Effects of rehydration of alumina on its structural properties, surface acidity, and HDN activity of quinoline
Effects of rehydration of alumina on its structural properties, surface acidity, and HDN activity of quinoline
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DOI：
10.1016/j.apcata.2012.06.017
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发表时间：
2012-09
影响因子：
5.5
通讯作者：
Guangci Li;Yunqi Liu;Zhe Tang;Chenguang Liu
中科院分区：
文献类型：
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作者：
Guangci Li;Yunqi Liu;Zhe Tang;Chenguang Liu
通过初始氧化铝在不同水热条件下的再水合脱水得到一系列氧化铝。为了研究再水化温度对所得氧化铝物理化学性质的影响，应用了X射线粉末衍射、氮气吸附、扫描/透射电子显微镜、傅里叶变换红外、热重分析和27Al MAS NMR等技术。结果表明，随着处理温度的升高，氧化铝颗粒的晶体尺寸和形貌发生变化，且氧化铝微晶主要沿两个表面取向生长。因此，氧化铝的结构性质发生了变化。此外，再水化过程不仅增加了弱酸位点，还增加了强酸位点，这与γ-Al2O3的（111）和（110）表面的生长密切相关。这两种类型的酸位点源自配位不饱和四重铝原子。对一系列Ni(Mo)催化剂进行了TPR，结果表明，再水化过程同时增加了氧化铝表面的酸度和碱度，从而分别增强了Ni和Mo物种与氧化铝的相互作用力。这种相互作用与喹啉在相应 NiMo/γ-Al2O3 催化剂上的加氢脱氮 (HDN) 活性密切相关。
A series of aluminas were obtained through rehydration–dehydration of the initial alumina under different hydrothermal conditions. To investigate the influences of rehydration temperature on the physicochemical properties of the as-obtained aluminas, several techniques were applied, such as X-ray powder diffraction, nitrogen adsorption, scanning/transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, and27Al MAS NMR. The results show that crystal size and morphology of alumina particles changed as the treatment temperature was increased, and alumina crystallites grew mainly along two surface orientations. Consequently, the changes in textural properties of the aluminas took place. In addition, the rehydration process increased not only the weak acid sites but also the strong acid sites, which is closely related to the growth of the (111) and (110) surfaces of γ-Al2O3. The two type acid sites were originated from coordinately unsaturated four-fold aluminum atoms. TPR for a series of Ni(Mo) catalysts were carried out and the results show that rehydration process increased the surface acidity and basicity of alumina simultaneously, which enhanced the interacting force of Ni and Mo species with aluminas respectively. This interaction is closely related to the hydrodenitrogenation (HDN) activity of quinoline over the corresponding NiMo/γ-Al2O3catalysts.