Catalysis Database

Redox behavior and selective oxidation properties of mesoporous titano- and zirconosilicate MCM-41 molecular sieves

K., Chaudhari and Rajaram , Bal and D. , Srinivas and A.J. , Chandwadkar and S., Sivasanker (2001) Redox behavior and selective oxidation properties of mesoporous titano- and zirconosilicate MCM-41 molecular sieves. Microporous and Mesoporous Materials , 50 . 209-218.

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Abstract

Mesoporous titano- and zirconosilicate molecular sieves, Ti-MCM-41 and Zr-MCM-41, respectively, with Si/M ratios in the range from 11 to 96 (M ¼ Ti or Zr), have been synthesized by the hydrothermal method and characterized by XRD, XRF, N2 adsorption and diffusive reflectance UV–Vis (DRUV–Vis), FT-IR and electron spin resonance (ESR) spectroscopic techniques. The redox behavior and selective oxidation properties of these materials have been investigated. ESR of samples reduced with LiAlH4 (298 K) and H2 (673–873 K) reveals two types of metal ion species: species I0 located inside the pore walls and species I00 located at the pore surface. The reduced species I00 are highly reactive towards oxygen and form M(O 2 ) radicals. The M(O 2 ) radicals were also observed when the samples were reacted with aqueous H2O2 or tert-butylhydroperoxide (TBHP). ESR studies reveal that Ti-MCM-41 is easier to reduce and reoxidize than Zr-MCM-41. The DRUV–Vis spectra are consistent with a monoatomic dispersion of the metal ions. In the samples with high metal loading the presence of a nanocrystalline metal oxide phase cannot be ruled out. Both Ti-MCM-41 and Zr-MCM-41 catalyze the hydroxylation of 1-naphthol with aqueous H2O2 and the epoxidation of norbornylene with TBHP.

Item Type:Article
Subjects:Science > Chemistry
ID Code:135
Deposited By:INVALID USER
Deposited On:28 Feb 2007 13:33
Last Modified:18 Mar 2007 18:33

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