Production of fuel oil and combustible gases from pyrolysis of polystyrene waste: Kinetics and thermodynamics interpretation

Pyrolysis of waste polystyrene (PS) over cobalt doped copper oxide was performed employing thermogravimetry. Kinetic parameters were calculated, and average activation energy (Ea) values were observed as 95.13, 97.42, 102.49 and 109.19 kJ/mol, using Kissinger–Akahira–Sunose (KAS), Ozawa Flynn Wall (OFW), Friedman (FM) and Coats Redfern (CR) methods. Moreover, activation energy was found to increase with fraction conversion, which exhibited gradual degradation of waste polystyrene with weaker bonds broken first followed by stronger bonds. Waste polystyrene pyrolysis was also carried out in the temperature range of 340 to 420 °C, in N2 environment in a salt bath utilizing a Pyrex glass vessel and effect of temperature and time was investigated on the production of pyrolyzates. A maximum oil yield of 97.15% was obtained at optimum temperature of 380 °C, and reaction time of 40 min. The gas and liquid fractions were collected and analyzed by GC/MS. Methane was observed to be the major product along with propene and butene in trace quantities in gas fraction whereas fuel range aromatic components like toluene, benzene and ethyl benzene were detected in liquid fraction. Comparison of catalyzed and non-catalyzed reactions showed reduction in activation energy of the catalyzed reaction along with improvement in the quality of oil produced. Fuel properties of the oil formed were found like diesel and therefore have bright prospects for use as energy source.