Polystyrene pyrolysis using silica-alumina catalyst in fluidized bed reactor

Catalytic degradation of polystyrene (PS) at ambient pressure was investigated in this study. Samples of PS and catalyst were mixed in a semi-batch reactor. Experiments were carried out in a Pyrex reactor in different conditions, taking temperature and catalyst/PS mass ratio as variables to determine the kinetic parameters. The results indicated that increasing the temperature causes conversion increase. The products of the degradation mostly consist of liquid, gas, and solid residue. The pyrolysis of PS was examined as an effective way to recycle this polymer and recover its styrene monomer. Based on the weight loss of polymer sample, the reaction kinetic parameters are calculated and discussed in the paper. In addition, the effects of temperature and catalyst/polymer ratio were examined, comparing its result to the gaseous and liquid pyrolysis products. Since the oil product contained a high percentage of styrene monomer (>80 %), it is possible to use it directly for the reproduction of the polymer. The experiments indicated a unique catalytic performance for degradation of PS with selectivity to aromatics more than 99 %. The products contained styrene, as the major product, and ethyl benzene, indene, and propyl benzene to some amounts in the liquid. Order of reaction, pre-exponential factor and activation energies were determined using the nth order model technique method. According to the results E (activation energy) and A ₀ (Pre-exponential factor) are as the following 1.1326, 194 (kJ mol⁻¹) and 3.2668 × 10¹⁴ min⁻¹, respectively.