For understanding the pyrolysis mechanism of cellulose, four kinds of paths of pyrolytic reaction were designed for the thermal decomposition of the cellulose monomer (namely β-D-glucopyranose) according to related experimental results. At the UB3LYP/6-31G(d) level of density functional theory, the equilibrium geometries of the reactants and products were optimized and the standard thermodynamic parameters of every reaction path in different temperature ranges were calculated by the help of Gaussian 03 package. The thermodynamic calculation results show that all above reactions are endothermic processes and can take place spontaneously when temperature of reaction exceeds 550 K. According to thermodynamic points of view, the pyrolysis of cellulose monomers favors to produce low molecular weight products, e.g. hydroxyacetaldehyde, acetol and carbon monoxide.

Key words: cellulose monomer, pyrolysis mechanism, density functional theory, thermodynamic parameter