An experimental study on conversion of high-density polyethylene and polypropylene to liquid fuel

Pyrolysis of plastic material is a potential way for the conversion of plastic into hydrocarbon fuel. Thermal and catalytic pyrolysis of high-density polyethylene (HDPE) and polypropylene (PP) were conducted in a cylindrical stainless-steel reactor at temperatures ranging from 350 °C to 500 °C. Optimum temperatures for the maximum liquid fuel production of 65% were found to be 425 °C for HDPE and 470 °C for PP. A mixture of packaging plastics, virgin HDPE and PP (2:1:1) was also subjected to the reactor at 425 °C, and liquid, gas and solid yields of 55%, 25%, and 20% were observed. The reduction of temperature from 425 °C to 375 °C for HDPE and from 500 to 400 °C for PP was possible using Silica-Alumina catalyst. The liquid products consist of benzene, toluene, xylene, indene, etc. with the caloric value of 40.9 and 41.1 MJ/Kg for HDPE and PP, respectively, which indicated that the liquid would be able to serve as alternative source of energy. Later, nitrogen as a carrier gas was introduced and liquid conversion increased from 65 to 80% at 425 °C for HDPE and from 65 to 75% at 470 °C for PP in thermal pyrolysis. The paper also reviewed key parameters influencing pyrolysis like temperature, catalysts, and carrier gas. In addition, this paper discussed several perspectives for optimising liquid oil production. Conversion of plastic polymers into fuel by thermal and catalytic processes will be very relevant to recover resources from plastic waste and will also help to decrease the load of plastic wastes in landfill sites.