Study on CO2 co-gasification of cellulose and high-density polyethylene via TG-FTIR and ReaxFF MD

CO2 co-gasification of solid waste and biomass presents an approach for the comprehensive utilization of waste materials, biomass and carbon dioxide. In this study, the CO2 co-gasification of cellulose and high-density polyethylene was explored utilizing TG-FTIR method and ReaxFF MD simulation. The thermal behavior, synergistic effect, volatile release characteristics, activation energy and reaction mechanism were thoroughly analyzed. The experimental findings indicated that CO2 co-gasification involved four stages: drying, cellulose pyrolysis, polyethylene pyrolysis and semi-coke gasification. Co-gasification inhibited cellulose pyrolysis but promoted polyethylene pyrolysis, with the most pronounced promoting effect occurring at 40% polyethylene content. The absorbance curve suggested that CO release was associated with cellulose pyrolysis and the reaction between cellulose coke and CO2, and C-H release was related to the pyrolysis of cellulose and polyethylene. Co-gasification alleviated the energy barrier, with the greatest effect occurring at 40% polyethylene content. The simulated results confirmed that the promotion of polyethylene pyrolysis was attributed to the connection of radicals from cellulose with polyethylene. Additionally, the combination of hydrocarbon radicals and hydrogen from polyethylene and cellulose contributed to gas production. This investigation provides insights into the thermochemical conversion characteristics for CO2 co-gasification of biomass and high-density polyethylene.