Selective production of ethyl levulinate from levulinic acid by lipase-immobilized mesoporous silica nanoflowers composite

Mesoporous silica nanoflowers bearing -NH2 groups were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) with reverse microemulsion method, following with the grafting of -NH2 groups by the post modification with (3-Aminopropyl) trimethoxysilane (APTMS). The lipase from C. antarctica was immobilized on the as-synthesized amino-grafted mesoporous silica nanoflowers to fabricate the lipase-immobilized mesoporous silica nanoflowers composite, which was applied for the catalytic transformation of biomass-derived levulinic acid to biofuel ethyl levulinate (EL), and exhibited excellent catalytic activity. An ethyl levulinate yield as high as 99.5% could be achieved at 40 °C in 8 h reaction time, which was much higher than that catalyzed by the free lipase (67.9%) under the identical conditions. The immobilized lipase showed good stability and recyclability that ethyl levulinate yields above 68% could be remained after seven recycle times. This work represents a novel strategy to construct the immobilized biocatalyst for the production of bio-based chemicals.