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

The coumarone-contained linkage is one of the most important linkages in the lignin structure. 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. The calculation results indicate that the energy barrier of the cleavage reaction of OCα bond in pyrolytic pathway (2) is obviously lower than that of CβCα bond 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- hydroxyphenyl-ethanal, guaiacol, 8-methoxy-coumarone, formaldehyde and so on.122