[Pyrolytic depolymerization mechanism of a lignin model compound with α-O-4 linkage].

To understand the pyrolysis mechanism of lignin with α-O-4 linkage, 4-(3-hydroxy-1-phenoxypropyl)-phenol was selected as an α-O-4 type lignin dimer model compound, and its pyrolysis process was studied by density functional theory with M06-2X method at 6-31+G (d,p) level. Equilibrium geometries of the reactant, intermediates, transition states and products were fully optimized. The activation energies in each pyrolysis pathway were calculated. The dimer decomposed mainly through the homolytic cleavage and concerted decomposition of the C(α)-O linkage. Pyrolytic products mainly included various phenolic compounds such as phenol, 4-methylphenol, 4-vinylphenol and p-coumaryl alcohol, as well as light compounds such as ethanol, methanol and formaldehyde. Pyrolytic depolymerization process has its potential in biomass-based fuels.