Study on carbon rearrangements of CO₂co-feeding pyrolysis of corn stover and oak wood

Pyrolysis has been broadly applied to biomass valorization process to convert solid biomass waste into three phase value-added products such as biochar, pyrolytic oil, and pyrolytic gas. The carbon rearrangement process is highly affected by contents of cellulose, hemicellulose, and lignin due to their different structures. In this respect, this study laid great emphasis on the thermolytic behaviors of cellulosic corn stover (CS) and lignin-rich oak wood (OW) to understand carbon reallocations of them as a case study. In addition, CO2 was employed as a reaction medium for biomass pyrolysis to control the carbon redistribution between CO2 and CS/OW in line with the achievement of sustainable thermo-chemical conversion of biomass consuming a greenhouse gas (i.e., CO2). Lignin-rich OW showed higher tolerance to thermal degradation, thereby resulting in more biochar and less pyrolytic oil formations. During the CO2-assisted pyrolysis, carbon redistribution was appeared between liquid and gas phase products. This showed the gas phase reactions (GPRs) between volatilized liquid pyrolysates and CO2 with additional CO formation. To expedite the GPRs, Ni/SiO2 catalyst was employed. The CO2-assisted catalytic pyrolysis of CS and OW significantly improved dehydrogenation and deoxygenation, showing more than one order of magnitude higher production of H2 and CO.