Catalytic oxidation of thiophenes and thioethers with hydrogen peroxide in the presence of W-containing layered double hydroxides

Abstract

Layered double hydroxides (LDH) with Mg 2+ and Al 3+ cations in the brucite-like layer and W-containing anions in the interlayer have been prepared by direct ion exchange of a MgAl-NO 3 LDH precursor with tungstate anions. The W-containing catalysts have been characterised by elemental chemical analysis, powder X-ray diffraction, Raman and UV-DR spectroscopies, thermogravimetric analysis and nitrogen adsorption. The results indicate the presence of both WO 4 2− and W 7O 24 6− anions in the interlayer gallery. The catalytic oxidation of organic sulfides and thiophene derivatives using hydrogen peroxide as oxidizing agent, in the presence of W-containing layered double hydroxide as catalyst, was investigated using various organic solvents miscible with water. It was found that W-containing LDHs are active catalysts promoting the fast oxidation of sulfur containing organic compounds with 30% H 2O 2 under very mild reaction conditions, but the catalytic activity depends on the nature of the W-containing anions. Other factors, like as the structure of the sulfur-containing organic compounds, the reaction temperature and solvent also influence the catalytic conversion.