A Rapid-heating Copper Block Reactor System for Improved Isothermal Kinetics of Polyethylene Pyrolysis

Developing continuous-flow pyrolysis reactor systems is essential to meet the increasing demand for plastic pyrolysis oil. Most literature polymer pyrolysis kinetic studies use non-isothermal thermal gravimetric (TG) equipment or batch systems. Most systems are characterized by having a prolonged heating times which may lead to a significant polymer conversion before reaching the isothermal temperature, affecting the kinetic measurements. We present a novel, affordable, copper-block semi-batch reactor system that reaches the desired reaction temperature in less than four minutes. Through simulation, we demonstrate the superiority of this system over the commonly used stainless-steel reactors. We utilized this system to measure the isothermal kinetics of PE pyrolysis at temperatures between 411 and 449 °C. Employing a discrete lump methodology, we identified a five-lump reaction model: three polymer chains with descending molecular weights (S1, S2, S3), liquid (L), and gas (G), with reactions progressing in series and then in parallel. The initial decomposition steps exhibited similar activation energies of 360±17 and 357±06 kJ/mol, indicating that molecular weight has little effect on the initial PE pyrolysis rate. The parallel paths producing liquid and gas had activation energies of 288±02 and 179±13 kJ/mol. The proposed system facilitates accurate isothermal kinetic data measurement, enabling the design of improved continuous-flow reactor systems for plastics pyrolysis, ultimately contributing to global sustainability goals.