Improved qualty bio-crude from hydrothermal liquefaction of oak wood assisted by zero-valent metals

The production of bio-fuels is becoming one of the biggest challenges of this decade. In this context, the interest on hydrothermal liquefaction (HTL) is continuously growing. In this work, the HTL of oak wood to produce a high-quality bio-crude is proposed. The effect of the use of zero-valent metals (ZVMs) as hydrogen producers (Fe and Zn) and hydrodeoxygenation catalysts (Ni and Co) on bio-crude quality is investigated. The tests were conducted at 330 °C in micro-batch reactors at different reaction times in the presence of ZVMs. Fe and Zn are oxidized by subcritical water producing active hydrogen, which is used to stabilize biomass fragments during the process and to be used in hydrodeoxygenation reactions in the presence of Ni and Co. The results show that the use of hydrogen producers significantly affects bio-crude yields, which increase by 20% with respect to the blank test when Fe is used. Furthermore, the synergic effect between the hydrogen producers (Fe and Zn) and the catalysts (Ni and Co) was tested. The results pointed out an enhancement of the bio-crude quality with an increase in the H/C ratio and a decrease in the O/C ratio, and also, looking at the bio-crude composition, the hydrogenation extent is clearly proven, for example, 2-cyclopenten-1-ones increase at the expense of furan derivatives.