Hydroxylation of phenol with hydrogen peroxide catalyzed by Ti-SBA-12 and Ti-SBA-16

We report here, for the first time, the application of ordered, three-dimensional, mesoporous titanosilicates, Ti-SBA-12 and Ti-SBA-16, as reusable solid catalysts, for hydroxylation of phenol, an industrially important organic transformation. The reactions were conducted using 30% aqueous H2O2 as oxidant. The catalysts of this work are more efficient than the hitherto known mesoporous Ti-silicates. They are more para-product selective than TS-1 and other titanosilicates. Ti-SBA-12 exhibited higher activity and hydroquinone/catechol selectivity (by nearly two times) than Ti-SBA-16. H2O2 efficiency of ∼90 mol% was obtained. Our study reveals that framework substituted Ti with pseudo-tetrahedral geometry, three-dimensional mesoporosity as well as surface structure are the unique features responsible for the high catalytic activity and selectivity of these titanosilicate catalysts.

Phenol hydroxylation activity of ordered, three-dimensional, mesoporous titanosilicates, Ti-SBA-12 and Ti-SBA-16 prepared by direct hydrothermal synthesis is reported, for the first time, using 30% aqueous H2O2 as oxidant.Figure optionsDownload high-quality image (97 K)Download as PowerPoint slideHighlights
► Phenol hydroxylation with H2O2 catalyzed by Ti-SBA-12 and Ti-SBA-16.
► More efficient catalysts than the known mesoporous titanosilicates.
► Very high para-product selectivity and catalyst reusability.
► Framework substituted Ti with pseudo tetrahedral geometry are the active sites.