Hydrothermal liquefaction of microalgae for biocrude production: Improving the biocrude properties with vacuum distillation

This paper proposes a two-part process for producing biocrude with reduced impurities. The biocrude was produced from hydrothermal liquefaction (HTL) of Spirulina sp. and Tetraselmis sp. in a batch reactor at both 300 and 350 degrees C, 5 min, and 16% w/w solid feed composition. The resultant biocrudes were vacuum distilled at a maximum temperature of 360 degrees C. It was shown that biocrude quality could be enhanced without using catalyst by vacuum distillation (VD). The biocrude yield for Spirulina sp. was 36 wt% at 300 degrees C, 42 wt% at 350 degrees C, and for Tetraselmis sp. was 34 wt% at 300 degrees C, and 58 wt% at 350 degrees C. VD of Spirulina sp. biocrude obtained at 300 and 350 degrees C led to 62 and 67 wt% distilled biocrudes yield, respectively. VD of Tetraselmis sp. biocrude obtained at 300 degrees C was 70 wt%, and 73 wt% at 350 degrees C. The higher heating values (HHV) increased from 32 MJ/kg to 40 MJ/kg. There were substantial reductions in oxygen, metallic content, and boiling point ranges in distilled biocrudes. (C) 2014 Elsevier Ltd. All rights reserved.