Study of Reducing Destruction of Lignin by FT-IR Spectroscopy

Lignin preparations were obtained from harsh flax fiber and material exposed to an alkaline solution of sodium borohydride using the Bjerkman extraction method. Peaks of individual vibrations of all types of covalent bonds in the functional groups of the biopolymer were identified. The mechanism of lignin destruction induced by destabilization of the ether bond adjacent to the carbonyl being reduced in the propane link of the macromolecule was confirmed. Reduction of the carbonyl was accompanied by a doubling of the intensity of the absorption band of alkyl hydroxyls and a fourfold increase in the number of hydroxyaryl groups, which was indicative of the accumulation of structural units in the free phenolic form in the system. The dynamics of structural transformations were compared. The duration of serial-parallel processes of polymer reduction and destruction was estimated.