Catalytic oxidation of m-xylene by ozone in the liquid phase

Abstract

This work reports the selective oxidation of m-xylene by ozone in the liquid phase. It is established that the main direction of the reaction is the destruction of the aromatic system when ozone interacts with m-xylene. It is shown that the selective oxidation of m-xylene by ozone occurs at the temperature of 200С in the system Mn(II)–СН3СООН–Н2SO4 with the yield of 3-toluic acid equal to 75–78%. 3-toluyl alcohol and 3-toluyl aldehyde are formed as intermediate oxidation products. At the deeper stages of the reaction, after complete consumption of m-xylene, the following oxidation products of the second methyl group appear in the system: 3-carboxybenzaldehyde, 3-carboxybenzyl alcohol, and isophthalic acid. It is found that the intermediate products are more resistant to the destructive action of O3 than the original m-xylene. The yield of oxidation products with a preserved aromatic system depends on the nature of the functional group. The kinetics of the main stages of the catalytic oxidation of m-xylene and intermediate reaction products is studied. A mechanism of catalysis is proposed, according to which the role of ozone is to generate an oxidized form of the metal, and selective oxidation occurs when the substrate interacts with Mn(III). An increase in the reaction temperature contributes to an increase in the selectivity of the process. Still, it leads to an increase in the depth of oxidation and, accordingly, the concentration of isophthalic acid.