Abstract: In order to optimize the yield of levoglucosan (LG) during cellulose pyrolysis, a model based on modified Brodio-Shafizadeh (B-S) mechanism model was brought out to simulate the process of decomposition and formation of active cellulose, LG and hydroxyl-acetaldehyde (HAA). Simulation results show that cellulosic material is constrained in a middle temperature condition during a rather long period of time, since heat transferred from the surrounding can not meet the endothermic need of primary cracking reaction, which virtually forms the essential condition for biomass pyrolysis to yield bio-oil. Being the most important product of cellulose pyrolysis, LG does not undergo any intensive secondary cracking, while almost all HAA is originated from the decomposition of AC. In addition, concentration differences among LG and other competitive compounds in fabric structure are determined by the competitive abilities of the corresponding reactions. This is validated by the increased accumulation tendency of HAA concentration during the late period of pyrolysis process,indicating its superiority to LG formation in consumption of AC. Secondary reactions of volatiles occur largely in gaseous phase rather than in solid phase. Both long residence time of volatiles and high temperature will induce high decomposition of LG. Therefore, to optimize the yield of LG, middle radiant-source temperature and short gas residence time are necessary. In order to optimize the yield of bio-oil, gas residence time can be slightly longer.

Key words: cellulose, pyrolysis, levoglucosan, simulation