Sequential pyrolysis of coal and biomass: Influence of coal-derived volatiles on property of biochar

Coal and biomass are two important carbonaceous feedstock and their co-pyrolysis has been proven to modify the fuel properties of resulting oil and char. Nevertheless, how do the volatiles from coal impact the property of biochar from biomass is largely unknown. In this study, sequential pyrolysis of coal in upper bed with sawdust, cellulose, or lignin in lower bed at 600 degrees C was investigated. The volatiles from the pyrolysis of coal did react with the biochar from biomass, which promoted cracking reactions and resulted in the formation of more gases at expense of biochar. The coal-derived volatiles enhanced the cracking or gasification of sugar derivatives and impacted the evolution of aromatic phenols. Furthermore, coal-derived volatiles also promoted the cracking or deoxygenation of oxygen-containing functionalities, making the biochar carbon-rich with higher crystallinity but reduced the thermal stability. Additionally, the hydrophilicity and the evolution of functionalities on surface biochar was also significantly affected by the volatiles from pyrolysis of coal.