Biodiesel purification by column chromatography and liquid-liquid extraction using green solvents

Biodiesel purification through acid-catalyzed in situ transesterification of dry biomass of Chlorella pyrenoidosa was evaluated by liquid-liquid extraction and column chromatography, using the solvents hexane, 2-methyltetrahydrofuran (2-MeTHF), and cyclopentyl methyl ether (CPME). The purified biodiesel were characterized through their chemical composition and physicochemical characteristics. The results showed that the purified biodiesel presented a purity level higher than 96.5%, and the purities obtained with CPME were very close to those obtained with hexane. Concerning physicochemical characteristics, biodiesel purified with green solvents showed higher densities and viscosities, but compliant with the European and North American quality standards. The difficulty to evaporate residual water from biodiesel purified with 2-MeTHF after the liquid-liquid extraction process required that biodiesel was left in decantation for 24 h, which resulted in a biodiesel with water content exceeding 0.05%(mass). Biodiesel purified with green solvents, mainly by column chromatography using CPME as eluent, show great potential to replace hexane in the biodiesel purification process, and the price of these solvents is the only factor limiting their large-scale use. (AU)