An experimental study of the competing processes of evaporation and polymerization of levoglucosan in cellulose pyrolysis

While levoglucosan is a major pyrolysis product of cellulose, the yields reported in the literature vary significantly depending upon experimental conditions. In the present paper, we found that during pyrolysis in a micropyrolyzer, levoglucosan yield from cellulose can decrease significantly as sample size increases. According to our previous research, levoglucosan not only evaporates, but also forms polymers at elevated temperatures and these polymers can further dehydrate to char and low molecular weight volatiles such as water, furfural, furan, and acids. These results strongly suggest that experimental variables may influence the competing processes of evaporation and polymerization of levoglucosan during cellulose decomposition, and thereby affect the final yield of levoglucosan. In this paper, the influence of various experimental variables on the evaporation and polymerization of levoglucosan is evaluated in experiments conducted with a thermogravimetric analyzer. The pyrolytic residues are then quantified using a high performance liquid chromatography method. Experimental variables include sample size, ventilation condition, sweep gas, heating rate, and moisture content. The results show that all of the tested variables affect the competing processes of evaporation and polymerization of levoglucosan, and consequently affect the final recovery of levoglucosan. (C) 2012 Elsevier B.V. All rights reserved.