Development of Carbon-Based Solid Acid Catalysts Using a Lipid-Extracted Alga, Dunaliella tertiolecta, for Esterification

Novel carbon-based solid acid catalysts were synthesized through a sustainable route from lipid-extracted microalgal residue of Dunaliella tertiolecta, for biodiesel production. Two carbon-based solid acid catalysts were prepared by surface modification of bio-char with sulfuric acid (H2SO4) and sulfuryl chloride (SO2Cl2), respectively. The treated catalysts were characterized and their catalytic activities were evaluated by esterification of oleic acid. The esterification catalytic activity of the SO2Cl2-treated bio-char was higher (11.5 mmol Prod..h(-1).g Cat.(-1)) than that of commercial catalyst silica-supported Nafion SAC-13 (2.3 mmol Prod..h(-1) center dot g Cat.(-1)) and H2SO4-treated bio-char (5.7 mmol Prod..h(-1).g Cat.(-1)). Reusability of the catalysts was examined. The catalytic activity of the SO2Cl2-modified catalyst was sustained from the second run after the initial activity dropped after the first run and kept the same activity until the fifth run. It was higher than that of first-used Nafion. These experimental results demonstrate that catalysts from lipid-extracted algae have great potential for the economic and environmentfriendly production of biodiesel.