Synthesis, characterization and catalytic activity of oleic acid-coated TiO2 nanoparticles carrying MoO2 (acac)2 in the oxidation of olefins and sulfides using economical peroxides

Abstract

Titanium oxide nanoparticles were synthesized by a modified polymerized complex derived sol–gel method followed by coating with oleic acid (OA) to modify their surface. The reaction with MoO₂ (acac)₂ yielded the TiO₂–OA–MoO₂ nanocomposite as a supported cis-dioxomolybdenum complex. The structural and morphological characterization of the as-prepared TiO₂ and TiO₂–OA–MoO₂ were carried out by different techniques such as XRD, FT-IR, TGA and TEM. The catalytic activity of the TiO₂–OA–MoO₂ nanocomplex in the epoxidation of olefins and oxidation of sulfides to sulfoxides using H₂O₂ in ethanol as a safe solvent was investigated. The reactions also proceeded efficiently in the presence of tert-butylhydroperoxide (TBHP). Good/high yields and excellent selectivity were obtained. The recovery of the title heterogeneous nanocatalyst was easy and efficient and its catalytic activity was strikingly different from other nanooxometals such as m-ZrO₂, MoO₃, Fe₃O₄ and TiO₂, as well as their nanocomposites such as TiO₂–OA, ZrO₂–OA–MoO₂, MoO₃–OA–MoO₂ and Fe₃O₄–OA–MoO₂.