The Analyses of Lignin Structure and Molecular Distribution of pH6 from Dissolved Kraft Lignin

The Chinese poplar was used as the raw material in this study. Conversational Kraft cooking was carried out. The acid-precipitating method was used to separate the dissolved lignin from the black liquor. The FT-IR spectra was quantitatively analyzed and compared in order to discover the change of lignin structures. The lignin 31P—NMR spectra of pH6 lignin samples was obtained and the functional groups of the lignin was quantitatively analyzed and compared in order to discover the change of lignin structures during Kraft cooking. Syrinl-OH was 50~60 percent, Guaiacyl-OH was 40~50 percent. The pH6 lignin samples of 31P-NMR spectra aliphatic OH was 2.75 m mol/g, COOH was 1.75 m mol/g, total phenolic OH 5.66 m mol/g. The molecular weight distribution curves of lignin samples obtained from gel permeation chromatography analysis system was shown that Mw was 1375g/mol, Mn was 2426 g/mol and polydispersity was 4424 g/mol.

The Analyses of Lignin Structure and Molecular Distribution of pH6 from Dissolved Soda-AQ Lignin

The Chinese poplar was used as the raw material in this study. Conversational Soda-AQ cooking was carried out. The acid-precipitating method was used to separate the dissolved lignin from the black liquor. The FT-IR spectra was quantitatively analyzed and compared in order to discover the change of lignin structures. The lignin 31P—NMR spectra of pH6 lignin samples was obtained and the functional groups of the lignin was quantitatively analyzed and compared in order to discover the change of lignin structures during Soda-AQ cooking. Syrinl-OH was 50~60 percent, Guaiacyl-OH was 40~50 percent. The pH6 lignin samples of 31P-NMR spectra aliphatic OH was 5.93 m mol/g, COOH was 0.99 m mol/g, total phenolic OH 7.07 m mol/g. The molecular weight distribution curves of lignin samples obtained from gel permeation chromatography analysis system was shown that Mw was 1506g/mol, Mn was 2888 g/mol and polydispersity was 5257 g/mol.