Ru-[bmim]BF4 的制备及催化苯选择加氢反应性能

以离子液体1-丁基-3-甲基咪唑四氟硼酸盐(bmim]BF4)-水混合溶剂为介质,采用化学还原法制备了Ru-bmim]BF4催化剂,并利用紫外-可见光谱、红外光谱、透射电镜、X射线衍射和X射线光电子能谱对催化剂进行了表征.结果表明,Ru在bmim]BF4中分散较好,粒径~2nm,且离子液体中咪唑阳离子与部分Ru形成了金属卡宾配合物.利用苯选择加氢反应对该催化剂性能进行了评价,发现Ru-卡宾配合物存在时,催化剂活性较低,但环己烯选择性较高.在本文反应条件下,苯转化率为12.2%,环己烯选择性为40.5%.重复使用该催化剂时,由于Ru-卡宾配合物在反应中转变为Ru0,其催化活性增加,但环己烯选择性下降.继续多次使用该催化剂,其性能基本保持稳定.

Preparation of Ru-[bmim]BF4 and Its Catalytic Performance for Selective Hydrogenation of Benzene

Ru-bmim]BF4 catalyst was prepared in the mixed solvent of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmim]BF4) and H2O by chemical reduction and was characterized by ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that Ru nanoparticles of about 2 nm were highly dispersed in the ionic liquid, and a Ru-carbene complex was obtained between imidazolium cations of bmim]BF4 and some of Ru particles. The catalytic performance of the catalyst for benzene selective hydrogenation was evaluated. The catalyst showed poor activity but high cyclohexene selectivity in the presence of the Ru-carbene complex. Cyclohexene selectivity was up to 40.5% at 12.2% benzene conversion. When the catalyst was reused, its catalytic activity increased but the selectivity declined. This was due to the transformation from Ru-carbene complex to Ru0 during the reaction process. In addition, the catalytic performance of Ru-bmim]BF4 remained stable when it was reused further.