Interaction characteristics and mechanism in the fast co-pyrolysis of cellulose and lignin model compounds

During biomass fast pyrolysis process, the interactions among biomass components will affect the pyrolytic products distribution. In this study, d-glucose and a β-O-4 type lignin model dimer (LMD, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol) were selected as the model compounds of cellulose and lignin. The interaction characteristics and mechanism during their fast co-pyrolysis process were investigated by combined pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) experiments and density functional theory (DFT) calculations. The Py–GC/MS results indicated that during fast co-pyrolysis process, the presence of LMD significantly decreased the formation of levoglucosan (LG) from d-glucose, while promoted the formation of linear carbonyls and furans. Meanwhile, the presence of d-glucose enhanced the decomposition of LMD to generate phenolic compounds. The DFT calculations revealed that d-glucose would interact with a homolysis radical of LMD to form a ten-membered ring transition state. The formed complex transition state changed the energy barriers of certain pyrolytic reactions of d-glucose and LMD, thus affecting the pyrolytic products distribution.