Staged pyrolysis of biomass to probe the evolution of fractions of bio-oil

Abstract

Bio-oil is a complex mixture of organics and each group of chemicals has a varied response to pyrolysis temperatures. This was investigated via the staged pyrolysis of poplar sawdust, cellulose, and lignin by consecutively increasing temperature to 250, 350, 450, and 550 °C, respectively. The results showed that 350 °C was the boundary temperature for formation of majority of organics from sawdust and cellulose and more than half of organics from lignin. The further increase of temperature to 550 °C mainly promoted the aromatization of reaction intermediates from aliphatic components. The staged pyrolysis also facilitated the charring reactions, generating the bio-oil with more light organics including anhydrate sugars, ketones, aldehydes, and phenolics. The enhanced charring reactions promoted the carbonization reactions via deoxygenation, making biochar carbon-rich and thermally more stable. Additionally, the staged pyrolysis also impacted the morphologies and evolution of the functionalities of biochar via influencing the volatile-char interactions.