Carbon monoxide and oxygen chemisorption and functionalities of sulphided Ni-W/Al2O3 hydrotreating catalysts
Carbon monoxide and oxygen chemisorption and functionalities of sulphided Ni-W/Al2O3 hydrotreating catalysts
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硫化Ni-W/Al2O3加氢处理催化剂的一氧化碳和氧化学吸附及其功能
DOI：
10.1016/0920-5861(88)87047-0
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发表时间：
1988
期刊：
影响因子：
5.3
通讯作者：
D. Cornet
中科院分区：
文献类型：
--
作者：
J. Duchet;J. Lavalley;Saïd Housni;D. Ouafi;J. Bachelier;M. Lakhdar;A. Mennour;D. Cornet
采用一氧化碳和氧化学吸附法研究了不同组成（0-36% WO3, 0-8% NiO）的Ni-W/ al2o3硫化催化剂上存在的表面位点的性质和数量。在273 K （CO）和333 K （O2）下，用脉冲法测量了气体吸收量。用傅里叶红外光谱进一步研究了CO在表面的结合。讨论了催化剂的不同功能，即C-S键和C-N键的氢解和加氢作用的意义。在脉冲实验中，单组分Ni或W/ al2o3催化剂上CO的化学吸附量可以忽略不计。在促进催化剂上，化学吸附量更为重要：它们可以与C-S和C-N的氢解活性相关，从而遵循促进剂效应。该相关性考虑了硫化、煅烧温度和失活对运行时间的影响，所有这些因素都改变了活性位点的数量，但没有改变它们的固有活性。CO吸附在促进催化剂上的红外光谱特征是在2090 cm−1处有一个条带，该条带在疏散后仍然存在，而在未促进的Ni或W硫化物上记录的条带在这些条件下不存在。2090 cm−1波段被分配给CO吸附在受邻近Ni离子影响的高还原W离子上，信号强度是催化剂组成和硫化过程的函数。此外，在富钨催化剂上发现了1830 cm−1的新谱带。氧化学吸附测量提供了补充数据。氧吸取量测量的是Ni- w相中启动子（Ni）离子的数量，但不能解释所有HDS位点，因为CO的吸附并不完全受到预吸附氧的阻碍。然而，氧似乎能够到达负责吡啶环氢化的位置。因此，结合CO和o2的化学吸附测量提供了与氢化活性的令人满意的相关性。然而，这些遗址的性质尚不清楚。
Carbon monoxide and oxygen chemisorption was used to investigate the nature and number of surface sites present over sulphided Ni-W/Al2O3catalysts with compositions varying over a wide range (0–36% WO3; 0–8% NiO). The gas uptakes were measured by the pulse method at 273 K (for CO) and 333 K (for O2). The binding of CO on the surface was further studied by FTIR spectroscopy. The significance of the results in terms of the different functions of the catalysts, namely hydrogenolysis of C-S and C-N bonds and hydrogenation, is discussed. In the pulse experiments, the amounts of CO chemisorbed on the single-component Ni or W/Al2O3catalysts are negligible. On the promoted catalysts, the amounts chemisorbed are much more important: they can be related to the activities for both C-S and C-N hydrogenolysis, and thus follow the promoter effect. The correlation accounts for the effects of sulphiding, calcination temperature and deactivation with running time, all of which modify the number of active sites, but not their intrinsic activity. The IR spectra of CO adsorbed on the promoted catalysts are characterized by a band at 2090 cm−1, which persists after evacuation, whereas the bands recorded over unpromoted Ni or W sulphide do not persist under these conditions. The 2090 cm−1band is assigned to CO adsorbed on highly reduces W ions influenced by neighbouring Ni ions, and the intensity of the signal is a function of both catalyst composition and sulphiding procedure. In addition, a new band at 1830 cm−1is recorded over the tungsten-rich promoted catalysts. Oxygen chemisorption measurements provide complementary data. The oxygen uptake measures the number of promoter (Ni) ions in the Ni-W phase, but does not account for all of the HDS sites as CO adsorption is not completely hampered by pre-adsorbed oxygen. However, it appears that oxygen is able to reach the sites responsible for hydrogenation of the pyridine ring. Thus, combining CO and O2chemisorption measurements provides a satisfactory correlation with the hydrogenation activity. The nature of the sites remains unclear, however.