Titanium-Doped Solid Core-Mesoporous Shell Silica Particles: Synthesis and Catalytic Properties in Selective Oxidation Reactions
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Near monodisperse spherical particles composed of a nonporous silica core covered by a Ti-doped hexagonally arranged mesoporous silica shell, Ti-SCMS, as well as spherical submicron-size particles of Ti-MCM-41, have been synthesized for the first time and characterized by elemental analysis, N2 adsorption, XRD, TEM and DR-UV spectroscopy. The mesoporous Ti,Si-shell has a thickness of about 45 nm and incorporates isolated Ti centers in tetrahedral coordination. Catalytic properties of Ti-SCMS and Ti-MCM-41 have been studied in selective oxidation of three representative bulky organic substrates, 2,3,6-trimethylphenol, methyl phenyl sulfide and caryophyllene, with aqueous H2O2 in MeCN medium. Ti-SCMS appeared to be more active and selective in the H2O2-based selective oxidation reactions compared to Ti-MCM-41, thus demonstrating an advantage of conducting a catalytic process in a thin mesoporous Ti,Si-shell.
KeywordsCore-shell structure Monodisperse silica particles Site-isolated Ti centers Selective oxidation H2O2
The work was partially supported by the Russian Foundation for Basic Research (grants 06-03-08102 and 05-03-34760).
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