Application of Co-Mn-Al sheet-like metal oxide catalysts in the liquid phase conversion of toluene to benzaldehyde

The main problems of liquid-phase oxidation of methylarenes to benzaldehydes are that the catalytic reaction rate is slow, benzaldehydes are easily over-oxidized to form benzoic acids, and a large amount of solvent is required. These problems make it difficult to realize the liquid phase catalytic oxidation of methylarenes to benzaldehydes in industrial production. Here, we report the catalytic oxidation of toluene to form benzaldehyde, by using N-hydroxyphthalimide (NHPI) as the radical catalyst, sheet-like Co-Mn-Al oxides (CMA-n) as the redox catalyst, and 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) as the solvent. CMA-n/NHPI was found to be highly active in catalyzing the oxidation of toluene to benzaldehyde. The use of HFIP as the solvent prevents the over-oxidation of benzaldehyde to benzoic acid. In addition, the reaction proceeded at a high concentration of toluene. The conversion rate of toluene reached 5826 μmol g−1 h−1, and the generation rate of benzaldehyde reached 4049 μmol g−1 h−1.