Production of phenol-rich bio-oil via a two-stage pyrolysis of wood

A two-stage pyrolysis of wood was conducted to produce a phenol-rich bio-oil. The two-stage pyrolysis process included auger and fluidized bed reactors connected in series. In this study, the effects of temperatures of the auger and fluidized bed reactors and the type of fluidizing medium were mainly investigated. The auger reactor temperature was varied from room temperature to about 290 °C, whereas the fluidized bed reactor temperature ranged from about 500 to 700 °C. As the auger reactor temperature rose from about 20 to 290 °C, the gas yield increased from 27 to 31 wt%. At about 290 °C, the production of phenol was greatly enhanced. A high fluidized bed reactor temperature favored the formation of phenol, efficiently exploiting the weakened bond strength between C (benzene) and methoxy group of lignin molecules caused by heat treatment in the auger reactor. The use of nitrogen as the fluidizing medium drastically increased phenol production, which was achieved by reducing reactions of phenol produced inside the fluidized bed reactor with other components. In the current study, the maximum phenol content in bio-oil reached about 16 wt%. Bio-oil with a high phenol content has good potential as a reactant in the phenol resin synthesis.