Combined TPS, XPS, EXAFS, and NO-TPD study of the sulfiding of Mo/Al2O3

The sulfiding of Mo/Al2O3 in H2S/Ar versus in H2S/H-2 has been studied by t emperature-programmed sulfiding (TPS), X-ray photon electron spectroscopy ( XPS), extended X-ray absorption fine structure (EXAFS). and temperature-pro grammed desorption of NO (NO-TPD). All the applied techniques agree on the sulfur content in the sulfided catalysts and the findings are in accord wit h a model for the H2S production reaction. The nucleation and growth of wel l-ordered MoS2 clusters are probed by XPS during sulfiding with and without the presence of hydrogen. The resulting dispersion of the MoS2 phase is ev aluated on the basis of XPS, EXAFS. and NO-TPD. and is found to be highest when the sulfiding occurs in the presence of hydrogen.