Catalytic liquid phase oxidation of p-xylene using transition metal substituted polyoxometalates

Liquid phase oxidation of p- xylene has been carried out in the presence of potassium salts of monosubstituted heteropoly compounds with tungsten as t he addenda atom and having the general formulae [XW11MLO39](8-n). xH(2)O wh ere X = P and Si, Mn+ = Co2+, Cu2+ and Mn2+ and L = H2O. The reactions are carried out in a halide free environment using air as the oxidant and water as the solvent at a temperature of 180 degreesC. High values of p-xylene c onversion to the order of 70% are obtained using K-6[SiW11Co(H2O)O-39]. 14H (2)O as catalyst The silicotungstate derivatives have been found to be more efficient catalysts than the phosphotungstate analogues for the oxidation of p-xylene. The product obtained is mainly p-toluic and terephthalic acids with minds quantities of p-tolualdehyde and p-methyl benzylalcohol. Influe nce of reaction parameters such as temperature, solvents and catalyst conce ntration on the oxidation reaction and its effect on product distribution h ave been examined.