非负载镍催化剂的2-乙基蒽醌加氢活性及其氢吸脱附性质

 分别制备了金属镍粉、兰尼镍、Ni-B非晶态合金及镧掺杂的Ni-B非晶态合金(Ni-B-La)催化剂,研究了催化剂的氢吸附和脱附性质以及对2-乙基蒽醌加氢反应的催化性能. 结果表明,金属镍粉、兰尼镍和Ni-B催化剂表面均具有两种氢吸附位: 弱吸附位和强吸附位. Ni-B-La催化剂表面只有氢的强吸附位,其强吸附氢量与兰尼镍相当. 推测只有氢的强吸附位是2-乙基蒽醌加氢反应的活性中心,并且Ni-B-La催化剂上的强吸附氢较兰尼镍上的更活泼,因而Ni-B-La非晶态合金催化剂对加氢反应的催化活性高于兰尼镍.

Activity of Ni-Based Catalysts for 2-Ethylanthraquinone Hydrogenation and Their Behavior for H2 Chemisorption and Desorption

Pure Ni powder, Raney Ni, Ni-B amorphous alloy, and Ni-B-La amorphous alloy catalysts were prepared, characterized by H 2-chemisorption and H 2-temperature-programmed desorption (H 2-TPD), and their activity for the hydrogenation of 2-ethylanthraquinone was studied. The characterization results show that there are two types of adsorption sites for hydrogen, weak adsorption sites and strong adsorption sites, existing on the surface of the pure Ni powder, Raney Ni, and Ni-B amorphous alloy catalysts, while only strong adsorption sites exist on the surface of Ni-B-La. The reaction results in combination with H 2-TPD data suggest that the hydrogen desorbed from the strong adsorption sites is active for the hydrogenation of 2-ethylanthraquinone to form 2-ethylanthrahydroquinone. The La additive effectively promotes the dispersion of surface Ni atoms and makes the surface more homogeneous, resulting in the formation of only strong adsorption sites on the surface of the catalyst. Compared with Raney Ni, the desorption peak in H 2-TPD profiles of Ni-B-La shifts to lower temperature, implying that the Ni-H bond on the surface is weakened and the H atom is thus more active. This might be the reason why the activity of the Ni-B-La amorphous alloy catalyst is higher than that of Raney Ni even though there is no appreciable difference in the amounts of the strongly adsorbed hydrogen between the two catalysts.