The use of niobium containing mesoporous molecular sieves in the liquid phase oxidation

Activity and selectivity of Nb containing MCM-41 materials in the liquid phase oxidation of methyl-phenyl sulphide (MeSPh) and hydroxylation of phenol with H2O2 are shown in this paper. Various reaction pathways depending on the nature of substrates and solvents are considered. The activity of NbMCM-41 samples is compared with that of VMCM-41 and bimetallic NbVMCM-41 materials. Vanadium, in the solid and in the liquid after leaching, is not active in the oxidation of MeSPh. The effect of solvents, reaction temperature, and a nature of the catalyst on the decomposition of H2O2 have been considered. Too fast H2O2 decomposition in water at 353 K is disadvantageous in the phenol hydroxylation on both NbMCM-41 and NbVMCM-41. MeSPh adsorption on Nb containing materials protects niobium leaching with H2O2 to methanol. The activity of NbMCM-41 in MeSPh oxidation can be correlated, to some extent, with the presence of defects, and that of NbVMCM-41 - with the formation of defects resulted from vanadium leaching.