Feedstock recycling of electric and electronic waste plastics: Fundamental investigation for feasibility studies

In the present investigation, we report the feedstock recycling of two major waste plastics from WEEE i.e., high impact polystyrene (HIPS) and acrylonitrile butadiene styrene copolymer with various brominated flame-retardants. The pyrolysis of heating impact polystyrene (HIPS-Br) with various brominated flame retardants at 430°C into fuel oil. Iron oxide carbon composite catalyst (Fe-C) was used for catalytic determination of liquid products. The effect of antimony oxide (Sb₂O₃: Synergist) in HIPS-Br containing decabromo diphenyl oxide (DDO) and decabromo diphenyl ethane (DDE) as flame retardant was investigated. The thermal degradation of HIPS-Br produced various brominated hydrocarbons and also hydrobromic acid (HBr) in addition to various hydrocarbons. The Synergist (Sb₂O ₃) reacted with the hydrogen bromide evolved during the pyrolysis process and formed the SbBr₃ in the liquid products. The presence of bromine content (organic and inorganic) in liquid products is not desirable to use as a fuel oil. The use of iron oxide carbon composite catalyst (Fe-C) during pyrolysis debrominated (ca. 99%) the bromine compounds from liquid products. The presence of Sb₂O₃ (5 wt%) decreased both the hydrogen bromide and brominated hydrocarbons by forming SbBr₃ and produced high quantity of lower hydrocarbons (C₇-C₁₁). The thermal degradation of brominated flame retardant (Br: 9.59 wt%) containing Acrylonitrile-Butadiene-Styrene copolymer (ABS-Br; 10 g) was carried out at 450°C using a semi batch operation using two different temperature programs. The heating rate was found to affect the quality of the degradation oil and yield of products (liquid, gas and residue). Data on the effect of the temperature program on the accumulation of liquid products was presented. It was found that the majority of the bromine was concentrated in the carbon residue and while majority of the nitrogen accumulates in the liquid products irrespective of degradation mode. The use of a one step constant heating rate process produced a higher liquid yield (39%), than a two step process (29%). Differences were also noted in the Br and N contained in the liquids produced by the two processes.