(354e) Heat and Mass Transfer Analysis of Temperature-Gradient Thermolysis Reactors for Plastic Upcycling

Driven by the steady increase of global production and consumption of plastics, the pollution caused by waste plastics continues to escalate. There is thus an urgent need for innovative technologies to address waste plastic issues. The recent development of catalyst- and hydrogen-free temperature-gradient thermolysis and upgrading processes (Xu et al., Science, 381, 666, 2023) are promising upcycling technologies that can transform discarded plastics into valuable chemicals. Nevertheless, the effective control of thermolysis to produce hydrocarbons of desirable chain lengths with high value remains a challenge. Fundamentally, such a challenge originates from the fact that the operation and product of temperature-gradient thermolysis is governed by the intricate interplay between a host of thermal, chemical, and physical processes. Here, we develop a mathematical model for temperature-gradient thermolysis of polyethylene by capturing the essential elements of the underlying physicochemical and transport processes. Simulations based on this model and the accompanying experiments revealed the essential role of operation temperatures in affecting the chain length distribution of hydrocarbons produced, and pointed to new opportunities for targeted chain length selection and enhanced reaction rates through the meticulous control of heat and mass transfer in the reactor. The insights gained here will help guide the design of next-generation thermolysis reactors for plastic upcycling, thus supporting the advancement toward large-scale industrial deployment.