Hydrothermal liquefaction of macroalgae with in-situ-hydrogen donor formic acid: Effects of process parameters on products yield and characterizations

Abstract Catalytic Hydrothermal liquefaction (HTL) of Ulva lactuca (UL) macroalgae over various amount of formic acid (FA) with solvents (water, ethanol and methanol) at different reaction temperatures (260, 280 and 300 °C), reaction holding times (15, 30 and 45 min.) with acidic ZSM-5 and basic MgO catalyst were investigated. Without catalyst, the maximum bio-oil yield was obtained 43.8 wt.% in ethanol-FA mixture at 280 °C for 30 min reaction time. However, the maximum bio-oil (55.2 wt.%) was obtained with basic metal MgO catalyst in the ethanol-FA solvent mixture compared to the acidic ZSM-5 catalyst (48.7 wt.%). When ethanol solvent used with MgO and ZSM-5 catalyst, the highest bio-oil yield 46.7 and 48.7 wt.% were observed. Selectively higher derivatives of hydrocarbon compounds were obtained with MgO in ethanol-FA solvent. However the phenolic compounds majorly were found with ZSM-5 catalyst. The higher carbon (69.5 %) and higher high heating value (HHV) (35.8 MJ/kg) was observed in case of MgO catalytic HTL bio-oil compared to the other HTL bio-oil. The use of catalysts in HTL increased the boiling point range of bio-oil and the higher boiling point range was observed in case of MgO and ZSM-5 catalytic bio-oil.