Covalent Immobilization of Heteropoly Acid in Magnetic Yolk-Shell Nanostructured Materials and its Catalytic Properties for the Preparation of Glycerol Monolaurate

Abstract

The yolk-shell structured Fe3O4@void@PMO-NH2-STA catalyst was successfully synthesized by connecting silicotungstic acid (STA; H4SiW12O40) with amino groups on the surface of periodic mesoporous organosilica (PMO). The catalyst was characterized by FT-IR, XRD, TG-DTG, SEM, TEM, XPS, VSM and nitrogen adsorption desorption. The characterization results showed that the large specific surface area of yolk-shell nanomaterial is conducive to a more uniform dispersion of silicotungstic acid on the carrier. The Fe3O4@void@PMO-NH2-STA catalyst showed a good catalytic activity during esterification of glycerol monolaurate (GML). Under the optimal conditions, the maximum GML yield achieved 83.8%, which was optimized by the response surface methodology based on a Box-Behnken design (BBD). Further studies confirmed that the Fe3O4@void@PMO-NH2-STA catalyst could be easily separated by external magnets and recycled several times. As a result of the covalent combination between silicotungstic acid and carrier, the catalyst has potential green and efficient industrial application prospects for the synthesis of GML.

Keywords: Yolk-shell, Silicotungstic acid, Covalent immobilization, Glycerol monolaurate, Response surface methodology