Physiochemical properties of transition metal-grafted MCM-48 prepared using matallocene precursors

A series of redox mesopore molecular sieves Ti-, V-, Zr- and Mo-MCM-48 were prepared by grafting the respective metallocene onto the MCM-48 host. XRD, TEM, and BET analysis of the transition metal substituted MCM-48 indicated that high crystallinity and pore structure were maintained after grafting. Grafting of the transition metal species to MCM-48 structure was confirmed by IR and UV-vis spectroscopy. The metallocene grafted MCM-48 samples were active for liquid phase oxidation of the bulky 2,6-di-tert-butyl phenol (2 ,6-DTBP) with aqueous H2O2. For a given metallocene concentration in grafti ng solutions, Mo was the least grafted element to MCM-48 surface, but its c atalytic activity was superior either to Ti- or Zr-grafted MCM-48. V-MCM-48 showed the highest catalytic activity. Chemical analysis of the mother Liq uor after reaction, however, showed substantial leaching for Mo and V. Ti a nd Zr also suffered mild leaching. Further silylation treatment to Ti- and V-MCM-48 could not prevent leaching. Activity for 2,6 DTBP oxidation deteri orated significantly upon silylation for Ti-MCM-48. (C) 2000 Elsevier Scien ce B.V. All rights reserved.