Pre-treatment of biomass with phosphoric acid prior to fast pyrolysis - A promising method for obtaining 1,6-anhydrosaccharides in high yields

Biomass was pre-treated with phosphoric acid and dried prior to analytical pyrolysis. The influence of pre-treatment parameters-i.e. concentration of phosphoric acid, its uptake by biomass, and drying temperature upon the pyrolysis process of various cellulose containing raw materials has been studied. The concentration of the impregnation solution should be chosen according to the sorption capacity of the cellulose feedstock. By varying the concentration of phosphoric acid, the pyrolysis of microcrystalline cellulose Thermocell(TM) may be directed toward elevated production of levoglucosan (40%) and levoglucosenone (34%). The protective role of lignin in birch wood towards the cellulose moiety is discussed in connection with radical scavenging properties of lignin. Birch wood treated with phosphoric acid solutions (having concentrations less than 2%) yields approx. 15% levoglucosan. At higher concentrations, a decline of the radical scavenging activity of lignin occurs, which increments the role of dehydration reactions, and, as a consequence, the formation of more levoglucosenone (17%). (C) 2003 Elsevier Science B.V. All rights reserved.