Microscopic reaction mechanism for CO2 gasification of cellulose based on reactive force field molecular dynamics simulations

Gasification is the key process of biomass conversion and utilization, which has been proved to be one of the most promising technologies. In this study, the CO2 gasification process of cellulose was explored by reactive force field molecular dynamics simulations. Firstly, the distribution of average local ionization energy was analyzed. The results showed that the oxygen and hydrogen atoms might be reactive sites. In addition, the product evolution, bond-breaking behavior and carbon conversion during CO2 gasification were investigated. It was found that the bond dissociation energy of glycosidic bond was low and the bond breaking was easy to occur. The CO2 gasification of cellulose was divided into two stages, first the cellulose molecules broke down into small molecular fragments, and then they reacted with CO2. Finally, the effects of CO2/steam ratio and CO2/O2 ratio on the gasification process were analyzed. As the CO2/steam ratio decreased, the H2 yield increased, while the CO yield decreased. With the increase of CO2/O2 ratio, the carbon conversion rate had little change, while the contribution of CO2 gasification to carbon conversion decreased from 99.07% to 50%. The research provides a reference for revealing the microscopic mechanism for CO2 gasification of biomass.