猝冷速度对骨架Ni催化剂结构和催化性能的影响

在5种不同猝冷速度下制备Ni-Al合金,然后以碱处理并活化得到多孔猝冷骨架Ni催化剂.通过电感耦合等离子发射光谱(ICP)、X射线粉末衍射(XRD)、H₂-程序升温脱附(H₂-TPD)和氮物理吸附等方法对催化剂的物理化学性质进行了表征.结果发现,随着冷却速度的增加,活化后的催化剂具有更多的残余Ni₂Al₃相、更低的比表面积、更大的孔容和孔径、更小的Ni晶粒、更大的Ni-Ni间距和更加单一的活性位.另外,还发现在肉桂醛选择加氢反应中,冷却速度的提高也促进了催化剂的活性和对目标产物3-苯丙醛选择性的提高.以RQNi₅为催化剂,加氢产物3-苯丙醛的收率达到88.8%,转化率为98.4%,明显优于工业上广泛使用的RaneyNi催化剂.同时,对猝冷骨架Ni催化剂的结构与催化性能之间的关系进行了讨论.

Effect of Rapid Quenching Speed on the Structure and Catalytic Properties of the Skeletal Ni Catalysts

A series of rapidly quenched skeletal Ni catalysts were prepared by alkali leaching of Ni-Al alloys solidified at different cooling rates. It has been found that the higher cooling rate leads to more residual Ni-2Al-3 phase, lower surface area, larger average pore size and porosity, smaller mean crystallite size, larger unit-cell parameter and more uniform active site. The relationship between the structure and catalytic behavior of the rapidly quenched skeletal Ni was discussed by using cinnamaldehyde selective hydrogenation as the probe reaction.