X-ray photoelectron spectroscopy and temperature-programmed desorption studies of nitrided molybdena-alumina catalyst

The relationship between the Mo oxidation states measured by X-ray photoele ctron spectroscopy (XPS) and the NHX species was discussed based on results of temperature-programmed desorption (TPD). From the XPS analysis, the maj or Mo oxidation states were found to be Mo3+ and Mo4+ for 1.0-18.7 wt% Mo/A l2O3 nitrided at 973 K. The TPD results indicated that the desorption of ni trogen and hydrogen from the nitrided Mo/Al2O3 were deconvoluted to those o f NHX {alpha(N) (NHX, X = 0), beta(N) and gamma(N) (NHX, X = 0.6 to 1.5)} a dsorbed on molybenum species. The nitrogen species (NHX, X = 0) adsorb only on Mo3+ ions of the 973 K-nitrided Mo/Al2O3, but NHX species (X = 0.6-1.5) adsorb on either Mo3+ or Mo4+ ions.