Magnetic SBA-15 functionalized with superacid: a trifunctional catalyst for selective Glyceride production

Abstract

SBA-15 with the presence of superparamagnetic nanoparticles (Fe₃O₄) was successfully synthesized through co-precipitation method as magnetic SBA-15 (mSBA-15). Via post synthesis method, 12-tungstophosphoric acid, HPW (20 wt%) was impregnated into the mSBA-15 and was used as a catalyst for the selective esterification of glycerol and lauric acid to produce monoglyceride and diglyceride. The synthesized materials were characterized using Fourier-transformed infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The interaction between SBA-15 and iron oxide (Fe₃O₄) was elucidated and it was deduced as the electrostatic interaction to form mSBA-15. On the other hand, the interaction between the mSBA-15 and HPW was understood as the hydrogen bonding between the silanol groups and electron rich Keggin HPW anions. The highest lauric acid conversion (81.16%) with the monoglyceride selectivity (36.07 %) and diglyceride selectivity (35.96 %) were shown at 150 ℃ in 6 hours from the catalyzed reaction over magnetic catalyst with 3 wt% and molar ratio with 4:1. In order to prevent the formation of unwanted by-product (triglyceride), the selectivity esterification to form monoglyceride and diglyceride was clearly demonstrated via the used of the synthesized catalyst, HPW/mSBA-15. The effects of the catalyst weightage (1 - 5 wt.%), the reaction temperature (110 - 150 ℃) and the reactant ratio (2:1 - 6:1) were systematically interpreted. The magnetic catalyst was found to be completely extracted by a magnet after the reaction was completed, illustrating the extractability of the synthesized catalyst.