Compositional insights and valorization pathways for carbonaceous material deposited during bio-oil thermal treatment.

This work analyses the composition, morphology, and thermal behavior of the carbonaceous materials deposited during the thermal treatment of bio-oil (thermal pyrolytic lignin-TPL). The bio-oil was obtained by flash pyrolysis of lignocellulosic biomass (pine sawdust), and the TPLs were obtained in the 400-700 °C range. The TPLs were characterized by performing elemental analysis; (13)C NMR, Raman, FTIR, and X-ray photoelectron spectroscopy; SEM; and temperature-programmed oxidation analyzed by differential thermogravimetry and differential scanning calorimetry. The results are compared to a commercial lignin (CL). The TPLs have lower oxygen and hydrogen contents and a greater aromaticity and structural order than the CL material. Based on these features, different valorization routes are proposed: the TPL obtained at 500 °C is suitable for use as a fuel, and the TPL obtained at 700 °C has a suitable morphology and composition for use as an adsorbent or catalyst support.