摘要
In order to better understand the pyrolysis process of cellulose, the decomposition of levoglucosan and glyceraldehyde, which are important intermediate products of cellulose, are simulated by quantum simulation. Thermodynamic analysis of four possible reaction pathways for levoglucosan is conducted by quantum chemistry.The reaction process of glyceraldehyde is checked, and the intermediates and the activation energies of the process are given. The simulation results indicate that the three well-established chemical pathways for levoglucosan in literature can spontaneously occur within the pyrolysis temperature range from 500 to 1 000 K. However, the reaction pathway involving the formation of erythrose cannot be accepted since the free energy ΔG is estimated to be above zero during the pyrolysis process. Through the analysis of glyceraldehyde decomposition by the transition state theory, decarbonylation and dehydration may be the dominant pathways for glyceraldehyde decomposition. The quantum simulation for determining the chemical pathway of glyceraldehyde and levoglucosan can give a conceptual and methodological guide for searching possible chemical pathways of cellulose pyrolysis or other macromolecules in biomass.
为了更好地理解纤维素热解过程，对纤维素热解中重要中间产物---左旋葡聚糖和甘油醛的反应过程进行了量子化学模拟．对左旋葡聚糖的4条可能反应路径进行了热力学分析，并且对甘油醛的反应能垒进行了计算，给出了其反应过程中的过渡态和活化能．计算结果表明，文献提出的左旋葡聚糖的3条反应路径在500～1000 K下均能自发进行，但左旋葡聚糖生成四碳糖的反应不能自发进行，因为该路径的自由能ΔG总是大于0．通过过渡态理论对甘油醛热解过程的分析表明，脱羰反应和脱水反应是主要的反应路径．采用量子化学模拟甘油醛和左旋葡聚糖的分解路径为寻找纤维素及其他生物质大分子的热解反应路径提供了理念和方法上指导．
基金
The National High Technology Research and Development Program of China(863 Program)(No.2012AA051801)
