Characterization of the structures and active sites in sulfided CoMoAl2O3 and NiMoAl2O3 catalysts by NO chemisorption
Characterization of the structures and active sites in sulfided CoMoAl2O3 and NiMoAl2O3 catalysts by NO chemisorption
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DOI：
10.1016/0021-9517(83)90010-6
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发表时间：
1983-12
影响因子：
7.3
通讯作者：
N. Topsoe;H. Topsøe
中科院分区：
文献类型：
--
作者：
N. Topsoe;H. Topsøe
用红外光谱法和容量法研究了硫化态Co Al 2 O3、Ni Al 2 O3、Mo Al 2 O3、Co γ-Mo Al 2 O3和Ni γ-Mo Al 2 O3催化剂中NO的吸附。噻吩加氢脱硫（HDS）活性的测量得到的催化含义。在这些研究中，催化剂中活性物质的含量和煅烧温度是不同的。红外波段被观察到是非常不同的NO吸附在Co，Ni，和Mo原子，是敏感的元素的表面浓度，表面相的性质和硫化或还原的程度。对于Mo-Al 2 O3催化剂，NO主要吸附在MoS 2类结构的边缘或角位上，因此，NO的吸附反映了MoS 2类结构的边缘分散性。在Co/Mo Al 2 O3和Ni/Mo Al 2 O3催化剂中，红外光谱同时给出了Co或Ni助剂原子上NO吸附和Mo原子上NO吸附的信息.可以看出，添加促进剂原子导致在Mo原子上的吸附减少。这表明促进剂原子占据了MoS 2“载体”的边缘位置。位于这样的位置的Co原子被发现是与那些存在于所谓的Co Mo S的结构确定以前通过穆斯堡尔发射光谱。结果表明，该催化剂具有类似的Ni-Mo-S结构，其HDS活性与NO的化学吸附量和Mo原子上NO的吸附量无关。然而，对于所有的催化剂的HDS活性和NO的吸附量的Co或Ni促进剂原子之间观察到一个很好的相关性。这进一步支持了“Co_xMo_xS模型”，其中促进剂原子的主要作用是产生具有比未促进位点更高的内在HDS活性的新位点（与促进剂原子相关）。吡啶，这是已知的是一个部分HDS毒药，观察到阻止大部分的NO吸附位点。
Infrared and volumetric studies of NO adsorption have been used to elucidate the type of surface structures present in sulfided Co Al 2 O 3, Ni Al 2 O 3, Mo Al 2 O 3, Co Mo Al 2 O 3, and Ni Mo Al 2 O 3 catalysts. Catalytic implications were obtained from measurements of thiophene hydrodesulfurization (HDS) activities. The content of active material in the catalysts and calcination temperature were varied in these studies. The ir bands were observed to be very different for NO adsorbed on Co, Ni, and Mo atoms and are sensitive to the surface concentration of the element, the nature of the surface phase and the extent of sulfiding or reduction. For Mo Al 2 O 3 catalysts, the NO most probably adsorbs on edge or corner sites of MoS 2-like structures and the adsorption therefore reflects the edge dispersion of these structures. In the case of the promoted Co Mo Al 2 O 3 and Ni Mo Al 2 O 3 catalysts, the ir studies give simultaneous information on the NO adsorption occurring on the Co or Ni promoter atoms and that occurring on the Mo atoms. It is seen that the addition of promoter atoms results in a decreased adsorption on the Mo atoms. This indicates that the promoter atoms occupy edge positions of the MoS 2 “support”. The Co atoms located in such positions are found to be related to those present in the so-called Co Mo S structure identified previously by Mössbauer emission spectroscopy. Evidence for similar Ni-Mo-S type structures is found. The HDS activity correlated neither with the total amount of chemisorbed NO nor with the amount of NO adsorbed on the Mo atoms. However, for all the catalysts a good correlation was observed between the HDS activity and the amount of NO adsorbed on the Co or Ni promoter atoms. This further supports the “Co Mo S model” in which the primary role of the promoter atoms is to create new sites (associated with the promoter atoms) with higher intrinsic HDS activity than that of the unpromoted sites. Pyridine, which is known to be a partial HDS poison, was observed to block a large fraction of the NO adsorption sites.