ABSTRACT
This study investigated the pyrolysis of lignin pyrolysis in a temperature region from 200 to 800⯰C, aiming to understand influence of pyrolysis temperature on evolution of structures of the resulting char. The results showed that fusion of the ring structure initiated at 200⯰C, where the C/H ratio in the char was equal to that in naphthalene (two fused rings). The C/H ratio in the char obtained at 350⯰C corresponded to that in pyrene (four fused rings), while the char produced at 550⯰C was equivalent to 20 fused benzene rings in terms of C/H ratio. The increasing pyrolysis temperature also shifted the oxygen-containing functionalities such as the carbonyl, esters, ketones in the bio-oil to the ether functionality that had a higher thermal stability. The DRIFTS study of pyrolysis of lignin showed that drastic changes of the functionalities and the internal structure of the char occurred in a narrow temperature region from 520 to 530⯰C. The carbonyl functionality and the aliphatic structure were eliminated, and new conjugated π-bond systems formed.
