Hard'' vs. Soft'' Templating Synthesis of Mesoporous Nb2O5 Catalysts for Oxidation Reactions

Nanoporous niobia with crystalline walls has been formed within the mesopores and on the outer surface of SBA-15 and FDU-1 by impregnation with niobium salts followed by calcination and silica template removal. The influence of niobium source and silica templates on the physicochemical properties of niobia particles was evaluated by powder X-ray diffraction, nitrogen adsorption, scanning electron microscopy, temperature-programmed reduction and thermogravimetry. The resulting nanoniobia was tested in the liquid phase oxidation of cyclohexene with hydrogen peroxide and appeared to be catalytically active contrary to amorphous niobia.