Upgrading Pyrolysis Oil by Catalytic Hydrodeoxygenation Reaction in Supercritical Ethanol with Different Hydrogen Sources

• Both in-situ and ex-situ hydrogen source for bio-oil upgrading were studied. • In-situ hydrogen source showed better performance at mild temperatures (260, 300℃). • Ex-situ hydrogen source demonstrated better performance at high temperatures (325, 350℃). • Upgraded oil with 37 MJ/kg HHV was generated at 300℃ by in-situ hydrogen source. • 85 % degree of de-oxygenation was obtained at 350℃ with ex-situ hydrogen source. The effects of hydrogen sources (hydrogen gas as an ex-situ hydrogen source and formic acid as an in-situ hydrogen source) on upgrading of pyrolysis oil by hydrodeoxygenation (HDO) in supercritical ethanol were comparatively investigated in this study for the first time. Effects of catalysts (5%Ru/C and 10%Ni-6%Mo-5%W/Al 2 O 3 ), time and temperature on the product yields and quality of upgraded oil were investigated comparatively with different hydrogen sources. An interesting result was obtained, demonstrating that the in-situ hydrogen (formic acid) showed better HDO performance at mild temperatures (260, 300 ℃), while the HDO of pyrolysis oil with ex-situ hydrogen (H 2 gas) at higher temperatures (325 or 350 ℃) with respects to degree of deoxygenation and the quality of the produced upgraded oils. HDO of the woody derived pyrolysis oil with total acid number (TAN) of 136.0 mgKOH/g at 350 ℃ for 2 h over Ru/C catalyst with formic acid or hydrogen gas resulted in 74% and 85% degree of de-oxygenation, respectively, producing high quality upgraded oils with TAN of 35.3 mgKOH/g and 50.1 mgKOH/g and HHV of 39.5 MJ/kg and 43.0 MJ/kg, respectively.