Coupled effect of pyrolysis temperature and HNO3 pretreatment on sugarcane bagasse fast pyrolysis for levoglucosan production

This work aimed to evaluate the potential of HNO₃ (0.1 wt%) in the pretreatment of sugarcane bagasse as a strategy to intensify levoglucosan production, before subjecting it to fast pyrolysis under different temperature conditions. The experiments were conducted in a pyroprobe reactor coupled to a GC/MS at temperatures ranging from 350 to 600 °C, with 50 °C intervals. Thus, in addition to the impact of nitric acid on levoglucosan yield, the formation profile of other pyrolytic derivatives during the thermochemical conversion of biomass is reported. The best results regarding levoglucosan yield were obtained when pyrolysis was performed at 450 °C, resulting in approximately twice the amount of levoglucosan obtained from sugarcane bagasse after treating the biomass with acid compared to the control (untreated biomass), while the profiles of the other pyrolytic derivatives identified showed different and lower behaviors after acid washing of the biomass. The observed effect may be due not only to the removal of alkali and alkaline earth metals, whose catalytic activity influences the pyrolytic pathways, but also to the probable partial removal of lignin and/or hemicellulose fractions by the acid washing. On the other hand, despite the observed increase in levoglucosan formation, the results obtained with HNO₃ at 0.1 % by biomass weight do not seem to be a good alternative for the intensification of the target compound, when compared with other acids used in washing/passivation procedures of sugarcane bagasse under similar experimental conditions.