MoO3@SiO2 nanoreactors: Synthesis with a thermal decomposition strategy and catalysis on alkenes epoxidation

A general thermal decomposition strategy is reported to fabricate MoO 3 @SiO 2 nanoreactors , with a mesoporous silica shell and embedded MoO 3 nanoparticles . The novel preparation procedure involves mixing certain mass ratio of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O (AMM) and hollow mesoporous silica spheres (HMSS) by grinding, fusion and thermal decomposition of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O under calcination and removing the residual via filtration. The as-prepared MoO 3 @SiO 2 nanoreactors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), N 2 adsorption/desorption and X-ray photoelectron spectra (XPS). The nanoreactors were utilized in epoxidation of alkenes and displayed high catalytic activity and stability. The mass ratio of AMM and HMSS greatly affected the properties and catalytic performance of the nanoreactors. The optimal mass ratio of AMM: HMSS has been confirmed as 1/2. After reacting for 12 h with H 2 O 2 (50 wt%) as oxidant, conversion and selectivity of optimal MoO 3 @SiO 2 -400-1/2 almost reached up to 98% and 99%, respectively. Furthermore, the catalyst still had high conversion (78%) and selectivity (95%) at 4 h epoxidation of cyclooctene after recycling for 6 runs. Kinetics study was also carried out and demonstrated the epoxidation of alkenes follows the first order model.