Characterization and catalytic evaluation of mesoporous and microporous molecular sieves containing niobium

The synthesis and characterization of the novel microporous aluminophosphate NbAPO-5 is described. The novel material has been studied by X-ray powder diffraction, SEM, TG/DTA-MS, electron spin resonance, and ultraviolet-visible (UV-Vis) spectroscopy The catalytic properties have been tested in the epoxidation of 1-hexene and cyclohexene, respectively, in comparison with niobium-containing silicalite-1 and NbMCM-41. The results of the physical characterization indicate that it is possible to prepare niobium-containing aluminophosphates, where isolated Nb(V) species are connected to framework defect sites via formation of Nb-O-P or Nb-O-Al bonds. The results of this study allow the preparation of microporous and mesoporous niobium-containing molecular sieves which are active catalysts in oxidation reactions. (C) 2002 Elsevier Science B.V. All rights reserved.