Preparation of Ru-[bmim]BF4 Catalyst Using NaBH4 as Reducing Agent and Its Performance in Selective Hydrogenation of Benzene

Abstract

A Ru-[bmim]BF 4 catalyst was prepared in a mixture of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ) and H 2 O using NaBH 4 as a reducing agent. The Ru-[bmim]BF 4 catalyst showed higher selectivity for cyclohexene than a catalyst reduced by N 2 H 4 ·H 2 O because of the influence of boron. When Ru-[bmim]BF 4 was reused, higher activity and lower selectivity were obtained because the number of Ru active sites increased through leaching of the ionic liquid. The used catalyst also contained ZnOHF formed in the reaction between F − and ZnSO 4 , which was an additive in the reaction. Under the influence of the ionic liquid as a template, ZnOHF grew along the (001) direction and exhibited rod-like morphology. 在离子液体 1-丁基-3-甲基咪唑四氟硼酸盐 ([bmim]BF 4 )-水混合介质中, 以 NaBH 4 为还原剂制备了 Ru-[bmim]BF 4 催化剂, 并用于苯选择加氢反应. 结果表明, 相对于 N 2 H 4 ·H 2 O 还原制备的催化剂, 本催化剂具有明显较高的环己烯选择性, 当苯转化率为 49.5% 时, 环己烯选择性可达 34.1%, 这是由于硼的作用所致. 重复使用时, 由于离子液体的流失, 暴露的 Ru 活性中心增多, 因而苯转化率升高, 但环己烯选择性下降, 同时生成了 ZnOHF. 这是离子液体中 F – 与 ZnSO 4 反应而得; 并且在离子液体的模板作用下, ZnOHF 沿着 (001) 方向生长, 从而形成了一维棒状形貌. Ru-[bmim]BF 4 shows higher selectivity for cyclohexene in the hydrogenation of benzene when NaBH 4 is used as a reductant because of the significant effect of boron.