The oxidation of styrene by chromium–silica heterogeneous catalyst prepared from rice husk

Chromium was incorporated into the silica matrix extracted from rice husk in basic, neutral and acidic medium. The prepared catalysts were labeled as RHCr-10, RHCr-7 and RHCr-3 according to their pH. The specific surface area of RHCr-10, RHCr-7 and RHCr-3 was determined to be 144, 143 and 564 m2 g−1, respectively. The XRD results showed the catalysts to be amorphous. RHCr-3 showed better catalytic activity with 99.92% conversion of styrene. Benzaldehyde was the major product with styrene oxide, phenyl acetaldehyde, acetophenone, 1-phenylethanol, phenylglyoxal, styrene glycol and benzoic acid as by-products. Leaching of chromium was minimal and RHCr-3 could be recycled several times.