Highly efficient tungsten trioxide containing mesocellular silica foam catalyst in the O-heterocyclization of cycloocta-1,5-diene with aqueous H2O2 Original Research Article

WO3-containing mesocellular silica foam (MCF) catalysts have been synthesized via an in situ method by using tetraethyl orthosilicate (TEOS) and sodium tungstate as the precursors and via a traditional impregnation method. All catalysts are highly efficient in the O-heterocyclization of cycloocta-1,5-diene (COD) (see Scheme 1 in Section 3.2) to 2,6-dihydroxy-9-oxabicyclo[3.3.1]nonane (1) and 2-hydroxy-9-oxabicyclo[3.3.1]nonane-6-one (2) with a COD conversion up to 100% and (1 + 2) selectivity up to 98%. The WOx species are well dispersed in the W-containing catalysts via the in situ method with the WO3 loading up to 20 wt.%, as proved by XRD, TEM, Raman, and UV–vis DRS. TPR and XRD results show that the WO3–MCF catalysts derived from the in situ method show much stronger interactions between active tungsten oxide species and the MCF support than the WO3/MCF obtained by the traditional impregnation method. The in situ method-derived catalyst also shows far better stability than the impregnation one according to the results from the recycling experiment.