Study on structure and thermal stability properties of lignin during thermostabilization and carbonization

Soda lignin was first thermostabilized prior to carbonization. The composition, structures and thermal properties of treated lignin were investigated by EA, TGA-MS, C-13 NMR,TGA, and Raman. EA and TGA-MS results showed that the hydrogen content decreased continuously and the oxygen content increased up to 260 degrees C then decreased and the carbon content increased passively during thermostabilization. C-13 NMR results revealed that thermostabilization could be divided into three stages according to the evolution of the oxygenated structures content: <260 degrees C, 260-290 degrees C, >290 degrees C. Raman analysis showed that R values at each carbonization temperature were concave-down and non-symmetrical parabolic type and the 260 degrees C thermostabilized lignin after 1400 degrees C carbonized obtained the minimum R value 1.84. TGA results indicated that overall yields reflecting thermal stability of the thermostabilized samples, especially thermostabilized at 260-290 degrees C, were higher than that of untreated lignin. (C) 2013 Elsevier B.V. All rights reserved.