离子液体在Wacker反应中的应用

Application of Ionic Liquids in Wacker Reaction

在60℃及2 MPa条件下,以PdCl2-CuCl2为催化剂,分别在无溶剂、酸性水溶液、1-丁基-3-甲基咪唑六氟磷酸盐(bmimPF6)离子液体为溶剂研究了分子氧氧化1-庚烯生成2-庚酮的Wacker反应。结果表明,在无溶剂、酸性水溶液、bmimPF6溶剂中,均可以得到目标产物2-庚酮,反应6 h后转化率均可达90%以上。在离子液体bmimPF6中,2-庚酮的选择性高于无溶剂和酸性水溶液中的结果。分别在酸性水溶液、bmimPF6溶剂中进行催化剂重复使用实验,研究不同溶剂中催化剂的稳定性。结果显示,在离子液体bmimPF6中催化剂的活性更加稳定,表明可以用离子液体取代传统的有毒、易挥发溶剂进行Wacker反应。

This paper reports the preparation of three alkyl imidazalium ionic liquids, 1-butyl-3-methylimid- azolium chloride （ bmimCl ）, 1 -butyl-3-methylimidazolium tetrafluoroborate （ bmimBF4 ） and 1-butyl-3-methylimidazolium hexafluorophosphate（bmimPF6）. At 60℃ and under 2 MPa, the Wacker reaction of 1-heptene oxidized with molecular oxygen to 2-heptanone with PdCI2-CuCI2 as the catalyst was studied in different reaction media, bmimPF6, acidic aqueous solution and solvent-free. Ii shows that 2-heptanone is formed in all of the above three cases and the conversions can reach 90% after a reaction time of 6 h. However, the selectivity in bmimPF6 for 2-heptanone is much higher than those in acidic aqueous solution and in heptene （solventfree）. In order to study the stability of the catalyst, the experiments were repeated in acidic aqueous solution and in bmimPF6 solvent. The results show that the palladium chloride catalyst is more stable in bmimPF6. It indicates that ionic liquids can be used as an alternative for the traditional, toxic, volatile organic solvents for Wacker reaction.