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Laser Raman Spectra of molybdena supported at different concentration on the surface of y-A12O3 -prepared by both impregnation and physical mixtures- have been recorded. Formation of polymolybdate species, depending on Mo loading and time and temperature of calcination, has been detected in both series of samples.

A study is carried out by FT-IR spectroscopy of the carbonate species formed upon interaction of CO2 with alumina and vanadia-alumina catalysts doped with sodium. It is found that the presence of sodium enhances the ability of the catalyst surface to adsorb CO2, yielding to carbonate formation. The species formed changes in the presence of vanadium, shifting the νCOO stretching bands towards higher wavenumbers than those recorded in Na-Al2O3 systems.