Low-temperature isomerization of 1-butene on Mo₂N/γ-Al₂O₃ catalyst studied by in situ FT-IR spectroscopy

The adsorption and reaction of 1-butene on Mo₂N/γ-Al₂O₃ catalyst have been studied by in situ FT-IR spectroscopy at low temperatures, 145 K to room temperature (RT). The adsorbed 1-butene can be converted to cis- and trans-2-butenes below 201 K on Mo₂N/γ-Al₂O₃ catalyst. The result of coadsorption of 1-butene with CO indicates that 1-butene is mainly adsorbed on the surface Mo sites of the nitrided catalyst. No isomerization of adsorbed 1-butene and 2-butenes on reduced passivated Mo₂N/γ-Al₂O₃ sample below RT is observed. It is suggested that the double-bond migration (DBM) of 1-butene is mainly proceeded via an alkyl species on the surface cus Mo sites of Mo₂N/γ-Al₂O₃ catalyst. This resembles the behaviors of Group VIII metals in the isomerization of butenes. The incorporated nitrogen atoms are proposed to devote to both the valence state of surface Mo sites and the interaction between 1-butene and the nitrided catalyst. A possible path from 1-butene conversion to 2-butenes on Mo₂N/γ-Al₂O₃ catalyst is proposed.