Hydrothermal wood processing using borax decahydrate and sodium borohydride

• Beech wood was converted into bio-oils at 250, 300 and 350 °C.
• The use of additives increased the bio-crude yields.
• The highest bio-crude yield was achieved with borax decahydrate.
• The compositions of different extracts of bio-crude were affected with the additives.

Hydrothermal liquefaction experiments were carried out at 250, 300 and 350 °C with the use of an additive (either borax decahydrate (Na2B4O7·10H2O) or sodium borohydride (NaBH4)). The effects of both temperature and types of additives on the product distributions and bio-crude compositions were viewed. The use of additives (either Na2B4O7·10H2O or NaBH4) increased bio-crude yields at all liquefaction temperatures. The highest bio-crude yield was achieved with Na2B4O7·10H2O at 300 °C. The use of additives (either Na2B4O7·10H2O or NaBH4) decreased the char yield at 300 and 350 °C. The heating values of ether extracts from all experimental runs including the run without additives were close to each other. However, the heating values of the acetone extract from chemical runs were higher than the heating values of the non-chemical run. The highest heating value of the acetone extract was 28.05 MJ kg−1 and it was obtained from the run with Na2B4O7·10H2O at 300 °C. The identified compounds in ether extracts and acetone extracts were mainly oxygenated compounds. The compositions of ether extract and acetone extract were affected when using additives.