Characterization of sago palm (Metroxylon sagu) lignin by analytical pyrolysis

Dioxane lignin prepared from sago palm (Metroxylon sagu) was characterized by analytical pyrolysis coupled to gas chromatography-mass spectrometry. Large abundances of the p-hydroxybenzoates ester-linked to the lignin were proven by analytical pyrolysis as well as by mild alkaline treatment that produced p-hydroxybenzoic acid in 16.3% yield. Pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) before and after alkaline treatment also showed the presence of ester- and ether-linked p-hydroxybenzoates. Quantitative results of pyrolysis showed that the sago palm lignin is of syringyl type. The relative abundances of TMAH/pyrolysis products derived from the syringyl beta-aryl ether substructures were 4.9 times those of the guaiacyl equivalents. Proton nuclear magnetic resonance analysis also showed the presence of the p-hydroxybenzoates and the predominance of the syringyl moiety over the guaiacyl ones in the sago palm lignin.