Characteristics of waxy oils from the pyrolysis of waste polyethylene and polypropylene using a new-type fluidized bed reactor

This study focuses on converting waste polyolefins, specifically polyethylene and polypropylene, into waxy oils that can be effectively used as feedstock for fluid catalytic cracking units. The primary objective of this research is to identify the optimal pyrolysis conditions that maximize the yield and quality of waxy oils derived from these waste plastics. In addition, the study investigates the effects of process variables and the use of CaO as a chlorine scavenger on the composition and purity of the resulting oils. Experiments were conducted using a fluidized bed reactor system to ensure uniform heat transfer and efficient cracking. The key parameters examined included reaction temperature, type of fluidizing medium (nitrogen or pyrolysis gas), and the presence of CaO. The pyrolysis of waste polyethylene under nitrogen at 528 °C produced the highest waxy oil yield of 88 wt,%, with n-monoalkenes and n-alkadienes as the major components. For waste polypropylene, the maximum waxy oil yield of 82 wt% was obtained at 517 °C under nitrogen. The waxy oils contained low levels of metals (below 10 ppm) and a reduced organic chlorine content (11 ppm when using CaO), making them suitable for catalytic processing. The high-purity waxy oils produced can serve as suitable feedstock for fluid catalytic cracking units, thereby reducing dependence on fossil-derived hydrocarbons. This approach supports circular economy practices by transforming plastic waste into valuable refinery inputs and can be applied in the petrochemical and energy industries to enhance resource efficiency, reduce environmental pollution, and promote sustainable waste-to-fuel technologies.