Transesterification of a vegetal oil with methanol catalyzed by a silica fibre reinforced aerogel encapsulated lipase
Résumé
A commercial lipase solution from Candida antartica, Lipozyme1, was encapsulated in silica aerogels reinforced with silica quartz fibre felt. This biocatalyst was applied in biodiesel synthesis by direct transesterification of sunflower seed oil with methanol, without any other solvent. With a molar ratio of methanol to oil of 1, the encapsulated enzyme achieved ~90% methanol conversion after 50 h at 40°C. The recycling activity increased by ~40% after the first test, then it slowly decreased in further tests to reach an activity still 20% higher than initially, during the fifth test. Textural and structural analysis of the aerogels before and after catalytic tests showed that this improvement was associated with a modification of the liquid medium inside the aerogel, by preferential adsorption of glycerol. The aerogel samples were also compared to a commercial CALB product immobilized on polymer beads with a different enzyme loading, from Fluka. This product showed a better activity during the first test but its activity decreased by 20% during a second test.