Aerobic oxidation of cyclohexane with γ-alumina supported metallophthalocyanines in the gas phase Original Research Article

Unsubstituted phthalocyanines of Co, Fe and Mn supported on γ-alumina were synthesized and characterized with UV–vis and IR spectroscopic techniques. Catalytic activities of the supported phthalocyanines for oxidation of cyclohexane to cyclohexanol and cyclohexanone by air were studied in the gas phase in the absence of solvents and reducing agents. These metallophthalocyanines (MPc) supported on γ-alumina were effective catalysts in a temperature range of 300–400 °C at 1 atm of air. Under these reaction conditions, the order of catalytic activities is as follows: CoPc/γ-alumina > FePc/γ-alumina > MnPc/γ-alumina. When the reaction was catalyzed with γ-alumina without any phthalocyanines, the reaction yield and conversion were reduced considerably compared to those of supported γ-alumina. With 10% CoPc supported on γ-alumina and under our experimental conditions, the conversion percent of cyclohexane is 32.6% with 37.3% selectivity of cyclohexanol + cyclohexanone and 17.4% cyclohexene at 340 °C. To achieve higher conversion of cyclohexane and better selectivity toward cyclohexanone + cyclohexanol, factors such as type and percentage of the metallophthalocyanine, reaction temperature and space velocity were studied, and optimized conditions were investigated.