Production of medium-chain structured lipids using dual acidic ionic liquids supported on Fe3O4@SiO2 composites as magnetically recyclable catalysts

The purpose of this work is to develop robust and stable catalysts for production of low-calorie lipids in a heterogeneous manner to meet the demand of green food engineering. To accomplish this, magnetic Fe3O4@SiO2 support was prepared, and then dual acidic ionic liquid, 1-(propyl-3-sulfonate)imidazolium hydrogen sulfate, was bound onto the magnetic support via covalent attachments to prepare solid acid catalysts. The so-prepared solid catalyst was characterized by Brönsted acidity determination, elemental analysis, XRD, FT-IR, TEM, VSM, and N2 adsorption-desorption techniques. Results showed that the ionic liquid was successfully immobilized on the Fe3O4@SiO2 support, and the structure of magnetic support remained unchangeable after the functionalization. This solid catalyst displayed a strong magnetic responsiveness, allowing it to be easily separated by an external magnet. By using this magnetic catalyst, soybean oil was acidolyzed with caprylic and capric acids to produce medium-chain structured lipids. The medium-chain fatty acids incorporated into triacylglycerols were determined by GC techniques, and the total incorporations of caprylic and capric acids were found to be 42.5% over the catalyst. Moreover, the solid catalyst could be reused efficiently for several cycles without appreciable loss of its activity.