Structure-activity relationships in hydroprocessing of aromatic and heteroaromatic model compounds over sulphided NiO-MoO3/γ-Al2O3 and Nio-WO3/ γ -Al2O3 catalysts; chemical evidence for the existence of two types of catalytic sites
Structure-activity relationships in hydroprocessing of aromatic and heteroaromatic model compounds over sulphided NiO-MoO3/γ-Al2O3 and Nio-WO3/ γ -Al2O3 catalysts; chemical evidence for the existence of two types of catalytic sites
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DOI：
10.1016/0920-5861(88)87049-4
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发表时间：
1988-12
期刊：
影响因子：
5.3
通讯作者：
C. Moreau;Claudine Aubert;R. Durand;N. Zmimita;P. Geneste
中科院分区：
文献类型：
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作者：
C. Moreau;Claudine Aubert;R. Durand;N. Zmimita;P. Geneste
以含氮模型化合物吡啶、喹啉、吖啶、吡咯和咔唑为研究对象，在340℃、70 bar的条件下，在NiO-MoO3/ al2o3和NiO-WO3/ al2o3催化剂上进行了间歇加氢反应，发现杂芳环的饱和总是发生在C- n键（通常是Csp3-N键）裂解之前。杂芳环的氢化速率主要受环的芳香性（π-电子离域）的影响，而不受氮原子的碱度的影响。另一方面，在没有空间效应的情况下，氮原子的碱度对Csp3-N键的裂解有很大的影响。在相同的实验条件下，研究了通式C6H5X中X为电负性原子（OR， NHR， SR, Br, Cl， F）的底物加氢处理。苯基部分的加氢速率和Csp2-X键的氢解速率均与取代基常数σoR相关，该常数表示分子中π电子通过共振离域。高给电子取代基如NHR和OR （R=H, C6H5）的氢化反应优于氢解反应；相反，对于像SR （R=H, C6H5）或卤素（Cl, Br）等具有少量电子的取代基，氢解反应比氢化反应更有利。这种相关性的存在构成了两个不同催化位点存在的化学证据，一个负责与吸电子特征相关的氢化反应，另一个负责与供电子特征相关的Csp2-X键的氢解反应。
The hydroprocessing of nitrogen-containing model compounds such as pyridine, quinoline, acridine, pyrrole and carbazole was studied using a batch method at 340°C and 70 bar H2over sulphided NiO-MoO3/Al2O3and NiO-WO3/Al2O3catalysts, where it was found that saturation of the heteroaromatic rings always occurs prior to any cleavage of C-N bonds, generally Csp3-N bonds. The rates of hydrogenation of the heteroaromatic rings were shown to be mostly influenced by the aromaticity of these rings (π-electron delocalization) and not by the basicity of the nitrogen atom. On the other hand, the basicity of nitrogen atoms considerably influences the cleavage of Csp3-N bonds in the absence of steric effects.The hydroprocessing of substrates of general formula C6H5X, where X is an electronegative atom (OR, NHR, SR, Br, Cl, F) was also studied under the same experimental conditions. The rates of hydrogenation of the phenyl moiety and the rates of hydrogenolysis of the Csp2-X bond are both correlated with the same substituent constant, σoR, which represents the delocalization of π-electrons in the molecule by resonance. Hydrogenation is favoured over hydrogenolysis for highly electron-donating substituents such as NHR and OR (R=H, C6H5); conversely, hydrogenolysis is favoured over hydrogenation for slightly electron-donating substituents such as SR (R=H, C6H5) or halogens (Cl, Br). The presence of such correlations constitutes chemical evidence for the existence of two distinct catalytic sites, one responsible for hydrogenation associated with an electron-withdrawing character and the other responsible for the hydrogenolysis of Csp2-X bonds associated with an electron-donating character.