Effect of texture and structure on the catalytic activity of mesoporous niobosilicates for the oxidation of cyclohexene

Abstract

Two different kinds of niobosilicate mesoporous molecular sieves (Nb-MMS) materials have been synthesized. Both substituted derivatives of the silica-based mesoporous molecular sieves (NbMCM-41 and NbSBA-15) were prepared with the hexagonal structure and one-dimensional mesopores. It is possible to optimize the activity of Nb-MMS catalysts in the epoxidation of cyclohexene by adjusting the isolation of niobium species. NbSBA-15 material prepared from niobium(V) chloride and NbMCM-41 from niobium(V) oxalate show up to five times greater activity as compared to other Nb-MMS catalysts studied in this work and prepared by different methods. This high activity is accompanied by an isolation of niobium centers as evidenced by FTIR spectroscopy combined with NO adsorption.