Selective liquid phase oxidation of toluene with air

Catalysis of simple cobalt tetraphenylporphyrin for selective liquid phase oxidation of toluene with air is first reported. By the catalysis of simple cobalt tetraphenylporphyrin, the selective oxidation of toluene with air in the absence of any solvents or promoters will produce benzaldehyde and benzyl alcohol. Compared with the present synthetic method of benzaldehyde and benzyl alcohol by the chlorination of toluene followed by hydrolysis, which has been used in the world industry, the new method has the advantage of friendly environmental effects. The researchers found that the reaction time, temperature, air pressure, the amount of catalyst and the flow rates of air influenced the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol. By the use of 3.2 × 10−5 M cobalt tetraphenylporphyrin as catalyst, toluene oxidation with air under the optimum conditions of 160 °C and 0.8 MPa and 0.04 m3/h airflow produced benzaldehyde and benzyl alcohol at 60% selectivity and 8.9% conversion of toluene. The mole turnover numbers of the catalyst was about 25,000. A possible mechanism is also suggested.