Thermo-chemical recovery of styrene from polystyrene waste

Styrene was recovered from polystyrene by thermo-chemical treatment in a nitrogen atmosphere carried out at 330$ sp circ$C to 410$ sp circ$C, for 30 to 60 minutes. Up to 70% of the polystyrene was converted to styrene at a reaction temperature of 406$ sp circ$C and reaction time of 45 minutes. The styrene yield increased with temperature. At the lower temperatures, the molecular weight of the polystyrene was reduced from 138 000 to 8 900. At the higher temperatures, the polystyrene residue obtained consisted mainly of styrene dimer and trimer. The use of catalysts was evaluated. The catalysts were mixed with the polystyrene in 10% by weight mixtures. They were: silica-alumina, poly($ alpha$-methylstyrene), an antioxidant (2,2$ sp prime$-Methylenebis(4-methyl-6-tert-butyl phenol)), and zeolite. The above catalysts were found to have no effect on the thermal degradation of polystyrene under the conditions of the present study. The initial rate of thermal degradation of polystyrene was found to fit a first order model. The activation energy obtained was 181 kJ/mol, which is in accordance with literature values