Extraction, characterization, purification and catalytic upgrading of algae lipids to fuel-like hydrocarbons

Abstract

The extraction, characterization, purification and upgrading of algal lipids was examined, utilizing Scenedesmus acutus microalgae grown with flue gas from a coal-fired power plant. Lipid extraction was achieved using a procedure based on the Bligh-Dyer method, modified so as to utilize a significantly decreased solvent:biomass ratio than the original protocol. Both activated carbon and K10 montmorillonite were found to function as efficient adsorbents for the removal of chlorophyll, phospholipids and sterols from the crude algae oil. The yield of purified lipids using this approach was similar to that obtained by in situ transesterification of the lipids in Scenedesmus acutus, confirming that adsorption is an effective method for the removal of nonesterifiable lipids. During the deoxygenation of the purified algae oil at 260 °C over a Ni-Al layered double hydroxide catalyst, deactivation of the catalyst was observed, attributed to the presence of highly unsaturated lipid chains which can act as poisons by adsorbing strongly to the catalyst surface and/or acting as precursors to coke formation. However, upgrading at 300 °C gave better results, the liquid product consisting of ~99 wt% hydrocarbons, diesel-like (C10-C20) hydrocarbons constituting 76 wt% of the liquid after 4 h on stream.

Microalgae as a potential source for biodiesel production: techniques, methods, and other challenges

“…Microalgae are autotrophic microorganisms with a high photosynthetic efficiency; they are important source of lipids, hydrocarbons, and other complex oils for biodiesel ; besides, they can produce other valuable fuels like bioethanol, biomethane, and biohydrogen .…”

Direct hydrodeoxygenation of algal lipids extracted from Chlorella alga

“…With these methods, it was possible to remove most of the chlorophylls. In addition, phospholipids and sterols were also totally removed, but the amounts of ash, sulphur and nitrogen were only partially decreased and the main feed components after montmorillonite adsorption were fatty acids, about 40%, with only 8% glycerides . In the current work, fatty acids, in addition to sulphur and nitrogen impurities, adsorbed strongly on the catalyst surface and retarded the HDO activity.…”

“…In the current case, the algal oil, which also contains triglycerides, was not easy to purify with this clay because of its different structure from that of FAME. In very recent work, crude algal oil has been purified using acidic K10 montmorillonite clay or alternatively active charcoal . With these methods, it was possible to remove most of the chlorophylls.…”

“…Comparison between these catalysts is not, however, straightforward, as the reactions were performed at different temperature and residence times. Extraction, characterization, purification and upgrading of Scenedesmus acutus has been demonstrated in a recent paper . The work investigated HDO of purified algal oil with a Ni–Al layered double hydroxide catalyst at 260 °C and 40 bar hydrogen in a continuous tubular reactor.…”

Experimental validation of hindered settling models and flux theory applied in continuous flow process for harvesting Acutodesmus obliquus

“…Microalgae are autotrophic microorganisms that can synthesize their own nutrients with high photosynthetic efficiency. They are an important source of lipids, hydrocarbons, and other oils, aimed at biofuel production . In addition, microalgae can grow using nutrients, carbon dioxide, and photosynthetic agent .…”