XPS and TPR studies of nitrided molybdena-alumina

The relationship between the surface molybdenum species and adsorbed nitrog en species on nitrided 1.0-18.7% MoO3/Al2O3 was elucidated by XPS and tempe rature-programmed reduction (TPR). The MoO3/Al2O3 samples were nitrided by temperature-programmed reaction with NH3. From the XPS analysis, Mo3+ and M o4+ ions were predominant on the surface of the nitrided Mo/Al2O3 samples. From the TPR measurement, the ammonia desorption was due to nitrogen specie s adsorbed on alumina. The nitrogen desorption was due to two kinds of nitr ogen desorption from the structures of gamma-Mo2N and beta-Mo2N0.78 and fou r kinds of nitrogen desorption from NHX species adsorbed on MoO2, Mo3+ ion (gamma-Mo2N), Mo2+ ion (molybdenum nitride on alumina such as highly disper sed molybdenum nitride), and alumina.