Structures and pyrolytic characteristics of organosolv lignins from typical softwood, hardwood and herbaceous biomass

Three typical lignins from pine (softwood), poplar (hardwood), and bamboo (herbaceous biomass) were isolated using organosolv dioxane. Their chemical structures were identified and the pyrolytic characteristics were investigated comprehensively. The results indicated that pine lignin possessed the highest content of guaiacyl (G) units, the least β-O-4′ aryl ether linkages and best thermal-stability. A high selectivity of 77.26 % for guaiacol-type products from pine lignin was obtained at 400 °C. Bamboo lignin had the most uniform molecular distribution and 40.31 % p-coumarate (pCA) units. The dominant pyrolytic product of bamboo lignin was 4-vinyl phenol with a high content up to 32.64 % at 500 °C. 48.17 % p-hydroxybenzoates (PB) and abundant syringyl (S) units existed in poplar lignin, and phenol was the predominant pyrolytic product with the maximum content of 23.19 % at 600 °C.