Synthesis, Characterization, and Catalytic Properties of Ti, V, and Zr-HMS Prepared by Metallocene Grafting

Ti, V, and Zr-HMS molecular sieves were prepared by grafting the respective metallocene onto the pure silica HMS, XRD, N₂-physisorption, TEM, UV-Vis spectroscopy and elemental analysis were performed to characterize the samples prepared. The XRD patterns of the metal-grafted samples exhibited well-defined (100) reflections, and the intensity remained almost constant as with pure silica HMS. Surface area, hysteresis loop in N₂ adsorption isotherms and N₂ volume adsorbed decreased after metal grafting. The order of catalytic activity for 2,6-di-tert-butylphenol (2,6-DTBP) oxidation using H₂O₂ was V-HMS (91.5 % conversion) Ti-HMS(20.3 %) Zr-HMS(8.4 %). Metal leaching was detected for all the grafted samples in the reaction media; V-HMS(22 wt.%) Zr-HMS(3 wt.%) > Ti-HMS(2 wt.%). For V-HMS and Zr-HMS, further reaction after catalyst filtration indicated significant contribution to the reaction by the dissolved species.