Tertiary recycling of waste polystyrene using magnesium impregnated catalysts into valuable products

•Synthesis of magnesium impregnated catalyst for degradation of polystyrene.•Magnesium impregnated on alumina, montmorillonite and charcoal with salt of Mg.•Wet impregnation method was used for catalyst preparation.•15% Mg–Al2O3 was found with higher selectivity.•The liquid yield was 95.47 ± 0.12 wt.% with higher yield of benzene, toluene, ethylbenzene, styrene and α-methylstyrene.

Magnesium impregnated catalysts were synthesized and used for tertiary recycling of waste expanded polystyrene. The degradation reactions were carried out in a Pyrex glass reactor in batch mode and the influence of magnesium impregnated catalysts on degradation of WEPS was studied. Different parameters like degradation temperature, reaction time and polymer to catalysts ration were optimized. The results from degradation experiments were compared at their respective optimum conditions. The yield of liquid product was 95.47 ± 0.12 wt.% maximum with 15% Mg–Al2O3 catalyst and also found with higher selectivity than Mg, 20% Mg–Mmn and 20% Mg–AC catalysts. The yield of benzene, toluene, ethylbenzene, styrene and α-methylstyrene was maximum using 15% Mg–Al2O3 catalyst. Whereas the yield of product was in a narrow range using 15% Mg–Al2O3 catalysts. The mechanism of formation of different products was also explained.