wt% pyrolytic oil (experimentally validated at 57.10 wt%). Fe/SiC was subsequently evaluated under these conditions. Quantitative GC–MS/MS revealed that oil produced with SiC contained 60.8 wt% monocyclic aromatics; Fe/SiC increased this to 82 wt% through catalytic cracking of polycyclic aromatic hydrocarbons (PAHs). Critically, Fe/SiC achieved > 98 % reduction in total oil-phase bromine content (from 4.24 to < 0.08 wt% Br). A process-energy balance based on measured electrical energy consumption (16.2 MJ/kg), together with catalyst-preparation energy and condenser cooling duty, indicated an overall energy efficiency of approximately 55 %. These results establish MAP with Fe/SiC as an effective route for simultaneous resource recovery and hazardous halogen removal from e-waste ABS.