Extraction of microalgae oil and further production for second-generation biodiesel

To efficiently convert the microalgae to valuable and renewable fuels, the microalgae oil was first extracted and then transformed into the second-generation biodiesel. Among all solvents that were used for the microalgae oil extraction, the polar single solvent system methanol achieved the optimal value (47.8% extraction yield) because the polar cell membrane was easily dissolved by the polar solvent. Hexadecanoic acid (38.54%) and docosanoic acid (54.39%) dominated in fatty acid of microalgae oil. In the catalytic deoxygenation of microalgae oil, the Co-Al nanosheet displayed a higher performance than Co/Al₂O₃ because of its high Co content and lamellar structure, exposing massive Co sites with high dispersion and small particle size. Moreover, when the reaction temperature was raised to 240 °C, the 100% conversion and 100% alkane yield were obtained, and the further temperature rise in temperature led to the cracking reaction.