Selective hydrogenation of crotonaldehyde on Pt/ZnCl2/SiO2 catalysts
Selective hydrogenation of crotonaldehyde on Pt/ZnCl2/SiO2 catalysts
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DOI：
10.1016/j.jcat.2005.07.008
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发表时间：
2005-10
影响因子：
7.3
通讯作者：
F. Ammari;C. Milone;R. Touroude
中科院分区：
文献类型：
--
作者：
F. Ammari;C. Milone;R. Touroude
制备了沉积在两种不同载体上的 5 wt% Pt，该载体由沉积在二氧化硅上的 3 和 1/6 当量 ZnCl2 单层（称为 Pt30 和 Pt2）制成，并在巴豆醛的选择性加氢中进行了测试。以硝酸四氨铂作为金属盐前体制备铂基催化剂。这些催化剂在运行期间的活性和选择性方面表现出非常不同的催化行为。 Pt2 比 Pt30 活性更高，但对巴豆醇形成的选择性较低。在Pt30催化剂上，随着还原温度的升高，巴豆醇形成的选择性增加，而活性没有显着变化。当催化剂在400℃还原时，巴豆醇的选择性>80%。它的行为类似于由六氯铂酸前体制备的 Pt/ZnO 催化剂 [F. Ammari，J. Lamotte，R. Touroude，J. Catal。 221（2004）32]。相反，随着还原温度的升高，Pt2 样品对巴豆醇的选择性降低，活性增加。通过BET、X射线衍射、X射线光电子能谱、透射电子显微镜和傅里叶变换红外吡啶吸附对催化剂进行了广泛的表征。 Pt30 的较高选择性是通过 Zn 和氯的协同效应来解释的。催化剂表面存在的氯含量越多，导致载体的路易斯酸度增加；此外，观察到PtZn合金的形成。与我们之前的发现一致，我们提出，通过与锌合金化和载体的路易斯酸性来改变铂的电子性质，通过有利于分子末端氧与电子修饰的铂原子的结合来改变巴豆醛的吸附模式。
5 wt% Pt deposited on two different supports made of 3 and 1/6 equivalent monolayers of ZnCl2deposited on silica (termed Pt30 and Pt2) were prepared and tested in the selective hydrogenation of crotonaldehyde. Pt-based catalysts were prepared starting from tetraammine platinum nitrate as a metallic salt precursor. These catalysts showed very different catalytic behaviors in terms of the activity and the selectivity during time on stream. Pt2 was more active than Pt30 but less selective toward the formation of crotyl alcohol. On the Pt30 catalyst, the selectivity to the formation of crotyl alcohol increased with the reduction temperature, whereas the activity did not change significantly. When the catalyst was reduced at 400 °C, the selectivity to crotyl alcohol was >80%. It behaved similarly to Pt/ZnO catalysts prepared from hexachloroplatinic acid precursor [F. Ammari, J. Lamotte, R. Touroude, J. Catal. 221 (2004) 32]. In contrast, the Pt2 sample showed a decrease in the selectivity to crotyl alcohol and an increase in the activity with increasing reduction temperature. The catalysts were extensively characterized by BET, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Fourier transform infrared pyridine adsorption. The higher selectivity of Pt30 is explained by a synergetic effect of Zn and chlorine. The greater amount of chlorine present on the catalyst surface led to an increase in the Lewis acidity of the support; moreover, the formation of PtZn alloy was observed. In agreement with our previous findings, we propose that modification of the electronic properties of platinum both from alloying to Zn and from the Lewis acidity of the support changes the adsorption mode of crotonaldehyde by favoring the binding of terminal oxygen of the molecule to the electronically modified platinum atoms.