Thermal, thermo-oxidative, and catalytic degradation of palm kernel shells using a continuous two-stage pyrolysis process for the production of phenols-rich bio-oil

In this study, a two-stage process having an auger reactor (300 °C) and a fluidized bed reactor (550–650 °C) was applied to produce phenols-rich bio-oils from the thermal, thermo-oxidative, and catalytic degradation of palm kernel shells (PKS). The two-stage process has a feature of being able to separately produce two different bio-oils: a holocellulose-derived bio-oil and a lignin-derived bio-oil. Main focus of the study was to investigate the effects of fluidized bed reactor temperature, the addition of oxygen, and K₃PO₄ on product distribution and yields of phenolic compounds. As the fluidized bed reactor temperature increased under N₂, the phenol content in bio-oil from the fluidized bed reactor increased steadily from 8.3 to 14.0 wt%, with the maximum phenol yield (3.3 g/100 g PKS) at the fluidized bed reactor temperature of 600 °C. In the thermo-oxidative degradation of PKS conducted at a fluidized bed reactor temperature of 550 °C with an oxygen concentration of 1.5 vol%, a high phenol content in bio-oil (10.0 wt%) and a high phenol yield (3.3 g/100 g PKS) could be obtained. Further, the catalytic degradation with K₃PO₄ greatly increased the phenol content (15.0–27.3 wt%) in viscous phase bio-oil, while decreasing the phenol yield (1.6 g/100 g PKS).