Mg-Al-Cr2O7 Hydrotalcite-Like Catalysts Synthesized at Different pH Values for Styrene Oxidation

Abstract

Dichromate anions were intercalated between two consecutive hydroxide layers of [Mg_0.6Al_0.4(OH)₂]^0.40+ via co-precipitation at different pH conditions. The physico-chemical properties of the obtained solids were examined by physical methods such as X-ray diffraction (XRD), Infrared (IR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and Energy-Dispersive Spectroscopy (EDS). The experimental results indicated that the amount of dichromate anions in the catalysts varies with the pH media. Also, the morphology, structure and chemical composition of the materials depends strongly on the preparation conditions. The Mg-Al-Cr₂O₇ hydrotalcite-like compounds are used as heterogeneous catalysts for the styrene oxidation with H₂O₂ at mild conditions. The styrene conversion is about 20-50% while styrene selectivity remains rather high.