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Advisor(s)
Abstract(s)
This work aims to evaluate the structural characteristics and study the oxidative depolymerization of lignins
obtained from hardwood and softwood sulfite liquors. Lignins were obtained after ultrafiltration and freeze-
drying of the sulfite liquors and characterized based on inorganic content, nitrobenzene oxidation, 13C NMR,
and molecular weight determination. The structural characteristics achieved allow evaluating the potential of
each lignin through oxidative depolymerization to produce added-value phenolic monomers. Hardwood and
softwood lignins were submitted to alkaline oxidation with oxygen and the reaction conditions optimized to
obtain a final oxidation mixture with the maximum yield of phenolic monomers. Through oxidation with O2,
hardwood lignin generates mostly syringaldehyde while lignin from softwood biomass mainly produces vanillin;
moreover, a lower reaction time and the interruption of O2 admission avoid the degradation of the oxidation
products in the final mixture for both lignins, more evidenced to hardwood lignin due to its higher reactivity.
From the results, it is possible to conclude that a phenolic aldehyde-rich oxidation mixture could be obtained,
confirming the viability of lignin as raw material to produce added-value products as vanillin and
syringaldehyde.
Description
Keywords
Sulfite liquor Lignin Structural characterization Oxidative depolymerization Phenolic monomers
Pedagogical Context
Citation
Casimiro, Filipa M.; Costa, Carina A.E.; Vega-Aguilar, Carlos; Rodrigues, Alírio (2022). Hardwood and softwood lignins from sulfite liquors: Structural characterization and valorization through depolymerization. International Journal of Biological Macromolecules. EISSN 0141-8130. 215, p. 272-279
Publisher
Elsevier