OXIDATIVE AMMONOLYSIS OF THE EUCALYPTUS-GRANDIS KRAFT LIGNIN

The ammonolysis of kraft lignin produces an insoluble polymer which is very difficult to characterize. This work employed solid state C-13 NMR spectroscopy to follow the structural changes occurring in this lignin during the reaction. The C-13 NMR solution spectra of milled wood lignin and kraft lignin, and the FTIR spectrum of the ammonolytic product were also used. During the ammonolysis, the kraft lignin is converted into a very insoluble product which cannot be regarded as a lignin at all. This polymer contains amide, non-oxygenated aliphatic, ammonium, and amine groups. SP/MAS C-13 NMR spectroscopy with pulse delay close to 100 s is more reliable than the CP/MAS technique for quantitative studies of lignins.