Volatile-char interactions during biomass pyrolysis: Contribution of amino group on graphitized carbon nanotube to xylose evolution based on experimental and theoretical studies

Char surface functional group has been shown to play an important role in volatile-char interactions during biomass pyrolysis, which are known to be effective for the modification of the pyrolysis products. Using xylose and amino-modified graphitized carbon nanotube (CNT-NH2) as model compounds, the contribution of the designated surface functional group to the evolution of pyrolysis volatile was investigated in this paper by combined theoretical and experimental approaches. The results showed that the interactions between xylose and CNT-NH2 significantly prevented the ring-opening reaction of xylose to form the most typical anhydrosugar, xylosan, while the ring-contraction reaction of xylose was facilitated to yield furfural. The Density Functional Theory (DFT) calculations demonstrated that two medium hydrogen bonds were formed between the amino group and two hydroxyl groups (1-OH and 3-OH) of xylose with a binding energy of −11.67 kcal/mol, leading to diverse changes in the Mayer bond orders of xylose and thus varying pyrolysis pathways.