Production of high-quality biofuel via ethanol liquefaction of pretreated natural microalgae. (March 2020)

• Record Type: Journal Article
• Authors: Zhou, Yingdong; Chen, Yaguang; Li, Mingyu; Hu, Changwei
• Is Part Of: Renewable energy. Volume 147(2020)Part 1
• Page Start: 293
• Page End: 301
• Publication Date: 2020-03
• Subjects: Pretreatment -- Natural microalgae -- Ethanol liquefaction -- High-quality biocrude -- Catalyst-free conversion; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2019.08.136
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: The conversion of algal lipids to fatty acid alkyl esters is a promising way for the production of high-grade biofuel, due to the lower oxygen content of lipids than that of saccharides and proteins. Herein, a catalyst-free conversion process of natural microalgae cyanobacteria was developed for biodiesel production. The conversion involved two steps: (1) pretreatment of raw microalgae by Soxhlet extraction of lipids or hydrothermal treatment for extraction of saccharides and part of proteins at 200 °C; (2) liquefaction of raw and pretreated samples in sub/supercritical ethanol. In the first step, a maximum lipid yield of 6.5 wt% was extracted by Soxhlet extraction, while the hydrothermal treatment dissolved saccharides and a part of proteins. The composition of biocrude obtained from raw algae was complex, containing hydrocarbons, N-containing compounds, esters, fatty acids and other oxy-compounds. The biocrude from lipid extracted algae had a poor quality, from which the degradation of proteins was facilitated. Better yet, the extraction of saccharides and part of proteins by hydrothermal pretreatment simplified the composition (mainly fatty acid ethyl esters), reduced the nitrogen content (<4%) and improved the higher heating value (∼41 MJ kg −1 ) for biocrude. Graphical abstract: Liquefaction of algae pretreated by Soxhlet extraction produced biocrude with more nitrogen containing compounds, while the biocrude with a high quality was obtained from algae pretreated via hydrothermal treatment. Image 1 Highlights: Hydrothermal treatment of algae separated saccharides and part of proteins. Extraction of lipids facilitated the conversion of proteins. The overall conversion of algae was promoted by pretreatment. The biocrude obtained from SPEA had HHV about 41 MJ kg −1 . Hydrothermal treatment simplified the composition of biocrude.