Molecular Mechanism Study of the Kinetics and Product Yields during Copyrolysis of Biomass and Solid Wastes: ReaxFF-MD Method Approach

Copyrolysis is a potential method for the collaborative disposal of biomass and plastics. There is an interaction between biomass and plastics during copyrolysis. In this work, a combination of ReaxFF-MD simulation and experimental validation was used to investigate the pyrolysis reaction process of the biomass and plastic, observing the evolution of free radicals at the molecular level and exploring the distribution of pyrolysis products. TG-MS results show that reaction temperature ranges for cellulose and PVC are 296–400 and 267–480 °C, respectively. HCl is the main product of PVC pyrolysis, and mixing with cellulose will reduce the yield of HCl. The ReaxFF method was used to model the pyrolysis of cellulose and PVC. The modeling temperature is much higher than the real reaction temperature, which is attributed to the time scale of picoseconds of ReaxFF-MD modeling. Modeling results show that the yield of HCl of the cellulose/PVC mixture is obviously lower than that of pure PVC. When mixed with cellulose, the HCl release is largely inhibited and more chlorine elements are retained in the pyrolysis hydrocarbon fraction or solid products.