Thermal degradation of polystyrene wastes in various solvents

Abstract

Thermal polystyrene (PS) degradation was investigated in this work harnessing a high-pressure autoclave surrounded by a furnace. n-pentane, cyclohexane (CH), and toluene were used separately as the simplest representatives of aliphatic, cyclic, and aromatic solvents. One experiment was solventless. Without solvent at 400 °C, waste samples accrued the weight percentages of 32.0, 46.8, and 21.2 for the solid residue and the liquid and gaseous products respectively. Solvent employment is strongly recommended because it almost doubled the liquid yield while substantially reducing the solid residue to less than 5% and making the total conversion exceed 95%. A solvent:PS ratio of around 2:1 appeared to suffice. From 350 to 450 °C, the operating temperature had only a vague effect on this phase distribution. GC analyses identified methane, C2, C3, and C4 in the gaseous products. GC/MS results showed that cyclohexane usage rendered liquid products of ethyl benzene, methyl ethyl benzene, 1-phenyl naphthalene 1,1-bicyclohexyl, 2-cyclohexyl ethyl benzene. Toluene employment as solvent gave ethyl benzene, methyl ethyl benzene, 1-phenyl naphthalene propyl benzene, 1,2-dimethyl benzene.