Preparation of a magnetic solid acid Fe3O4@PS-SO3H and its use in hydrolysis of cellulose

BACKGROUND

In order to improve the catalytic performance and stability of magnetic solid acid for cellulose hydrolysis in the aqueous phase, this study first modified the surface of magnetite (Fe₃O₄) nanoparticles (NPs) with oleic acid. Then, in an oil-in-water (O/W) emulsion system, polystyrene (PS) was coated on the Fe₃O₄ NPs through emulsion polymerization. Finally, magnetic solid acid Fe₃O₄@PS-SO₃H was prepared by sulfonation.

RESULTS

The obtained Fe₃O₄@PS-SO₃H was characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, infrared, X-ray diffraction, X-ray photoelectron spectroscopy and thermogravimetric analysis, and its acid densityand magnetic properties determined. Applied to cellulose hydrolysis, it exhibited 35.28 emu·g⁻¹ saturation magnetization and 3.56 mmol·g⁻¹ maximum acid density. At 140 °C and 1:1 acid to substrate ratio, cellulose hydrolysis with Fe₃O₄@PS-SO₃H gave a glucose yield of ≤64.14% in 10 h. The solid acid was conveniently recycled with a magnet and reused for further cellulose hydrolysis. It maintained good catalytic activities after five cycles.

CONCLUSION

The magnetic solid acid with a polystyrene backbone prepared by emulsion polymerization exhibits efficient and stable catalytic performance, in line with the trend of green development in ‘bio-refining’, and lays the foundation for the development of composite solid acids. © 2024 Society of Chemical Industry (SCI).