Preparation and catalytic properties of rare earth amides obtained by reactions of En or Yb metals with liquid ammonia

摘要

By controlling the preparative conditions, rare earth amides (Eu(NH_2)2, Yb(NH_2)2 and Yb(NH2)3) were successfully prepared from the reaction of Eu or Yb metals with liquid ammonia. The reaction of Yb metals with ammonia gradually proceeded to produce Yb(NH_2)_2 with subsequent conversion into Yb(NH_2)_3, while the Eu/NH_3 system yielded exclusively Eu(NH_2)_2. The different decomposition products obtained during thermal treatments of the rare earth amides were characterized by temperature-programmed desorption (TPD) and XRD icclmiques. The decomposition products such as imide and nitride were identified and the temperature ranges suitable for forming these products were also determined. The structural changes of the Eu/NH_3 and Yb/NH_3 systems through vailed steps were related to the catalytic activity for the hydrogenation of ethene or benzene. The rare earth imide and nitride showed high hydrogenation activity.