Different pyrolytic pathways of levoglucosan in vapor-and liquid/solid-phases

Influence of the amount of levoglucosan-loading on the pyrolysis behavior was studied in N-2 at 400 degrees C with a dual-space closed ampoule reactor. The results indicated that the pyrolytic pathways are different between vapor- and liquid/solid-phases. Relative contribution of these two pyrolysis conditions changed depending on the amount of levoglucosan-loading. In vapor-phase, levoglucosan was selectively converted to the non-condensable gas (mainly CO and CO2), while char and other condensable low molecular-weight (MW) products (furfural, 5-hydroxymethyl furfural, glycolaldehyde, hydroxyacetone, acetic acid and formic acid) were formed more selectively in liquid/solid-phase. Furthermore, the aldehydes and hydroxyacetone formed from the pyrolysis in liquid/solid-phase were found to stabilize levoglucosan in vapor-phase. Clearly-observed isotope effect with acetaldehyde-1-d(1) suggested that the vapor-phase gasification of levoglucosan proceeds in a radical-chain mechanism. (C) 2008 Elsevier B.V. All rights reserved.