Exploration of the synergistic effect of co-pyrolysis of biomass and waste plastics based on ReaxFF-MD and DFT

Abstract

Co-pyrolysis of biomass and waste plastics is a strategy to achieve efficient waste management and obtain valuable fuels. In this paper, cellulose (CE) and polyethylene (PE) were chosen as representatives of biomass and plastics to investigate the synergistic effects of the main products during co-pyrolysis. The synergistic mechanisms are clarified at the microscopic level by ReaxFF-MD. Mainly, the ·H and CnHm· fragments from PE fracture combine with the intermediate products from CE cracking to generate additional oil and gas products. By using DFT theory to calculate the reaction energy barrier of the main products in the CE/PE co-pyrolysis process, it is found that the reaction energy barrier of furans and ethylene in the separate pyrolysis process is higher than that in the co-pyrolysis process, indicating that the co-pyrolysis process is more prone to reaction generation, leading to more significant synergistic effects. With the increase of temperature, the positive synergistic effect of product can be enhanced within a certain temperature range. But the synergistic oil yield then decreases with further increase of temperature. The synergistic effect is most significant when the material ratio is 1:1. More oxygenated compounds can be obtained by increasing the percentage of CE while more hydrocarbons can be obtained by increasing the percentage of PE.