Enhancement of microalgae bio-oil quality via hydrothermal liquefaction using functionalized carbon nanotubes

Herein, the carbon nanotubes with different functional groups were used to catalyze the hydrothermal liquefaction process. It indicated that the carbon nanotubes exhibited high stability under hydrothermal conditions (340 degrees C and 60 min), moreover, it may improve the hydrogen content and simultaneously reduce the oxygen, nitrogen and sulfur content of the bio-oil. In particular, the -COOH modified carbon nanotube increased the higher heating value of the bio-oil from 35.8 MJ/kg to 37.6 MJ/kg. Gas chromatography with mass spectrometer analysis showed that carbon nanotube resulted in more hydrocarbons in the bio-oil (47% of the total peak area) than that of the control bio-oil (28% of the total peak area). In addition, the -COOH modified carbon nanotube could increase the low boiling fraction (<400 degrees C) of the bio-oil to from 68.1 wt% to 77.9 wt%. At last, the role of different carbon nanotubes during hydrothermal liquefaction of microalgae was theoretically elucidated. This study demonstrated that carbon nanotubes are promising catalysts for improvement of bio-oil quality from hydrothermal liquefaction of microalgae, which is beneficial for downstream bio-oil upgrading as transportation fuels in future industrialization of hydrothermal liquefaction. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrated that carbon nanotubes are promising catalysts for improving the quality of bio-oil from hydrothermal liquefaction of microalgae, as they can increase hydrogen content, reduce oxygen, nitrogen, and sulfur content, as well as enhance higher heating value and low-boiling fraction of the bio-oil.