Optimization of Liquid Phase Generation by Catalyzed Pyrolysis of PET Plastic Waste
Plastic waste management remains a critical global challenge due to the continuous increase in polyethylene terephthalate (PET) production and the limitations of conventional recycling methods. Chemical recycling through pyrolysis represents a sustainable alternative for converting PET waste into fuels and valuable chemicals; however, liquid phase production remains limited in many systems. This study investigates the effect of catalytic pyrolysis using Nickel (II) Chloride (NiCl₂) compared to aluminum oxide (Al₂O₃) to enhance product generation from PET waste using computational modeling.
COMSOL Multiphysics® was used to develop a two-dimensional axisymmetric reactor model representative of a fixed-bed pyrolysis system. The model evaluated PET depolymerization using three configurations: non-catalytic pyrolysis, catalytic pyrolysis with Al₂O₃, and catalytic pyrolysis with NiCl₂. Reaction kinetics were implemented using Arrhenius-based parameters obtained from experimental literature. PET degradation was simplified into two representative product groups: High Volatility Products (HVP) and Low Volatility Products (LVP). All simulations were performed under identical operating conditions to ensure direct comparison between configurations.
The results show that catalytic configurations significantly increased product concentrations compared to the non-catalytic case. Both catalysts exhibited similar behavior, with maximum HVP and LVP concentrations of approximately 8.0 × 10⁻¹⁵ mol/m³ at steady state under operating conditions of 698 K and 0.1 m/s. The NiCl₂ catalyst produced approximately 0.33% higher product concentration and reached steady state slightly faster than Al₂O₃, with differences between catalysts remaining below 1%. Parametric analysis confirmed that higher temperatures increased product concentration, while higher flow velocity reduced residence time and product yield.
This study concludes that Nickel (II) Chloride demonstrates comparable performance to aluminum oxide as a catalyst for PET pyrolysis under the modeled conditions. The developed 2D axisymmetric COMSOL model successfully validates reactor parameters and provides a reliable foundation for future three-dimensional modeling. Although performance differences were minimal, the results support further investigation of NiCl₂ in studies focused on liquid phase generation and optimization of catalytic pyrolysis for chemical recycling of PET plastic waste.
