Gas-Phase Reactions of Glyceraldehyde and 1,3-Dihydroxyacetone as Models for Levoglucosan Conversion during Biomass Gasification

Levoglucosan, the major intermediate in wood gasification, is decomposed selectively to C-1/C-2 fragments at 550-600 degrees C. Kinetic analyses suggest that radical chain mechanisms with the involvement of short-lived carbonyl intermediates explain the lower production of larger fragments. To address this hypothesis, the gas-phase reactivities of glyceraldehyde (Gald), 1,3-dihydroxyacetone (DHA), and glycerol, as simple C-3 model compounds, were compared at 400-800 degrees C under N-2 flow at residence times of 0.9-1.4s. Retro-aldol fragmentation and dehydration proceeded for the pyrolysis of Gald/DHA at 400 degrees C, far below the 600 degrees C decomposition point of glycerol. Pyrolysis of Gald/DHA generated exclusively syngas (CO and H-2). On the basis of the results of theoretical calculations, the effects of carbonyl intermediates on reactivity were explained by postulating uni- and bimolecular reactions, although the bimolecular reactions became less effective at elevated temperatures.