Influence of Surface Modification of Ti−SBA15 Catalysts on the Epoxidation Mechanism for Cyclohexene with Aqueous Hydrogen Peroxide

Citations Over TimeTop 10% of 2005 papers

Abstract

The thermolytic molecular precursor method was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA15 support. The resulting surface Si-OH/Ti-OH sites of the Ti-SBA15 catalysts were modified with a series of (N,N-dimethylamino)trialkylsilanes, Me(2)N-SiMe(2)(R) (where R = Me, (n)Bu, or (n)Oc). Compared with the unmodified catalysts, the surface-modified catalysts are more active in the oxidation of cyclohexene with H(2)O(2) and exhibit a significantly higher selectivity (up to 58%) for cyclohexene oxide formation (vs allylic oxidation products). In situ Fourier transform infrared (FTIR) and diffuse reflectance UV visible (DRUV-vis) spectroscopies were used to probe this phenomenon, and it was determined that active sites with capped titanol centers, (SiO(surface))(3)Ti(OSiR(3)), likely undergo Ti-OOH formation upon addition of H(2)O(2) in a manner analogous to that for active sites of the type (SiO(surface))(3)TiOH. On the basis of the observation of similar Ti-OOH intermediates for both species, the electron-withdrawing effects on the Ti(IV) active site, resulting from the surface modification, are likely responsible for the observed increase in selectivity.

Related Papers

• → Synthesis of (−)-hinokinin by oxidation of (−)-cubebin catalyzed by biomimetic metalloporphyrin catalytic systems(2008)11 cited
• Study on Operation Conditions for Liquid Phase Selective Hydrogenation of Benzene to Cyclohexene over Ru-M-B/ZrO_2 Catalyst(2002)
• → Selective dimerization of cyclohexene over a Re2O7-B2O3/Al2O3 catalyst under mild conditions(2021)1 cited
• Selective Hydrogenation of Benzene to Cyclohexene by a Novel Ru-Zn Catalyst(2006)
• THE PROPERTIES OF TITANIUM SILICALITE CATALYST WITH DIFFERENT TS-1 CONTENTS(2004)