Biodiesel Production from Microalgae by Supercritical Methanolysis

G. SOTO; P. HEGEL; C. POPOVICH; C. DAMIANI; S. PEREDA; P. LEONARDI

San Fransisco

Simposio; ISSF 2012 10th International Symposium on Supercritical Fluids; 2012

Mono-alkyl esters derived from vegetable oils or animal fats, i.e. biodiesel, is being used in several countries around the world as an alternative diesel fuel. Most of the current biodiesel production uses vegetable oils (i.e. soybean, rapeseed, sunflower oil) and methanol as raw material with a homogeneous catalyst (NaOH/KOH) in the transesterification process. However, biodiesel from oil crops cannot realistically satisfy the existing demand for transport fuels. Recent studies show that microalgae appear to be a source of renewable biodiesel that would be capable of meeting the global demand for transport fuels. The conventional alkali-catalyzed biodiesel process is very sensitive to the purity ofthe reactants. In order to prevent saponification during the reaction, free fatty acids and water content of the feed must be below 0.5 wt. % and 0.05 wt.%, respectively. Therefore, only pure refined vegetable oil is an appropriate raw material for the alkali-catalyzed transesterification. The non-catalytic supercritical methanol process is an interesting alternativeto produce biodiesel from non-edible low cost oils since the absence of the basic catalyst allows the processing of feedstock with high content of water and free fatty acids.In this work the biodiesel production from wet microalgae with supercritical methanol is studied in a batch stainless steel reactor. The reaction conditions were fixed according to previous works in 30 min., 553 K and 200 bar. A fatty esters content of 90 wt. % in the final refined reaction products was obtained, which correspond to 18 wt. % of esters respect to the initial biomass processed.