Quantitative study of the pyrolysis of levoglucosan to generate small molecular gases

Biomass pyrolysis can be used to obtain clean fuels, such as liquids or gases, and is a promising approach to biomass energy utilization. Levoglucosan (LG) is an important product of biomass pyrolysis. The study of its thermal decomposition process is helpful for understanding the mechanisms underlying biomass pyrolysis. We investigated the decomposition of LG using a density functional theory method based on quantum mechanics. In this paper, we studied 23 possible reaction paths for LG pyrolysis to generate small molecular gases and 51 compounds (including reactants, intermediates, and products), and quantified the 47 transition states involved in the pathway. The optimal reaction path of CO₂ is ring opening → decarboxylation, with an energy span of 301 kJ mol^-1. The optimal reaction pathway for CO is dehydration → alcohol-ketone tautomerization → ring opening → decarbonylation, with an energy span of 286 kJ mol^-1. Therefore, it is theoretically simpler to produce CO from LG than to generate CO₂. Moreover, by analysing the dehydration reaction in the pathway, we observed that dehydration is beneficial to the production of CO by LG, but is not conducive to the formation of CO₂.