Study on pyrolysis behaviors of non-woody lignins with TG-FTIR and Py-GC/MS

To explore the potential values of lignins extracted from different agricultural wastes (e.g., walnut shell, wheat straw, cotton stalk, rice husk, bamboo, rape straw, corncob and peanut shell), pyrolysis behaviors of eight non-woody lignins were studied with TG-FTIR and Py-GC/MS. The TG-FTIR results indicated that the conversion of lignin and the evolution of main gaseous products were deeply influenced by the biomass species. Compared with the woody lignin, the phenylpropane unit present in the non-woody lignins would enhance the ability of condensation and lead to the formation of biochar. Also, differentiation of pyrolysis products was performed by Py-GC/MS. Corresponding to the classification of lignin types, the relative contents of syringol products from G type lignin were significantly less than those of the other two lignins (GS and HGS types). Compared with commercial alkali lignin (CAL, 6.7%), a high proportion of catechol type compounds was obtained from the peanut shell [37.5%] and cotton stalk [27.6%] lignins. Furthermore, the amount of styrene and 4-hydroxy-3-methoxystyrene was closely related to the content of hemicellulose in raw materials.