Abstract
Tin-silicalite-1 (MFI) prepared by hydrothermal synthesis has been used as catalyst in the hydroxylation of phenol with aqueous H 2O 2. Isolated Sn 4+ ions which are probably attached to the defect silanols are active in this reaction. At optimum conditions, a H 2O 2 efficiency of 70% and a ortho to para product ratio of 1.6 have been achieved. The solvent used has a strong influence on the activity. The UV-Vis spectral studies indicate that acetone and acetonitrile probably coordinate strongly with Sn 4+ centers preventing the solvolysis of the Si O Sn units and the formation of peroxo intermediate. Methanol probably causes the cleavage of Si O Sn bond to form Si OH and Sn OMe species. Water was found to be an efficient solvent. The formation of EPR active radical ion in presence of H 2O 2 and H 2O and its attenuation in presence of acetone, acetonitrile and methanol support the above conclusion.
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