A study on co-pyrolysis mechanisms of biomass and polyethylene via ReaxFF molecular dynamic simulation and density functional theory

Abstract

Co-pyrolysis of biomass and waste plastics is a long-term strategy to achieve efficient waste management and generate valuable fuels. The cellulose and polyethylene were chosen as typical representatives for biomass and plastics in this work. Reactive force field molecular dynamic and density functional theory were employed to investigate the co-pyrolysis mechanism of cellulose and polyethylene which were not readily achieved only by experiments. The hydrocarbon and H radicals from polyethylene respectively interact with the alcoholic groups and furans which contributes to producing alcohols and suppresses the generation of aldehydes and ketones. The energy barriers of rate controlling steps for producing long-chain alcohols (about 669.40 kJ/mol) in co-pyrolysis of cellulose and polyethylene are obviously smaller than those for producing oxy-compounds in cellulose pyrolysis alone. The formations of furan alcohols are easy with low energy barriers (22.19, 16.40 and 22.66 kJ/mol, respectively) in the presence of polyethylene. The co-pyrolysis of cellulose and polyethylene also promotes the formation of CH. The polyethylene has a positive effect on the improvement of major co-pyrolysis products. The reactive force field molecular dynamic simulation and density functional theory seems promising to determine the co-pyrolysis mechanisms of biomass and waste plastics at microcosmic level and help to produce high-quality fuels.