Hydrotalcite like compounds with low Mo-loading active catalysts for selective oxidation of cyclohexene with hydrogen peroxide

Several Mo-containing hydrotalcite-like compounds (HTlcs-Mo) were prepared by different ionic exchange procedures using as parent a synthetic hydrotalcite Mg3Al(OH)8(CO3)0.5·2H2O with a composition similar to the natural occurring mineral. Their physico-chemical properties determined by chemical and TG-DTA analyses, XRD, BET, FTIR, SEM-EDX, DR-UV-vis and Raman spectroscopy, were compared to those of two HTlcs-Mo prepared by direct synthesis at constant pH = 10 and low or respectively high supersaturation. The catalytic activity of these solids towards cyclohexene oxidation with hydrogen peroxide was investigated. The catalytic activity was mainly influenced by the basic properties of the catalysts, which varied depending on the preparation procedure. The best catalysts for hydroperoxidation were found to be those having a low Mo content (about 2.5-2.8%) in the form of MoO42− species, and higher Mg concentration in the brucite layer. The catalysts containing also Mo7O246− species were more active for epoxidation.