Investigation on reaction mechanism for CO2 gasification of softwood lignin by ReaxFF MD method

As an important component of biomass, lignin greatly affects the overall conversion efficiency of biomass. In this paper, the microscopic reaction mechanism for CO2 gasification of softwood lignin was investigated by reactive force field molecular dynamics simulation. The whole process of CO2 gasification of softwood lignin was divided into two stages, i.e., the pyrolysis of softwood lignin macromolecule, and the reaction of molecular fragments with CO2. During the pyrolysis stage, the softwood lignin macromolecule first decomposed into fragments containing benzene rings by C–O–C bonds breaking. Then, the benzene rings opened to form carbon chains and broke down. During the gasification stage, CO2 reacted with lignin fragments to produce CO, while H2O molecules provided H for the generation of H2 and hydrocarbon gases. The proportion of products could be adjusted to meet specific industrial needs via changing the CO2/steam ratio. The activation energy of CO2/steam gasification was not much different from that of steam gasification, so it would not have a great impact on the occurrence of the reaction. This work provides a theoretical basis for the production of high-quality gasification products.