Microalgae liquefaction in ethanol to produce high-quality fuels: Effect of magnetic nanoparticles on nitrogen transformation

As the representative of the 3rd generation feedstock of biodiesel, microalgae show extraordinary advantages for energy demands. Magnetic separation is a proven and effective method for microalgae harvesting. This study aims to investigate the effect of unrecovered magnetite-based nanoparticles (Fe3O4 NPs) after microalgae har-vesting on the bio-oil quality, especially nitrogen content in the subsequent production. Co-liquefaction of Chlorella Vulgaris mixed with three residual amounts (1 wt%, 5 wt%, and 10 wt% of microalgae addition) Fe3O4 NPs in ethanol at 220 and 260 degrees C were performed. Ethanol can provide hydrogen in situ during liquefaction, and the catalytic activity of Fe3O4 to hydrogenation reaction enhances the yield and quality of bio-oil. At 260 degrees C and 5 wt% NPs dosage, the bio-oil yield can reach up to 79.71%. The addition of NPs reduces the relative N content of bio-oil by more than 16.90%. GC/MS analysis shows that the nitrogen heterocyclic compounds are significantly reduced about 60%; instead, hydrocarbons are increased in the bio-oil. It implies that Fe3O4 NPs are beneficial to the denitrogenation of bio-oil during microalgae liquefaction in ethanol.