A theoretical research on pyrolysis reactions mechanism of coumarone-contained lignin model compound

Abstract

The coumarone-contained linkage is one of the most important linkages in the lignin structure. To understand the pyrolysis reactions mechanism of lignin, the pyrolysis processes of coumarone-contained lignin model compound were theoretically investigated by employing density functional theory method M062X with the 6-31++G(d, p) basis set. Four possible pyrolytic reaction pathways were proposed and the standard kinetic parameters in all reaction pathways were calculated. The calculation results indicate that the energy barrier of the cleavage reaction of OCα bond (244.2kJ/mol) in pyrolytic pathway (2) is obviously lower than that of the cleavage reaction of CβCα bond (405.1kJ/mol) in pyrolytic pathway (1), and guaiacol and 8-methoxy-coumarone are formed more easily through pyrolytic pathway (4). The reaction pathways (2) and (4) are the major pyrolytic reaction channels, and the major products of coumarone-contained lignin model compound pyrolysis are 4-methyl-2-methoxy-phenol, 3-methoxy-2-hydroxylphenyl-ethanal, guaiacol, 8-methoxy-coumarone, formaldehyde and so on.