Study on the hydrodeoxygenative upgrading of crude bio-oil produced from woody biomass by fast pyrolysis

Crude bio-oil produced from fast pyrolysis of yellow poplar wood was subjected to HDO (hydrodeoxygenation) for the purpose of reducing water content as well as increasing heating value. HDO was performed in an autoclave reactor at three different reaction factors: temperature (250–370 °C), reaction time (40–120 min), and Pd/C catalyst loading (0–6 wt%) under hydrogen atmosphere. After completion of HDO, gas, char, and two immiscible liquid products (light oil and heavy oil) were obtained. Liquid products were less acidic and contained less water than crude bio-oil. Water content of heavy oil was ranged between 0.4 wt% and 1.9 wt%. Heating values of heavy oil were estimated between 28.7 and 37.4 MJ/kg, which was about twice higher than that of crude bio-oil. Elemental analysis revealed that heavy oil had a lower O/C ratio (0.17–0.36) than crude bio-oil (0.71). H/C ratio of heavy oil decreased from 1.50 to 1.32 with an increase of temperature from 250 °C to 350 °C, respectively.