Thermo-Catalytic Versus Thermo-Chemical Recycling of Polystyrene Waste

Degradation of polystyrene was carried out thermally and thermo-chemically in order to compare between the conversion of polystyrene in both cases. The catalyzed thermal degradation was achieved without solvents in an autoclave at pressure range 20-50 bar and temperature range 300-400 degrees C in presence of 1 % Al2O3 as a catalyst. The thermo-chemical degradation was achieved by two solvents namely, supercritical cyclohexane and supercritical ethyl cyclohexane under the same reaction conditions. It was found that conversion of polystyrene increased in the thermo-chemical process than in thermal process. Furthermore, it was found that the conversion process increases with rising temperature and pressure. It also was found that high molecular-weight compounds decreased but oligomers and monomers increased with rising temperature. Polystyrene rapidly degraded after reaching a prescribed temperature of 400 degrees C, the degree of degradation was nearly about 95 % after 1 h in presence of ethyl cyclohexane, 89 % in presence of cyclohexane and about 81 % only in absence of the solvent (thermal degradation).