Evolution of several Ni and Ni–MgO catalysts during the hydrogenation reaction of adiponitrile
Evolution of several Ni and Ni–MgO catalysts during the hydrogenation reaction of adiponitrile
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DOI：
10.1016/j.apcata.2004.06.008
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发表时间：
2004-09
影响因子：
5.5
通讯作者：
M. Serra;P. Salagre;Y. Cesteros;F. Medina;J. Sueiras
中科院分区：
文献类型：
--
作者：
M. Serra;P. Salagre;Y. Cesteros;F. Medina;J. Sueiras
在两种不同的反应条件下，研究了两种体相Ni(一种商用Raney-Ni和一种制备的晶态Ni)和两种Ni-MgO催化剂在常压下气相加氢216h后表面性质的变化。采用不同的技术对催化反应前后的催化剂进行了表征。Raney-Ni和Ni-MgO催化剂的活性随反应时间的延长而变化，直至达到恒定的转化率和选择性。反应后，所有催化剂的金属面积均减小。有趣的是，当使用高空速的反应条件时，这种下降幅度较小，比表面积略有增加，这有利于缩合产物的解吸，并导致一定程度的颗粒解聚。Raney-Ni的高加氢能力和Ni-MgO催化剂的碱性使其比制备的块状Ni催化剂获得了更高的转化率。扫描电子显微镜观察到，晶态Ni和Ni-MgO催化剂中存在一定的八面体颗粒，这与在较少的加氢条件下反应216h后保持了较高的6-氨基己腈选择性(约80%)有关。
The changes of the surface properties of two bulk Ni (one commercial Raney-Ni and one prepared crystalline Ni) and two Ni–MgO catalysts were studied after the hydrogenation of adiponitrile in the gas phase at atmospheric pressure for 216h at two different reaction conditions. Catalysts before and after the catalytic reaction were characterized by different techniques. Raney-Ni and Ni–MgO catalysts show an evolution of activity with the reaction time until reaching constant conversion and selectivity values. The metallic area decreases after reaction for all catalysts. Interestingly, this decrease is lower and the surface area slightly increases when using reaction conditions of high space velocity, which favour the desorption of condensation products and results in a certain disagglomeration of particles. The high hydrogenation ability of Raney-Ni and the basicity of Ni–MgO catalysts allow them to achieve much higher conversions than the bulk Ni catalyst prepared. The presence of defined octahedral particles, observed for the crystalline Ni and Ni–MgO catalysts by SEM, has been related to the constant high value of selectivity to 6-aminohexanenitrile (around 80%) maintained after 216h of reaction at less hydrogenating conditions.