Sulfur effect on Mo₂N/γ-Al₂O₃ catalyst studied by in situ FT-IR spectroscopy

In situ FTIR spectroscopy was used to characterize the sulfur effect of thiophene and H₂S on Mo₂N/γ-Al₂O₃ catalyst. CO adsorption was used to study the effect of thiophene and H₂S on surface of the Mo₂N/γ-Al₂O₃ catalyst. The adsorbed thiophene had strong electronic interaction with the Mo₂N/γ-Al₂O₃ and did not sulfide the surface of the catalyst at < 673 K. While in the presence of H₂, the surface of the Mo₂N/γ-Al₂O₃ could be partially sulfided by thiophene at ≥ 373 K, the adsorbed thiophene simultaneously decomposed or hydrodesulfurized on the catalyst. Compared to thiophene, H₂S had a stronger interaction with the Mo₂N/γ-Al₂O₃ and could slightly sulfide the catalyst surface even at room temperature. An H₂S/H₂ mixture deeply sulfided the catalyst surface at ~ 373 K. A renitridation using ammonia at 873 K could partially regenerate the surface of the sulfided nitride catalyst, showing that some formation of sulfur species on the nitrided catalyst is irreversible. However, when the catalyst is oxidized and then renitrided, the nitrided surface could be fully regenerated. The sulfur effect on a reduced passivated Mo₂N/γ-Al₂O₃ catalyst was also studied.