Influence of silica on formation of levoglucosan from carbohydrates by pyrolysis

Levoglucosan is one of the most abundant pyrolysis products formed from carbohydrates and a good chemical tracer of biomass combustion. Formation of levoglucosan from glucose, maltose, maltotriose, cellulose, and starch with and without silica and tetramethylammonium hydroxide (TMAH) by pyrolysis was studied. TMAH was employed as a methylating agent. Influence of the sizes and spatial structures of the carbohydrates on the formation of levoglucosan by pyrolysis was examined. Levoglucosan was formed only when TMAH was not used. By adding silica to glucose, levoglucosan was not formed. When maltose, maltotriose, and cellulose were mixed with silica, relative abundances of levoglucosan decreased. On the contrary, for starch, the relative abundance of levoglucosan was increased by adding silica. Silica effect on the formation of levoglucosan was explained with hydrogen bonds between silica and carbohydrates.