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Pyrolysis of High-Ash Natural Microalgae from Water Blooms: Effects of Acid Pretreatment

Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, 29 Wangjiang Road, Chengdu 610064, China
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Toxins 2021, 13(8), 542; https://doi.org/10.3390/toxins13080542
Received: 19 June 2021 / Revised: 26 July 2021 / Accepted: 27 July 2021 / Published: 3 August 2021
(This article belongs to the Section Marine and Freshwater Toxins)
Natural microalgae (NA, cyanobacteria) collected from Taihu Lake (Jiangsu, China) were used for biofuel production through pyrolysis. The microalgae were de-ashed via pretreatment with deionized water and hydrochloric acid, and the samples obtained were noted as 0 M, 0.1 M, 1 M, 2 M, 4 M, 6 M, 8 M, respectively, according to the concentration of hydrochloric acid used in the pretreatment. Pyrolysis experiments were carried out at 500 °C for 2 h. The products were examined by various techniques to identify the influence of the ash on the pyrolysis behavior. The results showed that the ash inhibited the thermal transformation of microalgae. The 2 mol/L hydrochloric acid performed the best in removing ash and the liquid yield increased from 34.4% (NA) to 40.5% (2 M). Metal-oxides (mainly CaO, MgO, Al2O3) in ash promoted the reaction of hexadecanoic acid and NH3 to produce more hexadecanamide, which was further dehydrated to hexadecanenitrile. After acid pretreatment, significant improvement in the selectivity of hexadecanoic acid was observed, ranging from 22.4% (NA) to 58.8% (4 M). The hydrocarbon compounds in the liquid product increased from 12.90% (NA) to 26.67% (2 M). Furthermore, the acid pretreatment enhanced the content of C9–C16 compounds and the HHV values of bio-oil. For natural microalgae, the de-ashing pretreatment before pyrolysis was essential for improving the biocrude yield and quality, as well as the biomass conversion efficiency. View Full-Text
Keywords: microalgae; pretreatment; pyrolysis; de-ashing; bio-oil microalgae; pretreatment; pyrolysis; de-ashing; bio-oil
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MDPI and ACS Style

Liu, L.; Liu, Y.; Wang, W.; Wang, Y.; Li, G.; Hu, C. Pyrolysis of High-Ash Natural Microalgae from Water Blooms: Effects of Acid Pretreatment. Toxins 2021, 13, 542. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13080542

AMA Style

Liu L, Liu Y, Wang W, Wang Y, Li G, Hu C. Pyrolysis of High-Ash Natural Microalgae from Water Blooms: Effects of Acid Pretreatment. Toxins. 2021; 13(8):542. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13080542

Chicago/Turabian Style

Liu, Longfei, Yichen Liu, Wenli Wang, Yue Wang, Guiying Li, and Changwei Hu. 2021. "Pyrolysis of High-Ash Natural Microalgae from Water Blooms: Effects of Acid Pretreatment" Toxins 13, no. 8: 542. https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13080542

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