Microscopic mechanism for CO2-assisted co-gasification of polyethylene and softwood lignin: A reactive force field molecular dynamics study.

Co-gasification of biomass and waste plastic to produce syngas and value-added products is an attractive technology for renewable energy utilization and waste disposal. CO 2 as a gasifying agent has received much attention as it can act as carbon source and oxidant in the reaction. In this paper, the feasibility and characteristics of CO 2 -assisted co-gasification of polyethylene and softwood lignin were explored. Simulation results showed that the lignin macromolecule began to decompose through C–O–C bond breaking and the PE chain gradually decomposed through C–C bond breaking. CO 2 -assisted co-gasification showed a negative synergistic effect on gas yield at the early stage, which delayed the reaction, but showed a positive synergistic effect at the late stage. The reaction between CO 2 and carbon-containing fragments greatly promoted CO production. The hydrogen and hydrocarbon radicals from PE were actively involved in H 2 and hydrocarbon gas production. Compared with O 2 -assisted co-gasification, the CO 2 -assisted and CO 2 /O 2 -assisted co-gasification yielded more CO, hydrocarbon gases and combustible gases and increased the lower heating value of gas product. This work sheds light on the underlying mechanisms of CO 2 -assisted co-gasification of polyethylene and softwood, and would be helpful for the development of this technology. • CO 2 -assisted co-gasification of softwood lignin and polyethylene is explored. • Synergistic effect at the late stage of co-gasification promotes gas production. • Polyethylene provides hydrogen and hydrocarbon radicals during co-gasification. • The addition of CO 2 increases the gas yield and the lower heating value of syngas. [ABSTRACT FROM AUTHOR]