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p-Nitrobenzoic acid could be efficiently prepared from aerobic oxidation ofp-nitrotoluene using manganese dioxide (MnO2) andN-hydroxyphthalimide (NHPI) as catalysts. The conditions of oxidation were also optimaized: 97 % conversion ofp-nitrotoluene and 89 % isolated yield ofp-nitrobenzoic acid could be obtained at 110 °C under 0.4 MPa for 4 h in presence of 10 mol% NHPI and 10 mol% MnO2.

Manganese oxides, which are easily prepared, simple to use and capable of being recycled, have been employed as catalyst in the selective oxidation of toluene to benzoic acid for the first time. Molecular oxygen was used as oxidant under additive- and solvent-free conditions. As a result, 39% conversion of toluene and 93% selectivity of benzoic acid were achieved.

A high-yield synthesis of p-hydroxybenzaldehyde from p-cresol and molecular oxygen was achieved over a CuMn-oxide supported carbon catalyst. The reaction parameters such as pressure, stirring speed, reaction temperature, solvent, and the amount of sodium hydroxide in the reaction media were optimized. As a result, a high conversion of p-cresol (99%) and a high selectivity to p-hydroxybenzaldehyde (96%) were realized at the same time. Catalyst separation and recycling tests clearly showed that the reaction proceeded on the heterogeneous catalyst but not on dissolved species.

Copper and manganese were found to be two concordant partners in the synthesis of p-hydroxybenzaldehyde from p-cresol; under mild conditions, this research realised 95.6% selectivity for p-hydroxybenzaldehyde at 98.5% conversion of p-cresol.