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

Molecular mechanisms for the gas-phase degradation of levoglucosan, the major intermediate in cellulose gasification, were studied by kinetic analysis at 550-700 degrees C (residence time: 0.11-0.45 s), 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 57.4 kcal mol(-1)), which is supported by the selective formation of acrolein and glyoxal at 500 degrees 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. (C) 2017 Elsevier B.V. All rights reserved.