Oxidation of Dibenzothiophene by Hydrogen Peroxide Catalyzed by Solid Bases

Abstract The oxidation of dibenzothiophene by hydrogen peroxide was performed at 333 K using hydrotalcite and MgLa mixed oxide as catalysts and nitriles or methanol as solvents. High activity is found only after calcination followed by rehydration of hydrotalcite. The kinetics involves competitive adsorption of the reactants. Of the nitriles, acetonitrile is the best solvent, while much lower reaction rates are observed in methanol. Decomposition of hydrogen peroxide into oxygen is also observed for hydrotalcites and is the major reaction above 353 K. This reaction does not occur in the absence of nitrile and is faster over the MgLa mixed oxide of higher basic strength, in agreement with the decomposition of an iminoperacid intermediate formed by the base-catalyzed addition of hydrogen peroxide to the nitrile. The activity increases with increasing Mg/Al ratio due to a lower rate of H 2 O 2 decomposition attributed to a lower basicity of the solid.