A Magnetically Recyclable Nanocomposite Catalyst for Olefin Epoxidation

Significance

Molybdenum oxide nanoparticles have been incorporated into a mesoporous silica shell and coated on silica-coated magnetite nanoparticles for use as a magnetically separable heterogeneous epoxidation catalyst. The hematite particles 1 were coated with tetraethoxysilane (TEOS) to give the dense-silica-coated hematite particles 2. The mesoporous silica shell was formed on 2 by a mixture of TEOS and n-octadecyltrimethoxysilane (C18TMS), and the resulting nanocomposite was calcined to give the mesoporous hematite particles 3. Treatment of 3 with ammonium molybdate, followed by reduction with hydrogen, afforded Mag-Mo-Nano catalyst 4. The epoxidation of various cis-olefines with tert-butyl peroxide took place in the presence of 1 mol% of catalyst 4 to give the corresponding epoxides in 76-99% yields (eq. 1). This catalyst was separated from the reaction mixture with an external magnet, and reused six times in the epoxidation of cis-cyclooctene with no significant loss of activity (eq. 2).