Oxidation of cyclohexylamine over modified alumina by molecular oxygen

The oxidation of cyclohexylamine over high surface alumina was studied. To characterize the prepared product, BET surface, NH3-TPD and FT-IR spectra, were used. By using different amines during hydrolysis of aluminium alcoholate one can modify the specific surface area, pore volume, pore size distribution, powder density and the acidity of the formed alumina. The changed structure of alumina significantly influences its activity and selectivity in the oxidation of cyclohexylamine. The maximum of conversion can be increased from 15% up to 35% and the selectivity to cyclohexanone oxime from 40% up to 60% by using amine during alumina preparation. Impregnation of the prepared alumina by silicotungstic heteropolyacid enhances the selectivity of oxime formation up to 70%. The main product of the reaction in the inert atmosphere is N-cyclohexylidene–cyclohexylamine at conversions of cyclohexylamine below 1%.

The oxidation of cyclohexylamine over alumina with high surface and modified pore size distribution was studied. The catalysts prepared by sol–gel method allowed higher conversion of cyclohexylamine and selectivity of cyclohexanone oxime formation compared to the commercial alumina under atmospheric pressure. Further increase of selectivity was achieved by impregnation of alumina by silicotungstic acid.Figure optionsDownload as PowerPoint slide