Unraveling the synergistic development of carbon skeleton and pore networks involved in lignin pyrolysis

Abstract

To gain new insights into lignin pyrolysis, the synergistic development of carbon skeleton and pore networks in a wide temperature range of 200–800 °C was unraveled. The relative abundance of aromatic carbon structures increased exponentially with increasing temperature, as determined by 13C NMR deconvolution. Additionally, the g-factor type of radicals changed from O-centered (g-factor <2.0030) to C-centered (g-factor >2.0040) radicals. The evolution of the char macromolecules structure from disorder to order was principally characterized by a decrease in aromatic spacing (d002, 3.36→3.37 Å) and an increase in stacking degree (Lc, 7.89→8.67 Å) and aromaticity (fa, 75.19%→96.94%). fa has a strong negative linear correlation with d002 (R2 = 0.965). Ternary quadratic polynomials can relate specific surface area, total pore volume, and relative carbon content to the pore fractal dimension. The hypothesized chemical reaction networks and synergistic development of carbon skeleton and pore networks are essential for lignin effective valorization by a pyrolysis-based biorefinery strategies.