Computational study on pyrolysis mechanism of β-5 linked lignin dimers
Lignin is a highly complex amorphous three-dimensional network polymer connected by C—O bond and C—C bond.Understanding the bond cleavage mechanism during lignin pyrolysis is cru-cial for advancing efficient pyrolysis technology,as it serves as a significant avenue to harness lignin's potential.In this paper,the density functional theory method was employed to investigate the process of a lignin dimer model compound that contains β-5 linkages.The calculation results show that the most likely initial reaction is the five-membered ring-opening reaction between benzene rings,in which the bond dissociation energies(BDEs)of the Cα—O bond and Cα—Cβ bond are 163.9 kJ/mol and 212.9 kJ/mol,respectively.These reactions are the main ring-opening reactions.By comparing the cleavage of β-5 linkages among the dimers that carry methyl,methoxy,hydroxyl,n-propyl,and other branched chains,it is found that the BDEs of the Cα—O bond and Cα—Cβ bond are at a minimum when hydroxyl,propyl,and hydroxymethyl groups are attached to the two benzene rings and the five-membered ring,re-spectively.Homolytic cleavage of the Cα—O bond is always the initial reaction,and the continuous frac-ture of the Cα—O and Cα—Cβ bonds is the main path to break the five-membered ring.
万方数据
维普
