Polyvanadate dominant vanadia-alumina composite aerogels prepared by a non-alkoxide sol-gel method

Vanadia-alumina composite aerogels were synthesized by a cogelation method using alcoholic solutions of metal chlorides under acidic conditions. The resulting aerogels exhibited high surface areas and narrow pore size distributions in the mesoporous region. The vanadium oxides existing on the surface of the aerogels predominantly developed into polyvanadates in terms of chemical structure following the introduction of V species up to 40 wt.% with 500 degrees C calcination. The intensities of the Raman spectra for the polyvanadates increased with vanadia content, while Raman bands shifted towards lower wavenumbers with decreasing vanadia content due to weak V-O bonds. Homogeneity of the surface vanadates on the aerogels was much higher than that on the impregnated materials, as observed in temperature programmed reduction and NH3 temperature programmed desorption patterns.