Kinetics and molecular mechanisms for the gas-phase degradation of levoglucosan as a cellulose gasification intermediate

Abstract

Molecular mechanisms for the gas-phase degradation of levoglucosan, the major intermediate in cellulose gasification, were studied by kinetic analysis at 550–700°C (residence time: 0.11–0.45s), and a mixed mechanism including heterolysis and radical chain reactions is suggested. Density functional theory calculations indicated that one of the cyclic Grob reactions can proceed (Ea 57.4kcalmol−1), which is supported by the selective formation of acrolein and glyoxal at 500°C. Nevertheless, contributions of these heterolytic reactions were suggested to be smaller than radical chain reactions, which would proceed via the C- and O-centered radicals. Influences of the bicyclic ring and the hydrocarbon/oxygenated gas selectivity are also discussed. These results provide insights into the upgrading of the gasification processes of cellulosic biomass.