Impact of tire char as a catalyst on product yields and reaction kinetics for waste polypropylene pyrolysis towards a circular economy

The article explores the possibility of extracting pyrolytic oil (PO) and hydrogen-rich gaseous products from pyrolysis (thermal/catalytic) of waste polypropylene (WPP). The tire char, obtained from thermal pyrolysis of waste two-wheeler tires, acts as a catalyst. The non-isothermal thermal degradation of WPP using a thermogravimetric apparatus (TGA) reveals that the decomposition range lies between 230 and 490 °C, and the same is reduced in the presence of catalyst tire char. The study evaluates 212–230 kJ/mol activation energies under thermal and 190–210 kJ/mol with catalytic conditions. The study in a batch reactor over 450–600 °C produced the maximum PO yield of 76.20% at 550 °C, with gaseous and solids of 13.10% and 10.70%, respectively. The superior quality PO (74.64%) with higher transparency and lower viscosity is produced via catalytic pyrolysis. The lower yield is offset by a higher gaseous yield (12.45%) with a hydrogen content of 6.2% (v/v). The main focus is to optimise the process conditions – temperature, heating rate, and catalyst proportion and to extract the reaction activation energies under the optimum conditions. The study supports the circular economy initiatives by encouraging the scientific utilisation of plastic wastes to produce clean fuels.