Co-production and upgrading of multiple products from hydrothermal carbonization of microalgae with organic solvent
Bin Zhang1, Jingmiao Zhang1, Ao Xia1
1Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing 400044, China; Institute of Engineering Thermophysics, School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China.
Abstract:
Hydrothermal carbonization facilitates microalgae utilization but suffers from low product quality, with no effective solutions. This study investigated the product characteristics and quality enhancement methods of hydrochar, bio-oil, and carbon dots prepared through hydrothermal carbonization of microalgae assisted by non-polar organic solvents (petroleum ether and n-hexane) and polar organic solvents (ethyl acetate, isopropanol, and ethanol). The results showed that non-polar organic solvents were more effective than polar organic solvents in extracting fatty acids hydrolyzed from lipids into the organic phase, reducing amidation with amino acids and lowering bio-oil nitrogen content by 47.0%, with n-hexane exhibiting the best effect. They also promoted Maillard reactions, increasing hydrochar and carbon dots yields by 41.2% and 63.3% while boosting nitrogen content by 48.9% and 15.7%, respectively. This study explored the co-production and upgrading of multiple products in microalgae hydrothermal carbonization with organic solvent assistance, offering insights into process optimization for efficient utilization of microalgae.
