Dispersion of molybdena on the surface of titania: the effect of potassium
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Molybdena/titania systems doped with potassium have been prepared by impregnation of the support with aqueous solutions of ammonium heptamolybdate and studied to assess the effect of the alkaline cation on their surface and structural properties. Simultaneous or consecutive (first potassium, then molybdenum) methods have been tested. Characterization has been carried out by X-ray diffraction, Fourier-transformed infrared and visible-ultraviolet (diffuse reflectance) spectroscopies and nitrogen adsorption at low temperature. It was concluded that both the relative amounts of Mo and K, and the method of preparation, determine the nature and dispersion of the species formed upon calcination at 773 K. Simultaneous incorporation of both cations favours formation of potassium polymolybdates, and if the amount of molybdenum is above the stoichiometric value for these Mo-K-O compounds, molybdena is also formed.
KeywordsNitrogen Polymer Spectroscopy Ammonium Potassium
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