Surface characterization and hydrogenation properties of several nickel/α-alumina catalysts
Surface characterization and hydrogenation properties of several nickel/α-alumina catalysts
复制标题
DOI：
10.1039/ft9938903507
复制
发表时间：
1993
期刊：
影响因子：
--
通讯作者：
F. Medina;P. Salagre;J. Sueiras;J. Fierro
中科院分区：
文献类型：
--
作者：
F. Medina;P. Salagre;J. Sueiras;J. Fierro
本文研究了几种镍/α-Al_2O_3催化剂的化学制备、X射线光电子能谱（XPS）、还原活化能、程序升温还原（TPR）、X射线衍射（XRD）和催化活性。XPS结果表明，在高于623 K的温度下，非化学计量NiO在α-Al 2 O3上完全还原，随着Ni含量的增加和还原温度的降低，表面Ni的分散度增加。α-Al 2 O3负载的非化学计量比NiO的还原活化能高于未负载的非化学计量比NiO。TPR结果表明，α-Al_2O_3负载的非化学计量比NiO的还原起始温度和终止温度均高于未负载NiO，证实了α-Al_2O_3对NiO还原的抑制作用。XRD分析表明，随着还原温度的升高，样品中存在α-Al 2 O3、NiO和Ni相，且晶粒尺寸增大。催化转化率随着镍含量的增加而增加，并且在较低的镍含量、高的空速和较高的金属烧结下，对6-氨基己腈的选择性增加，这可能是由于存在较高含量的负责产生6-氨基己腈的特定晶体位点。提出了一种机制。
Studies of the chemical preparation, X-ray photoelectron spectra (XPS), activation energies of reduction, temperature-programmed reduction (TPR), X-ray diffraction (XRD) and catalytic activities of several nickel/α-alumina catalysts have been carried out for the catalytic hydrogenation of hexanedinitrile, in a continuous process at 1 atm pressure, 443 K, and in the absence of ammonia. XPS results show complete reduction of non-stoichiometric NiO on α-alumina at temperatures higher than 623 K and higher surface nickel dispersion with increasing nickel content and decreasing reduction temperatures. Activation energies of reduction for the α-alumina-supported non-stoichiometric NiO were higher than those of the unsupported non-stoichiometric NiO. TPR results show that the initial and final temperatures of reduction of the α-alumina-supported non-stoichiometric NiO are higher with unsupported NiO, confirming the inhibiting effect of α-alumina on NiO reduction. XRD measurements show the presence of α-alumina, NiO and Ni phases, and also the increase in crystallite size with increasing reduction temperature. Catalytic conversions increase with the nickel content and selectivities toward 6-aminohexanenitrile increase at lower nickel contents, high space velocities, and higher metallic sintering, probably owing to the presence of a higher content of specific crystal sites responsible for the production of 6-aminohexanenitrile. A mechanism is proposed.