Directional Valorization Of Eucalyptus Waste Into Value-Added Chemicals By A Novel Two-Staged Controllable Pyrolysis Process

Fast pyrolysis is a promising way to convert biomass waste into value-added chemicals, but current approaches give poor yield and selectivity for the desired chemicals (e.g. anhydrosugars). This study reported a novel two-staged controllable pyrolysis process consisting of torrefaction of H2SO4-impregnated eucalyptus waste and subsequent fast pyrolysis for achieving directional valorization of eucalyptus waste. Under different torrefaction temperature and holding time, the performance of two-staged controllable pyrolysis of 0.5%H2SO4-impregnated eucalyptus waste was evaluated. The highest total yield of levoglucosan (82.4%, based on cellulose) was obtained by torrefaction at 300 degrees C with a holding time of 240 s followed by fast pyrolysis at 550 degrees C, while the highest total yield of xylosan (17.0%, based on hemicellulose) was obtained from torrefaction at 280 degrees C with a holding time of 20 s combined with subsequent fast pyrolysis at 550 degrees C. It is demonstrated that H2SO4 impregnation can achieve the directional valorization of holocellulose into anhydrosugars during torrefaction at low temperature, while evidently inhibiting the degradation of lignin and the formation of non-condensable gas and Cl-C4 light oxygenates. The unreacted holocellulose and lignin in torrefied eucalyptus waste can be further converted into anhydmsugars and phenols via subsequent fast pyrolysis. This study provides a very simple and efficient strategy to achieve staged and directional valorization of holocellulose and lignin in biomass waste into value-added chemicals.