Effect of Sb2O3 in brominated heating impact polystyrene (HIPS-Br) on thermal degradation and debromination by iron oxide carbon composite catalyst (Fe-C)

The iron oxide carbon composite catalyst (Fe-C) was prepared and used for catalytic debromination process during pyrolysis of heating impact polystyrene (HIPS-Br) with various brominated flame retardants at 430 °C into fuel oil. 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 (Sb2O3) 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). Thermogravimetric analysis (TGA) revealed that the presence of Sb2O3 in HIPS-Br decreased the degradation temperature. Powder X-ray diffraction results showed the presence of Fe3O4 phase in fresh Fe-C. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) shows the presence of Sb and Br in used Fe-C catalyst in the degradation process.