Comparative studies of thermal degradation between larch lignin and manchurian ash lignin

The thermal degradation and charring of both larch lignin and manchurian ash lignin in the condensed phase were comparatively investigated by using TGA, FTIR and XPS. TGA experimental results showed that larch lignin produced more char residue than manchurian ash lignin under pure nitrogen at high temperature. This demonstrated that the carbon backbone of larch lignin was more stable than that of manchurian ash lignin. This is attributed to more carbon-carbon bonds existing in larch lignin than in manchurian ash lignin. Under air condition, the lignin completely was decomposed to form volatiles at high temperature. There was no char residue in either larch lignin or manchurian ash lignin. This was because oxygen catalyzed the oxidative reactions of C-C and C-H bonds, which is supported by FTIR. FTIR and XPS data indicated that the cleavage of aliphatic ester bonds took place mainly under pure nitrogen, and more aromatic rings remained in the condensed phase. Manchurian ash lignin showed a high crosslinking rate based upon the relative intensity of C1s and C1s (C-C) and an obvious increase of the ratio of carbon to oxygen. Different thermal degradation of both larch lignin and manchurian ash lignin under pure nitrogen and air has been proved by TGA, FTIR and XPS. (C) 2002 Elsevier Science Ltd. All rights reserved.