Nb-containing mesoporous materials of MCF type-Acidic and oxidative properties

The new niobium-containing mesoporous catalysts based on MCF structure were prepared by niobium introduction via grafting and co-precipitation. The materials were characterised by N-2 adsorption, XRD, UV-vis, pyridine adsorption followed by FTIR and test reactions. Three various Nb precursors were applied: ammonium oxalate complex, ethoxide and chloride. It is documented by UV-vis that the best isolation of Nb species is reached when NbO(C2O4)(2)(NH4)center dot H2O is applied for grafting and the same sample reveals the highest acidity determined by the test reaction-2-propanol conversion and pyridine adsorption combined with FTIR study. Niobium-containing MCF materials reveal both acidic and oxidative properties. The redox centres are active in the presence of oxygen and lead to very high selectivity in formaldehyde production from methanol. For liquid phase oxidation of cyclohexene with hydrogen peroxide both kinds of centres are active. Oxidative one causes the formation of epoxide, and acidic sites lead to the ring opening and dial production. (C) 2008 Elsevier B.V. All rights reserved.