Porous core–shell Fe3O4@CuSiO3 microsphere as effective catalyst for styrene epoxidation

The porous core–shell Fe3O4@CuSiO3 catalyst were synthesized via a multi-step preparation method including StÖber method and hydrothermal process. The morphological, magnetic and physicochemical studies demonstrated a successful fabrication of the targeted material. This catalyst possessed a spherical morphology with a magnetic core and protective porous shell. The Fe3O4 core not only offered a convenient way for magnetic recycling, but also worked as an electron donor to increase the electron density on the CuSiO3 shell. The catalytic performance of the synthesized material was investigated in the styrene epoxidation with tert-butyl hydroperoxide as oxidant. On account of the synergy effect between Fe3O4 and CuSiO3, the porous core–shell Fe3O4@CuSiO3 catalyst showed styrene conversion significantly higher compared to those of pure Fe3O4, pure CuSiO3 and physically mixed catalyst (Fe3O4 + CuSiO3). In particularly, the catalytic activity of the Fe3O4@CuSiO3 was retained after the recyclability test and re-calcination, which confirmed that the Fe3O4@CuSiO3 catalyst was easily separated, highly stable and could be used six times without significantly affecting its structural order. Moreover, the kinetic study revealed the activation energy of Fe3O4@CuSiO3 in styrene epoxidation was 45.4 kJ/mol. The possible free radical mechanism for the styrene epoxidation based on the Fe3O4@CuSiO3 catalyst was proposed.