Novel mesoporous composites of gallia nanoparticles and silica as catalysts for the epoxidation of alkenes with hydrogen peroxide

A new class of structured mesoporous materials consisting of gallium oxide nanoparticles embedded and stabilised in a silica matrix was designed, synthesised and tested as catalysts for the epoxidation of various alkenes with aqueous hydrogen peroxide. The structure and texture of the mesoporous gallia-silica composites were elucidated by powder X-ray diffraction, isothermal N sorption and TEM. The most active epoxidation catalysts are the materials containing 80 and 90% of GaO nanoparticles. These materials give much higher epoxide yields compared to the parent nanoparticles, thus demonstrating the positive effect of structuring on the catalytic performance. The synthesis of the mesoporous gallia-silica composite catalysts was optimised by investigating the effect of the calcination conditions. Finally, different methods for recycling the catalysts were studied. Mild calcination at 250 °C for 3 h under controlled N flow was identified as the most suitable treatment to retain the catalytic activity upon reuse.