Bio-oil as a source of renewable chemicals: the chemistry of pyrolytic lignin

Pyrolytic lignin from beech wood bio-oil was fractionated into low molecular mass (LMM) and high molecular mass (HMM). A comprehensive characterization by FTIR, GPC, TG, GC/MS, and multidimensional NMR spectroscopy was employed to analyze the individual fractions. Additionally, advanced characterization was carried out using ultra-high-resolution mass spectrometry (UHRMS). The data reveal that the LMM fraction has a higher prevalence of phenolic monomers due to homolytic cleavage of the RC-OAr linkage in aryl-O-alkyl ether bonds corroborating with GC/MS results. On the other hand, the HMM fraction shows a higher degree of polymerization and a wider molecular mass distribution, predominantly comprising carbohydrate derivatives by GC/MS. UHRMS data proved to be valuable in characterizing the monomers and oligomers present in each fraction, offering insights for future applications and the development of value-added products. Overall, this work significantly advances the current knowledge of pyrolytic lignin structures, opening opportunities for innovative technological bioproducts.