Catalytic Behavior of Metal Active Sites From Modified Mesoporous Silicas in Oxidation of Organic Compounds

Abstract

The ordered mesoporous silicas containing transition metals are versatile catalytic materials for oxidation of a wide range of organic compounds. In order to obtain active catalysts, different active redox metal sites have been introduced into specific locations (mesoporous channels and framework) of ordered mesoporous silicas (OMSs). All the reported results evidenced that localization of metal ions, their interaction with another metal (bimetallic catalysts) and the support, with typical properties of the ordered mesoporous silica, influenced the oxidation state, respectively their redox properties. To support this, the results regarding the specific properties of transitional metals in the ordered structure of silica, obtained using various characterization methods, were presented. The activity of metal sites in the oxidation reactions was evidenced in various applications carried out in the liquid or gaseous phase. The oxidation of various organic compounds in liquid phase with H 2 O 2 (especially aromatic compounds and of alcohols) and in gas phase with oxygen from air was presented for a variety of metal-modified OMSs. The active sites and possible reaction mechanisms were presented for some catalytic systems. The immobilization of multiple metal active species on new ordered porous frameworks and their synergistic interactions remain topics of interest in the future.

Design of Silica Nanoparticles-Supported Metal Catalyst by Wet Impregnation with Catalytic Performance for Tuning Carbon Nanotubes Growth

“…According to the formula of Kerkhof and Moulijn [59], this decrease can be a consequence of a higher metal dispersion on the silica support. The decrease in the ratio after reduction at a temperature higher than 600 • C could be initiated by the migration of metal atoms inside the support [60] or the encapsulation of the metal by silica atoms coming from the support [61]. On the other hand, for both Co-and Fe-supported catalysts, the metal content resulted in a slight increase of about 10% after calcination.…”