Alkene and thioether oxidations with H2O2 over Ti- and V-containing mesoporous mesophase catalysts

Well-organized Ti- and V-containing silicate mesoporous mesophase materials (MMM) were synthesized using C16H33N(CH3)(3)Br and characterized by elemen tal analysis, IR, DRS-UV, XRD, and N-2 adsorption. Catalytic properties of these materials in alkene and thioether oxidations with aqueous H2O2 were e xamined. The structure-activity study was performed for the C16-(Ti,Si)-MMM catalysts with the Si/Ti atomic ratio ranged from 19 to 166. The samples w ith the Si/Ti atomic ratio in the range of 49-124 showed the highest cataly tic activities. Both structure perfection of the silicate matrix and degree of isolation of titanium ions in it appeared to be crucial factors determi ning catalytic activity of C16-(Ti,Si)-MMM in alkene oxidation. For efficie nt oxidation of more nucleophilic substrates (thioethers) the structural pe rfection of the C16-(Ti,Si)-MMM catalysts was less important. No titanium l eaching occurred even in 1.1 M H2O2 solution at 353 K, whereas vanadium lea ching was already pronounced at [H2O2] = 0.05 M and room temperature. The o xidation processes proved to be true heterogeneous for C16-(Ti,Si)-MMM and mostly homogeneous for C16-(V,Si)-MMM. (C) 2001 Elsevier Science B.V. All r ights reserved.