Pyrolysis of sawdust impregnated with xylose: Tailoring property of biochar with sugar-derived intermediates

Cellulose and hemicellulose are major components of woody biomass, pyrolysis of which would inevitably produce anhydrate sugars or sugar-like organics. These sugars might tailor property of biochar via interactions when they pass through inner and outer surface of biochar, which were investigated herein in pyrolysis of poplar sawdust impregnated with various loading of xylose, a model sugar from hemicellulose, at 600 degrees C. The results suggested that the addition of xylose enhanced the cracking reactions to form more gaseous products but less biochar and bio-oil. Nevertheless, the intermediates from xylose enhanced aromatization of volatiles to form more light phenolics while aided precipitation of heavy organics on surface of biochar. The accelerated carbonization, deoxygenation and dehydrogenation reactions with presence of xylose enhanced aromatization reactions, making the biochar carbon-rich with increased heating value, crystallinity and hydrophobicity. Additionally, xylose addition could substantially enhance thermal stability of the biochar, even with loading of only 5 wt%. The DRIFTS characterization showed that the degradation of xylose produced abundant carbonylscontaining species that react with organics on surface of biochar, forming large aromatics of fused ring structures.