The co-pyrolysis interactionsof isolated lignins and cellulose by experiments and theoretical calculations

The development of biofuels from waste biomass pyrolysis is inhibited due to the unclear interactions of lignin structures and cellulose. Here, the co-pyrolysis of isolated lignins and cellulose was fully explored. The levoglucosan production from the co-pyrolysis of cellulose and pine lignin reduced about 1 time as compared to pure cellulose pyrolysis. Contrarily, the contents of levoglucosan and phenolic compounds were improved via adding poplar or bamboo lignins. The high contents of C–C bonds (58.0%) and G-type structure were contained in pine lignin. The high contents of C–O bonds (36.6%) and the G-H-type structures were involved in poplar lignin, and the high contents of O–CO bonds (3.4%) and the G-H-S-type structures were concluded in bamboo lignin. Theoretical calculations revealed that the C–C bonds had higher bond energy than the C–O–C bonds. A carbon-rich pool could be formed via the pyrolysis of pine lignin due to the high contents of C–C bonds, which could cause the secondary cracking of targeted products. The oxygen-enriched pool could be produced by the pyrolysis of poplar or bamboo lignins due to the high contents of C–O bonds, thus promoting the formation of levoglucosan and phenols compounds during co-pyrolysis.