Hydrodeoxygenation of the aqueous fraction of bio-oil with Ru/C and Pt/C catalysts

• Hydrogenation of the water soluble fraction of bio-oil with Ru/C and Pt/C was studied.
• Low temperature hydrogenation produced mainly ethylene/propylene glycols and sorbitol.
• Sorbitol was hydrogenated to mono-alcohols and diols at high temperature.
• 45 carbon% of gasoline additive oxygenates and valuable C2 to C6 diols were produced.
• The product distribution can be controlled by modifying pressure and temperature.

In this paper we discuss the continuous flow hydrogenation of the water soluble fraction of bio-oil (WSBO) with Ru/C and Pt/C catalysts. Temparatures higher then 125 °C lead to homogeneous reactions within the aqueous phase of bio-oil. Low temperature hydrogenation (LTH) at 125 °C over Ru/C catalyst and with WHSV of 1.5–3 h−1 was required to stabilize the bio-oil so higher temperature hydrogenation (HTH) could occur. The main products from LTH were ethylene and propylene glycols and sorbitol. At these temperatures only small amounts of acetic acid (AA), levoglucosan, furanone, phenol and phenol substitutes were hydrogenated. In the HTH step, the sorbitol was hydrogenated to mono-alcohols and diols by hydrogenolysis and secondary hydrogenation reactions. Up to 45% carbon in WSBO was converted to useful products (gasoline-cuts and diols) in the HTH step over Pt/C catalyst at 250 °C and WHSV of 3 h−1. The reactions product distribution can be controlled by modifying operating pressure and temperature. The production of gasoline range compounds (C4–C6 alkanes and C1–C6 alcohols) is favoured at low pressure (750 psi). Increasing the reaction pressure decreased the amount of carbon that was converted into gas phase products.

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